texlive[60574] Master: penlight (21sep21)

commits+karl at tug.org commits+karl at tug.org
Tue Sep 21 21:48:23 CEST 2021


Revision: 60574
          http://tug.org/svn/texlive?view=revision&revision=60574
Author:   karl
Date:     2021-09-21 21:48:22 +0200 (Tue, 21 Sep 2021)
Log Message:
-----------
penlight (21sep21)

Modified Paths:
--------------
    trunk/Master/tlpkg/bin/tlpkg-ctan-check
    trunk/Master/tlpkg/libexec/ctan2tds
    trunk/Master/tlpkg/tlpsrc/collection-luatex.tlpsrc

Added Paths:
-----------
    trunk/Master/texmf-dist/doc/luatex/penlight/
    trunk/Master/texmf-dist/doc/luatex/penlight/README.md
    trunk/Master/texmf-dist/doc/luatex/penlight/penlight.pdf
    trunk/Master/texmf-dist/doc/luatex/penlight/penlight.tex
    trunk/Master/texmf-dist/tex/luatex/penlight/
    trunk/Master/texmf-dist/tex/luatex/penlight/penlight.lua
    trunk/Master/texmf-dist/tex/luatex/penlight/penlight.sty
    trunk/Master/texmf-dist/tex/luatex/penlight/penlightextras.lua
    trunk/Master/tlpkg/tlpsrc/penlight.tlpsrc

Added: trunk/Master/texmf-dist/doc/luatex/penlight/README.md
===================================================================
--- trunk/Master/texmf-dist/doc/luatex/penlight/README.md	                        (rev 0)
+++ trunk/Master/texmf-dist/doc/luatex/penlight/README.md	2021-09-21 19:48:22 UTC (rev 60574)
@@ -0,0 +1,29 @@
+# penlight  -- Lua libraries for use in LuaLaTeX
+
+This LuaLaTeX package provides a thin-wrapper to use the [penlight](https://github.com/lunarmodules/Penlight) Lua libraries with LuaLaTeX. It uses the `luapackageloader` package.
+
+
+
+# License
+
+Copyright (C) 2021 Kale Ewasiuk
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
+ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
+OR OTHER DEALINGS IN THE SOFTWARE.


Property changes on: trunk/Master/texmf-dist/doc/luatex/penlight/README.md
___________________________________________________________________
Added: svn:eol-style
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Added: trunk/Master/texmf-dist/doc/luatex/penlight/penlight.pdf
===================================================================
(Binary files differ)

Index: trunk/Master/texmf-dist/doc/luatex/penlight/penlight.pdf
===================================================================
--- trunk/Master/texmf-dist/doc/luatex/penlight/penlight.pdf	2021-09-21 19:46:31 UTC (rev 60573)
+++ trunk/Master/texmf-dist/doc/luatex/penlight/penlight.pdf	2021-09-21 19:48:22 UTC (rev 60574)

Property changes on: trunk/Master/texmf-dist/doc/luatex/penlight/penlight.pdf
___________________________________________________________________
Added: svn:mime-type
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+application/pdf
\ No newline at end of property
Added: trunk/Master/texmf-dist/doc/luatex/penlight/penlight.tex
===================================================================
--- trunk/Master/texmf-dist/doc/luatex/penlight/penlight.tex	                        (rev 0)
+++ trunk/Master/texmf-dist/doc/luatex/penlight/penlight.tex	2021-09-21 19:48:22 UTC (rev 60574)
@@ -0,0 +1,95 @@
+% Kale Ewasiuk (kalekje at gmail.com)
+% 2021-09-20
+%
+% Copyright (C) 2021 Kale Ewasiuk
+%
+% Permission is hereby granted, free of charge, to any person obtaining a copy
+% of this software and associated documentation files (the "Software"), to deal
+% in the Software without restriction, including without limitation the rights
+% to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+% copies of the Software, and to permit persons to whom the Software is
+% furnished to do so, subject to the following conditions:
+%
+% The above copyright notice and this permission notice shall be included in
+% all copies or substantial portions of the Software.
+%
+% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+% ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+% TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+% PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT
+% SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
+% ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+% ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+% OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
+% OR OTHER DEALINGS IN THE SOFTWARE.
+
+\documentclass{article}
+\usepackage{url}
+\begin{document}
+
+    \section*{Penlight -- Lua libraries for use in LuaLaTeX}
+    v. 2021-09-20, Kale Ewasiuk, \url{kalekje at gmail.com}\\\\
+
+        The official documentation for the Lua library can be found here:\\
+  \mbox{\url{https://stevedonovan.github.io/Penlight/api/manual/01-introduction.md.html#}}
+    \\
+
+    \subsection*{Required Package Option}
+    The first option sent to this package MUST be one of: \\
+    \texttt{[penlight]} \ \ \  or \ \ \  \texttt{[pl]}.\\
+    All Penlight sub-modules are then available under this global variable by either\\
+    \texttt{penlight.XYZ} or \texttt{pl.XYZ}
+
+
+
+    \subsection*{Additional Package Options}
+
+    \noindent
+    \begin{tabular}{lp{4.5in}}
+    \texttt{stringx} & will import additional string functions into the string meta table.\\
+                    & this will be ran in pre-amble: \texttt{require('pl.stringx').import()}\\
+                        & \hspace*{-4em}\url{https://stevedonovan.github.io/Penlight/api/libraries/pl.stringx.html}\\\\
+    \texttt{format} & allows \% operator for Python-style string formating\\
+            & this will be ran in pre-amble: \texttt{require('pl.text').format\_operator()}\\
+                & \hspace*{-4em}\url{https://stevedonovan.github.io/Penlight/api/libraries/pl.text.html}\\\\
+    \texttt{func} & allows placehold expressions eg. \texttt{\_1+1} to be used \\
+                & this will be ran in pre-amble: \texttt{penlight.utils.import('pl.func')}\\
+                & \hspace*{-4em}\url{https://stevedonovan.github.io/Penlight/api/libraries/pl.func.html}\\\\
+    \texttt{extras} & adds some additional functions. Adds functions to some Penlight sub-modules. The following Lua globals will be defined:
+                \texttt{close\_bkt\_cnt,
+                    add\_bkt\_cnt,
+                    reset\_bkt\_cnt,
+                    \_NumBkts,
+                \_xTrue,
+                \_xFalse,
+                \_xNoValue,
+                \_\_SKIP\_TEX\_\_,
+                hasval,
+                mod, mod2,
+                }\\
+    \end{tabular}
+    \\\\
+
+    If you want to use Penlight (and extras) with the \texttt{texlua} intrepreter (no document made, only for Lua files, useful for testing),
+    you can access it by the following:
+     \begin{verbatim}
+    package.path = package.path .. ';'..'path/to/texmf/tex/latex/penlight/?.lua'
+    penlight = require('penlight')
+    __SKIP_TEX__ = true  --only required if you want to use
+                         --penlightextras without a LaTeX run
+    require('penlightextras')
+    \end{verbatim}
+
+
+
+
+
+    \section*{}
+    Disclaimer: I am not the author of the Lua Penlight library.
+    Penlight is Copyright \textcopyright  2009-2016 Steve Donovan, David Manura.
+    The distribution of Penlight used for this library is:
+\url{https://github.com/lunarmodules/penlight}\\
+    The author of this library has merged all Lua sub-modules into one file for this package.
+
+
+\end{document}
\ No newline at end of file


Property changes on: trunk/Master/texmf-dist/doc/luatex/penlight/penlight.tex
___________________________________________________________________
Added: svn:eol-style
## -0,0 +1 ##
+native
\ No newline at end of property
Added: trunk/Master/texmf-dist/tex/luatex/penlight/penlight.lua
===================================================================
--- trunk/Master/texmf-dist/tex/luatex/penlight/penlight.lua	                        (rev 0)
+++ trunk/Master/texmf-dist/tex/luatex/penlight/penlight.lua	2021-09-21 19:48:22 UTC (rev 60574)
@@ -0,0 +1,13705 @@
+
+---------------------------------------------------------
+----------------Auto generated code block----------------
+---------------------------------------------------------
+
+do
+    local searchers = package.searchers or package.loaders
+    local origin_seacher = searchers[2]
+    searchers[2] = function(path)
+        local files =
+        {
+------------------------
+-- Modules part begin --
+------------------------
+
+["pl.xml"] = function()
+--------------------
+-- Module: 'pl.xml'
+--------------------
+--- XML LOM Utilities.
+--
+-- This implements some useful things on [LOM](http://matthewwild.co.uk/projects/luaexpat/lom.html) documents, such as returned by `lxp.lom.parse`.
+-- In particular, it can convert LOM back into XML text, with optional pretty-printing control.
+-- It is s based on stanza.lua from [Prosody](http://hg.prosody.im/trunk/file/4621c92d2368/util/stanza.lua)
+--
+--     > d = xml.parse "<nodes><node id='1'>alice</node></nodes>"
+--     > = d
+--     <nodes><node id='1'>alice</node></nodes>
+--     > = xml.tostring(d,'','  ')
+--     <nodes>
+--        <node id='1'>alice</node>
+--     </nodes>
+--
+-- Can be used as a lightweight one-stop-shop for simple XML processing; a simple XML parser is included
+-- but the default is to use `lxp.lom` if it can be found.
+-- <pre>
+-- Prosody IM
+-- Copyright (C) 2008-2010 Matthew Wild
+-- Copyright (C) 2008-2010 Waqas Hussain--
+-- classic Lua XML parser by Roberto Ierusalimschy.
+-- modified to output LOM format.
+-- http://lua-users.org/wiki/LuaXml
+-- </pre>
+-- See @{06-data.md.XML|the Guide}
+--
+-- Dependencies: `pl.utils`
+--
+-- Soft Dependencies: `lxp.lom` (fallback is to use basic Lua parser)
+-- @module pl.xml
+
+local utils = require 'pl.utils'
+local split         =   utils.split;
+local t_insert      =  table.insert;
+local t_concat      =  table.concat;
+local t_remove      =  table.remove;
+local s_match       =  string.match;
+local tostring      =      tostring;
+local setmetatable  =  setmetatable;
+local getmetatable  =  getmetatable;
+local pairs         =         pairs;
+local ipairs        =        ipairs;
+local type          =          type;
+local next          =          next;
+local print         =         print;
+local unpack        =  utils.unpack;
+local s_gsub        =   string.gsub;
+local s_find        =   string.find;
+local pcall,require,io     =   pcall,require,io
+
+local _M = {}
+local Doc = { __type = "doc" };
+Doc.__index = Doc;
+
+--- create a new document node.
+-- @param tag the tag name
+-- @param attr optional attributes (table of name-value pairs)
+function _M.new(tag, attr)
+    local doc = { tag = tag, attr = attr or {}, last_add = {}};
+    return setmetatable(doc, Doc);
+end
+
+--- parse an XML document.  By default, this uses lxp.lom.parse, but
+-- falls back to basic_parse, or if use_basic is true
+-- @param text_or_file  file or string representation
+-- @param is_file whether text_or_file is a file name or not
+-- @param use_basic do a basic parse
+-- @return a parsed LOM document with the document metatatables set
+-- @return nil, error the error can either be a file error or a parse error
+function _M.parse(text_or_file, is_file, use_basic)
+    local parser,status,lom
+    if use_basic then parser = _M.basic_parse
+    else
+        status,lom = pcall(require,'lxp.lom')
+        if not status then parser = _M.basic_parse else parser = lom.parse end
+    end
+    if is_file then
+        local f,err = io.open(text_or_file)
+        if not f then return nil,err end
+        text_or_file = f:read '*a'
+        f:close()
+    end
+    local doc,err = parser(text_or_file)
+    if not doc then return nil,err end
+    if lom then
+        _M.walk(doc,false,function(_,d)
+            setmetatable(d,Doc)
+        end)
+    end
+    return doc
+end
+
+---- convenient function to add a document node, This updates the last inserted position.
+-- @param tag a tag name
+-- @param attrs optional set of attributes (name-string pairs)
+function Doc:addtag(tag, attrs)
+    local s = _M.new(tag, attrs);
+    (self.last_add[#self.last_add] or self):add_direct_child(s);
+    t_insert(self.last_add, s);
+    return self;
+end
+
+--- convenient function to add a text node.  This updates the last inserted position.
+-- @param text a string
+function Doc:text(text)
+    (self.last_add[#self.last_add] or self):add_direct_child(text);
+    return self;
+end
+
+---- go up one level in a document
+function Doc:up()
+    t_remove(self.last_add);
+    return self;
+end
+
+function Doc:reset()
+    local last_add = self.last_add;
+    for i = 1,#last_add do
+        last_add[i] = nil;
+    end
+    return self;
+end
+
+--- append a child to a document directly.
+-- @param child a child node (either text or a document)
+function Doc:add_direct_child(child)
+    t_insert(self, child);
+end
+
+--- append a child to a document at the last element added
+-- @param child a child node (either text or a document)
+function Doc:add_child(child)
+    (self.last_add[#self.last_add] or self):add_direct_child(child);
+    return self;
+end
+
+--accessing attributes: useful not to have to expose implementation (attr)
+--but also can allow attr to be nil in any future optimizations
+
+--- set attributes of a document node.
+-- @param t a table containing attribute/value pairs
+function Doc:set_attribs (t)
+    for k,v in pairs(t) do
+        self.attr[k] = v
+    end
+end
+
+--- set a single attribute of a document node.
+-- @param a attribute
+-- @param v its value
+function Doc:set_attrib(a,v)
+    self.attr[a] = v
+end
+
+--- access the attributes of a document node.
+function Doc:get_attribs()
+    return self.attr
+end
+
+local function is_text(s) return type(s) == 'string' end
+
+--- function to create an element with a given tag name and a set of children.
+-- @param tag a tag name
+-- @param items either text or a table where the hash part is the attributes and the list part is the children.
+function _M.elem(tag,items)
+    local s = _M.new(tag)
+    if is_text(items) then items = {items} end
+    if _M.is_tag(items) then
+       t_insert(s,items)
+    elseif type(items) == 'table' then
+       for k,v in pairs(items) do
+           if is_text(k) then
+               s.attr[k] = v
+               t_insert(s.attr,k)
+           else
+               s[k] = v
+           end
+       end
+    end
+    return s
+end
+
+--- given a list of names, return a number of element constructors.
+-- @param list  a list of names, or a comma-separated string.
+-- @usage local parent,children = doc.tags 'parent,children' <br>
+--  doc = parent {child 'one', child 'two'}
+function _M.tags(list)
+    local ctors = {}
+    if is_text(list) then list = split(list,'%s*,%s*') end
+    for _,tag in ipairs(list) do
+        local ctor = function(items) return _M.elem(tag,items) end
+        t_insert(ctors,ctor)
+    end
+    return unpack(ctors)
+end
+
+local templ_cache = {}
+
+local function template_cache (templ)
+    if is_text(templ) then
+        if templ_cache[templ] then
+            templ = templ_cache[templ]
+        else
+            local str,err = templ
+            templ,err = _M.parse(str,false,true)
+            if not templ then return nil,err end
+            templ_cache[str] = templ
+        end
+    elseif not _M.is_tag(templ) then
+        return nil, "template is not a document"
+    end
+    return templ
+end
+
+local function is_data(data)
+    return #data == 0 or type(data[1]) ~= 'table'
+end
+
+local function prepare_data(data)
+    -- a hack for ensuring that $1 maps to first element of data, etc.
+    -- Either this or could change the gsub call just below.
+    for i,v in ipairs(data) do
+        data[tostring(i)] = v
+    end
+end
+
+--- create a substituted copy of a document,
+-- @param templ  may be a document or a string representation which will be parsed and cached
+-- @param data  a table of name-value pairs or a list of such tables
+-- @return an XML document
+function Doc.subst(templ, data)
+    local err
+    if type(data) ~= 'table' or not next(data) then return nil, "data must be a non-empty table" end
+    if is_data(data) then
+        prepare_data(data)
+    end
+    templ,err = template_cache(templ)
+    if err then return nil, err end
+    local function _subst(item)
+        return _M.clone(templ,function(s)
+            return s:gsub('%$(%w+)',item)
+        end)
+    end
+    if is_data(data) then return _subst(data) end
+    local list = {}
+    for _,item in ipairs(data) do
+        prepare_data(item)
+        t_insert(list,_subst(item))
+    end
+    if data.tag then
+        list = _M.elem(data.tag,list)
+    end
+    return list
+end
+
+
+--- get the first child with a given tag name.
+-- @param tag the tag name
+function Doc:child_with_name(tag)
+    for _, child in ipairs(self) do
+        if child.tag == tag then return child; end
+    end
+end
+
+local _children_with_name
+function _children_with_name(self,tag,list,recurse)
+    for _, child in ipairs(self) do if type(child) == 'table' then
+        if child.tag == tag then t_insert(list,child) end
+        if recurse then _children_with_name(child,tag,list,recurse) end
+    end end
+end
+
+--- get all elements in a document that have a given tag.
+-- @param tag a tag name
+-- @param dont_recurse optionally only return the immediate children with this tag name
+-- @return a list of elements
+function Doc:get_elements_with_name(tag,dont_recurse)
+    local res = {}
+    _children_with_name(self,tag,res,not dont_recurse)
+    return res
+end
+
+-- iterate over all children of a document node, including text nodes.
+function Doc:children()
+    local i = 0;
+    return function (a)
+            i = i + 1
+            return a[i];
+    end, self, i;
+end
+
+-- return the first child element of a node, if it exists.
+function Doc:first_childtag()
+    if #self == 0 then return end
+    for _,t in ipairs(self) do
+        if type(t) == 'table' then return t end
+    end
+end
+
+function Doc:matching_tags(tag, xmlns)
+    xmlns = xmlns or self.attr.xmlns;
+    local tags = self;
+    local start_i, max_i, v = 1, #tags;
+    return function ()
+            for i=start_i,max_i do
+                v = tags[i];
+                if (not tag or v.tag == tag)
+                and (not xmlns or xmlns == v.attr.xmlns) then
+                    start_i = i+1;
+                    return v;
+                end
+            end
+        end, tags, start_i;
+end
+
+--- iterate over all child elements of a document node.
+function Doc:childtags()
+    local i = 0;
+    return function (a)
+        local v
+            repeat
+                i = i + 1
+                v = self[i]
+                if v and type(v) == 'table' then return v; end
+            until not v
+        end, self[1], i;
+end
+
+--- visit child element  of a node and call a function, possibility modifying the document.
+-- @param callback  a function passed the node (text or element). If it returns nil, that node will be removed.
+-- If it returns a value, that will replace the current node.
+function Doc:maptags(callback)
+    local is_tag = _M.is_tag
+    local i = 1;
+    while i <= #self do
+        if is_tag(self[i]) then
+            local ret = callback(self[i]);
+            if ret == nil then
+                t_remove(self, i);
+            else
+                self[i] = ret;
+                i = i + 1;
+            end
+        end
+    end
+    return self;
+end
+
+local xml_escape
+do
+    local escape_table = { ["'"] = "'", ["\""] = """, ["<"] = "<", [">"] = ">", ["&"] = "&" };
+    function xml_escape(str) return (s_gsub(str, "['&<>\"]", escape_table)); end
+    _M.xml_escape = xml_escape;
+end
+
+-- pretty printing
+-- if indent, then put each new tag on its own line
+-- if attr_indent, put each new attribute on its own line
+local function _dostring(t, buf, self, xml_escape, parentns, idn, indent, attr_indent)
+    local nsid = 0;
+    local tag = t.tag
+    local lf,alf = ""," "
+    if indent then lf = '\n'..idn end
+    if attr_indent then alf = '\n'..idn..attr_indent end
+    t_insert(buf, lf.."<"..tag);
+    local function write_attr(k,v)
+        if s_find(k, "\1", 1, true) then
+            local ns, attrk = s_match(k, "^([^\1]*)\1?(.*)$");
+            nsid = nsid + 1;
+            t_insert(buf, " xmlns:ns"..nsid.."='"..xml_escape(ns).."' ".."ns"..nsid..":"..attrk.."='"..xml_escape(v).."'");
+        elseif not(k == "xmlns" and v == parentns) then
+            t_insert(buf, alf..k.."='"..xml_escape(v).."'");
+        end
+    end
+    -- it's useful for testing to have predictable attribute ordering, if available
+    if #t.attr > 0 then
+        for _,k in ipairs(t.attr) do
+            write_attr(k,t.attr[k])
+        end
+    else
+        for k, v in pairs(t.attr) do
+            write_attr(k,v)
+        end
+    end
+    local len,has_children = #t;
+    if len == 0 then
+    local out = "/>"
+    if attr_indent then out = '\n'..idn..out end
+        t_insert(buf, out);
+    else
+        t_insert(buf, ">");
+        for n=1,len do
+            local child = t[n];
+            if child.tag then
+                self(child, buf, self, xml_escape, t.attr.xmlns,idn and idn..indent, indent, attr_indent );
+                has_children = true
+            else -- text element
+                t_insert(buf, xml_escape(child));
+            end
+        end
+        t_insert(buf, (has_children and lf or '').."</"..tag..">");
+    end
+end
+
+---- pretty-print an XML document
+--- @param t an XML document
+--- @param idn an initial indent (indents are all strings)
+--- @param indent an indent for each level
+--- @param attr_indent if given, indent each attribute pair and put on a separate line
+--- @param xml force prefacing with default or custom <?xml...>
+--- @return a string representation
+function _M.tostring(t,idn,indent, attr_indent, xml)
+    local buf = {};
+    if xml then
+        if type(xml) == "string" then
+            buf[1] = xml
+        else
+            buf[1] = "<?xml version='1.0'?>"
+        end
+    end
+    _dostring(t, buf, _dostring, xml_escape, nil,idn,indent, attr_indent);
+    return t_concat(buf);
+end
+
+Doc.__tostring = _M.tostring
+
+--- get the full text value of an element
+function Doc:get_text()
+    local res = {}
+    for i,el in ipairs(self) do
+        if is_text(el) then t_insert(res,el) end
+    end
+    return t_concat(res);
+end
+
+--- make a copy of a document
+-- @param doc the original document
+-- @param strsubst an optional function for handling string copying which could do substitution, etc.
+function _M.clone(doc, strsubst)
+    local lookup_table = {};
+    local function _copy(object,kind,parent)
+        if type(object) ~= "table" then
+            if strsubst and is_text(object) then return strsubst(object,kind,parent)
+            else return object
+            end
+        elseif lookup_table[object] then
+            return lookup_table[object]
+        end
+        local new_table = {};
+        lookup_table[object] = new_table
+        local tag = object.tag
+        new_table.tag = _copy(tag,'*TAG',parent)
+        if object.attr then
+            local res = {}
+            for attr,value in pairs(object.attr) do
+                res[attr] = _copy(value,attr,object)
+            end
+            new_table.attr = res
+        end
+        for index = 1,#object do
+            local v = _copy(object[index],'*TEXT',object)
+            t_insert(new_table,v)
+        end
+        return setmetatable(new_table, getmetatable(object))
+    end
+
+    return _copy(doc)
+end
+
+Doc.filter = _M.clone -- also available as method
+
+--- compare two documents.
+-- @param t1 any value
+-- @param t2 any value
+function _M.compare(t1,t2)
+    local ty1 = type(t1)
+    local ty2 = type(t2)
+    if ty1 ~= ty2 then return false, 'type mismatch' end
+    if ty1 == 'string' then
+        return t1 == t2 and true or 'text '..t1..' ~= text '..t2
+    end
+    if ty1 ~= 'table' or ty2 ~= 'table' then return false, 'not a document' end
+    if t1.tag ~= t2.tag then return false, 'tag  '..t1.tag..' ~= tag '..t2.tag end
+    if #t1 ~= #t2 then return false, 'size '..#t1..' ~= size '..#t2..' for tag '..t1.tag end
+    -- compare attributes
+    for k,v in pairs(t1.attr) do
+        if t2.attr[k] ~= v then return false, 'mismatch attrib' end
+    end
+    for k,v in pairs(t2.attr) do
+        if t1.attr[k] ~= v then return false, 'mismatch attrib' end
+    end
+    -- compare children
+    for i = 1,#t1 do
+        local yes,err = _M.compare(t1[i],t2[i])
+        if not yes then return err end
+    end
+    return true
+end
+
+--- is this value a document element?
+-- @param d any value
+function _M.is_tag(d)
+    return type(d) == 'table' and is_text(d.tag)
+end
+
+--- call the desired function recursively over the document.
+-- @param doc the document
+-- @param depth_first  visit child notes first, then the current node
+-- @param operation a function which will receive the current tag name and current node.
+function _M.walk (doc, depth_first, operation)
+    if not depth_first then operation(doc.tag,doc) end
+    for _,d in ipairs(doc) do
+        if _M.is_tag(d) then
+            _M.walk(d,depth_first,operation)
+        end
+    end
+    if depth_first then operation(doc.tag,doc) end
+end
+
+local html_empty_elements = { --lists all HTML empty (void) elements
+    br      = true,
+    img     = true,
+    meta    = true,
+    frame   = true,
+    area    = true,
+    hr      = true,
+    base    = true,
+    col     = true,
+    link    = true,
+    input   = true,
+    option  = true,
+    param   = true,
+    isindex = true,
+    embed = true,
+}
+
+local escapes = { quot = "\"", apos = "'", lt = "<", gt = ">", amp = "&" }
+local function unescape(str) return (str:gsub( "&(%a+);", escapes)); end
+
+--- Parse a well-formed HTML file as a string.
+-- Tags are case-insenstive, DOCTYPE is ignored, and empty elements can be .. empty.
+-- @param s the HTML
+function _M.parsehtml (s)
+    return _M.basic_parse(s,false,true)
+end
+
+--- Parse a simple XML document using a pure Lua parser based on Robero Ierusalimschy's original version.
+-- @param s the XML document to be parsed.
+-- @param all_text  if true, preserves all whitespace. Otherwise only text containing non-whitespace is included.
+-- @param html if true, uses relaxed HTML rules for parsing
+function _M.basic_parse(s,all_text,html)
+    local t_insert,t_remove = table.insert,table.remove
+    local s_find,s_sub = string.find,string.sub
+    local stack = {}
+    local top = {}
+
+    local function parseargs(s)
+      local arg = {}
+      s:gsub("([%w:%-_]+)%s*=%s*([\"'])(.-)%2", function (w, _, a)
+        if html then w = w:lower() end
+        arg[w] = unescape(a)
+      end)
+      if html then
+        s:gsub("([%w:%-_]+)%s*=%s*([^\"']+)%s*", function (w, a)
+          w = w:lower()
+          arg[w] = unescape(a)
+        end)
+      end
+      return arg
+    end
+
+    t_insert(stack, top)
+    local ni,c,label,xarg, empty, _, istart
+    local i = 1
+    local j
+    -- we're not interested in <?xml version="1.0"?>
+    _,istart = s_find(s,'^%s*<%?[^%?]+%?>%s*')
+    if not istart then -- or <!DOCTYPE ...>
+        _,istart = s_find(s,'^%s*<!DOCTYPE.->%s*')
+    end
+    if istart then i = istart+1 end
+    while true do
+        ni,j,c,label,xarg, empty = s_find(s, "<([%/!]?)([%w:%-_]+)(.-)(%/?)>", i)
+        if not ni then break end
+        if c == "!" then -- comment
+            -- case where there's no space inside comment
+            if not (label:match '%-%-$' and xarg == '') then
+                if xarg:match '%-%-$' then -- we've grabbed it all
+                    j = j - 2
+                end
+                -- match end of comment
+                _,j = s_find(s, "-->", j, true)
+            end
+        else
+            local text = s_sub(s, i, ni-1)
+            if html then
+                label = label:lower()
+                if html_empty_elements[label] then empty = "/" end
+            end
+            if all_text or not s_find(text, "^%s*$") then
+                t_insert(top, unescape(text))
+            end
+            if empty == "/" then  -- empty element tag
+                t_insert(top, setmetatable({tag=label, attr=parseargs(xarg), empty=1},Doc))
+            elseif c == "" then   -- start tag
+                top = setmetatable({tag=label, attr=parseargs(xarg)},Doc)
+                t_insert(stack, top)   -- new level
+            else  -- end tag
+                local toclose = t_remove(stack)  -- remove top
+                top = stack[#stack]
+                if #stack < 1 then
+                    error("nothing to close with "..label..':'..text)
+                end
+                if toclose.tag ~= label then
+                    error("trying to close "..toclose.tag.." with "..label.." "..text)
+                end
+                t_insert(top, toclose)
+            end
+        end
+        i = j+1
+    end
+    local text = s_sub(s, i)
+    if all_text or  not s_find(text, "^%s*$") then
+        t_insert(stack[#stack], unescape(text))
+    end
+    if #stack > 1 then
+        error("unclosed "..stack[#stack].tag)
+    end
+    local res = stack[1]
+    return is_text(res[1]) and res[2] or res[1]
+end
+
+local function empty(attr) return not attr or not next(attr) end
+local function is_element(d) return type(d) == 'table' and d.tag ~= nil end
+
+-- returns the key,value pair from a table if it has exactly one entry
+local function has_one_element(t)
+    local key,value = next(t)
+    if next(t,key) ~= nil then return false end
+    return key,value
+end
+
+local function append_capture(res,tbl)
+    if not empty(tbl) then -- no point in capturing empty tables...
+        local key
+        if tbl._ then  -- if $_ was set then it is meant as the top-level key for the captured table
+            key = tbl._
+            tbl._ = nil
+            if empty(tbl) then return end
+        end
+        -- a table with only one pair {[0]=value} shall be reduced to that value
+        local numkey,val = has_one_element(tbl)
+        if numkey == 0 then tbl = val end
+        if key then
+            res[key] = tbl
+        else -- otherwise, we append the captured table
+            t_insert(res,tbl)
+        end
+    end
+end
+
+local function make_number(pat)
+    if pat:find '^%d+$' then -- $1 etc means use this as an array location
+        pat = tonumber(pat)
+    end
+    return pat
+end
+
+local function capture_attrib(res,pat,value)
+    pat = make_number(pat:sub(2))
+    res[pat] = value
+    return true
+end
+
+local match
+function match(d,pat,res,keep_going)
+    local ret = true
+    if d == nil then d = '' end --return false end
+    -- attribute string matching is straight equality, except if the pattern is a $ capture,
+    -- which always succeeds.
+    if is_text(d) then
+        if not is_text(pat) then return false end
+        if _M.debug then print(d,pat) end
+        if pat:find '^%$' then
+            return capture_attrib(res,pat,d)
+        else
+            return d == pat
+        end
+    else
+    if _M.debug then print(d.tag,pat.tag) end
+        -- this is an element node. For a match to succeed, the attributes must
+        -- match as well.
+        -- a tagname in the pattern ending with '-' is a wildcard and matches like an attribute
+        local tagpat = pat.tag:match '^(.-)%-$'
+        if tagpat then
+            tagpat = make_number(tagpat)
+            res[tagpat] = d.tag
+        end
+        if d.tag == pat.tag or tagpat then
+
+            if not empty(pat.attr) then
+                if empty(d.attr) then ret =  false
+                else
+                    for prop,pval in pairs(pat.attr) do
+                        local dval = d.attr[prop]
+                        if not match(dval,pval,res) then ret = false;  break end
+                    end
+                end
+            end
+            -- the pattern may have child nodes. We match partially, so that {P1,P2} shall match {X,P1,X,X,P2,..}
+            if ret and #pat > 0 then
+                local i,j = 1,1
+                local function next_elem()
+                    j = j + 1  -- next child element of data
+                    if is_text(d[j]) then j = j + 1 end
+                    return j <= #d
+                end
+                repeat
+                    local p = pat[i]
+                    -- repeated {{<...>}} patterns  shall match one or more elements
+                    -- so e.g. {P+} will match {X,X,P,P,X,P,X,X,X}
+                    if is_element(p) and p.repeated then
+                        local found
+                        repeat
+                            local tbl = {}
+                            ret = match(d[j],p,tbl,false)
+                            if ret then
+                                found = false --true
+                                append_capture(res,tbl)
+                            end
+                        until not next_elem() or (found and not ret)
+                        i = i + 1
+                    else
+                        ret = match(d[j],p,res,false)
+                        if ret then i = i + 1 end
+                    end
+                until not next_elem() or i > #pat -- run out of elements or patterns to match
+                -- if every element in our pattern matched ok, then it's been a successful match
+                if i > #pat then return true end
+            end
+            if ret then return true end
+        else
+            ret = false
+        end
+        -- keep going anyway - look at the children!
+        if keep_going then
+            for child in d:childtags() do
+                ret = match(child,pat,res,keep_going)
+                if ret then break end
+            end
+        end
+    end
+    return ret
+end
+
+function Doc:match(pat)
+    local err
+    pat,err = template_cache(pat)
+    if not pat then return nil, err end
+    _M.walk(pat,false,function(_,d)
+        if is_text(d[1]) and is_element(d[2]) and is_text(d[3]) and
+           d[1]:find '%s*{{' and d[3]:find '}}%s*' then
+           t_remove(d,1)
+           t_remove(d,2)
+           d[1].repeated = true
+        end
+    end)
+
+    local res = {}
+    local ret = match(self,pat,res,true)
+    return res,ret
+end
+
+
+return _M
+
+
+end,
+
+["pl.app"] = function()
+--------------------
+-- Module: 'pl.app'
+--------------------
+--- Application support functions.
+-- See @{01-introduction.md.Application_Support|the Guide}
+--
+-- Dependencies: `pl.utils`, `pl.path`
+-- @module pl.app
+
+local io,package,require = _G.io, _G.package, _G.require
+local utils = require 'pl.utils'
+local path = require 'pl.path'
+
+local app = {}
+
+--- return the name of the current script running.
+-- The name will be the name as passed on the command line
+-- @return string filename
+function app.script_name()
+    if _G.arg and _G.arg[0] then
+        return _G.arg[0]
+    end
+    return utils.raise("No script name found")
+end
+
+--- prefixes the current script's path to the Lua module path.
+-- Applies to both the source and the binary module paths. It makes it easy for
+-- the main file of a multi-file program to access its modules in the same directory.
+-- `base` allows these modules to be put in a specified subdirectory, to allow for
+-- cleaner deployment and resolve potential conflicts between a script name and its
+-- library directory.
+--
+-- Note: the path is prefixed, so it is searched first when requiring modules.
+-- @string base optional base directory (absolute, or relative path).
+-- @treturn string the current script's path with a trailing slash
+function app.require_here (base)
+    local p = path.dirname(app.script_name())
+    if not path.isabs(p) then
+        p = path.join(path.currentdir(),p)
+    end
+    if p:sub(-1,-1) ~= path.sep then
+        p = p..path.sep
+    end
+    if base then
+        if path.is_windows then
+            base = base:gsub('/','\\')
+        end
+        if path.isabs(base) then
+            p = base .. path.sep
+        else
+            p = p..base..path.sep
+        end
+    end
+    local so_ext = path.is_windows and 'dll' or 'so'
+    local lsep = package.path:find '^;' and '' or ';'
+    local csep = package.cpath:find '^;' and '' or ';'
+    package.path = ('%s?.lua;%s?%sinit.lua%s%s'):format(p,p,path.sep,lsep,package.path)
+    package.cpath = ('%s?.%s%s%s'):format(p,so_ext,csep,package.cpath)
+    return p
+end
+
+--- return a suitable path for files private to this application.
+-- These will look like '~/.SNAME/file', with '~' as with expanduser and
+-- SNAME is the name of the script without .lua extension.
+-- If the directory does not exist, it will be created.
+-- @string file a filename (w/out path)
+-- @return a full pathname, or nil
+-- @return cannot create directory error
+-- @usage
+-- -- when run from a script called 'testapp' (on Windows):
+-- local app = require 'pl.app'
+-- print(app.appfile 'test.txt')
+-- -- C:\Documents and Settings\steve\.testapp\test.txt
+function app.appfile(file)
+    local sfullname, err = app.script_name()
+    if not sfullname then return utils.raise(err) end
+    local sname = path.basename(sfullname)
+    local name = path.splitext(sname)
+    local dir = path.join(path.expanduser('~'),'.'..name)
+    if not path.isdir(dir) then
+        local ret = path.mkdir(dir)
+        if not ret then return utils.raise('cannot create '..dir) end
+    end
+    return path.join(dir,file)
+end
+
+--- return string indicating operating system.
+-- @return 'Windows','OSX' or whatever uname returns (e.g. 'Linux')
+function app.platform()
+    if path.is_windows then
+        return 'Windows'
+    else
+        local f = io.popen('uname')
+        local res = f:read()
+        if res == 'Darwin' then res = 'OSX' end
+        f:close()
+        return res
+    end
+end
+
+--- return the full command-line used to invoke this script.
+-- It will not include the scriptname itself, see `app.script_name`.
+-- @return command-line
+-- @return name of Lua program used
+-- @usage
+-- -- execute:  lua -lluacov -e 'print(_VERSION)' myscript.lua
+--
+-- -- myscript.lua
+-- print(require("pl.app").lua())  --> "lua -lluacov -e 'print(_VERSION)'", "lua"
+function app.lua()
+    local args = _G.arg
+    if not args then
+        return utils.raise "not in a main program"
+    end
+
+    local cmd = {}
+    local i = -1
+    while true do
+        table.insert(cmd, 1, args[i])
+        if not args[i-1] then
+            return utils.quote_arg(cmd), args[i]
+        end
+        i = i - 1
+    end
+end
+
+--- parse command-line arguments into flags and parameters.
+-- Understands GNU-style command-line flags; short (`-f`) and long (`--flag`).
+--
+-- These may be given a value with either '=' or ':' (`-k:2`,`--alpha=3.2`,`-n2`),
+-- a number value can be given without a space. If the flag is marked
+-- as having a value, then a space-separated value is also accepted (`-i hello`),
+-- see the `flags_with_values` argument).
+--
+-- Multiple short args can be combined like so: ( `-abcd`).
+--
+-- When specifying the `flags_valid` parameter, its contents can also contain
+-- aliasses, to convert short/long flags to the same output name. See the
+-- example below.
+--
+-- Note: if a flag is repeated, the last value wins.
+-- @tparam {string} args an array of strings (default is the global `arg`)
+-- @tab flags_with_values any flags that take values, either list or hash
+-- table e.g. `{ out=true }` or `{ "out" }`.
+-- @tab flags_valid (optional) flags that are valid, either list or hashtable.
+-- If not given, everything
+-- will be accepted(everything in `flags_with_values` will automatically be allowed)
+-- @return a table of flags (flag=value pairs)
+-- @return an array of parameters
+-- @raise if args is nil, then the global `args` must be available!
+-- @usage
+-- -- Simple form:
+-- local flags, params = app.parse_args(nil,
+--      { "hello", "world" },  -- list of flags taking values
+--      { "l", "a", "b"})      -- list of allowed flags (value ones will be added)
+--
+-- -- More complex example using aliasses:
+-- local valid = {
+--     long = "l",           -- if 'l' is specified, it is reported as 'long'
+--     new = { "n", "old" }, -- here both 'n' and 'old' will go into 'new'
+-- }
+-- local values = {
+--     "value",   -- will automatically be added to the allowed set of flags
+--     "new",     -- will mark 'n' and 'old' as requiring a value as well
+-- }
+-- local flags, params = app.parse_args(nil, values, valid)
+--
+-- -- command:  myapp.lua -l --old:hello --value world param1 param2
+-- -- will yield:
+-- flags = {
+--     long = true,     -- input from 'l'
+--     new = "hello",   -- input from 'old'
+--     value = "world", -- allowed because it was in 'values', note: space separated!
+-- }
+-- params = {
+--     [1] = "param1"
+--     [2] = "param2"
+-- }
+function app.parse_args (args,flags_with_values, flags_valid)
+    if not args then
+        args = _G.arg
+        if not args then utils.raise "Not in a main program: 'arg' not found" end
+    end
+
+    local with_values = {}
+    for k,v in pairs(flags_with_values or {}) do
+        if type(k) == "number" then
+            k = v
+        end
+        with_values[k] = true
+    end
+
+    local valid
+    if not flags_valid then
+        -- if no allowed flags provided, we create a table that always returns
+        -- the keyname, no matter what you look up
+        valid = setmetatable({},{ __index = function(_, key) return key end })
+    else
+        valid = {}
+        for k,aliasses in pairs(flags_valid) do
+            if type(k) == "number" then         -- array/list entry
+                k = aliasses
+            end
+            if type(aliasses) == "string" then  -- single alias
+                aliasses = { aliasses }
+            end
+            if type(aliasses) == "table" then   -- list of aliasses
+                -- it's the alternate name, so add the proper mappings
+                for i, alias in ipairs(aliasses) do
+                    valid[alias] = k
+                end
+            end
+            valid[k] = k
+        end
+        do
+            local new_with_values = {}  -- needed to prevent "invalid key to 'next'" error
+            for k,v in pairs(with_values) do
+                if not valid[k] then
+                    valid[k] = k   -- add the with_value entry as a valid one
+                    new_with_values[k] = true
+                else
+                    new_with_values[valid[k]] = true  --set, but by its alias
+                end
+            end
+            with_values = new_with_values
+        end
+    end
+
+    -- now check that all flags with values are reported as such under all
+    -- of their aliasses
+    for k, main_alias in pairs(valid) do
+        if with_values[main_alias] then
+            with_values[k] = true
+        end
+    end
+
+    local _args = {}
+    local flags = {}
+    local i = 1
+    while i <= #args do
+        local a = args[i]
+        local v = a:match('^-(.+)')
+        local is_long
+        if not v then
+            -- we have a parameter
+            _args[#_args+1] = a
+        else
+            -- it's a flag
+            if v:find '^-' then
+                is_long = true
+                v = v:sub(2)
+            end
+            if with_values[v] then
+                if i == #args or args[i+1]:find '^-' then
+                    return utils.raise ("no value for '"..v.."'")
+                end
+                flags[valid[v]] = args[i+1]
+                i = i + 1
+            else
+                -- a value can also be indicated with = or :
+                local var,val =  utils.splitv (v,'[=:]', false, 2)
+                var = var or v
+                val = val or true
+                if not is_long then
+                    if #var > 1 then
+                        if var:find '.%d+' then -- short flag, number value
+                            val = var:sub(2)
+                            var = var:sub(1,1)
+                        else -- multiple short flags
+                            for i = 1,#var do
+                                local f = var:sub(i,i)
+                                if not valid[f] then
+                                    return utils.raise("unknown flag '"..f.."'")
+                                else
+                                    f = valid[f]
+                                end
+                                flags[f] = true
+                            end
+                            val = nil -- prevents use of var as a flag below
+                        end
+                    else  -- single short flag (can have value, defaults to true)
+                        val = val or true
+                    end
+                end
+                if val then
+                    if not valid[var] then
+                        return utils.raise("unknown flag '"..var.."'")
+                    else
+                        var = valid[var]
+                    end
+                    flags[var] = val
+                end
+            end
+        end
+        i = i + 1
+    end
+    return flags,_args
+end
+
+return app
+
+end,
+
+["pl.array2d"] = function()
+--------------------
+-- Module: 'pl.array2d'
+--------------------
+--- Operations on two-dimensional arrays.
+-- See @{02-arrays.md.Operations_on_two_dimensional_tables|The Guide}
+--
+-- The size of the arrays is determined by using the length operator `#` hence
+-- the module is not `nil` safe, and the usual precautions apply.
+--
+-- Note: all functions taking `i1,j1,i2,j2` as arguments will normalize the
+-- arguments using `default_range`.
+--
+-- Dependencies: `pl.utils`, `pl.tablex`, `pl.types`
+-- @module pl.array2d
+
+local tonumber,tostring,io,ipairs,string,table =
+    _G.tonumber,_G.tostring,_G.io,_G.ipairs,_G.string,_G.table
+local setmetatable,getmetatable = setmetatable,getmetatable
+
+local tablex = require 'pl.tablex'
+local utils = require 'pl.utils'
+local types = require 'pl.types'
+local imap,tmap,reduce,keys,tmap2,tset,index_by = tablex.imap,tablex.map,tablex.reduce,tablex.keys,tablex.map2,tablex.set,tablex.index_by
+local remove = table.remove
+local splitv,fprintf,assert_arg = utils.splitv,utils.fprintf,utils.assert_arg
+local byte = string.byte
+local stdout = io.stdout
+local min = math.min
+
+
+local array2d = {}
+
+local function obj (int,out)
+    local mt = getmetatable(int)
+    if mt then
+        setmetatable(out,mt)
+    end
+    return out
+end
+
+local function makelist (res)
+    return setmetatable(res, require('pl.List'))
+end
+
+--- return the row and column size.
+-- Size is calculated using the Lua length operator #, so usual precautions
+-- regarding `nil` values apply.
+-- @array2d a a 2d array
+-- @treturn int number of rows (`#a`)
+-- @treturn int number of cols (`#a[1]`)
+function array2d.size (a)
+    assert_arg(1,a,'table')
+    return #a,#a[1]
+end
+
+do
+    local function index (t,k)
+        return t[k]
+    end
+
+    --- extract a column from the 2D array.
+    -- @array2d a 2d array
+    -- @param j column index
+    -- @return 1d array
+    function array2d.column (a,j)
+        assert_arg(1,a,'table')
+        return makelist(imap(index,a,j))
+    end
+end
+local column = array2d.column
+
+--- extract a row from the 2D array.
+-- Added in line with `column`, for read-only purposes directly
+-- accessing a[i] is more performant.
+-- @array2d a 2d array
+-- @param i row index
+-- @return 1d array (copy of the row)
+function array2d.row(a,i)
+    assert_arg(1,a,'table')
+    local row = a[i]
+    local r = {}
+    for n,v in ipairs(row) do
+        r[n] = v
+    end
+    return makelist(r)
+end
+
+--- map a function over a 2D array
+-- @func f a function of at least one argument
+-- @array2d a 2d array
+-- @param arg an optional extra argument to be passed to the function.
+-- @return 2d array
+function array2d.map (f,a,arg)
+    assert_arg(2,a,'table')
+    f = utils.function_arg(1,f)
+    return obj(a,imap(function(row) return imap(f,row,arg) end, a))
+end
+
+--- reduce the rows using a function.
+-- @func f a binary function
+-- @array2d a 2d array
+-- @return 1d array
+-- @see pl.tablex.reduce
+function array2d.reduce_rows (f,a)
+    assert_arg(1,a,'table')
+    return tmap(function(row) return reduce(f,row) end, a)
+end
+
+--- reduce the columns using a function.
+-- @func f a binary function
+-- @array2d a 2d array
+-- @return 1d array
+-- @see pl.tablex.reduce
+function array2d.reduce_cols (f,a)
+    assert_arg(1,a,'table')
+    return tmap(function(c) return reduce(f,column(a,c)) end, keys(a[1]))
+end
+
+--- reduce a 2D array into a scalar, using two operations.
+-- @func opc operation to reduce the final result
+-- @func opr operation to reduce the rows
+-- @param a 2D array
+function array2d.reduce2 (opc,opr,a)
+    assert_arg(3,a,'table')
+    local tmp = array2d.reduce_rows(opr,a)
+    return reduce(opc,tmp)
+end
+
+--- map a function over two arrays.
+-- They can be both or either 2D arrays
+-- @func f function of at least two arguments
+-- @int ad order of first array (`1` if `a` is a list/array, `2` if it is a 2d array)
+-- @int bd order of second array (`1` if `b` is a list/array, `2` if it is a 2d array)
+-- @tab a 1d or 2d array
+-- @tab b 1d or 2d array
+-- @param arg optional extra argument to pass to function
+-- @return 2D array, unless both arrays are 1D
+function array2d.map2 (f,ad,bd,a,b,arg)
+    assert_arg(1,a,'table')
+    assert_arg(2,b,'table')
+    f = utils.function_arg(1,f)
+    if ad == 1 and bd == 2 then
+        return imap(function(row)
+            return tmap2(f,a,row,arg)
+        end, b)
+    elseif ad == 2 and bd == 1 then
+        return imap(function(row)
+            return tmap2(f,row,b,arg)
+        end, a)
+    elseif ad == 1 and bd == 1 then
+        return tmap2(f,a,b)
+    elseif ad == 2 and bd == 2 then
+        return tmap2(function(rowa,rowb)
+            return tmap2(f,rowa,rowb,arg)
+        end, a,b)
+    end
+end
+
+--- cartesian product of two 1d arrays.
+-- @func f a function of 2 arguments
+-- @array t1 a 1d table
+-- @array t2 a 1d table
+-- @return 2d table
+-- @usage product('..',{1,2},{'a','b'}) == {{'1a','2a'},{'1b','2b'}}
+function array2d.product (f,t1,t2)
+    f = utils.function_arg(1,f)
+    assert_arg(2,t1,'table')
+    assert_arg(3,t2,'table')
+    local res = {}
+    for i,v in ipairs(t2) do
+        res[i] = tmap(f,t1,v)
+    end
+    return res
+end
+
+--- flatten a 2D array.
+-- (this goes over columns first.)
+-- @array2d t 2d table
+-- @return a 1d table
+-- @usage flatten {{1,2},{3,4},{5,6}} == {1,2,3,4,5,6}
+function array2d.flatten (t)
+    local res = {}
+    local k = 1
+    local rows, cols = array2d.size(t)
+    for r = 1, rows do
+        local row = t[r]
+        for c = 1, cols do
+            res[k] = row[c]
+            k = k + 1
+        end
+    end
+    return makelist(res)
+end
+
+--- reshape a 2D array. Reshape the aray by specifying a new nr of rows.
+-- @array2d t 2d array
+-- @int nrows new number of rows
+-- @bool co use column-order (Fortran-style) (default false)
+-- @return a new 2d array
+function array2d.reshape (t,nrows,co)
+    local nr,nc = array2d.size(t)
+    local ncols = nr*nc / nrows
+    local res = {}
+    local ir,ic = 1,1
+    for i = 1,nrows do
+        local row = {}
+        for j = 1,ncols do
+            row[j] = t[ir][ic]
+            if not co then
+                ic = ic + 1
+                if ic > nc then
+                    ir = ir + 1
+                    ic = 1
+                end
+            else
+                ir = ir + 1
+                if ir > nr then
+                    ic = ic + 1
+                    ir = 1
+                end
+            end
+        end
+        res[i] = row
+    end
+    return obj(t,res)
+end
+
+--- transpose a 2D array.
+-- @array2d t 2d array
+-- @return a new 2d array
+function array2d.transpose(t)
+  assert_arg(1,t,'table')
+  local _, c = array2d.size(t)
+  return array2d.reshape(t,c,true)
+end
+
+--- swap two rows of an array.
+-- @array2d t a 2d array
+-- @int i1 a row index
+-- @int i2 a row index
+-- @return t (same, modified 2d array)
+function array2d.swap_rows (t,i1,i2)
+    assert_arg(1,t,'table')
+    t[i1],t[i2] = t[i2],t[i1]
+    return t
+end
+
+--- swap two columns of an array.
+-- @array2d t a 2d array
+-- @int j1 a column index
+-- @int j2 a column index
+-- @return t (same, modified 2d array)
+function array2d.swap_cols (t,j1,j2)
+    assert_arg(1,t,'table')
+    for _, row in ipairs(t) do
+        row[j1],row[j2] = row[j2],row[j1]
+    end
+    return t
+end
+
+--- extract the specified rows.
+-- @array2d t 2d array
+-- @tparam {int} ridx a table of row indices
+-- @return a new 2d array with the extracted rows
+function array2d.extract_rows (t,ridx)
+    return obj(t,index_by(t,ridx))
+end
+
+--- extract the specified columns.
+-- @array2d t 2d array
+-- @tparam {int} cidx a table of column indices
+-- @return a new 2d array with the extracted colums
+function array2d.extract_cols (t,cidx)
+    assert_arg(1,t,'table')
+    local res = {}
+    for i = 1,#t do
+        res[i] = index_by(t[i],cidx)
+    end
+    return obj(t,res)
+end
+
+--- remove a row from an array.
+-- @function array2d.remove_row
+-- @array2d t a 2d array
+-- @int i a row index
+array2d.remove_row = remove
+
+--- remove a column from an array.
+-- @array2d t a 2d array
+-- @int j a column index
+function array2d.remove_col (t,j)
+    assert_arg(1,t,'table')
+    for i = 1,#t do
+        remove(t[i],j)
+    end
+end
+
+do
+    local function _parse (s)
+        local r, c = s:match 'R(%d+)C(%d+)'
+        if r then
+            r,c = tonumber(r),tonumber(c)
+            return r,c
+        end
+        c,r = s:match '(%a+)(%d+)'
+        if c then
+            local cv = 0
+            for i = 1, #c do
+              cv = cv * 26 + byte(c:sub(i,i)) - byte 'A' + 1
+            end
+            return tonumber(r), cv
+        end
+        error('bad cell specifier: '..s)
+    end
+
+    --- parse a spreadsheet range.
+    -- The range can be specified either as 'A1:B2' or 'R1C1:R2C2';
+    -- a special case is a single element (e.g 'A1' or 'R1C1')
+    -- @string s a range (case insensitive).
+    -- @treturn int start row
+    -- @treturn int start col
+    -- @treturn int end row
+    -- @treturn int end col
+    function array2d.parse_range (s)
+        assert_arg(1,s,'string')
+        s = s:upper()
+        if s:find ':' then
+            local start,finish = splitv(s,':')
+            local i1,j1 = _parse(start)
+            local i2,j2 = _parse(finish)
+            return i1,j1,i2,j2
+        else -- single value
+            local i,j = _parse(s)
+            return i,j
+        end
+    end
+end
+
+--- get a slice of a 2D array using spreadsheet range notation. @see parse_range
+-- @array2d t a 2D array
+-- @string rstr range expression
+-- @return a slice
+-- @see array2d.parse_range
+-- @see array2d.slice
+function array2d.range (t,rstr)
+    assert_arg(1,t,'table')
+    return array2d.slice(t,array2d.parse_range(rstr))
+end
+
+local default_range do
+    local function norm_value(v, max)
+        if not v then return v end
+        if v < 0 then
+            v = max + v + 1
+        end
+        if v < 1 then v = 1 end
+        if v > max then v = max end
+        return v
+    end
+
+    --- normalizes coordinates to valid positive entries and defaults.
+    -- Negative indices will be counted from the end, too low, or too high
+    -- will be limited by the array sizes.
+    -- @array2d t a 2D array
+    -- @int i1 start row (default 1)
+    -- @int j1 start col (default 1)
+    -- @int i2 end row   (default N)
+    -- @int j2 end col   (default M)
+    -- return i1, j1, i2, j2
+    function array2d.default_range (t,i1,j1,i2,j2)
+        local nr, nc = array2d.size(t)
+        i1 = norm_value(i1 or 1, nr)
+        j1 = norm_value(j1 or 1, nc)
+        i2 = norm_value(i2 or nr, nr)
+        j2 = norm_value(j2 or nc, nc)
+        return i1,j1,i2,j2
+    end
+    default_range = array2d.default_range
+end
+
+--- get a slice of a 2D array. Note that if the specified range has
+-- a 1D result, the rank of the result will be 1.
+-- @array2d t a 2D array
+-- @int i1 start row (default 1)
+-- @int j1 start col (default 1)
+-- @int i2 end row   (default N)
+-- @int j2 end col   (default M)
+-- @return an array, 2D in general but 1D in special cases.
+function array2d.slice (t,i1,j1,i2,j2)
+    assert_arg(1,t,'table')
+    i1,j1,i2,j2 = default_range(t,i1,j1,i2,j2)
+    local res = {}
+    for i = i1,i2 do
+        local val
+        local row = t[i]
+        if j1 == j2 then
+            val = row[j1]
+        else
+            val = {}
+            for j = j1,j2 do
+                val[#val+1] = row[j]
+            end
+        end
+        res[#res+1] = val
+    end
+    if i1 == i2 then res = res[1] end
+    return obj(t,res)
+end
+
+--- set a specified range of an array to a value.
+-- @array2d t a 2D array
+-- @param value the value (may be a function, called as `val(i,j)`)
+-- @int i1 start row (default 1)
+-- @int j1 start col (default 1)
+-- @int i2 end row   (default N)
+-- @int j2 end col   (default M)
+-- @see tablex.set
+function array2d.set (t,value,i1,j1,i2,j2)
+    i1,j1,i2,j2 = default_range(t,i1,j1,i2,j2)
+    local i = i1
+    if types.is_callable(value) then
+        local old_f = value
+        value = function(j)
+            return old_f(i,j)
+        end
+    end
+    while i <= i2 do
+        tset(t[i],value,j1,j2)
+        i = i + 1
+    end
+end
+
+--- write a 2D array to a file.
+-- @array2d t a 2D array
+-- @param f a file object (default stdout)
+-- @string fmt a format string (default is just to use tostring)
+-- @int i1 start row (default 1)
+-- @int j1 start col (default 1)
+-- @int i2 end row   (default N)
+-- @int j2 end col   (default M)
+function array2d.write (t,f,fmt,i1,j1,i2,j2)
+    assert_arg(1,t,'table')
+    f = f or stdout
+    local rowop
+    if fmt then
+        rowop = function(row,j) fprintf(f,fmt,row[j]) end
+    else
+        rowop = function(row,j) f:write(tostring(row[j]),' ') end
+    end
+    local function newline()
+        f:write '\n'
+    end
+    array2d.forall(t,rowop,newline,i1,j1,i2,j2)
+end
+
+--- perform an operation for all values in a 2D array.
+-- @array2d t 2D array
+-- @func row_op function to call on each value; `row_op(row,j)`
+-- @func end_row_op function to call at end of each row; `end_row_op(i)`
+-- @int i1 start row (default 1)
+-- @int j1 start col (default 1)
+-- @int i2 end row   (default N)
+-- @int j2 end col   (default M)
+function array2d.forall (t,row_op,end_row_op,i1,j1,i2,j2)
+    assert_arg(1,t,'table')
+    i1,j1,i2,j2 = default_range(t,i1,j1,i2,j2)
+    for i = i1,i2 do
+        local row = t[i]
+        for j = j1,j2 do
+            row_op(row,j)
+        end
+        if end_row_op then end_row_op(i) end
+    end
+end
+
+---- move a block from the destination to the source.
+-- @array2d dest a 2D array
+-- @int di start row in dest
+-- @int dj start col in dest
+-- @array2d src a 2D array
+-- @int i1 start row (default 1)
+-- @int j1 start col (default 1)
+-- @int i2 end row   (default N)
+-- @int j2 end col   (default M)
+function array2d.move (dest,di,dj,src,i1,j1,i2,j2)
+    assert_arg(1,dest,'table')
+    assert_arg(4,src,'table')
+    i1,j1,i2,j2 = default_range(src,i1,j1,i2,j2)
+    local nr,nc = array2d.size(dest)
+    i2, j2 = min(nr,i2), min(nc,j2)
+    --i1, j1 = max(1,i1), max(1,j1)
+    dj = dj - 1
+    for i = i1,i2 do
+        local drow, srow = dest[i+di-1], src[i]
+        for j = j1,j2 do
+            drow[j+dj] = srow[j]
+        end
+    end
+end
+
+--- iterate over all elements in a 2D array, with optional indices.
+-- @array2d a 2D array
+-- @bool indices with indices (default false)
+-- @int i1 start row (default 1)
+-- @int j1 start col (default 1)
+-- @int i2 end row   (default N)
+-- @int j2 end col   (default M)
+-- @return either `value` or `i,j,value` depending on the value of `indices`
+function array2d.iter(a,indices,i1,j1,i2,j2)
+    assert_arg(1,a,'table')
+    i1,j1,i2,j2 = default_range(a,i1,j1,i2,j2)
+    local i,j = i1,j1-1
+    local row = a[i]
+    return function()
+        j = j + 1
+        if j > j2 then
+            j = j1
+            i = i + 1
+            row = a[i]
+            if i > i2 then
+                return nil
+            end
+        end
+        if indices then
+            return i,j,row[j]
+        else
+            return row[j]
+        end
+    end
+end
+
+--- iterate over all columns.
+-- @array2d a a 2D array
+-- @return column, column-index
+function array2d.columns(a)
+  assert_arg(1,a,'table')
+  local n = #a[1]
+  local i = 0
+  return function()
+      i = i + 1
+      if i > n then return nil end
+      return column(a,i), i
+  end
+end
+
+--- iterate over all rows.
+-- Returns a copy of the row, for read-only purrposes directly iterating
+-- is more performant; `ipairs(a)`
+-- @array2d a a 2D array
+-- @return row, row-index
+function array2d.rows(a)
+  assert_arg(1,a,'table')
+  local n = #a
+  local i = 0
+  return function()
+      i = i + 1
+      if i > n then return nil end
+      return array2d.row(a,i), i
+  end
+end
+
+--- new array of specified dimensions
+-- @int rows number of rows
+-- @int cols number of cols
+-- @param val initial value; if it's a function then use `val(i,j)`
+-- @return new 2d array
+function array2d.new(rows,cols,val)
+    local res = {}
+    local fun = types.is_callable(val)
+    for i = 1,rows do
+        local row = {}
+        if fun then
+            for j = 1,cols do row[j] = val(i,j) end
+        else
+            for j = 1,cols do row[j] = val end
+        end
+        res[i] = row
+    end
+    return res
+end
+
+return array2d
+
+end,
+
+["pl.class"] = function()
+--------------------
+-- Module: 'pl.class'
+--------------------
+--- Provides a reuseable and convenient framework for creating classes in Lua.
+-- Two possible notations:
+--
+--    B = class(A)
+--    class.B(A)
+--
+-- The latter form creates a named class within the current environment. Note
+-- that this implicitly brings in `pl.utils` as a dependency.
+--
+-- See the Guide for further @{01-introduction.md.Simplifying_Object_Oriented_Programming_in_Lua|discussion}
+-- @module pl.class
+
+local error, getmetatable, io, pairs, rawget, rawset, setmetatable, tostring, type =
+    _G.error, _G.getmetatable, _G.io, _G.pairs, _G.rawget, _G.rawset, _G.setmetatable, _G.tostring, _G.type
+local compat
+
+-- this trickery is necessary to prevent the inheritance of 'super' and
+-- the resulting recursive call problems.
+local function call_ctor (c,obj,...)
+    local init = rawget(c,'_init')
+    local parent_with_init = rawget(c,'_parent_with_init')
+
+    if parent_with_init then
+        if not init then -- inheriting an init
+            init = rawget(parent_with_init, '_init')
+            parent_with_init = rawget(parent_with_init, '_parent_with_init')
+        end
+        if parent_with_init then -- super() points to one above whereever _init came from
+            rawset(obj,'super',function(obj,...)
+                call_ctor(parent_with_init,obj,...)
+            end)
+        end
+    else
+        -- Without this, calling super() where none exists will sometimes loop and stack overflow
+        rawset(obj,'super',nil)
+    end
+
+    local res = init(obj,...)
+    if parent_with_init then -- If this execution of call_ctor set a super, unset it
+        rawset(obj,'super',nil)
+    end
+
+    return res
+end
+
+--- initializes an __instance__ upon creation.
+-- @function class:_init
+-- @param ... parameters passed to the constructor
+-- @usage local Cat = class()
+-- function Cat:_init(name)
+--   --self:super(name)   -- call the ancestor initializer if needed
+--   self.name = name
+-- end
+--
+-- local pussycat = Cat("pussycat")
+-- print(pussycat.name)  --> pussycat
+
+--- checks whether an __instance__ is derived from some class.
+-- Works the other way around as `class_of`. It has two ways of using;
+-- 1) call with a class to check against, 2) call without params.
+-- @function instance:is_a
+-- @param some_class class to check against, or `nil` to return the class
+-- @return `true` if `instance` is derived from `some_class`, or if `some_class == nil` then
+-- it returns the class table of the instance
+-- @usage local pussycat = Lion()  -- assuming Lion derives from Cat
+-- if pussycat:is_a(Cat) then
+--   -- it's true, it is a Lion, but also a Cat
+-- end
+--
+-- if pussycat:is_a() == Lion then
+--   -- It's true
+-- end
+local function is_a(self,klass)
+    if klass == nil then
+        -- no class provided, so return the class this instance is derived from
+        return getmetatable(self)
+    end
+    local m = getmetatable(self)
+    if not m then return false end --*can't be an object!
+    while m do
+        if m == klass then return true end
+        m = rawget(m,'_base')
+    end
+    return false
+end
+
+--- checks whether an __instance__ is derived from some class.
+-- Works the other way around as `is_a`.
+-- @function some_class:class_of
+-- @param some_instance instance to check against
+-- @return `true` if `some_instance` is derived from `some_class`
+-- @usage local pussycat = Lion()  -- assuming Lion derives from Cat
+-- if Cat:class_of(pussycat) then
+--   -- it's true
+-- end
+local function class_of(klass,obj)
+    if type(klass) ~= 'table' or not rawget(klass,'is_a') then return false end
+    return klass.is_a(obj,klass)
+end
+
+--- cast an object to another class.
+-- It is not clever (or safe!) so use carefully.
+-- @param some_instance the object to be changed
+-- @function some_class:cast
+local function cast (klass, obj)
+    return setmetatable(obj,klass)
+end
+
+
+local function _class_tostring (obj)
+    local mt = obj._class
+    local name = rawget(mt,'_name')
+    setmetatable(obj,nil)
+    local str = tostring(obj)
+    setmetatable(obj,mt)
+    if name then str = name ..str:gsub('table','') end
+    return str
+end
+
+local function tupdate(td,ts,dont_override)
+    for k,v in pairs(ts) do
+        if not dont_override or td[k] == nil then
+            td[k] = v
+        end
+    end
+end
+
+local function _class(base,c_arg,c)
+    -- the class `c` will be the metatable for all its objects,
+    -- and they will look up their methods in it.
+    local mt = {}   -- a metatable for the class to support __call and _handler
+    -- can define class by passing it a plain table of methods
+    local plain = type(base) == 'table' and not getmetatable(base)
+    if plain then
+        c = base
+        base = c._base
+    else
+        c = c or {}
+    end
+
+    if type(base) == 'table' then
+        -- our new class is a shallow copy of the base class!
+        -- but be careful not to wipe out any methods we have been given at this point!
+        tupdate(c,base,plain)
+        c._base = base
+        -- inherit the 'not found' handler, if present
+        if rawget(c,'_handler') then mt.__index = c._handler end
+    elseif base ~= nil then
+        error("must derive from a table type",3)
+    end
+
+    c.__index = c
+    setmetatable(c,mt)
+    if not plain then
+        if base and rawget(base,'_init') then c._parent_with_init = base end -- For super and inherited init
+        c._init = nil
+    end
+
+    if base and rawget(base,'_class_init') then
+        base._class_init(c,c_arg)
+    end
+
+    -- expose a ctor which can be called by <classname>(<args>)
+    mt.__call = function(class_tbl,...)
+        local obj
+        if rawget(c,'_create') then obj = c._create(...) end
+        if not obj then obj = {} end
+        setmetatable(obj,c)
+
+        if rawget(c,'_init') or rawget(c,'_parent_with_init') then -- constructor exists
+            local res = call_ctor(c,obj,...)
+            if res then -- _if_ a ctor returns a value, it becomes the object...
+                obj = res
+                setmetatable(obj,c)
+            end
+        end
+
+        if base and rawget(base,'_post_init') then
+            base._post_init(obj)
+        end
+
+        return obj
+    end
+    -- Call Class.catch to set a handler for methods/properties not found in the class!
+    c.catch = function(self, handler)
+        if type(self) == "function" then
+            -- called using . instead of :
+            handler = self
+        end
+        c._handler = handler
+        mt.__index = handler
+    end
+    c.is_a = is_a
+    c.class_of = class_of
+    c.cast = cast
+    c._class = c
+
+    if not rawget(c,'__tostring') then
+        c.__tostring = _class_tostring
+    end
+
+    return c
+end
+
+--- create a new class, derived from a given base class.
+-- Supporting two class creation syntaxes:
+-- either `Name = class(base)` or `class.Name(base)`.
+-- The first form returns the class directly and does not set its `_name`.
+-- The second form creates a variable `Name` in the current environment set
+-- to the class, and also sets `_name`.
+-- @function class
+-- @param base optional base class
+-- @param c_arg optional parameter to class constructor
+-- @param c optional table to be used as class
+local class
+class = setmetatable({},{
+    __call = function(fun,...)
+        return _class(...)
+    end,
+    __index = function(tbl,key)
+        if key == 'class' then
+            io.stderr:write('require("pl.class").class is deprecated. Use require("pl.class")\n')
+            return class
+        end
+        compat = compat or require 'pl.compat'
+        local env = compat.getfenv(2)
+        return function(...)
+            local c = _class(...)
+            c._name = key
+            rawset(env,key,c)
+            return c
+        end
+    end
+})
+
+class.properties = class()
+
+function class.properties._class_init(klass)
+    klass.__index = function(t,key)
+        -- normal class lookup!
+        local v = klass[key]
+        if v then return v end
+        -- is it a getter?
+        v = rawget(klass,'get_'..key)
+        if v then
+            return v(t)
+        end
+        -- is it a field?
+        return rawget(t,'_'..key)
+    end
+    klass.__newindex = function (t,key,value)
+        -- if there's a setter, use that, otherwise directly set table
+        local p = 'set_'..key
+        local setter = klass[p]
+        if setter then
+            setter(t,value)
+        else
+            rawset(t,key,value)
+        end
+    end
+end
+
+
+return class
+
+
+end,
+
+["pl.compat"] = function()
+--------------------
+-- Module: 'pl.compat'
+--------------------
+----------------
+--- Lua 5.1/5.2/5.3 compatibility.
+-- Injects `table.pack`, `table.unpack`, and `package.searchpath` in the global
+-- environment, to make sure they are available for Lua 5.1 and LuaJIT.
+--
+-- All other functions are exported as usual in the returned module table.
+--
+-- NOTE: everything in this module is also available in `pl.utils`.
+-- @module pl.compat
+local compat = {}
+
+--- boolean flag this is Lua 5.1 (or LuaJIT).
+-- @field lua51
+compat.lua51 = _VERSION == 'Lua 5.1'
+
+--- boolean flag this is LuaJIT.
+-- @field jit
+compat.jit = (tostring(assert):match('builtin') ~= nil)
+
+--- boolean flag this is LuaJIT with 5.2 compatibility compiled in.
+-- @field jit52
+if compat.jit then
+    -- 'goto' is a keyword when 52 compatibility is enabled in LuaJit
+    compat.jit52 = not loadstring("local goto = 1")
+end
+
+--- the directory separator character for the current platform.
+-- @field dir_separator
+compat.dir_separator = _G.package.config:sub(1,1)
+
+--- boolean flag this is a Windows platform.
+-- @field is_windows
+compat.is_windows = compat.dir_separator == '\\'
+
+--- execute a shell command, in a compatible and platform independent way.
+-- This is a compatibility function that returns the same for Lua 5.1 and
+-- Lua 5.2+.
+--
+-- NOTE: Windows systems can use signed 32bit integer exitcodes. Posix systems
+-- only use exitcodes 0-255, anything else is undefined.
+--
+-- NOTE2: In Lua 5.2 and 5.3 a Windows exitcode of -1 would not properly be
+-- returned, this function will return it properly for all versions.
+-- @param cmd a shell command
+-- @return true if successful
+-- @return actual return code
+function compat.execute(cmd)
+    local res1,res2,res3 = os.execute(cmd)
+    if res2 == "No error" and res3 == 0 and compat.is_windows then
+      -- os.execute bug in Lua 5.2/5.3 not reporting -1 properly on Windows
+      -- this was fixed in 5.4
+      res3 = -1
+    end
+    if compat.lua51 and not compat.jit52 then
+        if compat.is_windows then
+            return res1==0,res1
+        else
+            res1 = res1 > 255 and res1 / 256 or res1
+            return res1==0,res1
+        end
+    else
+        if compat.is_windows then
+            return res3==0,res3
+        else
+            return not not res1,res3
+        end
+    end
+end
+
+----------------
+-- Load Lua code as a text or binary chunk (in a Lua 5.2 compatible way).
+-- @param ld code string or loader
+-- @param[opt] source name of chunk for errors
+-- @param[opt] mode 'b', 't' or 'bt'
+-- @param[opt] env environment to load the chunk in
+-- @function compat.load
+
+---------------
+-- Get environment of a function (in a Lua 5.1 compatible way).
+-- Not 100% compatible, so with Lua 5.2 it may return nil for a function with no
+-- global references!
+-- Based on code by [Sergey Rozhenko](http://lua-users.org/lists/lua-l/2010-06/msg00313.html)
+-- @param f a function or a call stack reference
+-- @function compat.getfenv
+
+---------------
+-- Set environment of a function (in a Lua 5.1 compatible way).
+-- @param f a function or a call stack reference
+-- @param env a table that becomes the new environment of `f`
+-- @function compat.setfenv
+
+if compat.lua51 then -- define Lua 5.2 style load()
+    if not compat.jit then -- but LuaJIT's load _is_ compatible
+        local lua51_load = load
+        function compat.load(str,src,mode,env)
+            local chunk,err
+            if type(str) == 'string' then
+                if str:byte(1) == 27 and not (mode or 'bt'):find 'b' then
+                    return nil,"attempt to load a binary chunk"
+                end
+                chunk,err = loadstring(str,src)
+            else
+                chunk,err = lua51_load(str,src)
+            end
+            if chunk and env then setfenv(chunk,env) end
+            return chunk,err
+        end
+    else
+        compat.load = load
+    end
+    compat.setfenv, compat.getfenv = setfenv, getfenv
+else
+    compat.load = load
+    -- setfenv/getfenv replacements for Lua 5.2
+    -- by Sergey Rozhenko
+    -- http://lua-users.org/lists/lua-l/2010-06/msg00313.html
+    -- Roberto Ierusalimschy notes that it is possible for getfenv to return nil
+    -- in the case of a function with no globals:
+    -- http://lua-users.org/lists/lua-l/2010-06/msg00315.html
+    function compat.setfenv(f, t)
+        f = (type(f) == 'function' and f or debug.getinfo(f + 1, 'f').func)
+        local name
+        local up = 0
+        repeat
+            up = up + 1
+            name = debug.getupvalue(f, up)
+        until name == '_ENV' or name == nil
+        if name then
+            debug.upvaluejoin(f, up, function() return name end, 1) -- use unique upvalue
+            debug.setupvalue(f, up, t)
+        end
+        if f ~= 0 then return f end
+    end
+
+    function compat.getfenv(f)
+        local f = f or 0
+        f = (type(f) == 'function' and f or debug.getinfo(f + 1, 'f').func)
+        local name, val
+        local up = 0
+        repeat
+            up = up + 1
+            name, val = debug.getupvalue(f, up)
+        until name == '_ENV' or name == nil
+        return val
+    end
+end
+
+
+--- Global exported functions (for Lua 5.1 & LuaJIT)
+-- @section lua52
+
+--- pack an argument list into a table.
+-- @param ... any arguments
+-- @return a table with field n set to the length
+-- @function table.pack
+if not table.pack then
+    function table.pack (...)       -- luacheck: ignore
+        return {n=select('#',...); ...}
+    end
+end
+
+--- unpack a table and return the elements.
+--
+-- NOTE: this version does NOT honor the n field, and hence it is not nil-safe.
+-- See `utils.unpack` for a version that is nil-safe.
+-- @param t table to unpack
+-- @param[opt] i index from which to start unpacking, defaults to 1
+-- @param[opt] t index of the last element to unpack, defaults to #t
+-- @return multiple return values from the table
+-- @function table.unpack
+-- @see utils.unpack
+if not table.unpack then
+    table.unpack = unpack           -- luacheck: ignore
+end
+
+--- return the full path where a file name would be matched.
+-- This function was introduced in Lua 5.2, so this compatibility version
+-- will be injected in Lua 5.1 engines.
+-- @string name file name, possibly dotted
+-- @string path a path-template in the same form as package.path or package.cpath
+-- @string[opt] sep template separate character to be replaced by path separator. Default: "."
+-- @string[opt] rep the path separator to use, defaults to system separator. Default; "/" on Unixes, "\" on Windows.
+-- @see path.package_path
+-- @function package.searchpath
+-- @return on success: path of the file
+-- @return on failure: nil, error string listing paths tried
+if not package.searchpath then
+    function package.searchpath (name,path,sep,rep)    -- luacheck: ignore
+        if type(name) ~= "string" then
+            error(("bad argument #1 to 'searchpath' (string expected, got %s)"):format(type(path)), 2)
+        end
+        if type(path) ~= "string" then
+            error(("bad argument #2 to 'searchpath' (string expected, got %s)"):format(type(path)), 2)
+        end
+        if sep ~= nil and type(sep) ~= "string" then
+            error(("bad argument #3 to 'searchpath' (string expected, got %s)"):format(type(path)), 2)
+        end
+        if rep ~= nil and type(rep) ~= "string" then
+            error(("bad argument #4 to 'searchpath' (string expected, got %s)"):format(type(path)), 2)
+        end
+        sep = sep or "."
+        rep = rep or compat.dir_separator
+        do
+          local s, e = name:find(sep, nil, true)
+          while s do
+            name = name:sub(1, s-1) .. rep .. name:sub(e+1, -1)
+            s, e = name:find(sep, s + #rep + 1, true)
+          end
+        end
+        local tried = {}
+        for m in path:gmatch('[^;]+') do
+            local nm = m:gsub('?', name)
+            tried[#tried+1] = nm
+            local f = io.open(nm,'r')
+            if f then f:close(); return nm end
+        end
+        return nil, "\tno file '" .. table.concat(tried, "'\n\tno file '") .. "'"
+    end
+end
+
+--- Global exported functions (for Lua < 5.4)
+-- @section lua54
+
+--- raise a warning message.
+-- This functions mimics the `warn` function added in Lua 5.4.
+-- @function warn
+-- @param ... any arguments
+if not warn then  -- luacheck: ignore
+    local enabled = false
+    function warn(arg1, ...)  -- luacheck: ignore
+        if type(arg1) == "string" and arg1:sub(1, 1) == "@" then
+            -- control message
+            if arg1 == "@on" then
+                enabled = true
+                return
+            end
+            if arg1 == "@off" then
+                enabled = false
+                return
+            end
+            return -- ignore unknown control messages
+        end
+        if enabled then
+          io.stderr:write("Lua warning: ", arg1, ...)
+          io.stderr:write("\n")
+        end
+    end
+end
+
+return compat
+
+end,
+
+["pl.comprehension"] = function()
+--------------------
+-- Module: 'pl.comprehension'
+--------------------
+--- List comprehensions implemented in Lua.
+--
+-- See the [wiki page](http://lua-users.org/wiki/ListComprehensions)
+--
+--    local C= require 'pl.comprehension' . new()
+--
+--    C ('x for x=1,10') ()
+--    ==> {1,2,3,4,5,6,7,8,9,10}
+--    C 'x^2 for x=1,4' ()
+--    ==> {1,4,9,16}
+--    C '{x,x^2} for x=1,4' ()
+--    ==> {{1,1},{2,4},{3,9},{4,16}}
+--    C '2*x for x' {1,2,3}
+--    ==> {2,4,6}
+--    dbl = C '2*x for x'
+--    dbl {10,20,30}
+--    ==> {20,40,60}
+--    C 'x for x if x % 2 == 0' {1,2,3,4,5}
+--    ==> {2,4}
+--    C '{x,y} for x = 1,2 for y = 1,2' ()
+--    ==> {{1,1},{1,2},{2,1},{2,2}}
+--    C '{x,y} for x for y' ({1,2},{10,20})
+--    ==> {{1,10},{1,20},{2,10},{2,20}}
+--    assert(C 'sum(x^2 for x)' {2,3,4} == 2^2+3^2+4^2)
+--
+-- (c) 2008 David Manura. Licensed under the same terms as Lua (MIT license).
+--
+-- Dependencies: `pl.utils`, `pl.luabalanced`
+--
+-- See @{07-functional.md.List_Comprehensions|the Guide}
+-- @module pl.comprehension
+
+local utils = require 'pl.utils'
+
+local status,lb = pcall(require, "pl.luabalanced")
+if not status then
+    lb = require 'luabalanced'
+end
+
+local math_max = math.max
+local table_concat = table.concat
+
+-- fold operations
+-- http://en.wikipedia.org/wiki/Fold_(higher-order_function)
+local ops = {
+  list = {init=' {} ', accum=' __result[#__result+1] = (%s) '},
+  table = {init=' {} ', accum=' local __k, __v = %s __result[__k] = __v '},
+  sum = {init=' 0 ', accum=' __result = __result + (%s) '},
+  min = {init=' nil ', accum=' local __tmp = %s ' ..
+                             ' if __result then if __tmp < __result then ' ..
+                             '__result = __tmp end else __result = __tmp end '},
+  max = {init=' nil ', accum=' local __tmp = %s ' ..
+                             ' if __result then if __tmp > __result then ' ..
+                             '__result = __tmp end else __result = __tmp end '},
+}
+
+
+-- Parses comprehension string expr.
+-- Returns output expression list <out> string, array of for types
+-- ('=', 'in' or nil) <fortypes>, array of input variable name
+-- strings <invarlists>, array of input variable value strings
+-- <invallists>, array of predicate expression strings <preds>,
+-- operation name string <opname>, and number of placeholder
+-- parameters <max_param>.
+--
+-- The is equivalent to the mathematical set-builder notation:
+--
+--   <opname> { <out> | <invarlist> in <invallist> , <preds> }
+--
+-- @usage   "x^2 for x"                 -- array values
+-- @usage  "x^2 for x=1,10,2"          -- numeric for
+-- @usage  "k^v for k,v in pairs(_1)"  -- iterator for
+-- @usage  "(x+y)^2 for x for y if x > y"  -- nested
+--
+local function parse_comprehension(expr)
+  local pos = 1
+
+  -- extract opname (if exists)
+  local opname
+  local tok, post = expr:match('^%s*([%a_][%w_]*)%s*%(()', pos)
+  local pose = #expr + 1
+  if tok then
+    local tok2, posb = lb.match_bracketed(expr, post-1)
+    assert(tok2, 'syntax error')
+    if expr:match('^%s*$', posb) then
+      opname = tok
+      pose = posb - 1
+      pos = post
+    end
+  end
+  opname = opname or "list"
+
+  -- extract out expression list
+  local out; out, pos = lb.match_explist(expr, pos)
+  assert(out, "syntax error: missing expression list")
+  out = table_concat(out, ', ')
+
+  -- extract "for" clauses
+  local fortypes = {}
+  local invarlists = {}
+  local invallists = {}
+  while 1 do
+    local post = expr:match('^%s*for%s+()', pos)
+    if not post then break end
+    pos = post
+
+    -- extract input vars
+    local iv; iv, pos = lb.match_namelist(expr, pos)
+    assert(#iv > 0, 'syntax error: zero variables')
+    for _,ident in ipairs(iv) do
+      assert(not ident:match'^__',
+             "identifier " .. ident .. " may not contain __ prefix")
+    end
+    invarlists[#invarlists+1] = iv
+
+    -- extract '=' or 'in' (optional)
+    local fortype, post = expr:match('^(=)%s*()', pos)
+    if not fortype then fortype, post = expr:match('^(in)%s+()', pos) end
+    if fortype then
+      pos = post
+      -- extract input value range
+      local il; il, pos = lb.match_explist(expr, pos)
+      assert(#il > 0, 'syntax error: zero expressions')
+      assert(fortype ~= '=' or #il == 2 or #il == 3,
+             'syntax error: numeric for requires 2 or three expressions')
+      fortypes[#invarlists] = fortype
+      invallists[#invarlists] = il
+    else
+      fortypes[#invarlists] = false
+      invallists[#invarlists] = false
+    end
+  end
+  assert(#invarlists > 0, 'syntax error: missing "for" clause')
+
+  -- extract "if" clauses
+  local preds = {}
+  while 1 do
+    local post = expr:match('^%s*if%s+()', pos)
+    if not post then break end
+    pos = post
+    local pred; pred, pos = lb.match_expression(expr, pos)
+    assert(pred, 'syntax error: predicated expression not found')
+    preds[#preds+1] = pred
+  end
+
+  -- extract number of parameter variables (name matching "_%d+")
+  local stmp = ''; lb.gsub(expr, function(u, sin)  -- strip comments/strings
+    if u == 'e' then stmp = stmp .. ' ' .. sin .. ' ' end
+  end)
+  local max_param = 0; stmp:gsub('[%a_][%w_]*', function(s)
+    local s = s:match('^_(%d+)$')
+    if s then max_param = math_max(max_param, tonumber(s)) end
+  end)
+
+  if pos ~= pose then
+    assert(false, "syntax error: unrecognized " .. expr:sub(pos))
+  end
+
+  --DEBUG:
+  --print('----\n', string.format("%q", expr), string.format("%q", out), opname)
+  --for k,v in ipairs(invarlists) do print(k,v, invallists[k]) end
+  --for k,v in ipairs(preds) do print(k,v) end
+
+  return out, fortypes, invarlists, invallists, preds, opname, max_param
+end
+
+
+-- Create Lua code string representing comprehension.
+-- Arguments are in the form returned by parse_comprehension.
+local function code_comprehension(
+    out, fortypes, invarlists, invallists, preds, opname, max_param
+)
+  local op = assert(ops[opname])
+  local code = op.accum:gsub('%%s',  out)
+
+  for i=#preds,1,-1 do local pred = preds[i]
+    code = ' if ' .. pred .. ' then ' .. code .. ' end '
+  end
+  for i=#invarlists,1,-1 do
+    if not fortypes[i] then
+      local arrayname = '__in' .. i
+      local idx = '__idx' .. i
+      code =
+        ' for ' .. idx .. ' = 1, #' .. arrayname .. ' do ' ..
+        ' local ' .. invarlists[i][1] .. ' = ' .. arrayname .. '['..idx..'] ' ..
+        code .. ' end '
+    else
+      code =
+        ' for ' ..
+        table_concat(invarlists[i], ', ') ..
+        ' ' .. fortypes[i] .. ' ' ..
+        table_concat(invallists[i], ', ') ..
+        ' do ' .. code .. ' end '
+    end
+  end
+  code = ' local __result = ( ' .. op.init .. ' ) ' .. code
+  return code
+end
+
+
+-- Convert code string represented by code_comprehension
+-- into Lua function.  Also must pass ninputs = #invarlists,
+-- max_param, and invallists (from parse_comprehension).
+-- Uses environment env.
+local function wrap_comprehension(code, ninputs, max_param, invallists, env)
+  assert(ninputs > 0)
+  local ts = {}
+  for i=1,max_param do
+    ts[#ts+1] = '_' .. i
+  end
+  for i=1,ninputs do
+    if not invallists[i] then
+      local name = '__in' .. i
+      ts[#ts+1] = name
+    end
+  end
+  if #ts > 0 then
+    code = ' local ' .. table_concat(ts, ', ') .. ' = ... ' .. code
+  end
+  code = code .. ' return __result '
+  --print('DEBUG:', code)
+  local f, err = utils.load(code,'tmp','t',env)
+  if not f then assert(false, err .. ' with generated code ' .. code) end
+  return f
+end
+
+
+-- Build Lua function from comprehension string.
+-- Uses environment env.
+local function build_comprehension(expr, env)
+  local out, fortypes, invarlists, invallists, preds, opname, max_param
+    = parse_comprehension(expr)
+  local code = code_comprehension(
+    out, fortypes, invarlists, invallists, preds, opname, max_param)
+  local f = wrap_comprehension(code, #invarlists, max_param, invallists, env)
+  return f
+end
+
+
+-- Creates new comprehension cache.
+-- Any list comprehension function created are set to the environment
+-- env (defaults to caller of new).
+local function new(env)
+  -- Note: using a single global comprehension cache would have had
+  -- security implications (e.g. retrieving cached functions created
+  -- in other environments).
+  -- The cache lookup function could have instead been written to retrieve
+  -- the caller's environment, lookup up the cache private to that
+  -- environment, and then looked up the function in that cache.
+  -- That would avoid the need for this <new> call to
+  -- explicitly manage caches; however, that might also have an undue
+  -- performance penalty.
+
+  if not env then
+    env = utils.getfenv(2)
+  end
+
+  local mt = {}
+  local cache = setmetatable({}, mt)
+
+  -- Index operator builds, caches, and returns Lua function
+  -- corresponding to comprehension expression string.
+  --
+  -- Example: f = comprehension['x^2 for x']
+  --
+  function mt:__index(expr)
+    local f = build_comprehension(expr, env)
+    self[expr] = f  -- cache
+    return f
+  end
+
+  -- Convenience syntax.
+  -- Allows comprehension 'x^2 for x' instead of comprehension['x^2 for x'].
+  mt.__call = mt.__index
+
+  cache.new = new
+
+  return cache
+end
+
+
+local comprehension = {}
+comprehension.new = new
+
+return comprehension
+
+end,
+
+["pl.config"] = function()
+--------------------
+-- Module: 'pl.config'
+--------------------
+--- Reads configuration files into a Lua table.
+--  Understands INI files, classic Unix config files, and simple
+-- delimited columns of values. See @{06-data.md.Reading_Configuration_Files|the Guide}
+--
+--    # test.config
+--    # Read timeout in seconds
+--    read.timeout=10
+--    # Write timeout in seconds
+--    write.timeout=5
+--    #acceptable ports
+--    ports = 1002,1003,1004
+--
+--    -- readconfig.lua
+--    local config = require 'config'
+--    local t = config.read 'test.config'
+--    print(pretty.write(t))
+--
+--    ### output #####
+--    {
+--      ports = {
+--        1002,
+--        1003,
+--        1004
+--      },
+--      write_timeout = 5,
+--      read_timeout = 10
+--    }
+--
+-- @module pl.config
+
+local type,tonumber,ipairs,io, table = _G.type,_G.tonumber,_G.ipairs,_G.io,_G.table
+
+local function split(s,re)
+    local res = {}
+    local t_insert = table.insert
+    re = '[^'..re..']+'
+    for k in s:gmatch(re) do t_insert(res,k) end
+    return res
+end
+
+local function strip(s)
+    return s:gsub('^%s+',''):gsub('%s+$','')
+end
+
+local function strip_quotes (s)
+    return s:gsub("['\"](.*)['\"]",'%1')
+end
+
+local config = {}
+
+--- like io.lines(), but allows for lines to be continued with '\'.
+-- @param file a file-like object (anything where read() returns the next line) or a filename.
+-- Defaults to stardard input.
+-- @return an iterator over the lines, or nil
+-- @return error 'not a file-like object' or 'file is nil'
+function config.lines(file)
+    local f,openf,err
+    local line = ''
+    if type(file) == 'string' then
+        f,err = io.open(file,'r')
+        if not f then return nil,err end
+        openf = true
+    else
+        f = file or io.stdin
+        if not file.read then return nil, 'not a file-like object' end
+    end
+    if not f then return nil, 'file is nil' end
+    return function()
+        local l = f:read()
+        while l do
+            -- only for non-blank lines that don't begin with either ';' or '#'
+            if l:match '%S' and not l:match '^%s*[;#]' then
+                -- does the line end with '\'?
+                local i = l:find '\\%s*$'
+                if i then -- if so,
+                    line = line..l:sub(1,i-1)
+                elseif line == '' then
+                    return l
+                else
+                    l = line..l
+                    line = ''
+                    return l
+                end
+            end
+            l = f:read()
+        end
+        if openf then f:close() end
+    end
+end
+
+--- read a configuration file into a table
+-- @param file either a file-like object or a string, which must be a filename
+-- @tab[opt] cnfg a configuration table that may contain these fields:
+--
+--  * `smart`  try to deduce what kind of config file we have (default false)
+--  * `variabilize` make names into valid Lua identifiers (default true)
+--  * `convert_numbers` try to convert values into numbers (default true)
+--  * `trim_space` ensure that there is no starting or trailing whitespace with values (default true)
+--  * `trim_quotes` remove quotes from strings (default false)
+--  * `list_delim` delimiter to use when separating columns (default ',')
+--  * `keysep` separator between key and value pairs (default '=')
+--
+-- @return a table containing items, or `nil`
+-- @return error message (same as @{config.lines}
+function config.read(file,cnfg)
+    local auto
+
+    local iter,err = config.lines(file)
+    if not iter then return nil,err end
+    local line = iter()
+    cnfg = cnfg or {}
+    if cnfg.smart then
+        auto = true
+        if line:match '^[^=]+=' then
+            cnfg.keysep = '='
+        elseif line:match '^[^:]+:' then
+            cnfg.keysep = ':'
+            cnfg.list_delim = ':'
+        elseif line:match '^%S+%s+' then
+            cnfg.keysep = ' '
+            -- more than two columns assume that it's a space-delimited list
+            -- cf /etc/fstab with /etc/ssh/ssh_config
+            if line:match '^%S+%s+%S+%s+%S+' then
+                cnfg.list_delim = ' '
+            end
+            cnfg.variabilize = false
+        end
+    end
+
+
+    local function check_cnfg (var,def)
+        local val = cnfg[var]
+        if val == nil then return def else return val end
+    end
+
+    local initial_digits = '^[%d%+%-]'
+    local t = {}
+    local top_t = t
+    local variabilize = check_cnfg ('variabilize',true)
+    local list_delim = check_cnfg('list_delim',',')
+    local convert_numbers = check_cnfg('convert_numbers',true)
+    local convert_boolean = check_cnfg('convert_boolean',false)
+    local trim_space = check_cnfg('trim_space',true)
+    local trim_quotes = check_cnfg('trim_quotes',false)
+    local ignore_assign = check_cnfg('ignore_assign',false)
+    local keysep = check_cnfg('keysep','=')
+    local keypat = keysep == ' ' and '%s+' or '%s*'..keysep..'%s*'
+    if list_delim == ' ' then list_delim = '%s+' end
+
+    local function process_name(key)
+        if variabilize then
+            key = key:gsub('[^%w]','_')
+        end
+        return key
+    end
+
+    local function process_value(value)
+        if list_delim and value:find(list_delim) then
+            value = split(value,list_delim)
+            for i,v in ipairs(value) do
+                value[i] = process_value(v)
+            end
+        elseif convert_numbers and value:find(initial_digits) then
+            local val = tonumber(value)
+            if not val and value:match ' kB$' then
+                value = value:gsub(' kB','')
+                val = tonumber(value)
+            end
+            if val then value = val end
+        elseif convert_boolean and value == 'true' then
+           return true
+        elseif convert_boolean and value == 'false' then
+           return false
+        end
+        if type(value) == 'string' then
+           if trim_space then value = strip(value) end
+           if not trim_quotes and auto and value:match '^"' then
+                trim_quotes = true
+            end
+           if trim_quotes then value = strip_quotes(value) end
+        end
+        return value
+    end
+
+    while line do
+        if line:find('^%[') then -- section!
+            local section = process_name(line:match('%[([^%]]+)%]'))
+            t = top_t
+            t[section] = {}
+            t = t[section]
+        else
+            line = line:gsub('^%s*','')
+            local i1,i2 = line:find(keypat)
+            if i1 and not ignore_assign then -- key,value assignment
+                local key = process_name(line:sub(1,i1-1))
+                local value = process_value(line:sub(i2+1))
+                t[key] = value
+            else -- a plain list of values...
+                t[#t+1] = process_value(line)
+            end
+        end
+        line = iter()
+    end
+    return top_t
+end
+
+return config
+
+end,
+
+["pl.data"] = function()
+--------------------
+-- Module: 'pl.data'
+--------------------
+--- Reading and querying simple tabular data.
+--
+--    data.read 'test.txt'
+--    ==> {{10,20},{2,5},{40,50},fieldnames={'x','y'},delim=','}
+--
+-- Provides a way of creating basic SQL-like queries.
+--
+--    require 'pl'
+--    local d = data.read('xyz.txt')
+--    local q = d:select('x,y,z where x > 3 and z < 2 sort by y')
+--    for x,y,z in q do
+--        print(x,y,z)
+--    end
+--
+-- See @{06-data.md.Reading_Columnar_Data|the Guide}
+--
+-- Dependencies: `pl.utils`, `pl.array2d` (fallback methods)
+-- @module pl.data
+
+local utils = require 'pl.utils'
+local _DEBUG = rawget(_G,'_DEBUG')
+
+local patterns,function_arg,usplit,array_tostring = utils.patterns,utils.function_arg,utils.split,utils.array_tostring
+local append,concat = table.insert,table.concat
+local gsub = string.gsub
+local io = io
+local _G,print,type,tonumber,ipairs,setmetatable = _G,print,type,tonumber,ipairs,setmetatable
+
+
+local data = {}
+
+local parse_select
+
+local function rstrip(s)
+    return (s:gsub('%s+$',''))
+end
+
+local function strip (s)
+    return (rstrip(s):gsub('^%s*',''))
+end
+
+-- This gives `l` the standard List metatable,
+-- pulling in the List module.
+local function makelist(l)
+    return setmetatable(l, require('pl.List'))
+end
+
+local function map(fun,t)
+    local res = {}
+    for i = 1,#t do
+        res[i] = fun(t[i])
+    end
+    return res
+end
+
+local function split(line,delim,csv,n)
+    local massage
+    -- CSV fields may be double-quoted and may contain commas!
+    if csv and line:match '"' then
+        line = line:gsub('"([^"]+)"',function(str)
+            local s,cnt = str:gsub(',','\001')
+            if cnt > 0 then massage = true end
+            return s
+        end)
+        if massage then
+            massage = function(s) return (s:gsub('\001',',')) end
+        end
+    end
+    local res = (usplit(line,delim,false,n))
+    if csv then
+        -- restore CSV commas-in-fields
+        if massage then res = map(massage,res) end
+        -- in CSV mode trailiing commas are significant!
+        if line:match ',$' then append(res,'') end
+    end
+    return makelist(res)
+end
+
+local function find(t,v)
+    for i = 1,#t do
+        if v == t[i] then return i end
+    end
+end
+
+local DataMT = {
+    column_by_name = function(self,name)
+        if type(name) == 'number' then
+            name = '$'..name
+        end
+        local arr = {}
+        for res in data.query(self,name) do
+            append(arr,res)
+        end
+        return makelist(arr)
+    end,
+
+    copy_select = function(self,condn)
+        condn = parse_select(condn,self)
+        local iter = data.query(self,condn)
+        local res = {}
+        local row = makelist{iter()}
+        while #row > 0 do
+            append(res,row)
+            row = makelist{iter()}
+        end
+        res.delim = self.delim
+        return data.new(res,split(condn.fields,','))
+    end,
+
+    column_names = function(self)
+        return self.fieldnames
+    end,
+}
+
+local array2d
+
+DataMT.__index = function(self,name)
+    local f = DataMT[name]
+    if f then return f end
+    if not array2d then
+        array2d = require 'pl.array2d'
+    end
+    return array2d[name]
+end
+
+--- return a particular column as a list of values (method).
+-- @param name either name of column, or numerical index.
+-- @function Data.column_by_name
+
+--- return a query iterator on this data (method).
+-- @string condn the query expression
+-- @function Data.select
+-- @see data.query
+
+--- return a row iterator on this data (method).
+-- @string condn the query expression
+-- @function Data.select_row
+
+--- return a new data object based on this query (method).
+-- @string condn the query expression
+-- @function Data.copy_select
+
+--- return the field names of this data object (method).
+-- @function Data.column_names
+
+--- write out a row (method).
+-- @param f file-like object
+-- @function Data.write_row
+
+--- write data out to file (method).
+-- @param f file-like object
+-- @function Data.write
+
+
+-- [guessing delimiter] We check for comma, tab and spaces in that order.
+-- [issue] any other delimiters to be checked?
+local delims = {',', '\t', ' ', ';'}
+
+local function guess_delim (line)
+    if line=='' then return ' ' end
+    for _,delim in ipairs(delims) do
+        if line:find(delim) then
+            return delim == ' ' and '%s+' or delim
+        end
+    end
+    return ' '
+end
+
+-- [file parameter] If it's a string, we try open as a filename. If nil, then
+-- either stdin or stdout depending on the mode. Otherwise, check if this is
+-- a file-like object (implements read or write depending)
+local function open_file (f,mode)
+    local opened, err
+    local reading = mode == 'r'
+    if type(f) == 'string' then
+        if f == 'stdin'  then
+            f = io.stdin
+        elseif f == 'stdout'  then
+            f = io.stdout
+        else
+            f,err = io.open(f,mode)
+            if not f then return nil,err end
+            opened = true
+        end
+    end
+    if f and ((reading and not f.read) or (not reading and not f.write)) then
+        return nil, "not a file-like object"
+    end
+    return f,nil,opened
+end
+
+--- read a delimited file in a Lua table.
+-- By default, attempts to treat first line as separated list of fieldnames.
+-- @param file a filename or a file-like object
+-- @tab cnfg parsing options
+-- @string cnfg.delim a string pattern to split fields
+-- @array cnfg.fieldnames (i.e. don't read from first line)
+-- @bool cnfg.no_convert (default is to try conversion on first data line)
+-- @tab cnfg.convert table of custom conversion functions with column keys
+-- @int cnfg.numfields indices of columns known to be numbers
+-- @bool cnfg.last_field_collect only split as many fields as fieldnames.
+-- @int cnfg.thousands_dot thousands separator in Excel CSV is '.'
+-- @bool cnfg.csv fields may be double-quoted and contain commas;
+-- Also, empty fields are considered to be equivalent to zero.
+-- @return `data` object, or `nil`
+-- @return error message. May be a file error, 'not a file-like object'
+-- or a conversion error
+function data.read(file,cnfg)
+    local count,line
+    local D = {}
+    if not cnfg then cnfg = {} end
+    local f,err,opened = open_file(file,'r')
+    if not f then return nil, err end
+    local thousands_dot = cnfg.thousands_dot
+    local csv = cnfg.csv
+    if csv then cnfg.delim = ',' end
+
+    -- note that using dot as the thousands separator (@thousands_dot)
+    -- requires a special conversion function! For CSV, _empty fields_ are
+    -- considered to default to numerial zeroes.
+    local tonumber = tonumber
+    local function try_number(x)
+        if thousands_dot then x = x:gsub('%.(...)','%1') end
+        if csv and x == '' then x = '0' end
+        local v = tonumber(x)
+        if v == nil then return nil,"not a number" end
+        return v
+    end
+
+    count = 1
+    line = f:read()
+    if not line then return nil, "empty file" end
+
+    -- first question: what is the delimiter?
+    D.delim = cnfg.delim and cnfg.delim or guess_delim(line)
+    local delim = D.delim
+
+    local conversion
+    local numfields = {}
+    local function append_conversion (idx,conv)
+        conversion = conversion or {}
+        append(numfields,idx)
+        append(conversion,conv)
+    end
+    if cnfg.numfields then
+        for _,n in ipairs(cnfg.numfields) do append_conversion(n,try_number) end
+    end
+
+    -- some space-delimited data starts with a space.  This should not be a column,
+    -- although it certainly would be for comma-separated, etc.
+    local stripper
+    if delim == '%s+' and line:find(delim) == 1 then
+        stripper = function(s)  return s:gsub('^%s+','') end
+        line = stripper(line)
+    end
+    -- first line will usually be field names. Unless fieldnames are specified,
+    -- we check if it contains purely numerical values for the case of reading
+    -- plain data files.
+    if not cnfg.fieldnames then
+        local fields,nums
+        fields = split(line,delim,csv)
+        if not cnfg.convert then
+            nums = map(tonumber,fields)
+            if #nums == #fields then -- they're ALL numbers!
+                append(D,nums) -- add the first converted row
+                -- and specify conversions for subsequent rows
+                for i = 1,#nums do append_conversion(i,try_number) end
+            else -- we'll try to check numbers just now..
+                nums = nil
+            end
+        else -- [explicit column conversions] (any deduced number conversions will be added)
+            for idx,conv in pairs(cnfg.convert) do append_conversion(idx,conv) end
+        end
+        if nums == nil then
+            cnfg.fieldnames = fields
+        end
+        line = f:read()
+        count = count + 1
+        if stripper then line = stripper(line) end
+    elseif type(cnfg.fieldnames) == 'string' then
+        cnfg.fieldnames = split(cnfg.fieldnames,delim,csv)
+    end
+    local nfields
+    -- at this point, the column headers have been read in. If the first
+    -- row consisted of numbers, it has already been added to the dataset.
+    if cnfg.fieldnames then
+        D.fieldnames = cnfg.fieldnames
+        -- [collecting end field] If @last_field_collect then we'll
+        -- only split as many fields as there are fieldnames
+        if cnfg.last_field_collect then
+            nfields = #D.fieldnames
+        end
+        -- [implicit column conversion] unless @no_convert, we need the numerical field indices
+        -- of the first data row. These can also be specified explicitly by @numfields.
+        if not cnfg.no_convert then
+            local fields = split(line,D.delim,csv,nfields)
+            for i = 1,#fields do
+                if not find(numfields,i) and try_number(fields[i]) then
+                    append_conversion(i,try_number)
+                end
+            end
+        end
+    end
+    -- keep going until finished
+    while line do
+        if not line:find ('^%s*$') then -- [blank lines] ignore them!
+            if stripper then line = stripper(line) end
+            local fields = split(line,delim,csv,nfields)
+            if conversion then -- there were field conversions...
+                for k = 1,#numfields do
+                    local i,conv = numfields[k],conversion[k]
+                    local val,err = conv(fields[i])
+                    if val == nil then
+                        return nil, err..": "..fields[i].." at line "..count
+                    else
+                        fields[i] = val
+                    end
+                end
+            end
+            append(D,fields)
+        end
+        line = f:read()
+        count = count + 1
+    end
+    if opened then f:close() end
+    if delim == '%s+' then D.delim = ' ' end
+    if not D.fieldnames then D.fieldnames = {} end
+    return data.new(D)
+end
+
+local function write_row (data,f,row,delim)
+    data.temp = array_tostring(row,data.temp)
+    f:write(concat(data.temp,delim),'\n')
+end
+
+function DataMT:write_row(f,row)
+    write_row(self,f,row,self.delim)
+end
+
+--- write 2D data to a file.
+-- Does not assume that the data has actually been
+-- generated with `new` or `read`.
+-- @param data 2D array
+-- @param file filename or file-like object
+-- @tparam[opt] {string} fieldnames list of fields (optional)
+-- @string[opt='\t'] delim delimiter (default tab)
+-- @return true or nil, error
+function data.write (data,file,fieldnames,delim)
+    local f,err,opened = open_file(file,'w')
+    if not f then return nil, err end
+    if not fieldnames then
+        fieldnames = data.fieldnames
+    end
+    delim = delim or '\t'
+    if fieldnames and #fieldnames > 0 then
+        f:write(concat(fieldnames,delim),'\n')
+    end
+    for i = 1,#data do
+        write_row(data,f,data[i],delim)
+    end
+    if opened then f:close() end
+    return true
+end
+
+
+function DataMT:write(file)
+    data.write(self,file,self.fieldnames,self.delim)
+end
+
+local function massage_fieldnames (fields,copy)
+    -- fieldnames must be valid Lua identifiers; ignore any surrounding padding
+    -- but keep the original fieldnames...
+    for i = 1,#fields do
+        local f = strip(fields[i])
+        copy[i] = f
+        fields[i] = f:gsub('%W','_')
+    end
+end
+
+--- create a new dataset from a table of rows.
+-- Can specify the fieldnames, else the table must have a field called
+-- 'fieldnames', which is either a string of delimiter-separated names,
+-- or a table of names. <br>
+-- If the table does not have a field called 'delim', then an attempt will be
+-- made to guess it from the fieldnames string, defaults otherwise to tab.
+-- @param d the table.
+-- @tparam[opt] {string} fieldnames optional fieldnames
+-- @return the table.
+function data.new (d,fieldnames)
+    d.fieldnames = d.fieldnames or fieldnames or ''
+    if not d.delim and type(d.fieldnames) == 'string' then
+        d.delim = guess_delim(d.fieldnames)
+        d.fieldnames = split(d.fieldnames,d.delim)
+    end
+    d.fieldnames = makelist(d.fieldnames)
+    d.original_fieldnames = {}
+    massage_fieldnames(d.fieldnames,d.original_fieldnames)
+    setmetatable(d,DataMT)
+    -- a query with just the fieldname will return a sequence
+    -- of values, which seq.copy turns into a table.
+    return d
+end
+
+local sorted_query = [[
+return function (t)
+    local i = 0
+    local v
+    local ls = {}
+    for i,v in ipairs(t) do
+        if CONDITION then
+            ls[#ls+1] = v
+        end
+    end
+    table.sort(ls,function(v1,v2)
+        return SORT_EXPR
+    end)
+    local n = #ls
+    return function()
+        i = i + 1
+        v = ls[i]
+        if i > n then return end
+        return FIELDLIST
+    end
+end
+]]
+
+-- question: is this optimized case actually worth the extra code?
+local simple_query = [[
+return function (t)
+    local n = #t
+    local i = 0
+    local v
+    return function()
+        repeat
+            i = i + 1
+            v = t[i]
+        until i > n or CONDITION
+        if i > n then return end
+        return FIELDLIST
+    end
+end
+]]
+
+local function is_string (s)
+    return type(s) == 'string'
+end
+
+local field_error
+
+local function fieldnames_as_string (data)
+    return concat(data.fieldnames,',')
+end
+
+local function massage_fields(data,f)
+    local idx
+    if f:find '^%d+$' then
+        idx = tonumber(f)
+    else
+        idx = find(data.fieldnames,f)
+    end
+    if idx then
+        return 'v['..idx..']'
+    else
+        field_error = f..' not found in '..fieldnames_as_string(data)
+        return f
+    end
+end
+
+
+local function process_select (data,parms)
+    --- preparing fields ----
+    field_error = nil
+    local fields = parms.fields
+    local numfields = fields:find '%$'  or #data.fieldnames == 0
+    if fields:find '^%s*%*%s*' then
+        if not numfields then
+            fields = fieldnames_as_string(data)
+        else
+            local ncol = #data[1]
+            fields = {}
+            for i = 1,ncol do append(fields,'$'..i) end
+            fields = concat(fields,',')
+        end
+    end
+    local idpat = patterns.IDEN
+    if numfields then
+        idpat = '%$(%d+)'
+    else
+        -- massage field names to replace non-identifier chars
+        fields = rstrip(fields):gsub('[^,%w]','_')
+    end
+    local massage_fields = utils.bind1(massage_fields,data)
+    local ret = gsub(fields,idpat,massage_fields)
+    if field_error then return nil,field_error end
+    parms.fields = fields
+    parms.proc_fields = ret
+    parms.where = parms.where or  'true'
+    if is_string(parms.where) then
+        parms.where = gsub(parms.where,idpat,massage_fields)
+        field_error = nil
+    end
+    return true
+end
+
+
+parse_select = function(s,data)
+    local endp
+    local parms = {}
+    local w1,w2 = s:find('where ')
+    local s1,s2 = s:find('sort by ')
+    if w1 then -- where clause!
+        endp = (s1 or 0)-1
+        parms.where = s:sub(w2+1,endp)
+    end
+    if s1 then -- sort by clause (must be last!)
+        parms.sort_by = s:sub(s2+1)
+    end
+    endp = (w1 or s1 or 0)-1
+    parms.fields = s:sub(1,endp)
+    local status,err = process_select(data,parms)
+    if not status then return nil,err
+    else return parms end
+end
+
+--- create a query iterator from a select string.
+-- Select string has this format: <br>
+-- FIELDLIST [ where LUA-CONDN [ sort by FIELD] ]<br>
+-- FIELDLIST is a comma-separated list of valid fields, or '*'. <br> <br>
+-- The condition can also be a table, with fields 'fields' (comma-sep string or
+-- table), 'sort_by' (string) and 'where' (Lua expression string or function)
+-- @param data table produced by read
+-- @param condn select string or table
+-- @param context a list of tables to be searched when resolving functions
+-- @param return_row if true, wrap the results in a row table
+-- @return an iterator over the specified fields, or nil
+-- @return an error message
+function data.query(data,condn,context,return_row)
+    local err
+    if is_string(condn) then
+        condn,err = parse_select(condn,data)
+        if not condn then return nil,err end
+    elseif type(condn) == 'table' then
+        if type(condn.fields) == 'table' then
+            condn.fields = concat(condn.fields,',')
+        end
+        if not condn.proc_fields then
+            local status,err = process_select(data,condn)
+            if not status then return nil,err end
+        end
+    else
+        return nil, "condition must be a string or a table"
+    end
+    local query
+    if condn.sort_by then -- use sorted_query
+        query = sorted_query
+    else
+        query = simple_query
+    end
+    local fields = condn.proc_fields or condn.fields
+    if return_row then
+        fields = '{'..fields..'}'
+    end
+    query = query:gsub('FIELDLIST',fields)
+    if is_string(condn.where) then
+        query = query:gsub('CONDITION',condn.where)
+        condn.where = nil
+    else
+       query = query:gsub('CONDITION','_condn(v)')
+       condn.where = function_arg(0,condn.where,'condition.where must be callable')
+    end
+    if condn.sort_by then
+        local expr,sort_var,sort_dir
+        local sort_by = condn.sort_by
+        local i1,i2 = sort_by:find('%s+')
+        if i1 then
+            sort_var,sort_dir = sort_by:sub(1,i1-1),sort_by:sub(i2+1)
+        else
+            sort_var = sort_by
+            sort_dir = 'asc'
+        end
+        if sort_var:match '^%$' then sort_var = sort_var:sub(2) end
+        sort_var = massage_fields(data,sort_var)
+        if field_error then return nil,field_error end
+        if sort_dir == 'asc' then
+            sort_dir = '<'
+        else
+            sort_dir = '>'
+        end
+        expr = ('%s %s %s'):format(sort_var:gsub('v','v1'),sort_dir,sort_var:gsub('v','v2'))
+        query = query:gsub('SORT_EXPR',expr)
+    end
+    if condn.where then
+        query = 'return function(_condn) '..query..' end'
+    end
+    if _DEBUG then print(query) end
+
+    local fn,err = utils.load(query,'tmp')
+    if not fn then return nil,err end
+    fn = fn() -- get the function
+    if condn.where then
+        fn = fn(condn.where)
+    end
+    local qfun = fn(data)
+    if context then
+        -- [specifying context for condition] @context is a list of tables which are
+        -- 'injected'into the condition's custom context
+        append(context,_G)
+        local lookup = {}
+        utils.setfenv(qfun,lookup)
+        setmetatable(lookup,{
+            __index = function(tbl,key)
+               -- _G.print(tbl,key)
+                for k,t in ipairs(context) do
+                    if t[key] then return t[key] end
+                end
+            end
+        })
+    end
+    return qfun
+end
+
+
+DataMT.select = data.query
+DataMT.select_row = function(d,condn,context)
+    return data.query(d,condn,context,true)
+end
+
+--- Filter input using a query.
+-- @string Q a query string
+-- @param infile filename or file-like object
+-- @param outfile filename or file-like object
+-- @bool dont_fail true if you want to return an error, not just fail
+function data.filter (Q,infile,outfile,dont_fail)
+    local d = data.read(infile or 'stdin')
+    local out = open_file(outfile or 'stdout')
+    local iter,err = d:select(Q)
+    local delim = d.delim
+    if not iter then
+        err = 'error: '..err
+        if dont_fail then
+            return nil,err
+        else
+            utils.quit(1,err)
+        end
+    end
+    while true do
+        local res = {iter()}
+        if #res == 0 then break end
+        out:write(concat(res,delim),'\n')
+    end
+end
+
+return data
+
+
+end,
+
+["pl.Date"] = function()
+--------------------
+-- Module: 'pl.Date'
+--------------------
+--- Date and Date Format classes.
+-- See  @{05-dates.md|the Guide}.
+--
+-- NOTE: the date module is deprecated! see
+-- https://github.com/lunarmodules/Penlight/issues/285
+--
+-- Dependencies: `pl.class`, `pl.stringx`, `pl.utils`
+-- @classmod pl.Date
+-- @pragma nostrip
+
+local class = require 'pl.class'
+local os_time, os_date = os.time, os.date
+local stringx = require 'pl.stringx'
+local utils = require 'pl.utils'
+local assert_arg,assert_string = utils.assert_arg,utils.assert_string
+
+
+utils.raise_deprecation {
+  source = "Penlight " .. utils._VERSION,
+  message = "the 'Date' module is deprecated, see https://github.com/lunarmodules/Penlight/issues/285",
+  version_removed = "2.0.0",
+  version_deprecated = "1.9.2",
+}
+
+
+local Date = class()
+Date.Format = class()
+
+--- Date constructor.
+-- @param t this can be either
+--
+--   * `nil` or empty - use current date and time
+--   * number - seconds since epoch (as returned by `os.time`). Resulting time is UTC
+--   * `Date` - make a copy of this date
+--   * table - table containing year, month, etc as for `os.time`. You may leave out year, month or day,
+-- in which case current values will be used.
+--   * year (will be followed by month, day etc)
+--
+-- @param ...  true if  Universal Coordinated Time, or two to five numbers: month,day,hour,min,sec
+-- @function Date
+function Date:_init(t,...)
+    local time
+    local nargs = select('#',...)
+    if nargs > 2 then
+        local extra = {...}
+        local year = t
+        t = {
+            year = year,
+            month = extra[1],
+            day = extra[2],
+            hour = extra[3],
+            min = extra[4],
+            sec = extra[5]
+        }
+    end
+    if nargs == 1 then
+        self.utc = select(1,...) == true
+    end
+    if t == nil or t == 'utc' then
+        time = os_time()
+        self.utc = t == 'utc'
+    elseif type(t) == 'number' then
+        time = t
+        if self.utc == nil then self.utc = true end
+    elseif type(t) == 'table' then
+        if getmetatable(t) == Date then -- copy ctor
+            time = t.time
+            self.utc = t.utc
+        else
+            if not (t.year and t.month) then
+                local lt = os_date('*t')
+                if not t.year and not t.month and not t.day then
+                    t.year = lt.year
+                    t.month = lt.month
+                    t.day = lt.day
+                else
+                    t.year = t.year or lt.year
+                    t.month = t.month or (t.day and lt.month or 1)
+                    t.day = t.day or 1
+                end
+            end
+            t.day = t.day or 1
+            time = os_time(t)
+        end
+    else
+        error("bad type for Date constructor: "..type(t),2)
+    end
+    self:set(time)
+end
+
+--- set the current time of this Date object.
+-- @int t seconds since epoch
+function Date:set(t)
+    self.time = t
+    if self.utc then
+        self.tab = os_date('!*t',t)
+    else
+        self.tab = os_date('*t',t)
+    end
+end
+
+--- get the time zone offset from UTC.
+-- @int ts seconds ahead of UTC
+function Date.tzone (ts)
+    if ts == nil then
+        ts = os_time()
+    elseif type(ts) == "table" then
+        if getmetatable(ts) == Date then
+            ts = ts.time
+        else
+            ts = Date(ts).time
+        end
+    end
+    local utc = os_date('!*t',ts)
+    local lcl = os_date('*t',ts)
+    lcl.isdst = false
+    return os.difftime(os_time(lcl), os_time(utc))
+end
+
+--- convert this date to UTC.
+function Date:toUTC ()
+    local ndate = Date(self)
+    if not self.utc then
+        ndate.utc = true
+        ndate:set(ndate.time)
+    end
+    return ndate
+end
+
+--- convert this UTC date to local.
+function Date:toLocal ()
+    local ndate = Date(self)
+    if self.utc then
+        ndate.utc = false
+        ndate:set(ndate.time)
+--~         ndate:add { sec = Date.tzone(self) }
+    end
+    return ndate
+end
+
+--- set the year.
+-- @int y Four-digit year
+-- @class function
+-- @name Date:year
+
+--- set the month.
+-- @int m month
+-- @class function
+-- @name Date:month
+
+--- set the day.
+-- @int d day
+-- @class function
+-- @name Date:day
+
+--- set the hour.
+-- @int h hour
+-- @class function
+-- @name Date:hour
+
+--- set the minutes.
+-- @int min minutes
+-- @class function
+-- @name Date:min
+
+--- set the seconds.
+-- @int sec seconds
+-- @class function
+-- @name Date:sec
+
+--- set the day of year.
+-- @class function
+-- @int yday day of year
+-- @name Date:yday
+
+--- get the year.
+-- @int y Four-digit year
+-- @class function
+-- @name Date:year
+
+--- get the month.
+-- @class function
+-- @name Date:month
+
+--- get the day.
+-- @class function
+-- @name Date:day
+
+--- get the hour.
+-- @class function
+-- @name Date:hour
+
+--- get the minutes.
+-- @class function
+-- @name Date:min
+
+--- get the seconds.
+-- @class function
+-- @name Date:sec
+
+--- get the day of year.
+-- @class function
+-- @name Date:yday
+
+
+for _,c in ipairs{'year','month','day','hour','min','sec','yday'} do
+    Date[c] = function(self,val)
+        if val then
+            assert_arg(1,val,"number")
+            self.tab[c] = val
+            self:set(os_time(self.tab))
+            return self
+        else
+            return self.tab[c]
+        end
+    end
+end
+
+--- name of day of week.
+-- @bool full abbreviated if true, full otherwise.
+-- @ret string name
+function Date:weekday_name(full)
+    return os_date(full and '%A' or '%a',self.time)
+end
+
+--- name of month.
+-- @int full abbreviated if true, full otherwise.
+-- @ret string name
+function Date:month_name(full)
+    return os_date(full and '%B' or '%b',self.time)
+end
+
+--- is this day on a weekend?.
+function Date:is_weekend()
+    return self.tab.wday == 1 or self.tab.wday == 7
+end
+
+--- add to a date object.
+-- @param t a table containing one of the following keys and a value:
+-- one of `year`,`month`,`day`,`hour`,`min`,`sec`
+-- @return this date
+function Date:add(t)
+    local old_dst = self.tab.isdst
+    local key,val = next(t)
+    self.tab[key] = self.tab[key] + val
+    self:set(os_time(self.tab))
+    if old_dst ~= self.tab.isdst then
+        self.tab.hour = self.tab.hour - (old_dst and 1 or -1)
+        self:set(os_time(self.tab))
+    end
+    return self
+end
+
+--- last day of the month.
+-- @return int day
+function Date:last_day()
+    local d = 28
+    local m = self.tab.month
+    while self.tab.month == m do
+        d = d + 1
+        self:add{day=1}
+    end
+    self:add{day=-1}
+    return self
+end
+
+--- difference between two Date objects.
+-- @tparam Date other Date object
+-- @treturn Date.Interval object
+function Date:diff(other)
+    local dt = self.time - other.time
+    if dt < 0 then error("date difference is negative!",2) end
+    return Date.Interval(dt)
+end
+
+--- long numerical ISO data format version of this date.
+function Date:__tostring()
+    local fmt = '%Y-%m-%dT%H:%M:%S'
+    if self.utc then
+        fmt = "!"..fmt
+    end
+    local t = os_date(fmt,self.time)
+    if self.utc then
+        return  t .. 'Z'
+    else
+        local offs = self:tzone()
+        if offs == 0 then
+            return t .. 'Z'
+        end
+        local sign = offs > 0 and '+' or '-'
+        local h = math.ceil(offs/3600)
+        local m = (offs % 3600)/60
+        if m == 0 then
+            return t .. ('%s%02d'):format(sign,h)
+        else
+            return t .. ('%s%02d:%02d'):format(sign,h,m)
+        end
+    end
+end
+
+--- equality between Date objects.
+function Date:__eq(other)
+    return self.time == other.time
+end
+
+--- ordering between Date objects.
+function Date:__lt(other)
+    return self.time < other.time
+end
+
+--- difference between Date objects.
+-- @function Date:__sub
+Date.__sub = Date.diff
+
+--- add a date and an interval.
+-- @param other either a `Date.Interval` object or a table such as
+-- passed to `Date:add`
+function Date:__add(other)
+    local nd = Date(self)
+    if Date.Interval:class_of(other) then
+        other = {sec=other.time}
+    end
+    nd:add(other)
+    return nd
+end
+
+Date.Interval = class(Date)
+
+---- Date.Interval constructor
+-- @int t an interval in seconds
+-- @function Date.Interval
+function Date.Interval:_init(t)
+    self:set(t)
+end
+
+function Date.Interval:set(t)
+    self.time = t
+    self.tab = os_date('!*t',self.time)
+end
+
+local function ess(n)
+    if n > 1 then return 's '
+    else return ' '
+    end
+end
+
+--- If it's an interval then the format is '2 hours 29 sec' etc.
+function Date.Interval:__tostring()
+    local t, res = self.tab, ''
+    local y,m,d = t.year - 1970, t.month - 1, t.day - 1
+    if y > 0 then res = res .. y .. ' year'..ess(y) end
+    if m > 0 then res = res .. m .. ' month'..ess(m) end
+    if d > 0 then res = res .. d .. ' day'..ess(d) end
+    if y == 0 and m == 0 then
+        local h = t.hour
+        if h > 0 then res = res .. h .. ' hour'..ess(h) end
+        if t.min > 0 then res = res .. t.min .. ' min ' end
+        if t.sec > 0 then res = res .. t.sec .. ' sec ' end
+    end
+    if res == '' then res = 'zero' end
+    return res
+end
+
+------------ Date.Format class: parsing and renderinig dates ------------
+
+-- short field names, explicit os.date names, and a mask for allowed field repeats
+local formats = {
+    d = {'day',{true,true}},
+    y = {'year',{false,true,false,true}},
+    m = {'month',{true,true}},
+    H = {'hour',{true,true}},
+    M = {'min',{true,true}},
+    S = {'sec',{true,true}},
+}
+
+--- Date.Format constructor.
+-- @string fmt. A string where the following fields are significant:
+--
+--   * d day (either d or dd)
+--   * y year (either yy or yyy)
+--   * m month (either m or mm)
+--   * H hour (either H or HH)
+--   * M minute (either M or MM)
+--   * S second (either S or SS)
+--
+-- Alternatively, if fmt is nil then this returns a flexible date parser
+-- that tries various date/time schemes in turn:
+--
+--  * [ISO 8601](http://en.wikipedia.org/wiki/ISO_8601), like `2010-05-10 12:35:23Z` or `2008-10-03T14:30+02`
+--  * times like 15:30 or 8.05pm  (assumed to be today's date)
+--  * dates like 28/10/02 (European order!) or 5 Feb 2012
+--  * month name like march or Mar (case-insensitive, first 3 letters); here the
+-- day will be 1 and the year this current year
+--
+-- A date in format 3 can be optionally followed by a time in format 2.
+-- Please see test-date.lua in the tests folder for more examples.
+-- @usage df = Date.Format("yyyy-mm-dd HH:MM:SS")
+-- @class function
+-- @name Date.Format
+function Date.Format:_init(fmt)
+    if not fmt then
+        self.fmt = '%Y-%m-%d %H:%M:%S'
+        self.outf = self.fmt
+        self.plain = true
+        return
+    end
+    local append = table.insert
+    local D,PLUS,OPENP,CLOSEP = '\001','\002','\003','\004'
+    local vars,used = {},{}
+    local patt,outf = {},{}
+    local i = 1
+    while i < #fmt do
+        local ch = fmt:sub(i,i)
+        local df = formats[ch]
+        if df then
+            if used[ch] then error("field appeared twice: "..ch,4) end
+            used[ch] = true
+            -- this field may be repeated
+            local _,inext = fmt:find(ch..'+',i+1)
+            local cnt = not _ and 1 or inext-i+1
+            if not df[2][cnt] then error("wrong number of fields: "..ch,4) end
+            -- single chars mean 'accept more than one digit'
+            local p = cnt==1 and (D..PLUS) or (D):rep(cnt)
+            append(patt,OPENP..p..CLOSEP)
+            append(vars,ch)
+            if ch == 'y' then
+                append(outf,cnt==2 and '%y' or '%Y')
+            else
+                append(outf,'%'..ch)
+            end
+            i = i + cnt
+        else
+            append(patt,ch)
+            append(outf,ch)
+            i = i + 1
+        end
+    end
+    -- escape any magic characters
+    fmt = utils.escape(table.concat(patt))
+   -- fmt = table.concat(patt):gsub('[%-%.%+%[%]%(%)%$%^%%%?%*]','%%%1')
+    -- replace markers with their magic equivalents
+    fmt = fmt:gsub(D,'%%d'):gsub(PLUS,'+'):gsub(OPENP,'('):gsub(CLOSEP,')')
+    self.fmt = fmt
+    self.outf = table.concat(outf)
+    self.vars = vars
+end
+
+local parse_date
+
+--- parse a string into a Date object.
+-- @string str a date string
+-- @return date object
+function Date.Format:parse(str)
+    assert_string(1,str)
+    if self.plain then
+        return parse_date(str,self.us)
+    end
+    local res = {str:match(self.fmt)}
+    if #res==0 then return nil, 'cannot parse '..str end
+    local tab = {}
+    for i,v in ipairs(self.vars) do
+        local name = formats[v][1] -- e.g. 'y' becomes 'year'
+        tab[name] = tonumber(res[i])
+    end
+    -- os.date() requires these fields; if not present, we assume
+    -- that the time set is for the current day.
+    if not (tab.year and tab.month and tab.day) then
+        local today = Date()
+        tab.year = tab.year or today:year()
+        tab.month = tab.month or today:month()
+        tab.day = tab.day or today:day()
+    end
+    local Y = tab.year
+    if Y < 100 then -- classic Y2K pivot
+        tab.year = Y + (Y < 35 and 2000 or 1999)
+    elseif not Y then
+        tab.year = 1970
+    end
+    return Date(tab)
+end
+
+--- convert a Date object into a string.
+-- @param d a date object, or a time value as returned by @{os.time}
+-- @return string
+function Date.Format:tostring(d)
+    local tm
+    local fmt = self.outf
+    if type(d) == 'number' then
+        tm = d
+    else
+        tm = d.time
+        if d.utc then
+            fmt = '!'..fmt
+        end
+    end
+    return os_date(fmt,tm)
+end
+
+--- force US order in dates like 9/11/2001
+function Date.Format:US_order(yesno)
+    self.us = yesno
+end
+
+--local months = {jan=1,feb=2,mar=3,apr=4,may=5,jun=6,jul=7,aug=8,sep=9,oct=10,nov=11,dec=12}
+local months
+local parse_date_unsafe
+local function create_months()
+    local ld, day1 = parse_date_unsafe '2000-12-31', {day=1}
+    months = {}
+    for i = 1,12 do
+        ld = ld:last_day()
+        ld:add(day1)
+        local mon = ld:month_name():lower()
+        months [mon] = i
+    end
+end
+
+--[[
+Allowed patterns:
+- [day] [monthname] [year] [time]
+- [day]/[month][/year] [time]
+
+]]
+
+local function looks_like_a_month(w)
+    return w:match '^%a+,*$' ~= nil
+end
+local is_number = stringx.isdigit
+local function tonum(s,l1,l2,kind)
+    kind = kind or ''
+    local n = tonumber(s)
+    if not n then error(("%snot a number: '%s'"):format(kind,s)) end
+    if n < l1 or n > l2 then
+        error(("%s out of range: %s is not between %d and %d"):format(kind,s,l1,l2))
+    end
+    return n
+end
+
+local function  parse_iso_end(p,ns,sec)
+    -- may be fractional part of seconds
+    local _,nfrac,secfrac = p:find('^%.%d+',ns+1)
+    if secfrac then
+        sec = sec .. secfrac
+        p = p:sub(nfrac+1)
+    else
+        p = p:sub(ns+1)
+    end
+    -- ISO 8601 dates may end in Z (for UTC) or [+-][isotime]
+    -- (we're working with the date as lower case, hence 'z')
+    if p:match 'z$' then -- we're UTC!
+        return  sec, {h=0,m=0}
+    end
+    p = p:gsub(':','') -- turn 00:30 to 0030
+    local _,_,sign,offs = p:find('^([%+%-])(%d+)')
+    if not sign then return sec, nil end -- not UTC
+
+    if #offs == 2 then offs = offs .. '00' end -- 01 to 0100
+    local tz = { h = tonumber(offs:sub(1,2)), m = tonumber(offs:sub(3,4)) }
+    if sign == '-' then tz.h = -tz.h; tz.m = -tz.m end
+    return sec, tz
+end
+
+function parse_date_unsafe (s,US)
+    s = s:gsub('T',' ') -- ISO 8601
+    local parts = stringx.split(s:lower())
+    local i,p = 1,parts[1]
+    local function nextp() i = i + 1; p = parts[i] end
+    local year,min,hour,sec,apm
+    local tz
+    local _,nxt,day, month = p:find '^(%d+)/(%d+)'
+    if day then
+        -- swop for US case
+        if US then
+            day, month = month, day
+        end
+        _,_,year = p:find('^/(%d+)',nxt+1)
+        nextp()
+    else -- ISO
+        year,month,day = p:match('^(%d+)%-(%d+)%-(%d+)')
+        if year then
+            nextp()
+        end
+    end
+    if p and not year and is_number(p) then -- has to be date
+        if #p < 4 then
+            day = p
+            nextp()
+        else -- unless it looks like a 24-hour time
+            year = true
+        end
+    end
+    if p and looks_like_a_month(p) then -- date followed by month
+        p = p:sub(1,3)
+        if not months then
+            create_months()
+        end
+        local mon = months[p]
+        if mon then
+            month = mon
+        else error("not a month: " .. p) end
+        nextp()
+    end
+    if p and not year and is_number(p) then
+        year = p
+        nextp()
+    end
+
+    if p then -- time is hh:mm[:ss], hhmm[ss] or H.M[am|pm]
+        _,nxt,hour,min = p:find '^(%d+):(%d+)'
+        local ns
+        if nxt then -- are there seconds?
+            _,ns,sec = p:find ('^:(%d+)',nxt+1)
+            --if ns then
+                sec,tz = parse_iso_end(p,ns or nxt,sec)
+            --end
+        else -- might be h.m
+            _,ns,hour,min = p:find '^(%d+)%.(%d+)'
+            if ns then
+                apm = p:match '[ap]m$'
+            else  -- or hhmm[ss]
+                local hourmin
+                _,nxt,hourmin = p:find ('^(%d+)')
+                if nxt then
+                   hour = hourmin:sub(1,2)
+                   min = hourmin:sub(3,4)
+                   sec = hourmin:sub(5,6)
+                   if #sec == 0 then sec = nil end
+                   sec,tz = parse_iso_end(p,nxt,sec)
+                end
+            end
+        end
+    end
+    local today
+    if year == true then year = nil end
+    if not (year and month and day) then
+        today = Date()
+    end
+    day = day and tonum(day,1,31,'day') or (month and 1 or today:day())
+    month = month and tonum(month,1,12,'month') or today:month()
+    year = year and tonumber(year) or today:year()
+    if year < 100 then -- two-digit year pivot around year < 2035
+        year = year + (year < 35 and 2000 or 1900)
+    end
+    hour = hour and tonum(hour,0,apm and 12 or 24,'hour') or 12
+    if apm == 'pm' then
+        hour = hour + 12
+    end
+    min = min and tonum(min,0,59) or 0
+    sec = sec and tonum(sec,0,60) or 0  --60 used to indicate leap second
+    local res = Date {year = year, month = month, day = day, hour = hour, min = min, sec = sec}
+    if tz then -- ISO 8601 UTC time
+        local corrected = false
+        if tz.h ~= 0 then res:add {hour = -tz.h}; corrected = true end
+        if tz.m ~= 0 then res:add {min = -tz.m}; corrected = true end
+        res.utc = true
+        -- we're in UTC, so let's go local...
+        if corrected then
+            res = res:toLocal()
+        end-- we're UTC!
+    end
+    return res
+end
+
+function parse_date (s)
+    local ok, d = pcall(parse_date_unsafe,s)
+    if not ok then -- error
+        d = d:gsub('.-:%d+: ','')
+        return nil, d
+    else
+        return d
+    end
+end
+
+return Date
+
+
+end,
+
+["pl.dir"] = function()
+--------------------
+-- Module: 'pl.dir'
+--------------------
+--- Listing files in directories and creating/removing directory paths.
+--
+-- Dependencies: `pl.utils`, `pl.path`
+--
+-- Soft Dependencies: `alien`, `ffi` (either are used on Windows for copying/moving files)
+-- @module pl.dir
+
+local utils = require 'pl.utils'
+local path = require 'pl.path'
+local is_windows = path.is_windows
+local ldir = path.dir
+local mkdir = path.mkdir
+local rmdir = path.rmdir
+local sub = string.sub
+local os,pcall,ipairs,pairs,require,setmetatable = os,pcall,ipairs,pairs,require,setmetatable
+local remove = os.remove
+local append = table.insert
+local assert_arg,assert_string,raise = utils.assert_arg,utils.assert_string,utils.raise
+
+local exists, isdir = path.exists, path.isdir
+local sep = path.sep
+
+local dir = {}
+
+local function makelist(l)
+    return setmetatable(l, require('pl.List'))
+end
+
+local function assert_dir (n,val)
+    assert_arg(n,val,'string',path.isdir,'not a directory',4)
+end
+
+local function filemask(mask)
+    mask = utils.escape(path.normcase(mask))
+    return '^'..mask:gsub('%%%*','.*'):gsub('%%%?','.')..'$'
+end
+
+--- Test whether a file name matches a shell pattern.
+-- Both parameters are case-normalized if operating system is
+-- case-insensitive.
+-- @string filename A file name.
+-- @string pattern A shell pattern. The only special characters are
+-- `'*'` and `'?'`: `'*'` matches any sequence of characters and
+-- `'?'` matches any single character.
+-- @treturn bool
+-- @raise dir and mask must be strings
+function dir.fnmatch(filename,pattern)
+    assert_string(1,filename)
+    assert_string(2,pattern)
+    return path.normcase(filename):find(filemask(pattern)) ~= nil
+end
+
+--- Return a list of all file names within an array which match a pattern.
+-- @tab filenames An array containing file names.
+-- @string pattern A shell pattern.
+-- @treturn List(string) List of matching file names.
+-- @raise dir and mask must be strings
+function dir.filter(filenames,pattern)
+    assert_arg(1,filenames,'table')
+    assert_string(2,pattern)
+    local res = {}
+    local mask = filemask(pattern)
+    for i,f in ipairs(filenames) do
+        if path.normcase(f):find(mask) then append(res,f) end
+    end
+    return makelist(res)
+end
+
+local function _listfiles(dirname,filemode,match)
+    local res = {}
+    local check = utils.choose(filemode,path.isfile,path.isdir)
+    if not dirname then dirname = '.' end
+    for f in ldir(dirname) do
+        if f ~= '.' and f ~= '..' then
+            local p = path.join(dirname,f)
+            if check(p) and (not match or match(f)) then
+                append(res,p)
+            end
+        end
+    end
+    return makelist(res)
+end
+
+--- return a list of all files in a directory which match a shell pattern.
+-- @string dirname A directory. If not given, all files in current directory are returned.
+-- @string mask  A shell pattern. If not given, all files are returned.
+-- @treturn {string} list of files
+-- @raise dirname and mask must be strings
+function dir.getfiles(dirname,mask)
+    assert_dir(1,dirname)
+    if mask then assert_string(2,mask) end
+    local match
+    if mask then
+        mask = filemask(mask)
+        match = function(f)
+            return path.normcase(f):find(mask)
+        end
+    end
+    return _listfiles(dirname,true,match)
+end
+
+--- return a list of all subdirectories of the directory.
+-- @string dirname A directory
+-- @treturn {string} a list of directories
+-- @raise dir must be a a valid directory
+function dir.getdirectories(dirname)
+    assert_dir(1,dirname)
+    return _listfiles(dirname,false)
+end
+
+local alien,ffi,ffi_checked,CopyFile,MoveFile,GetLastError,win32_errors,cmd_tmpfile
+
+local function execute_command(cmd,parms)
+   if not cmd_tmpfile then cmd_tmpfile = path.tmpname () end
+   local err = path.is_windows and ' > ' or ' 2> '
+    cmd = cmd..' '..parms..err..utils.quote_arg(cmd_tmpfile)
+    local ret = utils.execute(cmd)
+    if not ret then
+        local err = (utils.readfile(cmd_tmpfile):gsub('\n(.*)',''))
+        remove(cmd_tmpfile)
+        return false,err
+    else
+        remove(cmd_tmpfile)
+        return true
+    end
+end
+
+local function find_ffi_copyfile ()
+    if not ffi_checked then
+        ffi_checked = true
+        local res
+        res,alien = pcall(require,'alien')
+        if not res then
+            alien = nil
+            res, ffi = pcall(require,'ffi')
+        end
+        if not res then
+            ffi = nil
+            return
+        end
+    else
+        return
+    end
+    if alien then
+        -- register the Win32 CopyFile and MoveFile functions
+        local kernel = alien.load('kernel32.dll')
+        CopyFile = kernel.CopyFileA
+        CopyFile:types{'string','string','int',ret='int',abi='stdcall'}
+        MoveFile = kernel.MoveFileA
+        MoveFile:types{'string','string',ret='int',abi='stdcall'}
+        GetLastError = kernel.GetLastError
+        GetLastError:types{ret ='int', abi='stdcall'}
+    elseif ffi then
+        ffi.cdef [[
+            int CopyFileA(const char *src, const char *dest, int iovr);
+            int MoveFileA(const char *src, const char *dest);
+            int GetLastError();
+        ]]
+        CopyFile = ffi.C.CopyFileA
+        MoveFile = ffi.C.MoveFileA
+        GetLastError = ffi.C.GetLastError
+    end
+    win32_errors = {
+        ERROR_FILE_NOT_FOUND    =         2,
+        ERROR_PATH_NOT_FOUND    =         3,
+        ERROR_ACCESS_DENIED    =          5,
+        ERROR_WRITE_PROTECT    =          19,
+        ERROR_BAD_UNIT         =          20,
+        ERROR_NOT_READY        =          21,
+        ERROR_WRITE_FAULT      =          29,
+        ERROR_READ_FAULT       =          30,
+        ERROR_SHARING_VIOLATION =         32,
+        ERROR_LOCK_VIOLATION    =         33,
+        ERROR_HANDLE_DISK_FULL  =         39,
+        ERROR_BAD_NETPATH       =         53,
+        ERROR_NETWORK_BUSY      =         54,
+        ERROR_DEV_NOT_EXIST     =         55,
+        ERROR_FILE_EXISTS       =         80,
+        ERROR_OPEN_FAILED       =         110,
+        ERROR_INVALID_NAME      =         123,
+        ERROR_BAD_PATHNAME      =         161,
+        ERROR_ALREADY_EXISTS    =         183,
+    }
+end
+
+local function two_arguments (f1,f2)
+    return utils.quote_arg(f1)..' '..utils.quote_arg(f2)
+end
+
+local function file_op (is_copy,src,dest,flag)
+    if flag == 1 and path.exists(dest) then
+        return false,"cannot overwrite destination"
+    end
+    if is_windows then
+        -- if we haven't tried to load Alien/LuaJIT FFI before, then do so
+        find_ffi_copyfile()
+        -- fallback if there's no Alien, just use DOS commands *shudder*
+        -- 'rename' involves a copy and then deleting the source.
+        if not CopyFile then
+            if path.is_windows then
+                src = src:gsub("/","\\")
+                dest = dest:gsub("/","\\")
+            end
+            local res, err = execute_command('copy',two_arguments(src,dest))
+            if not res then return false,err end
+            if not is_copy then
+                return execute_command('del',utils.quote_arg(src))
+            end
+            return true
+        else
+            if path.isdir(dest) then
+                dest = path.join(dest,path.basename(src))
+            end
+            local ret
+            if is_copy then ret = CopyFile(src,dest,flag)
+            else ret = MoveFile(src,dest) end
+            if ret == 0 then
+                local err = GetLastError()
+                for name,value in pairs(win32_errors) do
+                    if value == err then return false,name end
+                end
+                return false,"Error #"..err
+            else return true
+            end
+        end
+    else -- for Unix, just use cp for now
+        return execute_command(is_copy and 'cp' or 'mv',
+            two_arguments(src,dest))
+    end
+end
+
+--- copy a file.
+-- @string src source file
+-- @string dest destination file or directory
+-- @bool flag true if you want to force the copy (default)
+-- @treturn bool operation succeeded
+-- @raise src and dest must be strings
+function dir.copyfile (src,dest,flag)
+    assert_string(1,src)
+    assert_string(2,dest)
+    flag = flag==nil or flag
+    return file_op(true,src,dest,flag and 0 or 1)
+end
+
+--- move a file.
+-- @string src source file
+-- @string dest destination file or directory
+-- @treturn bool operation succeeded
+-- @raise src and dest must be strings
+function dir.movefile (src,dest)
+    assert_string(1,src)
+    assert_string(2,dest)
+    return file_op(false,src,dest,0)
+end
+
+local function _dirfiles(dirname,attrib)
+    local dirs = {}
+    local files = {}
+    for f in ldir(dirname) do
+        if f ~= '.' and f ~= '..' then
+            local p = path.join(dirname,f)
+            local mode = attrib(p,'mode')
+            if mode=='directory' then
+                append(dirs,f)
+            else
+                append(files,f)
+            end
+        end
+    end
+    return makelist(dirs), makelist(files)
+end
+
+
+--- return an iterator which walks through a directory tree starting at root.
+-- The iterator returns (root,dirs,files)
+-- Note that dirs and files are lists of names (i.e. you must say path.join(root,d)
+-- to get the actual full path)
+-- If bottom_up is false (or not present), then the entries at the current level are returned
+-- before we go deeper. This means that you can modify the returned list of directories before
+-- continuing.
+-- This is a clone of os.walk from the Python libraries.
+-- @string root A starting directory
+-- @bool bottom_up False if we start listing entries immediately.
+-- @bool follow_links follow symbolic links
+-- @return an iterator returning root,dirs,files
+-- @raise root must be a directory
+function dir.walk(root,bottom_up,follow_links)
+    assert_dir(1,root)
+    local attrib
+    if path.is_windows or not follow_links then
+        attrib = path.attrib
+    else
+        attrib = path.link_attrib
+    end
+
+    local to_scan = { root }
+    local to_return = {}
+    local iter = function()
+        while #to_scan > 0 do
+            local current_root = table.remove(to_scan)
+            local dirs,files = _dirfiles(current_root, attrib)
+            for _, d in ipairs(dirs) do
+                table.insert(to_scan, current_root..path.sep..d)
+            end
+            if not bottom_up then
+                return current_root, dirs, files
+            else
+                table.insert(to_return, { current_root, dirs, files })
+            end
+        end
+        if #to_return > 0 then
+            return utils.unpack(table.remove(to_return))
+        end
+    end
+
+    return iter
+end
+
+--- remove a whole directory tree.
+-- Symlinks in the tree will be deleted without following them.
+-- @string fullpath A directory path (must be an actual directory, not a symlink)
+-- @return true or nil
+-- @return error if failed
+-- @raise fullpath must be a string
+function dir.rmtree(fullpath)
+    assert_dir(1,fullpath)
+    if path.islink(fullpath) then return false,'will not follow symlink' end
+    for root,dirs,files in dir.walk(fullpath,true) do
+        if path.islink(root) then
+            -- sub dir is a link, remove link, do not follow
+            if is_windows then
+                -- Windows requires using "rmdir". Deleting the link like a file
+                -- will instead delete all files from the target directory!!
+                local res, err = rmdir(root)
+                if not res then return nil,err .. ": " .. root end
+            else
+                local res, err = remove(root)
+                if not res then return nil,err .. ": " .. root end
+            end
+        else
+            for i,f in ipairs(files) do
+                local res, err = remove(path.join(root,f))
+                if not res then return nil,err .. ": " .. path.join(root,f) end
+            end
+            local res, err = rmdir(root)
+            if not res then return nil,err .. ": " .. root end
+        end
+    end
+    return true
+end
+
+
+do
+  local dirpat
+  if path.is_windows then
+      dirpat = '(.+)\\[^\\]+$'
+  else
+      dirpat = '(.+)/[^/]+$'
+  end
+
+  local _makepath
+  function _makepath(p)
+      -- windows root drive case
+      if p:find '^%a:[\\]*$' then
+          return true
+      end
+      if not path.isdir(p) then
+          local subp = p:match(dirpat)
+          if subp then
+            local ok, err = _makepath(subp)
+            if not ok then return nil, err end
+          end
+          return mkdir(p)
+      else
+          return true
+      end
+  end
+
+  --- create a directory path.
+  -- This will create subdirectories as necessary!
+  -- @string p A directory path
+  -- @return true on success, nil + errormsg on failure
+  -- @raise failure to create
+  function dir.makepath (p)
+      assert_string(1,p)
+      if path.is_windows then
+          p = p:gsub("/", "\\")
+      end
+      return _makepath(path.abspath(p))
+  end
+end
+
+--- clone a directory tree. Will always try to create a new directory structure
+-- if necessary.
+-- @string path1 the base path of the source tree
+-- @string path2 the new base path for the destination
+-- @func file_fun an optional function to apply on all files
+-- @bool verbose an optional boolean to control the verbosity of the output.
+--  It can also be a logging function that behaves like print()
+-- @return true, or nil
+-- @return error message, or list of failed directory creations
+-- @return list of failed file operations
+-- @raise path1 and path2 must be strings
+-- @usage clonetree('.','../backup',copyfile)
+function dir.clonetree (path1,path2,file_fun,verbose)
+    assert_string(1,path1)
+    assert_string(2,path2)
+    if verbose == true then verbose = print end
+    local abspath,normcase,isdir,join = path.abspath,path.normcase,path.isdir,path.join
+    local faildirs,failfiles = {},{}
+    if not isdir(path1) then return raise 'source is not a valid directory' end
+    path1 = abspath(normcase(path1))
+    path2 = abspath(normcase(path2))
+    if verbose then verbose('normalized:',path1,path2) end
+    -- particularly NB that the new path isn't fully contained in the old path
+    if path1 == path2 then return raise "paths are the same" end
+    local _,i2 = path2:find(path1,1,true)
+    if i2 == #path1 and path2:sub(i2+1,i2+1) == path.sep then
+        return raise 'destination is a subdirectory of the source'
+    end
+    local cp = path.common_prefix (path1,path2)
+    local idx = #cp
+    if idx == 0 then -- no common path, but watch out for Windows paths!
+        if path1:sub(2,2) == ':' then idx = 3 end
+    end
+    for root,dirs,files in dir.walk(path1) do
+        local opath = path2..root:sub(idx)
+        if verbose then verbose('paths:',opath,root) end
+        if not isdir(opath) then
+            local ret = dir.makepath(opath)
+            if not ret then append(faildirs,opath) end
+            if verbose then verbose('creating:',opath,ret) end
+        end
+        if file_fun then
+            for i,f in ipairs(files) do
+                local p1 = join(root,f)
+                local p2 = join(opath,f)
+                local ret = file_fun(p1,p2)
+                if not ret then append(failfiles,p2) end
+                if verbose then
+                    verbose('files:',p1,p2,ret)
+                end
+            end
+        end
+    end
+    return true,faildirs,failfiles
+end
+
+
+-- each entry of the stack is an array with three items:
+-- 1. the name of the directory
+-- 2. the lfs iterator function
+-- 3. the lfs iterator userdata
+local function treeiter(iterstack)
+    local diriter = iterstack[#iterstack]
+    if not diriter then
+      return -- done
+    end
+
+    local dirname = diriter[1]
+    local entry = diriter[2](diriter[3])
+    if not entry then
+      table.remove(iterstack)
+      return treeiter(iterstack) -- tail-call to try next
+    end
+
+    if entry ~= "." and entry ~= ".." then
+        entry = dirname .. sep .. entry
+        if exists(entry) then  -- Just in case a symlink is broken.
+            local is_dir = isdir(entry)
+            if is_dir then
+                table.insert(iterstack, { entry, ldir(entry) })
+            end
+            return entry, is_dir
+        end
+    end
+
+    return treeiter(iterstack) -- tail-call to try next
+end
+
+
+--- return an iterator over all entries in a directory tree
+-- @string d a directory
+-- @return an iterator giving pathname and mode (true for dir, false otherwise)
+-- @raise d must be a non-empty string
+function dir.dirtree( d )
+    assert( d and d ~= "", "directory parameter is missing or empty" )
+
+    local last = sub ( d, -1 )
+    if last == sep or last == '/' then
+        d = sub( d, 1, -2 )
+    end
+
+    local iterstack = { {d, ldir(d)} }
+
+    return treeiter, iterstack
+end
+
+
+--- Recursively returns all the file starting at _path_. It can optionally take a shell pattern and
+-- only returns files that match _shell_pattern_. If a pattern is given it will do a case insensitive search.
+-- @string start_path  A directory. If not given, all files in current directory are returned.
+-- @string shell_pattern A shell pattern. If not given, all files are returned.
+-- @treturn List(string) containing all the files found recursively starting at _path_ and filtered by _shell_pattern_.
+-- @raise start_path must be a directory
+function dir.getallfiles( start_path, shell_pattern )
+    assert_dir(1,start_path)
+    shell_pattern = shell_pattern or "*"
+
+    local files = {}
+    local normcase = path.normcase
+    for filename, mode in dir.dirtree( start_path ) do
+        if not mode then
+            local mask = filemask( shell_pattern )
+            if normcase(filename):find( mask ) then
+                files[#files + 1] = filename
+            end
+        end
+    end
+
+    return makelist(files)
+end
+
+return dir
+
+end,
+
+["pl.file"] = function()
+--------------------
+-- Module: 'pl.file'
+--------------------
+--- File manipulation functions: reading, writing, moving and copying.
+--
+-- This module wraps a number of functions from other modules into a
+-- file related module for convenience.
+--
+-- Dependencies: `pl.utils`, `pl.dir`, `pl.path`
+-- @module pl.file
+local os = os
+local utils = require 'pl.utils'
+local dir = require 'pl.dir'
+local path = require 'pl.path'
+
+local file = {}
+
+--- return the contents of a file as a string.
+-- This function is a copy of `utils.readfile`.
+-- @function file.read
+file.read = utils.readfile
+
+--- write a string to a file.
+-- This function is a copy of `utils.writefile`.
+-- @function file.write
+file.write = utils.writefile
+
+--- copy a file.
+-- This function is a copy of `dir.copyfile`.
+-- @function file.copy
+file.copy = dir.copyfile
+
+--- move a file.
+-- This function is a copy of `dir.movefile`.
+-- @function file.move
+file.move = dir.movefile
+
+--- Return the time of last access as the number of seconds since the epoch.
+-- This function is a copy of `path.getatime`.
+-- @function file.access_time
+file.access_time = path.getatime
+
+---Return when the file was created.
+-- This function is a copy of `path.getctime`.
+-- @function file.creation_time
+file.creation_time = path.getctime
+
+--- Return the time of last modification.
+-- This function is a copy of `path.getmtime`.
+-- @function file.modified_time
+file.modified_time = path.getmtime
+
+--- Delete a file.
+-- This function is a copy of `os.remove`.
+-- @function file.delete
+file.delete = os.remove
+
+return file
+
+end,
+
+["pl.func"] = function()
+--------------------
+-- Module: 'pl.func'
+--------------------
+--- Functional helpers like composition, binding and placeholder expressions.
+-- Placeholder expressions are useful for short anonymous functions, and were
+-- inspired by the Boost Lambda library.
+--
+--    > utils.import 'pl.func'
+--    > ls = List{10,20,30}
+--    > = ls:map(_1+1)
+--    {11,21,31}
+--
+-- They can also be used to _bind_ particular arguments of a function.
+--
+--    > p = bind(print,'start>',_0)
+--    > p(10,20,30)
+--    > start>   10   20  30
+--
+-- See @{07-functional.md.Creating_Functions_from_Functions|the Guide}
+--
+-- Dependencies: `pl.utils`, `pl.tablex`
+-- @module pl.func
+local type,setmetatable,getmetatable,rawset = type,setmetatable,getmetatable,rawset
+local concat,append = table.concat,table.insert
+local tostring = tostring
+local utils = require 'pl.utils'
+local pairs,rawget,unpack,pack = pairs,rawget,utils.unpack,utils.pack
+local tablex = require 'pl.tablex'
+local map = tablex.map
+local _DEBUG = rawget(_G,'_DEBUG')
+local assert_arg = utils.assert_arg
+
+local func = {}
+
+-- metatable for Placeholder Expressions (PE)
+local _PEMT = {}
+
+local function P (t)
+    setmetatable(t,_PEMT)
+    return t
+end
+
+func.PE = P
+
+local function isPE (obj)
+    return getmetatable(obj) == _PEMT
+end
+
+func.isPE = isPE
+
+-- construct a placeholder variable (e.g _1 and _2)
+local function PH (idx)
+    return P {op='X',repr='_'..idx, index=idx}
+end
+
+-- construct a constant placeholder variable (e.g _C1 and _C2)
+local function CPH (idx)
+    return P {op='X',repr='_C'..idx, index=idx}
+end
+
+func._1,func._2,func._3,func._4,func._5 = PH(1),PH(2),PH(3),PH(4),PH(5)
+func._0 = P{op='X',repr='...',index=0}
+
+function func.Var (name)
+    local ls = utils.split(name,'[%s,]+')
+    local res = {}
+    for i = 1, #ls do
+        append(res,P{op='X',repr=ls[i],index=0})
+    end
+    return unpack(res)
+end
+
+function func._ (value)
+    return P{op='X',repr=value,index='wrap'}
+end
+
+local repr
+
+func.Nil = func.Var 'nil'
+
+function _PEMT.__index(obj,key)
+    return P{op='[]',obj,key}
+end
+
+function _PEMT.__call(fun,...)
+    return P{op='()',fun,...}
+end
+
+function _PEMT.__tostring (e)
+    return repr(e)
+end
+
+function _PEMT.__unm(arg)
+    return P{op='unm',arg}
+end
+
+function func.Not (arg)
+    return P{op='not',arg}
+end
+
+function func.Len (arg)
+    return P{op='#',arg}
+end
+
+
+local function binreg(context,t)
+    for name,op in pairs(t) do
+        rawset(context,name,function(x,y)
+            return P{op=op,x,y}
+        end)
+    end
+end
+
+local function import_name (name,fun,context)
+    rawset(context,name,function(...)
+        return P{op='()',fun,...}
+    end)
+end
+
+local imported_functions = {}
+
+local function is_global_table (n)
+    return type(_G[n]) == 'table'
+end
+
+--- wrap a table of functions. This makes them available for use in
+-- placeholder expressions.
+-- @string tname a table name
+-- @tab context context to put results, defaults to environment of caller
+function func.import(tname,context)
+    assert_arg(1,tname,'string',is_global_table,'arg# 1: not a name of a global table')
+    local t = _G[tname]
+    context = context or _G
+    for name,fun in pairs(t) do
+        import_name(name,fun,context)
+        imported_functions[fun] = name
+    end
+end
+
+--- register a function for use in placeholder expressions.
+-- @func fun a function
+-- @string[opt] name an optional name
+-- @return a placeholder functiond
+function func.register (fun,name)
+    assert_arg(1,fun,'function')
+    if name then
+        assert_arg(2,name,'string')
+        imported_functions[fun] = name
+    end
+    return function(...)
+        return P{op='()',fun,...}
+    end
+end
+
+function func.lookup_imported_name (fun)
+    return imported_functions[fun]
+end
+
+local function _arg(...) return ... end
+
+function func.Args (...)
+    return P{op='()',_arg,...}
+end
+
+-- binary operators with their precedences (see Lua manual)
+-- precedences might be incremented by one before use depending on
+-- left- or right-associativity, space them out
+local binary_operators = {
+    ['or'] = 0,
+    ['and'] = 2,
+    ['=='] = 4, ['~='] = 4, ['<'] = 4, ['>'] = 4,  ['<='] = 4,   ['>='] = 4,
+    ['..'] = 6,
+    ['+'] = 8, ['-'] = 8,
+    ['*'] = 10, ['/'] = 10, ['%'] = 10,
+    ['^'] = 14
+}
+
+-- unary operators with their precedences
+local unary_operators = {
+    ['not'] = 12, ['#'] = 12, ['unm'] = 12
+}
+
+-- comparisons (as prefix functions)
+binreg (func,{And='and',Or='or',Eq='==',Lt='<',Gt='>',Le='<=',Ge='>='})
+
+-- standard binary operators (as metamethods)
+binreg (_PEMT,{__add='+',__sub='-',__mul='*',__div='/',__mod='%',__pow='^',__concat='..'})
+
+binreg (_PEMT,{__eq='=='})
+
+--- all elements of a table except the first.
+-- @tab ls a list-like table.
+function func.tail (ls)
+    assert_arg(1,ls,'table')
+    local res = {}
+    for i = 2,#ls do
+        append(res,ls[i])
+    end
+    return res
+end
+
+--- create a string representation of a placeholder expression.
+-- @param e a placeholder expression
+-- @param lastpred not used
+function repr (e,lastpred)
+    local tail = func.tail
+    if isPE(e) then
+        local pred = binary_operators[e.op] or unary_operators[e.op]
+        if pred then
+            -- binary or unary operator
+            local s
+            if binary_operators[e.op] then
+                local left_pred = pred
+                local right_pred = pred
+                if e.op == '..' or e.op == '^' then
+                    left_pred = left_pred + 1
+                else
+                    right_pred = right_pred + 1
+                end
+                local left_arg = repr(e[1], left_pred)
+                local right_arg = repr(e[2], right_pred)
+                s = left_arg..' '..e.op..' '..right_arg
+            else
+                local op = e.op == 'unm' and '-' or e.op
+                s = op..' '..repr(e[1], pred)
+            end
+            if lastpred and lastpred > pred then
+                s = '('..s..')'
+            end
+            return s
+        else -- either postfix, or a placeholder
+            local ls = map(repr,e)
+            if e.op == '[]' then
+                return ls[1]..'['..ls[2]..']'
+            elseif e.op == '()' then
+                local fn
+                if ls[1] ~= nil then -- was _args, undeclared!
+                    fn = ls[1]
+                else
+                    fn = ''
+                end
+                return fn..'('..concat(tail(ls),',')..')'
+            else
+                return e.repr
+            end
+        end
+    elseif type(e) == 'string' then
+        return '"'..e..'"'
+    elseif type(e) == 'function' then
+        local name = func.lookup_imported_name(e)
+        if name then return name else return tostring(e) end
+    else
+        return tostring(e) --should not really get here!
+    end
+end
+func.repr = repr
+
+-- collect all the non-PE values in this PE into vlist, and replace each occurence
+-- with a constant PH (_C1, etc). Return the maximum placeholder index found.
+local collect_values
+function collect_values (e,vlist)
+    if isPE(e) then
+        if e.op ~= 'X' then
+            local m = 0
+            for i = 1,#e do
+                local subx = e[i]
+                local pe = isPE(subx)
+                if pe then
+                    if subx.op == 'X' and subx.index == 'wrap' then
+                        subx = subx.repr
+                        pe = false
+                    else
+                        m = math.max(m,collect_values(subx,vlist))
+                    end
+                end
+                if not pe then
+                    append(vlist,subx)
+                    e[i] = CPH(#vlist)
+                end
+            end
+            return m
+        else -- was a placeholder, it has an index...
+            return e.index
+        end
+    else -- plain value has no placeholder dependence
+        return 0
+    end
+end
+func.collect_values = collect_values
+
+--- instantiate a PE into an actual function. First we find the largest placeholder used,
+-- e.g. _2; from this a list of the formal parameters can be build. Then we collect and replace
+-- any non-PE values from the PE, and build up a constant binding list.
+-- Finally, the expression can be compiled, and e.__PE_function is set.
+-- @param e a placeholder expression
+-- @return a function
+function func.instantiate (e)
+    local consts,values,parms = {},{},{}
+    local rep, err, fun
+    local n = func.collect_values(e,values)
+    for i = 1,#values do
+        append(consts,'_C'..i)
+        if _DEBUG then print(i,values[i]) end
+    end
+    for i =1,n do
+        append(parms,'_'..i)
+    end
+    consts = concat(consts,',')
+    parms = concat(parms,',')
+    rep = repr(e)
+    local fstr = ('return function(%s) return function(%s) return %s end end'):format(consts,parms,rep)
+    if _DEBUG then print(fstr) end
+    fun,err = utils.load(fstr,'fun')
+    if not fun then return nil,err end
+    fun = fun()  -- get wrapper
+    fun = fun(unpack(values)) -- call wrapper (values could be empty)
+    e.__PE_function = fun
+    return fun
+end
+
+--- instantiate a PE unless it has already been done.
+-- @param e a placeholder expression
+-- @return the function
+function func.I(e)
+    if rawget(e,'__PE_function')  then
+        return e.__PE_function
+    else return func.instantiate(e)
+    end
+end
+
+utils.add_function_factory(_PEMT,func.I)
+
+--- bind the first parameter of the function to a value.
+-- @function func.bind1
+-- @func fn a function of one or more arguments
+-- @param p a value
+-- @return a function of one less argument
+-- @usage (bind1(math.max,10))(20) == math.max(10,20)
+func.bind1 = utils.bind1
+func.curry = func.bind1
+
+--- create a function which chains two functions.
+-- @func f a function of at least one argument
+-- @func g a function of at least one argument
+-- @return a function
+-- @usage printf = compose(io.write,string.format)
+function func.compose (f,g)
+    return function(...) return f(g(...)) end
+end
+
+--- bind the arguments of a function to given values.
+-- `bind(fn,v,_2)` is equivalent to `bind1(fn,v)`.
+-- @func fn a function of at least one argument
+-- @param ... values or placeholder variables
+-- @return a function
+-- @usage (bind(f,_1,a))(b) == f(a,b)
+-- @usage (bind(f,_2,_1))(a,b) == f(b,a)
+function func.bind(fn,...)
+    local args = pack(...)
+    local holders,parms,bvalues,values = {},{},{'fn'},{}
+    local nv,maxplace,varargs = 1,0,false
+    for i = 1,args.n do
+        local a = args[i]
+        if isPE(a) and a.op == 'X' then
+            append(holders,a.repr)
+            maxplace = math.max(maxplace,a.index)
+            if a.index == 0 then varargs = true end
+        else
+            local v = '_v'..nv
+            append(bvalues,v)
+            append(holders,v)
+            append(values,a)
+            nv = nv + 1
+        end
+    end
+    for np = 1,maxplace do
+        append(parms,'_'..np)
+    end
+    if varargs then append(parms,'...') end
+    bvalues = concat(bvalues,',')
+    parms = concat(parms,',')
+    holders = concat(holders,',')
+    local fstr = ([[
+return function (%s)
+    return function(%s) return fn(%s) end
+end
+]]):format(bvalues,parms,holders)
+    if _DEBUG then print(fstr) end
+    local res = utils.load(fstr)
+    res = res()
+    return res(fn,unpack(values))
+end
+
+return func
+
+
+
+end,
+
+["pl.import_into"] = function()
+--------------------
+-- Module: 'pl.import_into'
+--------------------
+--------------
+-- PL loader, for loading all PL libraries, only on demand.
+-- Whenever a module is implicitly accesssed, the table will have the module automatically injected.
+-- (e.g. `_ENV.tablex`)
+-- then that module is dynamically loaded. The submodules are all brought into
+-- the table that is provided as the argument, or returned in a new table.
+-- If a table is provided, that table's metatable is clobbered, but the values are not.
+-- This module returns a single function, which is passed the environment.
+-- If this is `true`, then return a 'shadow table' as the module
+-- See @{01-introduction.md.To_Inject_or_not_to_Inject_|the Guide}
+
+-- @module pl.import_into
+
+return function(env)
+    local mod
+    if env == true then
+        mod = {}
+        env = {}
+    end
+    local env = env or {}
+
+    local modules = {
+        utils = true,path=true,dir=true,tablex=true,stringio=true,sip=true,
+        input=true,seq=true,lexer=true,stringx=true,
+        config=true,pretty=true,data=true,func=true,text=true,
+        operator=true,lapp=true,array2d=true,
+        comprehension=true,xml=true,types=true,
+        test = true, app = true, file = true, class = true,
+        luabalanced = true, permute = true, template = true,
+        url = true, compat = true,
+        -- classes --
+        List = true, Map = true, Set = true,
+        OrderedMap = true, MultiMap = true, Date = true,
+    }
+    rawset(env,'utils',require 'pl.utils')
+
+    for name,klass in pairs(env.utils.stdmt) do
+        klass.__index = function(t,key)
+            return require ('pl.'..name)[key]
+        end;
+    end
+
+    -- ensure that we play nice with libraries that also attach a metatable
+    -- to the global table; always forward to a custom __index if we don't
+    -- match
+
+    local _hook,_prev_index
+    local gmt = {}
+    local prevenvmt = getmetatable(env)
+    if prevenvmt then
+        _prev_index = prevenvmt.__index
+        if prevenvmt.__newindex then
+            gmt.__index = prevenvmt.__newindex
+        end
+    end
+
+    function gmt.hook(handler)
+        _hook = handler
+    end
+
+    function gmt.__index(t,name)
+        local found = modules[name]
+        -- either true, or the name of the module containing this class.
+        -- either way, we load the required module and make it globally available.
+        if found then
+            -- e..g pretty.dump causes pl.pretty to become available as 'pretty'
+            rawset(env,name,require('pl.'..name))
+            return env[name]
+        else
+            local res
+            if _hook then
+                res = _hook(t,name)
+                if res then return res end
+            end
+            if _prev_index then
+                return _prev_index(t,name)
+            end
+        end
+    end
+
+    if mod then
+        function gmt.__newindex(t,name,value)
+            mod[name] = value
+            rawset(t,name,value)
+        end
+    end
+
+    setmetatable(env,gmt)
+
+    return env,mod or env
+end
+
+end,
+
+["pl.init"] = function()
+--------------------
+-- Module: 'pl.init'
+--------------------
+--------------
+-- Entry point for loading all PL libraries only on demand, into the global space.
+-- Requiring 'pl' means that whenever a module is implicitly accesssed
+-- (e.g. `utils.split`)
+-- then that module is dynamically loaded. The submodules are all brought into
+-- the global space.
+--Updated to use @{pl.import_into}
+-- @module pl
+require'pl.import_into'(_G)
+
+if rawget(_G,'PENLIGHT_STRICT') then require 'pl.strict' end
+
+end,
+
+["pl.input"] = function()
+--------------------
+-- Module: 'pl.input'
+--------------------
+--- Iterators for extracting words or numbers from an input source.
+--
+--    require 'pl'
+--    local total,n = seq.sum(input.numbers())
+--    print('average',total/n)
+--
+-- _source_ is defined as a string or a file-like object (i.e. has a read() method which returns the next line)
+--
+-- See @{06-data.md.Reading_Unstructured_Text_Data|here}
+--
+-- Dependencies: `pl.utils`
+-- @module pl.input
+local strfind = string.find
+local strsub = string.sub
+local strmatch = string.match
+local utils = require 'pl.utils'
+local unpack = utils.unpack
+local pairs,type,tonumber = pairs,type,tonumber
+local patterns = utils.patterns
+local io = io
+
+local input = {}
+
+--- create an iterator over all tokens.
+-- based on allwords from PiL, 7.1
+-- @func getter any function that returns a line of text
+-- @string pattern
+-- @string[opt] fn  Optionally can pass a function to process each token as it's found.
+-- @return an iterator
+function input.alltokens (getter,pattern,fn)
+    local line = getter()  -- current line
+    local pos = 1           -- current position in the line
+    return function ()      -- iterator function
+        while line do         -- repeat while there are lines
+          local s, e = strfind(line, pattern, pos)
+          if s then           -- found a word?
+            pos = e + 1       -- next position is after this token
+            local res = strsub(line, s, e)     -- return the token
+            if fn then res = fn(res) end
+            return res
+          else
+            line = getter()  -- token not found; try next line
+            pos = 1           -- restart from first position
+          end
+        end
+        return nil            -- no more lines: end of traversal
+   end
+end
+local alltokens = input.alltokens
+
+-- question: shd this _split_ a string containing line feeds?
+
+--- create a function which grabs the next value from a source. If the source is a string, then the getter
+-- will return the string and thereafter return nil. If not specified then the source is assumed to be stdin.
+-- @param f a string or a file-like object (i.e. has a read() method which returns the next line)
+-- @return a getter function
+function input.create_getter(f)
+    if f then
+        if type(f) == 'string' then
+            local ls = utils.split(f,'\n')
+            local i,n = 0,#ls
+            return function()
+                i = i + 1
+                if i > n then return nil end
+                return ls[i]
+            end
+        else
+            -- anything that supports the read() method!
+            if not f.read then error('not a file-like object') end
+            return function() return f:read() end
+        end
+    else
+        return io.read  -- i.e. just read from stdin
+    end
+end
+
+--- generate a sequence of numbers from a source.
+-- @param f A source
+-- @return An iterator
+function input.numbers(f)
+    return alltokens(input.create_getter(f),
+        '('..patterns.FLOAT..')',tonumber)
+end
+
+--- generate a sequence of words from a source.
+-- @param f A source
+-- @return An iterator
+function input.words(f)
+    return alltokens(input.create_getter(f),"%w+")
+end
+
+local function apply_tonumber (no_fail,...)
+    local args = {...}
+    for i = 1,#args do
+        local n = tonumber(args[i])
+        if  n == nil then
+            if not no_fail then return nil,args[i] end
+        else
+            args[i] = n
+        end
+    end
+    return args
+end
+
+--- parse an input source into fields.
+-- By default, will fail if it cannot convert a field to a number.
+-- @param ids a list of field indices, or a maximum field index
+-- @string delim delimiter to parse fields (default space)
+-- @param f a source @see create_getter
+-- @tab opts option table, `{no_fail=true}`
+-- @return an iterator with the field values
+-- @usage for x,y in fields {2,3} do print(x,y) end -- 2nd and 3rd fields from stdin
+function input.fields (ids,delim,f,opts)
+  local sep
+  local s
+  local getter = input.create_getter(f)
+  local no_fail = opts and opts.no_fail
+  local no_convert = opts and opts.no_convert
+  if not delim or delim == ' ' then
+      delim = '%s'
+      sep = '%s+'
+      s = '%s*'
+  else
+      sep = delim
+      s = ''
+  end
+  local max_id = 0
+  if type(ids) == 'table' then
+    for i,id in pairs(ids) do
+      if id > max_id then max_id = id end
+    end
+  else
+    max_id = ids
+    ids = {}
+    for i = 1,max_id do ids[#ids+1] = i end
+  end
+  local pat = '[^'..delim..']*'
+  local k = 1
+  for i = 1,max_id do
+    if ids[k] == i then
+      k = k + 1
+      s = s..'('..pat..')'
+    else
+      s = s..pat
+    end
+    if i < max_id then
+      s = s..sep
+    end
+  end
+  local linecount = 1
+  return function()
+    local line,results,err
+    repeat
+        line = getter()
+        linecount = linecount + 1
+        if not line then return nil end
+        if no_convert then
+            results = {strmatch(line,s)}
+        else
+            results,err = apply_tonumber(no_fail,strmatch(line,s))
+            if not results then
+                utils.quit("line "..(linecount-1)..": cannot convert '"..err.."' to number")
+            end
+        end
+    until #results > 0
+    return unpack(results)
+  end
+end
+
+return input
+
+
+end,
+
+["pl.lapp"] = function()
+--------------------
+-- Module: 'pl.lapp'
+--------------------
+--- Simple command-line parsing using human-readable specification.
+-- Supports GNU-style parameters.
+--
+--      lapp = require 'pl.lapp'
+--      local args = lapp [[
+--      Does some calculations
+--        -o,--offset (default 0.0)  Offset to add to scaled number
+--        -s,--scale  (number)  Scaling factor
+--        <number> (number) Number to be scaled
+--      ]]
+--
+--      print(args.offset + args.scale * args.number)
+--
+-- Lines beginning with `'-'` are flags; there may be a short and a long name;
+-- lines beginning with `'<var>'` are arguments.  Anything in parens after
+-- the flag/argument is either a default, a type name or a range constraint.
+--
+-- See @{08-additional.md.Command_line_Programs_with_Lapp|the Guide}
+--
+-- Dependencies: `pl.sip`
+-- @module pl.lapp
+
+local status,sip = pcall(require,'pl.sip')
+if not status then
+    sip = require 'sip'
+end
+local match = sip.match_at_start
+local append,tinsert = table.insert,table.insert
+
+sip.custom_pattern('X','(%a[%w_%-]*)')
+
+local function lines(s) return s:gmatch('([^\n]*)\n') end
+local function lstrip(str)  return str:gsub('^%s+','')  end
+local function strip(str)  return lstrip(str):gsub('%s+$','') end
+local function at(s,k)  return s:sub(k,k) end
+
+local lapp = {}
+
+local open_files,parms,aliases,parmlist,usage,script
+
+lapp.callback = false -- keep Strict happy
+
+local filetypes = {
+    stdin = {io.stdin,'file-in'}, stdout = {io.stdout,'file-out'},
+    stderr = {io.stderr,'file-out'}
+}
+
+--- controls whether to dump usage on error.
+-- Defaults to true
+lapp.show_usage_error = true
+
+--- quit this script immediately.
+-- @string msg optional message
+-- @bool no_usage suppress 'usage' display
+function lapp.quit(msg,no_usage)
+    if no_usage == 'throw' then
+        error(msg)
+    end
+    if msg then
+        io.stderr:write(msg..'\n\n')
+    end
+    if not no_usage then
+        io.stderr:write(usage)
+    end
+    os.exit(1)
+end
+
+--- print an error to stderr and quit.
+-- @string msg a message
+-- @bool no_usage suppress 'usage' display
+function lapp.error(msg,no_usage)
+    if not lapp.show_usage_error then
+        no_usage = true
+    elseif lapp.show_usage_error == 'throw' then
+        no_usage = 'throw'
+    end
+    lapp.quit(script..': '..msg,no_usage)
+end
+
+--- open a file.
+-- This will quit on error, and keep a list of file objects for later cleanup.
+-- @string file filename
+-- @string[opt] opt same as second parameter of `io.open`
+function lapp.open (file,opt)
+    local val,err = io.open(file,opt)
+    if not val then lapp.error(err,true) end
+    append(open_files,val)
+    return val
+end
+
+--- quit if the condition is false.
+-- @bool condn a condition
+-- @string msg message text
+function lapp.assert(condn,msg)
+    if not condn then
+        lapp.error(msg)
+    end
+end
+
+local function range_check(x,min,max,parm)
+    lapp.assert(min <= x and max >= x,parm..' out of range')
+end
+
+local function xtonumber(s)
+    local val = tonumber(s)
+    if not val then lapp.error("unable to convert to number: "..s) end
+    return val
+end
+
+local types = {}
+
+local builtin_types = {string=true,number=true,['file-in']='file',['file-out']='file',boolean=true}
+
+local function convert_parameter(ps,val)
+    if ps.converter then
+        val = ps.converter(val)
+    end
+    if ps.type == 'number' then
+        val = xtonumber(val)
+    elseif builtin_types[ps.type] == 'file' then
+        val = lapp.open(val,(ps.type == 'file-in' and 'r') or 'w' )
+    elseif ps.type == 'boolean' then
+        return val
+    end
+    if ps.constraint then
+        ps.constraint(val)
+    end
+    return val
+end
+
+--- add a new type to Lapp. These appear in parens after the value like
+-- a range constraint, e.g. '<ival> (integer) Process PID'
+-- @string name name of type
+-- @param converter either a function to convert values, or a Lua type name.
+-- @func[opt] constraint optional function to verify values, should use lapp.error
+-- if failed.
+function lapp.add_type (name,converter,constraint)
+    types[name] = {converter=converter,constraint=constraint}
+end
+
+local function force_short(short)
+    lapp.assert(#short==1,short..": short parameters should be one character")
+end
+
+-- deducing type of variable from default value;
+local function process_default (sval,vtype)
+    local val, success
+    if not vtype or vtype == 'number' then
+        val = tonumber(sval)
+    end
+    if val then -- we have a number!
+        return val,'number'
+    elseif filetypes[sval] then
+        local ft = filetypes[sval]
+        return ft[1],ft[2]
+    else
+        if sval == 'true' and not vtype then
+            return true, 'boolean'
+        end
+        if sval:match '^["\']' then sval = sval:sub(2,-2) end
+
+        local ps = types[vtype] or {}
+        ps.type = vtype
+
+        local show_usage_error = lapp.show_usage_error
+        lapp.show_usage_error = "throw"
+        success, val = pcall(convert_parameter, ps, sval)
+        lapp.show_usage_error = show_usage_error
+        if success then
+          return val, vtype or 'string'
+        end
+
+        return sval,vtype or 'string'
+    end
+end
+
+--- process a Lapp options string.
+-- Usually called as `lapp()`.
+-- @string str the options text
+-- @tparam {string} args a table of arguments (default is `_G.arg`)
+-- @return a table with parameter-value pairs
+function lapp.process_options_string(str,args)
+    local results = {}
+    local varargs
+    local arg = args or _G.arg
+    open_files = {}
+    parms = {}
+    aliases = {}
+    parmlist = {}
+
+    local function check_varargs(s)
+        local res,cnt = s:gsub('^%.%.%.%s*','')
+        return res, (cnt > 0)
+    end
+
+    local function set_result(ps,parm,val)
+        parm = type(parm) == "string" and parm:gsub("%W", "_") or parm -- so foo-bar becomes foo_bar in Lua
+        if not ps.varargs then
+            results[parm] = val
+        else
+            if not results[parm] then
+                results[parm] = { val }
+            else
+                append(results[parm],val)
+            end
+        end
+    end
+
+    usage = str
+
+    for _,a in ipairs(arg) do
+      if a == "-h" or a == "--help" then
+        return lapp.quit()
+      end
+    end
+
+
+    for line in lines(str) do
+        local res = {}
+        local optparm,defval,vtype,constraint,rest
+        line = lstrip(line)
+        local function check(str)
+            return match(str,line,res)
+        end
+
+        -- flags: either '-<short>', '-<short>,--<long>' or '--<long>'
+        if check '-$v{short}, --$o{long} $' or check '-$v{short} $' or check '--$o{long} $' then
+            if res.long then
+                optparm = res.long:gsub('[^%w%-]','_')  -- I'm not sure the $o pattern will let anything else through?
+                if #res.rest == 1 then optparm = optparm .. res.rest end
+                if res.short then aliases[res.short] = optparm  end
+            else
+                optparm = res.short
+            end
+            if res.short and not lapp.slack then force_short(res.short) end
+            res.rest, varargs = check_varargs(res.rest)
+        elseif check '$<{name} $'  then -- is it <parameter_name>?
+            -- so <input file...> becomes input_file ...
+            optparm,rest = res.name:match '([^%.]+)(.*)'
+            optparm = optparm:gsub('%A','_')
+            varargs = rest == '...'
+            append(parmlist,optparm)
+        end
+        -- this is not a pure doc line and specifies the flag/parameter type
+        if res.rest then
+            line = res.rest
+            res = {}
+            local optional
+            -- do we have ([optional] [<type>] [default <val>])?
+            if match('$({def} $',line,res) or match('$({def}',line,res) then
+                local typespec = strip(res.def)
+                local ftype, rest = typespec:match('^(%S+)(.*)$')
+                rest = strip(rest)
+                if ftype == 'optional' then
+                    ftype, rest = rest:match('^(%S+)(.*)$')
+                    rest = strip(rest)
+                    optional = true
+                end
+                local default
+                if ftype == 'default' then
+                    default = true
+                    if rest == '' then lapp.error("value must follow default") end
+                else -- a type specification
+                    if match('$f{min}..$f{max}',ftype,res) then
+                        -- a numerical range like 1..10
+                        local min,max = res.min,res.max
+                        vtype = 'number'
+                        constraint = function(x)
+                            range_check(x,min,max,optparm)
+                        end
+                    elseif not ftype:match '|' then -- plain type
+                        vtype = ftype
+                    else
+                        -- 'enum' type is a string which must belong to
+                        -- one of several distinct values
+                        local enums = ftype
+                        local enump = '|' .. enums .. '|'
+                        vtype = 'string'
+                        constraint = function(s)
+                            lapp.assert(enump:match('|'..s..'|'),
+                              "value '"..s.."' not in "..enums
+                            )
+                        end
+                    end
+                end
+                res.rest = rest
+                typespec = res.rest
+                -- optional 'default value' clause. Type is inferred as
+                -- 'string' or 'number' if there's no explicit type
+                if default or match('default $r{rest}',typespec,res) then
+                    defval,vtype = process_default(res.rest,vtype)
+                end
+            else -- must be a plain flag, no extra parameter required
+                defval = false
+                vtype = 'boolean'
+            end
+            local ps = {
+                type = vtype,
+                defval = defval,
+                required = defval == nil and not optional,
+                comment = res.rest or optparm,
+                constraint = constraint,
+                varargs = varargs
+            }
+            varargs = nil
+            if types[vtype] then
+                local converter = types[vtype].converter
+                if type(converter) == 'string' then
+                    ps.type = converter
+                else
+                    ps.converter = converter
+                end
+                ps.constraint = types[vtype].constraint
+            elseif not builtin_types[vtype] and vtype then
+                lapp.error(vtype.." is unknown type")
+            end
+            parms[optparm] = ps
+        end
+    end
+    -- cool, we have our parms, let's parse the command line args
+    local iparm = 1
+    local iextra = 1
+    local i = 1
+    local parm,ps,val
+    local end_of_flags = false
+
+    local function check_parm (parm)
+        local eqi = parm:find '[=:]'
+        if eqi then
+            tinsert(arg,i+1,parm:sub(eqi+1))
+            parm = parm:sub(1,eqi-1)
+        end
+        return parm,eqi
+    end
+
+    local function is_flag (parm)
+        return parms[aliases[parm] or parm]
+    end
+
+    while i <= #arg do
+        local theArg = arg[i]
+        local res = {}
+        -- after '--' we don't parse args and they end up in
+        -- the array part of the result (args[1] etc)
+        if theArg == '--' then
+            end_of_flags = true
+            iparm = #parmlist + 1
+            i = i + 1
+            theArg = arg[i]
+            if not theArg then
+                break
+            end
+        end
+        -- look for a flag, -<short flags> or --<long flag>
+        if not end_of_flags and (match('--$S{long}',theArg,res) or match('-$S{short}',theArg,res)) then
+            if res.long then -- long option
+                parm = check_parm(res.long)
+            elseif #res.short == 1 or is_flag(res.short) then
+                parm = res.short
+            else
+                local parmstr,eq = check_parm(res.short)
+                if not eq then
+                    parm = at(parmstr,1)
+                    local flag = is_flag(parm)
+                    if flag and flag.type ~= 'boolean' then
+                    --if isdigit(at(parmstr,2)) then
+                        -- a short option followed by a digit is an exception (for AW;))
+                        -- push ahead into the arg array
+                        tinsert(arg,i+1,parmstr:sub(2))
+                    else
+                        -- push multiple flags into the arg array!
+                        for k = 2,#parmstr do
+                            tinsert(arg,i+k-1,'-'..at(parmstr,k))
+                        end
+                    end
+                else
+                    parm = parmstr
+                end
+            end
+            if aliases[parm] then parm = aliases[parm] end
+            if not parms[parm] and (parm == 'h' or parm == 'help') then
+                lapp.quit()
+            end
+        else -- a parameter
+            parm = parmlist[iparm]
+            if not parm then
+               -- extra unnamed parameters are indexed starting at 1
+               parm = iextra
+               ps = { type = 'string' }
+               parms[parm] = ps
+               iextra = iextra + 1
+            else
+                ps = parms[parm]
+            end
+            if not ps.varargs then
+                iparm = iparm + 1
+            end
+            val = theArg
+        end
+        ps = parms[parm]
+        if not ps then lapp.error("unrecognized parameter: "..parm) end
+        if ps.type ~= 'boolean' then -- we need a value! This should follow
+            if not val then
+                i = i + 1
+                val = arg[i]
+                theArg = val
+            end
+            lapp.assert(val,parm.." was expecting a value")
+        else -- toggle boolean flags (usually false -> true)
+            val = not ps.defval
+        end
+        ps.used = true
+        val = convert_parameter(ps,val)
+        set_result(ps,parm,val)
+        if builtin_types[ps.type] == 'file' then
+            set_result(ps,parm..'_name',theArg)
+        end
+        if lapp.callback then
+            lapp.callback(parm,theArg,res)
+        end
+        i = i + 1
+        val = nil
+    end
+    -- check unused parms, set defaults and check if any required parameters were missed
+    for parm,ps in pairs(parms) do
+        if not ps.used then
+            if ps.required then lapp.error("missing required parameter: "..parm) end
+            set_result(ps,parm,ps.defval)
+        end
+    end
+    return results
+end
+
+if arg then
+    script = arg[0]
+    script = script or rawget(_G,"LAPP_SCRIPT") or "unknown"
+    -- strip dir and extension to get current script name
+    script = script:gsub('.+[\\/]',''):gsub('%.%a+$','')
+else
+    script = "inter"
+end
+
+
+setmetatable(lapp, {
+    __call = function(tbl,str,args) return lapp.process_options_string(str,args) end,
+})
+
+
+return lapp
+
+
+
+end,
+
+["pl.lexer"] = function()
+--------------------
+-- Module: 'pl.lexer'
+--------------------
+--- Lexical scanner for creating a sequence of tokens from text.
+-- `lexer.scan(s)` returns an iterator over all tokens found in the
+-- string `s`. This iterator returns two values, a token type string
+-- (such as 'string' for quoted string, 'iden' for identifier) and the value of the
+-- token.
+--
+-- Versions specialized for Lua and C are available; these also handle block comments
+-- and classify keywords as 'keyword' tokens. For example:
+--
+--    > s = 'for i=1,n do'
+--    > for t,v in lexer.lua(s)  do print(t,v) end
+--    keyword for
+--    iden    i
+--    =       =
+--    number  1
+--    ,       ,
+--    iden    n
+--    keyword do
+--
+-- See the Guide for further @{06-data.md.Lexical_Scanning|discussion}
+-- @module pl.lexer
+
+local strfind = string.find
+local strsub = string.sub
+local append = table.insert
+
+
+local function assert_arg(idx,val,tp)
+    if type(val) ~= tp then
+        error("argument "..idx.." must be "..tp, 2)
+    end
+end
+
+local lexer = {}
+
+local NUMBER1  = '^[%+%-]?%d+%.?%d*[eE][%+%-]?%d+'
+local NUMBER1a = '^[%+%-]?%d*%.%d+[eE][%+%-]?%d+'
+local NUMBER2  = '^[%+%-]?%d+%.?%d*'
+local NUMBER2a = '^[%+%-]?%d*%.%d+'
+local NUMBER3  = '^0x[%da-fA-F]+'
+local NUMBER4  = '^%d+%.?%d*[eE][%+%-]?%d+'
+local NUMBER4a = '^%d*%.%d+[eE][%+%-]?%d+'
+local NUMBER5  = '^%d+%.?%d*'
+local NUMBER5a = '^%d*%.%d+'
+local IDEN = '^[%a_][%w_]*'
+local WSPACE = '^%s+'
+local STRING1 = "^(['\"])%1" -- empty string
+local STRING2 = [[^(['"])(\*)%2%1]]
+local STRING3 = [[^(['"]).-[^\](\*)%2%1]]
+local CHAR1 = "^''"
+local CHAR2 = [[^'(\*)%1']]
+local CHAR3 = [[^'.-[^\](\*)%1']]
+local PREPRO = '^#.-[^\\]\n'
+
+local plain_matches,lua_matches,cpp_matches,lua_keyword,cpp_keyword
+
+local function tdump(tok)
+    return tok,tok
+end
+
+local function ndump(tok,options)
+    if options and options.number then
+        tok = tonumber(tok)
+    end
+    return "number",tok
+end
+
+-- regular strings, single or double quotes; usually we want them
+-- without the quotes
+local function sdump(tok,options)
+    if options and options.string then
+        tok = tok:sub(2,-2)
+    end
+    return "string",tok
+end
+
+-- long Lua strings need extra work to get rid of the quotes
+local function sdump_l(tok,options,findres)
+    if options and options.string then
+        local quotelen = 3
+        if findres[3] then
+            quotelen = quotelen + findres[3]:len()
+        end
+        tok = tok:sub(quotelen, -quotelen)
+        if tok:sub(1, 1) == "\n" then
+            tok = tok:sub(2)
+        end
+    end
+    return "string",tok
+end
+
+local function chdump(tok,options)
+    if options and options.string then
+        tok = tok:sub(2,-2)
+    end
+    return "char",tok
+end
+
+local function cdump(tok)
+    return "comment",tok
+end
+
+local function wsdump (tok)
+    return "space",tok
+end
+
+local function pdump (tok)
+    return "prepro",tok
+end
+
+local function plain_vdump(tok)
+    return "iden",tok
+end
+
+local function lua_vdump(tok)
+    if lua_keyword[tok] then
+        return "keyword",tok
+    else
+        return "iden",tok
+    end
+end
+
+local function cpp_vdump(tok)
+    if cpp_keyword[tok] then
+        return "keyword",tok
+    else
+        return "iden",tok
+    end
+end
+
+--- create a plain token iterator from a string or file-like object.
+-- @tparam string|file s a string or a file-like object with `:read()` method returning lines.
+-- @tab matches an optional match table - array of token descriptions.
+-- A token is described by a `{pattern, action}` pair, where `pattern` should match
+-- token body and `action` is a function called when a token of described type is found.
+-- @tab[opt] filter a table of token types to exclude, by default `{space=true}`
+-- @tab[opt] options a table of options; by default, `{number=true,string=true}`,
+-- which means convert numbers and strip string quotes.
+function lexer.scan(s,matches,filter,options)
+    local file = type(s) ~= 'string' and s
+    filter = filter or {space=true}
+    options = options or {number=true,string=true}
+    if filter then
+        if filter.space then filter[wsdump] = true end
+        if filter.comments then
+            filter[cdump] = true
+        end
+    end
+    if not matches then
+        if not plain_matches then
+            plain_matches = {
+                {WSPACE,wsdump},
+                {NUMBER3,ndump},
+                {IDEN,plain_vdump},
+                {NUMBER1,ndump},
+                {NUMBER1a,ndump},
+                {NUMBER2,ndump},
+                {NUMBER2a,ndump},
+                {STRING1,sdump},
+                {STRING2,sdump},
+                {STRING3,sdump},
+                {'^.',tdump}
+            }
+        end
+        matches = plain_matches
+    end
+
+    local line_nr = 0
+    local next_line = file and file:read()
+    local sz = file and 0 or #s
+    local idx = 1
+
+    local tlist_i
+    local tlist
+
+    local first_hit = true
+
+    local function iter(res)
+        local tp = type(res)
+
+        if tlist then -- returning the inserted token list
+            local cur = tlist[tlist_i]
+            if cur then
+                tlist_i = tlist_i + 1
+                return cur[1], cur[2]
+            else
+                tlist = nil
+            end
+        end
+
+        if tp == 'string' then -- search up to some special pattern
+            local i1,i2 = strfind(s,res,idx)
+            if i1 then
+                local tok = strsub(s,i1,i2)
+                idx = i2 + 1
+                return '', tok
+            else
+                idx = sz + 1
+                return '', ''
+            end
+
+        elseif tp == 'table' then -- insert a token list
+            tlist_i = 1
+            tlist = res
+            return '', ''
+
+        elseif tp ~= 'nil' then -- return position
+            return line_nr, idx
+
+        else -- look for next token
+            if first_hit then
+                if not file then line_nr = 1 end
+                first_hit = false
+            end
+
+            if idx > sz then
+                if file then
+                    if not next_line then
+                      return -- past the end of file, done
+                    end
+                    s = next_line
+                    line_nr = line_nr + 1
+                    next_line = file:read()
+                    if next_line then
+                        s = s .. '\n'
+                    end
+                    idx, sz = 1, #s
+                else
+                    return -- past the end of input, done
+                end
+            end
+
+            for _,m in ipairs(matches) do
+                local pat = m[1]
+                local fun = m[2]
+                local findres = {strfind(s,pat,idx)}
+                local i1, i2 = findres[1], findres[2]
+                if i1 then
+                    local tok = strsub(s,i1,i2)
+                    idx = i2 + 1
+                    local ret1, ret2
+                    if not (filter and filter[fun]) then
+                        lexer.finished = idx > sz
+                        ret1, ret2 = fun(tok, options, findres)
+                    end
+                    if not file and tok:find("\n") then
+                        -- Update line number.
+                        local _, newlines = tok:gsub("\n", {})
+                        line_nr = line_nr + newlines
+                    end
+                    if ret1 then
+                        return ret1, ret2 -- found a match
+                    else
+                        return iter() -- tail-call to try again
+                    end
+                end
+            end
+        end
+    end
+
+    return iter
+end
+
+local function isstring (s)
+    return type(s) == 'string'
+end
+
+--- insert tokens into a stream.
+-- @param tok a token stream
+-- @param a1 a string is the type, a table is a token list and
+-- a function is assumed to be a token-like iterator (returns type & value)
+-- @string a2 a string is the value
+function lexer.insert (tok,a1,a2)
+    if not a1 then return end
+    local ts
+    if isstring(a1) and isstring(a2) then
+        ts = {{a1,a2}}
+    elseif type(a1) == 'function' then
+        ts = {}
+        for t,v in a1() do
+            append(ts,{t,v})
+        end
+    else
+        ts = a1
+    end
+    tok(ts)
+end
+
+--- get everything in a stream upto a newline.
+-- @param tok a token stream
+-- @return a string
+function lexer.getline (tok)
+    local _,v = tok('.-\n')
+    return v
+end
+
+--- get current line number.
+-- @param tok a token stream
+-- @return the line number.
+-- if the input source is a file-like object,
+-- also return the column.
+function lexer.lineno (tok)
+    return tok(0)
+end
+
+--- get the rest of the stream.
+-- @param tok a token stream
+-- @return a string
+function lexer.getrest (tok)
+    local _,v = tok('.+')
+    return v
+end
+
+--- get the Lua keywords as a set-like table.
+-- So `res["and"]` etc would be `true`.
+-- @return a table
+function lexer.get_keywords ()
+    if not lua_keyword then
+        lua_keyword = {
+            ["and"] = true, ["break"] = true,  ["do"] = true,
+            ["else"] = true, ["elseif"] = true, ["end"] = true,
+            ["false"] = true, ["for"] = true, ["function"] = true,
+            ["if"] = true, ["in"] = true,  ["local"] = true, ["nil"] = true,
+            ["not"] = true, ["or"] = true, ["repeat"] = true,
+            ["return"] = true, ["then"] = true, ["true"] = true,
+            ["until"] = true,  ["while"] = true
+        }
+    end
+    return lua_keyword
+end
+
+--- create a Lua token iterator from a string or file-like object.
+-- Will return the token type and value.
+-- @string s the string
+-- @tab[opt] filter a table of token types to exclude, by default `{space=true,comments=true}`
+-- @tab[opt] options a table of options; by default, `{number=true,string=true}`,
+-- which means convert numbers and strip string quotes.
+function lexer.lua(s,filter,options)
+    filter = filter or {space=true,comments=true}
+    lexer.get_keywords()
+    if not lua_matches then
+        lua_matches = {
+            {WSPACE,wsdump},
+            {NUMBER3,ndump},
+            {IDEN,lua_vdump},
+            {NUMBER4,ndump},
+            {NUMBER4a,ndump},
+            {NUMBER5,ndump},
+            {NUMBER5a,ndump},
+            {STRING1,sdump},
+            {STRING2,sdump},
+            {STRING3,sdump},
+            {'^%-%-%[(=*)%[.-%]%1%]',cdump},
+            {'^%-%-.-\n',cdump},
+            {'^%[(=*)%[.-%]%1%]',sdump_l},
+            {'^==',tdump},
+            {'^~=',tdump},
+            {'^<=',tdump},
+            {'^>=',tdump},
+            {'^%.%.%.',tdump},
+            {'^%.%.',tdump},
+            {'^.',tdump}
+        }
+    end
+    return lexer.scan(s,lua_matches,filter,options)
+end
+
+--- create a C/C++ token iterator from a string or file-like object.
+-- Will return the token type type and value.
+-- @string s the string
+-- @tab[opt] filter a table of token types to exclude, by default `{space=true,comments=true}`
+-- @tab[opt] options a table of options; by default, `{number=true,string=true}`,
+-- which means convert numbers and strip string quotes.
+function lexer.cpp(s,filter,options)
+    filter = filter or {space=true,comments=true}
+    if not cpp_keyword then
+        cpp_keyword = {
+            ["class"] = true, ["break"] = true,  ["do"] = true, ["sizeof"] = true,
+            ["else"] = true, ["continue"] = true, ["struct"] = true,
+            ["false"] = true, ["for"] = true, ["public"] = true, ["void"] = true,
+            ["private"] = true, ["protected"] = true, ["goto"] = true,
+            ["if"] = true, ["static"] = true,  ["const"] = true, ["typedef"] = true,
+            ["enum"] = true, ["char"] = true, ["int"] = true, ["bool"] = true,
+            ["long"] = true, ["float"] = true, ["true"] = true, ["delete"] = true,
+            ["double"] = true,  ["while"] = true, ["new"] = true,
+            ["namespace"] = true, ["try"] = true, ["catch"] = true,
+            ["switch"] = true, ["case"] = true, ["extern"] = true,
+            ["return"] = true,["default"] = true,['unsigned']  = true,['signed'] = true,
+            ["union"] =  true, ["volatile"] = true, ["register"] = true,["short"] = true,
+        }
+    end
+    if not cpp_matches then
+        cpp_matches = {
+            {WSPACE,wsdump},
+            {PREPRO,pdump},
+            {NUMBER3,ndump},
+            {IDEN,cpp_vdump},
+            {NUMBER4,ndump},
+            {NUMBER4a,ndump},
+            {NUMBER5,ndump},
+            {NUMBER5a,ndump},
+            {CHAR1,chdump},
+            {CHAR2,chdump},
+            {CHAR3,chdump},
+            {STRING1,sdump},
+            {STRING2,sdump},
+            {STRING3,sdump},
+            {'^//.-\n',cdump},
+            {'^/%*.-%*/',cdump},
+            {'^==',tdump},
+            {'^!=',tdump},
+            {'^<=',tdump},
+            {'^>=',tdump},
+            {'^->',tdump},
+            {'^&&',tdump},
+            {'^||',tdump},
+            {'^%+%+',tdump},
+            {'^%-%-',tdump},
+            {'^%+=',tdump},
+            {'^%-=',tdump},
+            {'^%*=',tdump},
+            {'^/=',tdump},
+            {'^|=',tdump},
+            {'^%^=',tdump},
+            {'^::',tdump},
+            {'^.',tdump}
+        }
+    end
+    return lexer.scan(s,cpp_matches,filter,options)
+end
+
+--- get a list of parameters separated by a delimiter from a stream.
+-- @param tok the token stream
+-- @string[opt=')'] endtoken end of list. Can be '\n'
+-- @string[opt=','] delim separator
+-- @return a list of token lists.
+function lexer.get_separated_list(tok,endtoken,delim)
+    endtoken = endtoken or ')'
+    delim = delim or ','
+    local parm_values = {}
+    local level = 1 -- used to count ( and )
+    local tl = {}
+    local function tappend (tl,t,val)
+        val = val or t
+        append(tl,{t,val})
+    end
+    local is_end
+    if endtoken == '\n' then
+        is_end = function(t,val)
+            return t == 'space' and val:find '\n'
+        end
+    else
+        is_end = function (t)
+            return t == endtoken
+        end
+    end
+    local token,value
+    while true do
+        token,value=tok()
+        if not token then return nil,'EOS' end -- end of stream is an error!
+        if is_end(token,value) and level == 1 then
+            append(parm_values,tl)
+            break
+        elseif token == '(' then
+            level = level + 1
+            tappend(tl,'(')
+        elseif token == ')' then
+            level = level - 1
+            if level == 0 then -- finished with parm list
+                append(parm_values,tl)
+                break
+            else
+                tappend(tl,')')
+            end
+        elseif token == delim and level == 1 then
+            append(parm_values,tl) -- a new parm
+            tl = {}
+        else
+            tappend(tl,token,value)
+        end
+    end
+    return parm_values,{token,value}
+end
+
+--- get the next non-space token from the stream.
+-- @param tok the token stream.
+function lexer.skipws (tok)
+    local t,v = tok()
+    while t == 'space' do
+        t,v = tok()
+    end
+    return t,v
+end
+
+local skipws = lexer.skipws
+
+--- get the next token, which must be of the expected type.
+-- Throws an error if this type does not match!
+-- @param tok the token stream
+-- @string expected_type the token type
+-- @bool no_skip_ws whether we should skip whitespace
+function lexer.expecting (tok,expected_type,no_skip_ws)
+    assert_arg(1,tok,'function')
+    assert_arg(2,expected_type,'string')
+    local t,v
+    if no_skip_ws then
+        t,v = tok()
+    else
+        t,v = skipws(tok)
+    end
+    if t ~= expected_type then error ("expecting "..expected_type,2) end
+    return v
+end
+
+return lexer
+
+end,
+
+["pl.List"] = function()
+--------------------
+-- Module: 'pl.List'
+--------------------
+--- Python-style list class.
+--
+-- **Please Note**: methods that change the list will return the list.
+-- This is to allow for method chaining, but please note that `ls = ls:sort()`
+-- does not mean that a new copy of the list is made. In-place (mutable) methods
+-- are marked as returning 'the list' in this documentation.
+--
+-- See the Guide for further @{02-arrays.md.Python_style_Lists|discussion}
+--
+-- See <a href="http://www.python.org/doc/current/tut/tut.html">http://www.python.org/doc/current/tut/tut.html</a>, section 5.1
+--
+-- **Note**: The comments before some of the functions are from the Python docs
+-- and contain Python code.
+--
+-- Written for Lua version Nick Trout 4.0; Redone for Lua 5.1, Steve Donovan.
+--
+-- Dependencies: `pl.utils`, `pl.tablex`, `pl.class`
+-- @classmod pl.List
+-- @pragma nostrip
+
+local tinsert,tremove,concat,tsort = table.insert,table.remove,table.concat,table.sort
+local setmetatable, getmetatable,type,tostring,string = setmetatable,getmetatable,type,tostring,string
+local tablex = require 'pl.tablex'
+local filter,imap,imap2,reduce,transform,tremovevalues = tablex.filter,tablex.imap,tablex.imap2,tablex.reduce,tablex.transform,tablex.removevalues
+local tsub = tablex.sub
+local utils = require 'pl.utils'
+local class = require 'pl.class'
+
+local array_tostring,split,assert_arg,function_arg = utils.array_tostring,utils.split,utils.assert_arg,utils.function_arg
+local normalize_slice = tablex._normalize_slice
+
+-- metatable for our list and map objects has already been defined..
+local Multimap = utils.stdmt.MultiMap
+local List = utils.stdmt.List
+
+local iter
+
+class(nil,nil,List)
+
+-- we want the result to be _covariant_, i.e. t must have type of obj if possible
+local function makelist (t,obj)
+    local klass = List
+    if obj then
+        klass = getmetatable(obj)
+    end
+    return setmetatable(t,klass)
+end
+
+local function simple_table(t)
+    return type(t) == 'table' and not getmetatable(t) and #t > 0
+end
+
+function List._create (src)
+    if simple_table(src) then return src end
+end
+
+function List:_init (src)
+    if self == src then return end -- existing table used as self!
+    if src then
+        for v in iter(src) do
+            tinsert(self,v)
+        end
+    end
+end
+
+--- Create a new list. Can optionally pass a table;
+-- passing another instance of List will cause a copy to be created;
+-- this will return a plain table with an appropriate metatable.
+-- we pass anything which isn't a simple table to iterate() to work out
+-- an appropriate iterator
+-- @see List.iterate
+-- @param[opt] t An optional list-like table
+-- @return a new List
+-- @usage ls = List();  ls = List {1,2,3,4}
+-- @function List.new
+
+List.new = List
+
+--- Make a copy of an existing list.
+-- The difference from a plain 'copy constructor' is that this returns
+-- the actual List subtype.
+function List:clone()
+    local ls = makelist({},self)
+    ls:extend(self)
+    return ls
+end
+
+--- Add an item to the end of the list.
+-- @param i An item
+-- @return the list
+function List:append(i)
+    tinsert(self,i)
+    return self
+end
+
+List.push = tinsert
+
+--- Extend the list by appending all the items in the given list.
+-- equivalent to 'a[len(a):] = L'.
+-- @tparam List L Another List
+-- @return the list
+function List:extend(L)
+    assert_arg(1,L,'table')
+    for i = 1,#L do tinsert(self,L[i]) end
+    return self
+end
+
+--- Insert an item at a given position. i is the index of the
+-- element before which to insert.
+-- @int i index of element before whichh to insert
+-- @param x A data item
+-- @return the list
+function List:insert(i, x)
+    assert_arg(1,i,'number')
+    tinsert(self,i,x)
+    return self
+end
+
+--- Insert an item at the begining of the list.
+-- @param x a data item
+-- @return the list
+function List:put (x)
+    return self:insert(1,x)
+end
+
+--- Remove an element given its index.
+-- (equivalent of Python's del s[i])
+-- @int i the index
+-- @return the list
+function List:remove (i)
+    assert_arg(1,i,'number')
+    tremove(self,i)
+    return self
+end
+
+--- Remove the first item from the list whose value is given.
+-- (This is called 'remove' in Python; renamed to avoid confusion
+-- with table.remove)
+-- Return nil if there is no such item.
+-- @param x A data value
+-- @return the list
+function List:remove_value(x)
+    for i=1,#self do
+        if self[i]==x then tremove(self,i) return self end
+    end
+    return self
+ end
+
+--- Remove the item at the given position in the list, and return it.
+-- If no index is specified, a:pop() returns the last item in the list.
+-- The item is also removed from the list.
+-- @int[opt] i An index
+-- @return the item
+function List:pop(i)
+    if not i then i = #self end
+    assert_arg(1,i,'number')
+    return tremove(self,i)
+end
+
+List.get = List.pop
+
+--- Return the index in the list of the first item whose value is given.
+-- Return nil if there is no such item.
+-- @function List:index
+-- @param x A data value
+-- @int[opt=1] idx where to start search
+-- @return the index, or nil if not found.
+
+local tfind = tablex.find
+List.index = tfind
+
+--- Does this list contain the value?
+-- @param x A data value
+-- @return true or false
+function List:contains(x)
+    return tfind(self,x) and true or false
+end
+
+--- Return the number of times value appears in the list.
+-- @param x A data value
+-- @return number of times x appears
+function List:count(x)
+    local cnt=0
+    for i=1,#self do
+        if self[i]==x then cnt=cnt+1 end
+    end
+    return cnt
+end
+
+--- Sort the items of the list, in place.
+-- @func[opt='<'] cmp an optional comparison function
+-- @return the list
+function List:sort(cmp)
+    if cmp then cmp = function_arg(1,cmp) end
+    tsort(self,cmp)
+    return self
+end
+
+--- Return a sorted copy of this list.
+-- @func[opt='<'] cmp an optional comparison function
+-- @return a new list
+function List:sorted(cmp)
+    return List(self):sort(cmp)
+end
+
+--- Reverse the elements of the list, in place.
+-- @return the list
+function List:reverse()
+    local t = self
+    local n = #t
+    for i = 1,n/2 do
+        t[i],t[n] = t[n],t[i]
+        n = n - 1
+    end
+    return self
+end
+
+--- Return the minimum and the maximum value of the list.
+-- @return minimum value
+-- @return maximum value
+function List:minmax()
+    local vmin,vmax = 1e70,-1e70
+    for i = 1,#self do
+        local v = self[i]
+        if v < vmin then vmin = v end
+        if v > vmax then vmax = v end
+    end
+    return vmin,vmax
+end
+
+--- Emulate list slicing.  like  'list[first:last]' in Python.
+-- If first or last are negative then they are relative to the end of the list
+-- eg. slice(-2) gives last 2 entries in a list, and
+-- slice(-4,-2) gives from -4th to -2nd
+-- @param first An index
+-- @param last An index
+-- @return a new List
+function List:slice(first,last)
+    return tsub(self,first,last)
+end
+
+--- Empty the list.
+-- @return the list
+function List:clear()
+    for i=1,#self do tremove(self) end
+    return self
+end
+
+local eps = 1.0e-10
+
+--- Emulate Python's range(x) function.
+-- Include it in List table for tidiness
+-- @int start A number
+-- @int[opt] finish A number greater than start; if absent,
+-- then start is 1 and finish is start
+-- @int[opt=1] incr an increment (may be less than 1)
+-- @return a List from start .. finish
+-- @usage List.range(0,3) == List{0,1,2,3}
+-- @usage List.range(4) = List{1,2,3,4}
+-- @usage List.range(5,1,-1) == List{5,4,3,2,1}
+function List.range(start,finish,incr)
+    if not finish then
+        finish = start
+        start = 1
+    end
+    if incr then
+    assert_arg(3,incr,'number')
+    if math.ceil(incr) ~= incr then finish = finish + eps end
+    else
+        incr = 1
+    end
+    assert_arg(1,start,'number')
+    assert_arg(2,finish,'number')
+    local t = List()
+    for i=start,finish,incr do tinsert(t,i) end
+    return t
+end
+
+--- list:len() is the same as #list.
+function List:len()
+    return #self
+end
+
+-- Extended operations --
+
+--- Remove a subrange of elements.
+-- equivalent to 'del s[i1:i2]' in Python.
+-- @int i1 start of range
+-- @int i2 end of range
+-- @return the list
+function List:chop(i1,i2)
+    return tremovevalues(self,i1,i2)
+end
+
+--- Insert a sublist into a list
+-- equivalent to 's[idx:idx] = list' in Python
+-- @int idx index
+-- @tparam List list list to insert
+-- @return the list
+-- @usage  l = List{10,20}; l:splice(2,{21,22});  assert(l == List{10,21,22,20})
+function List:splice(idx,list)
+    assert_arg(1,idx,'number')
+    idx = idx - 1
+    local i = 1
+    for v in iter(list) do
+        tinsert(self,i+idx,v)
+        i = i + 1
+    end
+    return self
+end
+
+--- General slice assignment s[i1:i2] = seq.
+-- @int i1  start index
+-- @int i2  end index
+-- @tparam List seq a list
+-- @return the list
+function List:slice_assign(i1,i2,seq)
+    assert_arg(1,i1,'number')
+    assert_arg(1,i2,'number')
+    i1,i2 = normalize_slice(self,i1,i2)
+    if i2 >= i1 then self:chop(i1,i2) end
+    self:splice(i1,seq)
+    return self
+end
+
+--- Concatenation operator.
+-- @within metamethods
+-- @tparam List L another List
+-- @return a new list consisting of the list with the elements of the new list appended
+function List:__concat(L)
+    assert_arg(1,L,'table')
+    local ls = self:clone()
+    ls:extend(L)
+    return ls
+end
+
+--- Equality operator ==.  True iff all elements of two lists are equal.
+-- @within metamethods
+-- @tparam List L another List
+-- @return true or false
+function List:__eq(L)
+    if #self ~= #L then return false end
+    for i = 1,#self do
+        if self[i] ~= L[i] then return false end
+    end
+    return true
+end
+
+--- Join the elements of a list using a delimiter.
+-- This method uses tostring on all elements.
+-- @string[opt=''] delim a delimiter string, can be empty.
+-- @return a string
+function List:join (delim)
+    delim = delim or ''
+    assert_arg(1,delim,'string')
+    return concat(array_tostring(self),delim)
+end
+
+--- Join a list of strings. <br>
+-- Uses `table.concat` directly.
+-- @function List:concat
+-- @string[opt=''] delim a delimiter
+-- @return a string
+List.concat = concat
+
+local function tostring_q(val)
+    local s = tostring(val)
+    if type(val) == 'string' then
+        s = '"'..s..'"'
+    end
+    return s
+end
+
+--- How our list should be rendered as a string. Uses join().
+-- @within metamethods
+-- @see List:join
+function List:__tostring()
+    return '{'..self:join(',',tostring_q)..'}'
+end
+
+--- Call the function on each element of the list.
+-- @func fun a function or callable object
+-- @param ... optional values to pass to function
+function List:foreach (fun,...)
+    fun = function_arg(1,fun)
+    for i = 1,#self do
+        fun(self[i],...)
+    end
+end
+
+local function lookup_fun (obj,name)
+    local f = obj[name]
+    if not f then error(type(obj).." does not have method "..name,3) end
+    return f
+end
+
+--- Call the named method on each element of the list.
+-- @string name the method name
+-- @param ... optional values to pass to function
+function List:foreachm (name,...)
+    for i = 1,#self do
+        local obj = self[i]
+        local f = lookup_fun(obj,name)
+        f(obj,...)
+    end
+end
+
+--- Create a list of all elements which match a function.
+-- @func fun a boolean function
+-- @param[opt] arg optional argument to be passed as second argument of the predicate
+-- @return a new filtered list.
+function List:filter (fun,arg)
+    return makelist(filter(self,fun,arg),self)
+end
+
+--- Split a string using a delimiter.
+-- @string s the string
+-- @string[opt] delim the delimiter (default spaces)
+-- @return a List of strings
+-- @see pl.utils.split
+function List.split (s,delim)
+    assert_arg(1,s,'string')
+    return makelist(split(s,delim))
+end
+
+--- Apply a function to all elements.
+-- Any extra arguments will be passed to the function.
+-- @func fun a function of at least one argument
+-- @param ... arbitrary extra arguments.
+-- @return a new list: {f(x) for x in self}
+-- @usage List{'one','two'}:map(string.upper) == {'ONE','TWO'}
+-- @see pl.tablex.imap
+function List:map (fun,...)
+    return makelist(imap(fun,self,...),self)
+end
+
+--- Apply a function to all elements, in-place.
+-- Any extra arguments are passed to the function.
+-- @func fun A function that takes at least one argument
+-- @param ... arbitrary extra arguments.
+-- @return the list.
+function List:transform (fun,...)
+    transform(fun,self,...)
+    return self
+end
+
+--- Apply a function to elements of two lists.
+-- Any extra arguments will be passed to the function
+-- @func fun a function of at least two arguments
+-- @tparam List ls another list
+-- @param ... arbitrary extra arguments.
+-- @return a new list: {f(x,y) for x in self, for x in arg1}
+-- @see pl.tablex.imap2
+function List:map2 (fun,ls,...)
+    return makelist(imap2(fun,self,ls,...),self)
+end
+
+--- apply a named method to all elements.
+-- Any extra arguments will be passed to the method.
+-- @string name name of method
+-- @param ... extra arguments
+-- @return a new list of the results
+-- @see pl.seq.mapmethod
+function List:mapm (name,...)
+    local res = {}
+    for i = 1,#self do
+      local val = self[i]
+      local fn = lookup_fun(val,name)
+      res[i] = fn(val,...)
+    end
+    return makelist(res,self)
+end
+
+local function composite_call (method,f)
+    return function(self,...)
+        return self[method](self,f,...)
+    end
+end
+
+function List.default_map_with(T)
+    return function(self,name)
+        local m
+        if T then
+            local f = lookup_fun(T,name)
+            m = composite_call('map',f)
+        else
+            m = composite_call('mapn',name)
+        end
+        getmetatable(self)[name] = m -- and cache..
+        return m
+    end
+end
+
+List.default_map = List.default_map_with
+
+--- 'reduce' a list using a binary function.
+-- @func fun a function of two arguments
+-- @return result of the function
+-- @see pl.tablex.reduce
+function List:reduce (fun)
+    return reduce(fun,self)
+end
+
+--- Partition a list using a classifier function.
+-- The function may return nil, but this will be converted to the string key '<nil>'.
+-- @func fun a function of at least one argument
+-- @param ... will also be passed to the function
+-- @treturn MultiMap a table where the keys are the returned values, and the values are Lists
+-- of values where the function returned that key.
+-- @see pl.MultiMap
+function List:partition (fun,...)
+    fun = function_arg(1,fun)
+    local res = {}
+    for i = 1,#self do
+        local val = self[i]
+        local klass = fun(val,...)
+        if klass == nil then klass = '<nil>' end
+        if not res[klass] then res[klass] = List() end
+        res[klass]:append(val)
+    end
+    return setmetatable(res,Multimap)
+end
+
+--- return an iterator over all values.
+function List:iter ()
+    return iter(self)
+end
+
+--- Create an iterator over a seqence.
+-- This captures the Python concept of 'sequence'.
+-- For tables, iterates over all values with integer indices.
+-- @param seq a sequence; a string (over characters), a table, a file object (over lines) or an iterator function
+-- @usage for x in iterate {1,10,22,55} do io.write(x,',') end ==> 1,10,22,55
+-- @usage for ch in iterate 'help' do do io.write(ch,' ') end ==> h e l p
+function List.iterate(seq)
+    if type(seq) == 'string' then
+        local idx = 0
+        local n = #seq
+        local sub = string.sub
+        return function ()
+            idx = idx + 1
+            if idx > n then return nil
+            else
+                return sub(seq,idx,idx)
+            end
+        end
+    elseif type(seq) == 'table' then
+        local idx = 0
+        local n = #seq
+        return function()
+            idx = idx + 1
+            if idx > n then return nil
+            else
+                return seq[idx]
+            end
+        end
+    elseif type(seq) == 'function' then
+        return seq
+    elseif type(seq) == 'userdata' and io.type(seq) == 'file' then
+        return seq:lines()
+    end
+end
+iter = List.iterate
+
+return List
+
+
+end,
+
+["pl.luabalanced"] = function()
+--------------------
+-- Module: 'pl.luabalanced'
+--------------------
+--- Extract delimited Lua sequences from strings.
+-- Inspired by Damian Conway's Text::Balanced in Perl. <br/>
+-- <ul>
+--   <li>[1] <a href="http://lua-users.org/wiki/LuaBalanced">Lua Wiki Page</a></li>
+--   <li>[2] http://search.cpan.org/dist/Text-Balanced/lib/Text/Balanced.pm</li>
+-- </ul> <br/>
+-- <pre class=example>
+-- local lb = require "pl.luabalanced"
+-- --Extract Lua expression starting at position 4.
+--  print(lb.match_expression("if x^2 + x > 5 then print(x) end", 4))
+--  --> x^2 + x > 5     16
+-- --Extract Lua string starting at (default) position 1.
+-- print(lb.match_string([["test\"123" .. "more"]]))
+-- --> "test\"123"     12
+-- </pre>
+-- (c) 2008, David Manura, Licensed under the same terms as Lua (MIT license).
+-- @class module
+-- @name pl.luabalanced
+
+local M = {}
+
+local assert = assert
+
+-- map opening brace <-> closing brace.
+local ends = { ['('] = ')', ['{'] = '}', ['['] = ']' }
+local begins = {}; for k,v in pairs(ends) do begins[v] = k end
+
+
+-- Match Lua string in string <s> starting at position <pos>.
+-- Returns <string>, <posnew>, where <string> is the matched
+-- string (or nil on no match) and <posnew> is the character
+-- following the match (or <pos> on no match).
+-- Supports all Lua string syntax: "...", '...', [[...]], [=[...]=], etc.
+local function match_string(s, pos)
+  pos = pos or 1
+  local posa = pos
+  local c = s:sub(pos,pos)
+  if c == '"' or c == "'" then
+    pos = pos + 1
+    while 1 do
+      pos = assert(s:find("[" .. c .. "\\]", pos), 'syntax error')
+      if s:sub(pos,pos) == c then
+        local part = s:sub(posa, pos)
+        return part, pos + 1
+      else
+        pos = pos + 2
+      end
+    end
+  else
+    local sc = s:match("^%[(=*)%[", pos)
+    if sc then
+      local _; _, pos = s:find("%]" .. sc .. "%]", pos)
+      assert(pos)
+      local part = s:sub(posa, pos)
+      return part, pos + 1
+    else
+      return nil, pos
+    end
+  end
+end
+M.match_string = match_string
+
+
+-- Match bracketed Lua expression, e.g. "(...)", "{...}", "[...]", "[[...]]",
+-- [=[...]=], etc.
+-- Function interface is similar to match_string.
+local function match_bracketed(s, pos)
+  pos = pos or 1
+  local posa = pos
+  local ca = s:sub(pos,pos)
+  if not ends[ca] then
+    return nil, pos
+  end
+  local stack = {}
+  while 1 do
+    pos = s:find('[%(%{%[%)%}%]\"\']', pos)
+    assert(pos, 'syntax error: unbalanced')
+    local c = s:sub(pos,pos)
+    if c == '"' or c == "'" then
+      local part; part, pos = match_string(s, pos)
+      assert(part)
+    elseif ends[c] then -- open
+      local mid, posb
+      if c == '[' then mid, posb = s:match('^%[(=*)%[()', pos) end
+      if mid then
+        pos = s:match('%]' .. mid .. '%]()', posb)
+        assert(pos, 'syntax error: long string not terminated')
+        if #stack == 0 then
+          local part = s:sub(posa, pos-1)
+          return part, pos
+        end
+      else
+        stack[#stack+1] = c
+        pos = pos + 1
+      end
+    else -- close
+      assert(stack[#stack] == assert(begins[c]), 'syntax error: unbalanced')
+      stack[#stack] = nil
+      if #stack == 0 then
+        local part = s:sub(posa, pos)
+        return part, pos+1
+      end
+      pos = pos + 1
+    end
+  end
+end
+M.match_bracketed = match_bracketed
+
+
+-- Match Lua comment, e.g. "--...\n", "--[[...]]", "--[=[...]=]", etc.
+-- Function interface is similar to match_string.
+local function match_comment(s, pos)
+  pos = pos or 1
+  if s:sub(pos, pos+1) ~= '--' then
+    return nil, pos
+  end
+  pos = pos + 2
+  local partt, post = match_string(s, pos)
+  if partt then
+    return '--' .. partt, post
+  end
+  local part; part, pos = s:match('^([^\n]*\n?)()', pos)
+  return '--' .. part, pos
+end
+
+
+-- Match Lua expression, e.g. "a + b * c[e]".
+-- Function interface is similar to match_string.
+local wordop = {['and']=true, ['or']=true, ['not']=true}
+local is_compare = {['>']=true, ['<']=true, ['~']=true}
+local function match_expression(s, pos)
+  pos = pos or 1
+  local _
+  local posa = pos
+  local lastident
+  local poscs, posce
+  while pos do
+    local c = s:sub(pos,pos)
+    if c == '"' or c == "'" or c == '[' and s:find('^[=%[]', pos+1) then
+      local part; part, pos = match_string(s, pos)
+      assert(part, 'syntax error')
+    elseif c == '-' and s:sub(pos+1,pos+1) == '-' then
+      -- note: handle adjacent comments in loop to properly support
+      -- backtracing (poscs/posce).
+      poscs = pos
+      while s:sub(pos,pos+1) == '--' do
+        local part; part, pos = match_comment(s, pos)
+        assert(part)
+        pos = s:match('^%s*()', pos)
+        posce = pos
+      end
+    elseif c == '(' or c == '{' or c == '[' then
+      _, pos = match_bracketed(s, pos)
+    elseif c == '=' and s:sub(pos+1,pos+1) == '=' then
+      pos = pos + 2  -- skip over two-char op containing '='
+    elseif c == '=' and is_compare[s:sub(pos-1,pos-1)] then
+      pos = pos + 1  -- skip over two-char op containing '='
+    elseif c:match'^[%)%}%];,=]' then
+      local part = s:sub(posa, pos-1)
+      return part, pos
+    elseif c:match'^[%w_]' then
+      local newident,newpos = s:match('^([%w_]+)()', pos)
+      if pos ~= posa and not wordop[newident] then -- non-first ident
+        local pose = ((posce == pos) and poscs or pos) - 1
+        while s:match('^%s', pose) do pose = pose - 1 end
+        local ce = s:sub(pose,pose)
+        if ce:match'[%)%}\'\"%]]' or
+           ce:match'[%w_]' and not wordop[lastident]
+        then
+          local part = s:sub(posa, pos-1)
+          return part, pos
+        end
+      end
+      lastident, pos = newident, newpos
+    else
+      pos = pos + 1
+    end
+    pos = s:find('[%(%{%[%)%}%]\"\';,=%w_%-]', pos)
+  end
+  local part = s:sub(posa, #s)
+  return part, #s+1
+end
+M.match_expression = match_expression
+
+
+-- Match name list (zero or more names).  E.g. "a,b,c"
+-- Function interface is similar to match_string,
+-- but returns array as match.
+local function match_namelist(s, pos)
+  pos = pos or 1
+  local list = {}
+  while 1 do
+    local c = #list == 0 and '^' or '^%s*,%s*'
+    local item, post = s:match(c .. '([%a_][%w_]*)%s*()', pos)
+    if item then pos = post else break end
+    list[#list+1] = item
+  end
+  return list, pos
+end
+M.match_namelist = match_namelist
+
+
+-- Match expression list (zero or more expressions).  E.g. "a+b,b*c".
+-- Function interface is similar to match_string,
+-- but returns array as match.
+local function match_explist(s, pos)
+  pos = pos or 1
+  local list = {}
+  while 1 do
+    if #list ~= 0 then
+      local post = s:match('^%s*,%s*()', pos)
+      if post then pos = post else break end
+    end
+    local item; item, pos = match_expression(s, pos)
+    assert(item, 'syntax error')
+    list[#list+1] = item
+  end
+  return list, pos
+end
+M.match_explist = match_explist
+
+
+-- Replace snippets of code in Lua code string <s>
+-- using replacement function f(u,sin) --> sout.
+-- <u> is the type of snippet ('c' = comment, 's' = string,
+-- 'e' = any other code).
+-- Snippet is replaced with <sout> (unless <sout> is nil or false, in
+-- which case the original snippet is kept)
+-- This is somewhat analogous to string.gsub .
+local function gsub(s, f)
+  local pos = 1
+  local posa = 1
+  local sret = ''
+  while 1 do
+    pos = s:find('[%-\'\"%[]', pos)
+    if not pos then break end
+    if s:match('^%-%-', pos) then
+      local exp = s:sub(posa, pos-1)
+      if #exp > 0 then sret = sret .. (f('e', exp) or exp) end
+      local comment; comment, pos = match_comment(s, pos)
+      sret = sret .. (f('c', assert(comment)) or comment)
+      posa = pos
+    else
+      local posb = s:find('^[\'\"%[]', pos)
+      local str
+      if posb then str, pos = match_string(s, posb) end
+      if str then
+        local exp = s:sub(posa, posb-1)
+        if #exp > 0 then sret = sret .. (f('e', exp) or exp) end
+        sret = sret .. (f('s', str) or str)
+        posa = pos
+      else
+        pos = pos + 1
+      end
+    end
+  end
+  local exp = s:sub(posa)
+  if #exp > 0 then sret = sret .. (f('e', exp) or exp) end
+  return sret
+end
+M.gsub = gsub
+
+
+return M
+
+end,
+
+["pl.Map"] = function()
+--------------------
+-- Module: 'pl.Map'
+--------------------
+--- A Map class.
+--
+--    > Map = require 'pl.Map'
+--    > m = Map{one=1,two=2}
+--    > m:update {three=3,four=4,two=20}
+--    > = m == M{one=1,two=20,three=3,four=4}
+--    true
+--
+-- Dependencies: `pl.utils`, `pl.class`, `pl.tablex`, `pl.pretty`
+-- @classmod pl.Map
+
+local tablex = require 'pl.tablex'
+local utils = require 'pl.utils'
+local stdmt = utils.stdmt
+local deepcompare = tablex.deepcompare
+
+local pretty_write = require 'pl.pretty' . write
+local Map = stdmt.Map
+local Set = stdmt.Set
+
+local class = require 'pl.class'
+
+-- the Map class ---------------------
+class(nil,nil,Map)
+
+function Map:_init (t)
+    local mt = getmetatable(t)
+    if mt == Set or mt == Map then
+        self:update(t)
+    else
+        return t -- otherwise assumed to be a map-like table
+    end
+end
+
+
+local function makelist(t)
+    return setmetatable(t, require('pl.List'))
+end
+
+--- list of keys.
+Map.keys = tablex.keys
+
+--- list of values.
+Map.values = tablex.values
+
+--- return an iterator over all key-value pairs.
+function Map:iter ()
+    return pairs(self)
+end
+
+--- return a List of all key-value pairs, sorted by the keys.
+function Map:items()
+    local ls = makelist(tablex.pairmap (function (k,v) return makelist {k,v} end, self))
+    ls:sort(function(t1,t2) return t1[1] < t2[1] end)
+    return ls
+end
+
+--- set a value in the map if it doesn't exist yet.
+-- @param key the key
+-- @param default value to set
+-- @return the value stored in the map (existing value, or the new value)
+function Map:setdefault(key, default)
+    local val = self[key]
+    if val ~= nil then
+        return val
+    end
+    self:set(key,default)
+   return default
+end
+
+--- size of map.
+-- note: this is a relatively expensive operation!
+-- @class function
+-- @name Map:len
+Map.len = tablex.size
+
+--- put a value into the map.
+-- This will remove the key if the value is `nil`
+-- @param key the key
+-- @param val the value
+function Map:set (key,val)
+    self[key] = val
+end
+
+--- get a value from the map.
+-- @param key the key
+-- @return the value, or nil if not found.
+function Map:get (key)
+    return rawget(self,key)
+end
+
+local index_by = tablex.index_by
+
+--- get a list of values indexed by a list of keys.
+-- @param keys a list-like table of keys
+-- @return a new list
+function Map:getvalues (keys)
+    return makelist(index_by(self,keys))
+end
+
+--- update the map using key/value pairs from another table.
+-- @tab table
+-- @function Map:update
+Map.update = tablex.update
+
+--- equality between maps.
+-- @within metamethods
+-- @tparam Map m another map.
+function Map:__eq (m)
+    -- note we explicitly ask deepcompare _not_ to use __eq!
+    return deepcompare(self,m,true)
+end
+
+--- string representation of a map.
+-- @within metamethods
+function Map:__tostring ()
+    return pretty_write(self,'')
+end
+
+return Map
+
+end,
+
+["pl.MultiMap"] = function()
+--------------------
+-- Module: 'pl.MultiMap'
+--------------------
+--- MultiMap, a Map which has multiple values per key.
+--
+-- Dependencies: `pl.utils`, `pl.class`, `pl.List`, `pl.Map`
+-- @classmod pl.MultiMap
+
+local utils = require 'pl.utils'
+local class = require 'pl.class'
+local List = require 'pl.List'
+local Map = require 'pl.Map'
+
+-- MultiMap is a standard MT
+local MultiMap = utils.stdmt.MultiMap
+
+class(Map,nil,MultiMap)
+MultiMap._name = 'MultiMap'
+
+function MultiMap:_init (t)
+    if not t then return end
+    self:update(t)
+end
+
+--- update a MultiMap using a table.
+-- @param t either a Multimap or a map-like table.
+-- @return the map
+function MultiMap:update (t)
+    utils.assert_arg(1,t,'table')
+    if Map:class_of(t) then
+        for k,v in pairs(t) do
+            self[k] = List()
+            self[k]:append(v)
+        end
+    else
+        for k,v in pairs(t) do
+            self[k] = List(v)
+        end
+    end
+end
+
+--- add a new value to a key.  Setting a nil value removes the key.
+-- @param key the key
+-- @param val the value
+-- @return the map
+function MultiMap:set (key,val)
+    if val == nil then
+        self[key] = nil
+    else
+        if not self[key] then
+            self[key] = List()
+        end
+        self[key]:append(val)
+    end
+end
+
+return MultiMap
+
+end,
+
+["pl.operator"] = function()
+--------------------
+-- Module: 'pl.operator'
+--------------------
+--- Lua operators available as functions.
+--
+-- (similar to the Python module of the same name)
+--
+-- There is a module field `optable` which maps the operator strings
+-- onto these functions, e.g. `operator.optable['()']==operator.call`
+--
+-- Operator strings like '>' and '{}' can be passed to most Penlight functions
+-- expecting a function argument.
+--
+-- @module pl.operator
+
+local strfind = string.find
+
+local operator = {}
+
+--- apply function to some arguments **()**
+-- @param fn a function or callable object
+-- @param ... arguments
+function operator.call(fn,...)
+    return fn(...)
+end
+
+--- get the indexed value from a table **[]**
+-- @param t a table or any indexable object
+-- @param k the key
+function  operator.index(t,k)
+    return t[k]
+end
+
+--- returns true if arguments are equal **==**
+-- @param a value
+-- @param b value
+function  operator.eq(a,b)
+    return a==b
+end
+
+--- returns true if arguments are not equal **~=**
+ -- @param a value
+-- @param b value
+function  operator.neq(a,b)
+    return a~=b
+end
+
+--- returns true if a is less than b **<**
+-- @param a value
+-- @param b value
+function  operator.lt(a,b)
+    return a < b
+end
+
+--- returns true if a is less or equal to b **<=**
+-- @param a value
+-- @param b value
+function  operator.le(a,b)
+    return a <= b
+end
+
+--- returns true if a is greater than b **>**
+-- @param a value
+-- @param b value
+function  operator.gt(a,b)
+    return a > b
+end
+
+--- returns true if a is greater or equal to b **>=**
+-- @param a value
+-- @param b value
+function  operator.ge(a,b)
+    return a >= b
+end
+
+--- returns length of string or table **#**
+-- @param a a string or a table
+function  operator.len(a)
+    return #a
+end
+
+--- add two values **+**
+-- @param a value
+-- @param b value
+function  operator.add(a,b)
+    return a+b
+end
+
+--- subtract b from a **-**
+-- @param a value
+-- @param b value
+function  operator.sub(a,b)
+    return a-b
+end
+
+--- multiply two values __*__
+-- @param a value
+-- @param b value
+function  operator.mul(a,b)
+    return a*b
+end
+
+--- divide first value by second **/**
+-- @param a value
+-- @param b value
+function  operator.div(a,b)
+    return a/b
+end
+
+--- raise first to the power of second **^**
+-- @param a value
+-- @param b value
+function  operator.pow(a,b)
+    return a^b
+end
+
+--- modulo; remainder of a divided by b **%**
+-- @param a value
+-- @param b value
+function  operator.mod(a,b)
+    return a%b
+end
+
+--- concatenate two values (either strings or `__concat` defined) **..**
+-- @param a value
+-- @param b value
+function  operator.concat(a,b)
+    return a..b
+end
+
+--- return the negative of a value **-**
+-- @param a value
+function  operator.unm(a)
+    return -a
+end
+
+--- false if value evaluates as true **not**
+-- @param a value
+function  operator.lnot(a)
+    return not a
+end
+
+--- true if both values evaluate as true **and**
+-- @param a value
+-- @param b value
+function  operator.land(a,b)
+    return a and b
+end
+
+--- true if either value evaluate as true **or**
+-- @param a value
+-- @param b value
+function  operator.lor(a,b)
+    return a or b
+end
+
+--- make a table from the arguments **{}**
+-- @param ... non-nil arguments
+-- @return a table
+function  operator.table (...)
+    return {...}
+end
+
+--- match two strings **~**.
+-- uses @{string.find}
+function  operator.match (a,b)
+    return strfind(a,b)~=nil
+end
+
+--- the null operation.
+-- @param ... arguments
+-- @return the arguments
+function  operator.nop (...)
+    return ...
+end
+
+---- Map from operator symbol to function.
+-- Most of these map directly from operators;
+-- But note these extras
+--
+--  * __'()'__  `call`
+--  * __'[]'__  `index`
+--  * __'{}'__ `table`
+--  * __'~'__   `match`
+--
+-- @table optable
+-- @field operator
+ operator.optable = {
+    ['+']=operator.add,
+    ['-']=operator.sub,
+    ['*']=operator.mul,
+    ['/']=operator.div,
+    ['%']=operator.mod,
+    ['^']=operator.pow,
+    ['..']=operator.concat,
+    ['()']=operator.call,
+    ['[]']=operator.index,
+    ['<']=operator.lt,
+    ['<=']=operator.le,
+    ['>']=operator.gt,
+    ['>=']=operator.ge,
+    ['==']=operator.eq,
+    ['~=']=operator.neq,
+    ['#']=operator.len,
+    ['and']=operator.land,
+    ['or']=operator.lor,
+    ['{}']=operator.table,
+    ['~']=operator.match,
+    ['']=operator.nop,
+}
+
+return operator
+
+end,
+
+["pl.OrderedMap"] = function()
+--------------------
+-- Module: 'pl.OrderedMap'
+--------------------
+--- OrderedMap, a map which preserves ordering.
+--
+-- Derived from `pl.Map`.
+--
+-- Dependencies: `pl.utils`, `pl.tablex`, `pl.class`, `pl.List`, `pl.Map`
+-- @classmod pl.OrderedMap
+
+local tablex = require 'pl.tablex'
+local utils = require 'pl.utils'
+local List = require 'pl.List'
+local index_by,tsort,concat = tablex.index_by,table.sort,table.concat
+
+local class = require 'pl.class'
+local Map = require 'pl.Map'
+
+local OrderedMap = class(Map)
+OrderedMap._name = 'OrderedMap'
+
+local rawset = rawset
+
+--- construct an OrderedMap.
+-- Will throw an error if the argument is bad.
+-- @param t optional initialization table, same as for @{OrderedMap:update}
+function OrderedMap:_init (t)
+    rawset(self,'_keys',List())
+    if t then
+        local map,err = self:update(t)
+        if not map then error(err,2) end
+    end
+end
+
+local assert_arg,raise = utils.assert_arg,utils.raise
+
+--- update an OrderedMap using a table.
+-- If the table is itself an OrderedMap, then its entries will be appended.
+-- if it s a table of the form `{{key1=val1},{key2=val2},...}` these will be appended.
+--
+-- Otherwise, it is assumed to be a map-like table, and order of extra entries is arbitrary.
+-- @tab t a table.
+-- @return the map, or nil in case of error
+-- @return the error message
+function OrderedMap:update (t)
+    assert_arg(1,t,'table')
+    if OrderedMap:class_of(t) then
+       for k,v in t:iter() do
+           self:set(k,v)
+       end
+    elseif #t > 0 then -- an array must contain {key=val} tables
+       if type(t[1]) == 'table' then
+           for _,pair in ipairs(t) do
+               local key,value = next(pair)
+               if not key then return raise 'empty pair initialization table' end
+               self:set(key,value)
+           end
+       else
+           return raise 'cannot use an array to initialize an OrderedMap'
+       end
+    else
+       for k,v in pairs(t) do
+           self:set(k,v)
+       end
+    end
+   return self
+end
+
+--- set the key's value.   This key will be appended at the end of the map.
+--
+-- If the value is nil, then the key is removed.
+-- @param key the key
+-- @param val the value
+-- @return the map
+function OrderedMap:set (key,val)
+    if rawget(self, key) == nil and val ~= nil then -- new key
+        self._keys:append(key) -- we keep in order
+        rawset(self,key,val)  -- don't want to provoke __newindex!
+    else -- existing key-value pair
+        if val == nil then
+            self._keys:remove_value(key)
+            rawset(self,key,nil)
+        else
+            self[key] = val
+        end
+    end
+    return self
+end
+
+OrderedMap.__newindex = OrderedMap.set
+
+--- insert a key/value pair before a given position.
+-- Note: if the map already contains the key, then this effectively
+-- moves the item to the new position by first removing at the old position.
+-- Has no effect if the key does not exist and val is nil
+-- @int pos a position starting at 1
+-- @param key the key
+-- @param val the value; if nil use the old value
+function OrderedMap:insert (pos,key,val)
+    local oldval = self[key]
+    val = val or oldval
+    if oldval then
+        self._keys:remove_value(key)
+    end
+    if val then
+        self._keys:insert(pos,key)
+        rawset(self,key,val)
+    end
+    return self
+end
+
+--- return the keys in order.
+-- (Not a copy!)
+-- @return List
+function OrderedMap:keys ()
+    return self._keys
+end
+
+--- return the values in order.
+-- this is relatively expensive.
+-- @return List
+function OrderedMap:values ()
+    return List(index_by(self,self._keys))
+end
+
+--- sort the keys.
+-- @func cmp a comparison function as for @{table.sort}
+-- @return the map
+function OrderedMap:sort (cmp)
+    tsort(self._keys,cmp)
+    return self
+end
+
+--- iterate over key-value pairs in order.
+function OrderedMap:iter ()
+    local i = 0
+    local keys = self._keys
+    local idx
+    return function()
+        i = i + 1
+        if i > #keys then return nil end
+        idx = keys[i]
+        return idx,self[idx]
+    end
+end
+
+--- iterate over an ordered map (5.2).
+-- @within metamethods
+-- @function OrderedMap:__pairs
+OrderedMap.__pairs = OrderedMap.iter
+
+--- string representation of an ordered map.
+-- @within metamethods
+function OrderedMap:__tostring ()
+    local res = {}
+    for i,v in ipairs(self._keys) do
+        local val = self[v]
+        local vs = tostring(val)
+        if type(val) ~= 'number' then
+            vs = '"'..vs..'"'
+        end
+        res[i] = tostring(v)..'='..vs
+    end
+    return '{'..concat(res,',')..'}'
+end
+
+return OrderedMap
+
+
+
+
+end,
+
+["pl.path"] = function()
+--------------------
+-- Module: 'pl.path'
+--------------------
+--- Path manipulation and file queries.
+--
+-- This is modelled after Python's os.path library (10.1); see @{04-paths.md|the Guide}.
+--
+-- NOTE: the functions assume the paths being dealt with to originate
+-- from the OS the application is running on. Windows drive letters are not
+-- to be used when running on a Unix system for example. The one exception
+-- is Windows paths to allow both forward and backward slashes (since Lua
+-- also accepts those)
+--
+-- Dependencies: `pl.utils`, `lfs`
+-- @module pl.path
+
+-- imports and locals
+local _G = _G
+local sub = string.sub
+local getenv = os.getenv
+local tmpnam = os.tmpname
+local package = package
+local append, concat, remove = table.insert, table.concat, table.remove
+local utils = require 'pl.utils'
+local assert_string,raise = utils.assert_string,utils.raise
+
+local res,lfs = _G.pcall(_G.require,'lfs')
+if not res then
+    error("pl.path requires LuaFileSystem")
+end
+
+local attrib = lfs.attributes
+local currentdir = lfs.currentdir
+local link_attrib = lfs.symlinkattributes
+
+local path = {}
+
+local function err_func(name, param, err, code)
+  local ret = ("%s failed"):format(tostring(name))
+  if param ~= nil then
+    ret = ret .. (" for '%s'"):format(tostring(param))
+  end
+  ret = ret .. (": %s"):format(tostring(err))
+  if code ~= nil then
+    ret = ret .. (" (code %s)"):format(tostring(code))
+  end
+  return ret
+end
+
+--- Lua iterator over the entries of a given directory.
+-- Implicit link to [`luafilesystem.dir`](https://keplerproject.github.io/luafilesystem/manual.html#reference)
+-- @function dir
+path.dir = lfs.dir
+
+--- Creates a directory.
+-- Implicit link to [`luafilesystem.mkdir`](https://keplerproject.github.io/luafilesystem/manual.html#reference)
+-- @function mkdir
+path.mkdir = function(d)
+  local ok, err, code = lfs.mkdir(d)
+  if not ok then
+    return ok, err_func("mkdir", d, err, code), code
+  end
+  return ok, err, code
+end
+
+--- Removes a directory.
+-- Implicit link to [`luafilesystem.rmdir`](https://keplerproject.github.io/luafilesystem/manual.html#reference)
+-- @function rmdir
+path.rmdir = function(d)
+  local ok, err, code = lfs.rmdir(d)
+  if not ok then
+    return ok, err_func("rmdir", d, err, code), code
+  end
+  return ok, err, code
+end
+
+--- Gets attributes.
+-- Implicit link to [`luafilesystem.attributes`](https://keplerproject.github.io/luafilesystem/manual.html#reference)
+-- @function attrib
+path.attrib = function(d, r)
+  local ok, err, code = attrib(d, r)
+  if not ok then
+    return ok, err_func("attrib", d, err, code), code
+  end
+  return ok, err, code
+end
+
+--- Get the working directory.
+-- Implicit link to [`luafilesystem.currentdir`](https://keplerproject.github.io/luafilesystem/manual.html#reference)
+-- @function currentdir
+path.currentdir = function()
+  local ok, err, code = currentdir()
+  if not ok then
+    return ok, err_func("currentdir", nil, err, code), code
+  end
+  return ok, err, code
+end
+
+--- Gets symlink attributes.
+-- Implicit link to [`luafilesystem.symlinkattributes`](https://keplerproject.github.io/luafilesystem/manual.html#reference)
+-- @function link_attrib
+path.link_attrib = function(d, r)
+  local ok, err, code = link_attrib(d, r)
+  if not ok then
+    return ok, err_func("link_attrib", d, err, code), code
+  end
+  return ok, err, code
+end
+
+--- Changes the working directory.
+-- On Windows, if a drive is specified, it also changes the current drive. If
+-- only specifying the drive, it will only switch drive, but not modify the path.
+-- Implicit link to [`luafilesystem.chdir`](https://keplerproject.github.io/luafilesystem/manual.html#reference)
+-- @function chdir
+path.chdir = function(d)
+  local ok, err, code = lfs.chdir(d)
+  if not ok then
+    return ok, err_func("chdir", d, err, code), code
+  end
+  return ok, err, code
+end
+
+--- is this a directory?
+-- @string P A file path
+function path.isdir(P)
+    assert_string(1,P)
+    if P:match("\\$") then
+        P = P:sub(1,-2)
+    end
+    return attrib(P,'mode') == 'directory'
+end
+
+--- is this a file?
+-- @string P A file path
+function path.isfile(P)
+    assert_string(1,P)
+    return attrib(P,'mode') == 'file'
+end
+
+-- is this a symbolic link?
+-- @string P A file path
+function path.islink(P)
+    assert_string(1,P)
+    if link_attrib then
+        return link_attrib(P,'mode')=='link'
+    else
+        return false
+    end
+end
+
+--- return size of a file.
+-- @string P A file path
+function path.getsize(P)
+    assert_string(1,P)
+    return attrib(P,'size')
+end
+
+--- does a path exist?
+-- @string P A file path
+-- @return the file path if it exists (either as file, directory, socket, etc), nil otherwise
+function path.exists(P)
+    assert_string(1,P)
+    return attrib(P,'mode') ~= nil and P
+end
+
+--- Return the time of last access as the number of seconds since the epoch.
+-- @string P A file path
+function path.getatime(P)
+    assert_string(1,P)
+    return attrib(P,'access')
+end
+
+--- Return the time of last modification as the number of seconds since the epoch.
+-- @string P A file path
+function path.getmtime(P)
+    assert_string(1,P)
+    return attrib(P,'modification')
+end
+
+---Return the system's ctime as the number of seconds since the epoch.
+-- @string P A file path
+function path.getctime(P)
+    assert_string(1,P)
+    return path.attrib(P,'change')
+end
+
+
+local function at(s,i)
+    return sub(s,i,i)
+end
+
+path.is_windows = utils.is_windows
+
+local sep, other_sep, seps
+-- constant sep is the directory separator for this platform.
+-- constant dirsep is the separator in the PATH environment variable
+if path.is_windows then
+    path.sep = '\\'; other_sep = '/'
+    path.dirsep = ';'
+    seps = { ['/'] = true, ['\\'] = true }
+else
+    path.sep = '/'
+    path.dirsep = ':'
+    seps = { ['/'] = true }
+end
+sep = path.sep
+
+--- are we running Windows?
+-- @class field
+-- @name path.is_windows
+
+--- path separator for this platform.
+-- @class field
+-- @name path.sep
+
+--- separator for PATH for this platform
+-- @class field
+-- @name path.dirsep
+
+--- given a path, return the directory part and a file part.
+-- if there's no directory part, the first value will be empty
+-- @string P A file path
+-- @return directory part
+-- @return file part
+-- @usage
+-- local dir, file = path.splitpath("some/dir/myfile.txt")
+-- assert(dir == "some/dir")
+-- assert(file == "myfile.txt")
+--
+-- local dir, file = path.splitpath("some/dir/")
+-- assert(dir == "some/dir")
+-- assert(file == "")
+--
+-- local dir, file = path.splitpath("some_dir")
+-- assert(dir == "")
+-- assert(file == "some_dir")
+function path.splitpath(P)
+    assert_string(1,P)
+    local i = #P
+    local ch = at(P,i)
+    while i > 0 and ch ~= sep and ch ~= other_sep do
+        i = i - 1
+        ch = at(P,i)
+    end
+    if i == 0 then
+        return '',P
+    else
+        return sub(P,1,i-1), sub(P,i+1)
+    end
+end
+
+--- return an absolute path.
+-- @string P A file path
+-- @string[opt] pwd optional start path to use (default is current dir)
+function path.abspath(P,pwd)
+    assert_string(1,P)
+    if pwd then assert_string(2,pwd) end
+    local use_pwd = pwd ~= nil
+    if not use_pwd and not currentdir() then return P end
+    P = P:gsub('[\\/]$','')
+    pwd = pwd or currentdir()
+    if not path.isabs(P) then
+        P = path.join(pwd,P)
+    elseif path.is_windows and not use_pwd and at(P,2) ~= ':' and at(P,2) ~= '\\' then
+        P = pwd:sub(1,2)..P -- attach current drive to path like '\\fred.txt'
+    end
+    return path.normpath(P)
+end
+
+--- given a path, return the root part and the extension part.
+-- if there's no extension part, the second value will be empty
+-- @string P A file path
+-- @treturn string root part (everything upto the "."", maybe empty)
+-- @treturn string extension part (including the ".", maybe empty)
+-- @usage
+-- local file_path, ext = path.splitext("/bonzo/dog_stuff/cat.txt")
+-- assert(file_path == "/bonzo/dog_stuff/cat")
+-- assert(ext == ".txt")
+--
+-- local file_path, ext = path.splitext("")
+-- assert(file_path == "")
+-- assert(ext == "")
+function path.splitext(P)
+    assert_string(1,P)
+    local i = #P
+    local ch = at(P,i)
+    while i > 0 and ch ~= '.' do
+        if seps[ch] then
+            return P,''
+        end
+        i = i - 1
+        ch = at(P,i)
+    end
+    if i == 0 then
+        return P,''
+    else
+        return sub(P,1,i-1),sub(P,i)
+    end
+end
+
+--- return the directory part of a path
+-- @string P A file path
+-- @treturn string everything before the last dir-separator
+-- @see splitpath
+-- @usage
+-- path.dirname("/some/path/file.txt")   -- "/some/path"
+-- path.dirname("file.txt")              -- "" (empty string)
+function path.dirname(P)
+    assert_string(1,P)
+    local p1 = path.splitpath(P)
+    return p1
+end
+
+--- return the file part of a path
+-- @string P A file path
+-- @treturn string
+-- @see splitpath
+-- @usage
+-- path.basename("/some/path/file.txt")  -- "file.txt"
+-- path.basename("/some/path/file/")     -- "" (empty string)
+function path.basename(P)
+    assert_string(1,P)
+    local _,p2 = path.splitpath(P)
+    return p2
+end
+
+--- get the extension part of a path.
+-- @string P A file path
+-- @treturn string
+-- @see splitext
+-- @usage
+-- path.extension("/some/path/file.txt") -- ".txt"
+-- path.extension("/some/path/file_txt") -- "" (empty string)
+function path.extension(P)
+    assert_string(1,P)
+    local _,p2 = path.splitext(P)
+    return p2
+end
+
+--- is this an absolute path?
+-- @string P A file path
+-- @usage
+-- path.isabs("hello/path")    -- false
+-- path.isabs("/hello/path")   -- true
+-- -- Windows;
+-- path.isabs("hello\path")    -- false
+-- path.isabs("\hello\path")   -- true
+-- path.isabs("C:\hello\path") -- true
+-- path.isabs("C:hello\path")  -- false
+function path.isabs(P)
+    assert_string(1,P)
+    if path.is_windows and at(P,2) == ":" then
+        return seps[at(P,3)] ~= nil
+    end
+    return seps[at(P,1)] ~= nil
+end
+
+--- return the path resulting from combining the individual paths.
+-- if the second (or later) path is absolute, we return the last absolute path (joined with any non-absolute paths following).
+-- empty elements (except the last) will be ignored.
+-- @string p1 A file path
+-- @string p2 A file path
+-- @string ... more file paths
+-- @treturn string the combined path
+-- @usage
+-- path.join("/first","second","third")   -- "/first/second/third"
+-- path.join("first","second/third")      -- "first/second/third"
+-- path.join("/first","/second","third")  -- "/second/third"
+function path.join(p1,p2,...)
+    assert_string(1,p1)
+    assert_string(2,p2)
+    if select('#',...) > 0 then
+        local p = path.join(p1,p2)
+        local args = {...}
+        for i = 1,#args do
+            assert_string(i,args[i])
+            p = path.join(p,args[i])
+        end
+        return p
+    end
+    if path.isabs(p2) then return p2 end
+    local endc = at(p1,#p1)
+    if endc ~= path.sep and endc ~= other_sep and endc ~= "" then
+        p1 = p1..path.sep
+    end
+    return p1..p2
+end
+
+--- normalize the case of a pathname. On Unix, this returns the path unchanged,
+-- for Windows it converts;
+--
+-- * the path to lowercase
+-- * forward slashes to backward slashes
+-- @string P A file path
+-- @usage path.normcase("/Some/Path/File.txt")
+-- -- Windows: "\some\path\file.txt"
+-- -- Others : "/Some/Path/File.txt"
+function path.normcase(P)
+    assert_string(1,P)
+    if path.is_windows then
+        return P:gsub('/','\\'):lower()
+    else
+        return P
+    end
+end
+
+--- normalize a path name.
+-- `A//B`, `A/./B`, and `A/foo/../B` all become `A/B`.
+--
+-- An empty path results in '.'.
+-- @string P a file path
+function path.normpath(P)
+    assert_string(1,P)
+    -- Split path into anchor and relative path.
+    local anchor = ''
+    if path.is_windows then
+        if P:match '^\\\\' then -- UNC
+            anchor = '\\\\'
+            P = P:sub(3)
+        elseif seps[at(P, 1)] then
+            anchor = '\\'
+            P = P:sub(2)
+        elseif at(P, 2) == ':' then
+            anchor = P:sub(1, 2)
+            P = P:sub(3)
+            if seps[at(P, 1)] then
+                anchor = anchor..'\\'
+                P = P:sub(2)
+            end
+        end
+        P = P:gsub('/','\\')
+    else
+        -- According to POSIX, in path start '//' and '/' are distinct,
+        -- but '///+' is equivalent to '/'.
+        if P:match '^//' and at(P, 3) ~= '/' then
+            anchor = '//'
+            P = P:sub(3)
+        elseif at(P, 1) == '/' then
+            anchor = '/'
+            P = P:match '^/*(.*)$'
+        end
+    end
+    local parts = {}
+    for part in P:gmatch('[^'..sep..']+') do
+        if part == '..' then
+            if #parts ~= 0 and parts[#parts] ~= '..' then
+                remove(parts)
+            else
+                append(parts, part)
+            end
+        elseif part ~= '.' then
+            append(parts, part)
+        end
+    end
+    P = anchor..concat(parts, sep)
+    if P == '' then P = '.' end
+    return P
+end
+
+--- relative path from current directory or optional start point
+-- @string P a path
+-- @string[opt] start optional start point (default current directory)
+function path.relpath (P,start)
+    assert_string(1,P)
+    if start then assert_string(2,start) end
+    local split,min,append = utils.split, math.min, table.insert
+    P = path.abspath(P,start)
+    start = start or currentdir()
+    local compare
+    if path.is_windows then
+        P = P:gsub("/","\\")
+        start = start:gsub("/","\\")
+        compare = function(v) return v:lower() end
+    else
+        compare = function(v) return v end
+    end
+    local startl, Pl = split(start,sep), split(P,sep)
+    local n = min(#startl,#Pl)
+    if path.is_windows and n > 0 and at(Pl[1],2) == ':' and Pl[1] ~= startl[1] then
+        return P
+    end
+    local k = n+1 -- default value if this loop doesn't bail out!
+    for i = 1,n do
+        if compare(startl[i]) ~= compare(Pl[i]) then
+            k = i
+            break
+        end
+    end
+    local rell = {}
+    for i = 1, #startl-k+1 do rell[i] = '..' end
+    if k <= #Pl then
+        for i = k,#Pl do append(rell,Pl[i]) end
+    end
+    return table.concat(rell,sep)
+end
+
+
+--- Replace a starting '~' with the user's home directory.
+-- In windows, if HOME isn't set, then USERPROFILE is used in preference to
+-- HOMEDRIVE HOMEPATH. This is guaranteed to be writeable on all versions of Windows.
+-- @string P A file path
+function path.expanduser(P)
+    assert_string(1,P)
+    if at(P,1) == '~' then
+        local home = getenv('HOME')
+        if not home then -- has to be Windows
+            home = getenv 'USERPROFILE' or (getenv 'HOMEDRIVE' .. getenv 'HOMEPATH')
+        end
+        return home..sub(P,2)
+    else
+        return P
+    end
+end
+
+
+---Return a suitable full path to a new temporary file name.
+-- unlike os.tmpname(), it always gives you a writeable path (uses TEMP environment variable on Windows)
+function path.tmpname ()
+    local res = tmpnam()
+    -- On Windows if Lua is compiled using MSVC14 os.tmpname
+    -- already returns an absolute path within TEMP env variable directory,
+    -- no need to prepend it.
+    if path.is_windows and not res:find(':') then
+        res = getenv('TEMP')..res
+    end
+    return res
+end
+
+--- return the largest common prefix path of two paths.
+-- @string path1 a file path
+-- @string path2 a file path
+-- @return the common prefix (Windows: separators will be normalized, casing will be original)
+function path.common_prefix (path1,path2)
+    assert_string(1,path1)
+    assert_string(2,path2)
+    -- get them in order!
+    if #path1 > #path2 then path2,path1 = path1,path2 end
+    local compare
+    if path.is_windows then
+        path1 = path1:gsub("/", "\\")
+        path2 = path2:gsub("/", "\\")
+        compare = function(v) return v:lower() end
+    else
+        compare = function(v) return v end
+    end
+    for i = 1,#path1 do
+        if compare(at(path1,i)) ~= compare(at(path2,i)) then
+            local cp = path1:sub(1,i-1)
+            if at(path1,i-1) ~= sep then
+                cp = path.dirname(cp)
+            end
+            return cp
+        end
+    end
+    if at(path2,#path1+1) ~= sep then path1 = path.dirname(path1) end
+    return path1
+    --return ''
+end
+
+--- return the full path where a particular Lua module would be found.
+-- Both package.path and package.cpath is searched, so the result may
+-- either be a Lua file or a shared library.
+-- @string mod name of the module
+-- @return on success: path of module, lua or binary
+-- @return on error: nil, error string listing paths tried
+function path.package_path(mod)
+    assert_string(1,mod)
+    local res, err1, err2
+    res, err1 = package.searchpath(mod,package.path)
+    if res then return res,true end
+    res, err2 = package.searchpath(mod,package.cpath)
+    if res then return res,false end
+    return raise ('cannot find module on path\n' .. err1 .. "\n" .. err2)
+end
+
+
+---- finis -----
+return path
+
+end,
+
+["pl.permute"] = function()
+--------------------
+-- Module: 'pl.permute'
+--------------------
+--- Permutation operations.
+--
+-- Dependencies: `pl.utils`, `pl.tablex`
+-- @module pl.permute
+local tablex = require 'pl.tablex'
+local utils = require 'pl.utils'
+local copy = tablex.deepcopy
+local append = table.insert
+local assert_arg = utils.assert_arg
+
+
+local permute = {}
+
+
+--- an iterator over all order-permutations of the elements of a list.
+-- Please note that the same list is returned each time, so do not keep references!
+-- @param a list-like table
+-- @return an iterator which provides the next permutation as a list
+function permute.order_iter(a)
+    assert_arg(1,a,'table')
+
+    local t = #a
+    local stack = { 1 }
+    local function iter()
+        local h = #stack
+        local n = t - h + 1
+
+        local i = stack[h]
+        if i > t then
+            return
+        end
+
+        if n == 0 then
+            table.remove(stack)
+            h = h - 1
+
+            stack[h] = stack[h] + 1
+            return a
+
+        elseif i <= n then
+
+            -- put i-th element as the last one
+            a[n], a[i] = a[i], a[n]
+
+            -- generate all permutations of the other elements
+            table.insert(stack, 1)
+
+        else
+
+            table.remove(stack)
+            h = h - 1
+
+            n = n + 1
+            i = stack[h]
+
+            -- restore i-th element
+            a[n], a[i] = a[i], a[n]
+
+            stack[h] = stack[h] + 1
+        end
+        return iter() -- tail-call
+    end
+
+    return iter
+end
+
+
+--- construct a table containing all the order-permutations of a list.
+-- @param a list-like table
+-- @return a table of tables
+-- @usage permute.order_table {1,2,3} --> {{2,3,1},{3,2,1},{3,1,2},{1,3,2},{2,1,3},{1,2,3}}
+function permute.order_table (a)
+    assert_arg(1,a,'table')
+    local res = {}
+    for t in permute.iter(a) do
+        append(res,copy(t))
+    end
+    return res
+end
+
+
+
+--- an iterator over all permutations of the elements of the given lists.
+-- @param ... list-like tables, they are nil-safe if a length-field `n` is provided (see `utils.pack`)
+-- @return an iterator which provides the next permutation as return values in the same order as the provided lists, preceeded by an index
+-- @usage
+-- local strs = utils.pack("one", nil, "three")  -- adds an 'n' field for nil-safety
+-- local bools = utils.pack(true, false)
+-- local iter = permute.list_iter(strs, bools)
+--
+-- print(iter())    --> 1, one, true
+-- print(iter())    --> 2, nil, true
+-- print(iter())    --> 3, three, true
+-- print(iter())    --> 4, one, false
+-- print(iter())    --> 5, nil, false
+-- print(iter())    --> 6, three, false
+function permute.list_iter(...)
+  local elements = {...}
+  local pointers = {}
+  local sizes = {}
+  local size = #elements
+  for i, list in ipairs(elements) do
+    assert_arg(i,list,'table')
+    pointers[i] = 1
+    sizes[i] = list.n or #list
+  end
+  local count = 0
+
+  return function()
+    if pointers[size] > sizes[size] then return end -- we're done
+    count = count + 1
+    local r = { n = #elements }
+    local cascade_up = true
+    for i = 1, size do
+      r[i] = elements[i][pointers[i]]
+      if cascade_up then
+        pointers[i] = pointers[i] + 1
+        if pointers[i] <= sizes[i] then
+          -- this list is not done yet, stop cascade
+          cascade_up = false
+        else
+          -- this list is done
+          if i ~= size then
+            -- reset pointer
+            pointers[i] = 1
+          end
+        end
+      end
+    end
+    return count, utils.unpack(r)
+  end
+end
+
+
+
+--- construct a table containing all the permutations of a set of lists.
+-- @param ... list-like tables, they are nil-safe if a length-field `n` is provided
+-- @return a list of lists, the sub-lists have an 'n' field for nil-safety
+-- @usage
+-- local strs = utils.pack("one", nil, "three")  -- adds an 'n' field for nil-safety
+-- local bools = utils.pack(true, false)
+-- local results = permute.list_table(strs, bools)
+-- -- results = {
+-- --   { "one, true, n = 2 }
+-- --   { nil, true, n = 2 },
+-- --   { "three, true, n = 2 },
+-- --   { "one, false, n = 2 },
+-- --   { nil, false, n = 2 },
+-- --   { "three", false, n = 2 },
+-- -- }
+function permute.list_table(...)
+  local iter = permute.list_iter(...)
+  local results = {}
+  local i = 1
+  while true do
+    local values = utils.pack(iter())
+    if values[1] == nil then return results end
+    for i = 1, values.n do values[i] = values[i+1] end
+    values.n = values.n - 1
+    results[i] = values
+    i = i + 1
+  end
+end
+
+
+-- backward compat, to be deprecated
+
+--- deprecated.
+-- @param ...
+-- @see permute.order_iter
+function permute.iter(...)
+  utils.raise_deprecation {
+    source = "Penlight " .. utils._VERSION,
+    message = "function 'iter' was renamed to 'order_iter'",
+    version_removed = "2.0.0",
+    deprecated_after = "1.9.2",
+  }
+
+  return permute.order_iter(...)
+end
+
+--- deprecated.
+-- @param ...
+-- @see permute.order_iter
+function permute.table(...)
+  utils.raise_deprecation {
+    source = "Penlight " .. utils._VERSION,
+    message = "function 'table' was renamed to 'order_table'",
+    version_removed = "2.0.0",
+    deprecated_after = "1.9.2",
+  }
+
+  return permute.order_table(...)
+end
+
+return permute
+
+end,
+
+["pl.pretty"] = function()
+--------------------
+-- Module: 'pl.pretty'
+--------------------
+--- Pretty-printing Lua tables.
+-- Also provides a sandboxed Lua table reader and
+-- a function to present large numbers in human-friendly format.
+--
+-- Dependencies: `pl.utils`, `pl.lexer`, `pl.stringx`, `debug`
+-- @module pl.pretty
+
+local append = table.insert
+local concat = table.concat
+local mfloor, mhuge = math.floor, math.huge
+local mtype = math.type
+local utils = require 'pl.utils'
+local lexer = require 'pl.lexer'
+local debug = require 'debug'
+local quote_string = require'pl.stringx'.quote_string
+local assert_arg = utils.assert_arg
+
+local original_tostring = tostring
+
+-- Patch tostring to format numbers with better precision
+-- and to produce cross-platform results for
+-- infinite values and NaN.
+local function tostring(value)
+    if type(value) ~= "number" then
+        return original_tostring(value)
+    elseif value ~= value then
+        return "NaN"
+    elseif value == mhuge then
+        return "Inf"
+    elseif value == -mhuge then
+        return "-Inf"
+    elseif (_VERSION ~= "Lua 5.3" or mtype(value) == "integer") and mfloor(value) == value then
+        return ("%d"):format(value)
+    else
+        local res = ("%.14g"):format(value)
+        if _VERSION == "Lua 5.3" and mtype(value) == "float" and not res:find("%.") then
+            -- Number is internally a float but looks like an integer.
+            -- Insert ".0" after first run of digits.
+            res = res:gsub("%d+", "%0.0", 1)
+        end
+        return res
+    end
+end
+
+local pretty = {}
+
+local function save_global_env()
+    local env = {}
+    env.hook, env.mask, env.count = debug.gethook()
+
+    -- env.hook is "external hook" if is a C hook function
+    if env.hook~="external hook" then
+        debug.sethook()
+    end
+
+    env.string_mt = getmetatable("")
+    debug.setmetatable("", nil)
+    return env
+end
+
+local function restore_global_env(env)
+    if env then
+        debug.setmetatable("", env.string_mt)
+        if env.hook~="external hook" then
+            debug.sethook(env.hook, env.mask, env.count)
+        end
+    end
+end
+
+--- Read a string representation of a Lua table.
+-- This function loads and runs the string as Lua code, but bails out
+-- if it contains a function definition.
+-- Loaded string is executed in an empty environment.
+-- @string s string to read in `{...}` format, possibly with some whitespace
+-- before or after the curly braces. A single line comment may be present
+-- at the beginning.
+-- @return a table in case of success.
+-- If loading the string failed, return `nil` and error message.
+-- If executing loaded string failed, return `nil` and the error it raised.
+function pretty.read(s)
+    assert_arg(1,s,'string')
+    if s:find '^%s*%-%-' then -- may start with a comment..
+        s = s:gsub('%-%-.-\n','')
+    end
+    if not s:find '^%s*{' then return nil,"not a Lua table" end
+    if s:find '[^\'"%w_]function[^\'"%w_]' then
+        local tok = lexer.lua(s)
+        for t,v in tok do
+            if t == 'keyword' and v == 'function' then
+                return nil,"cannot have functions in table definition"
+            end
+        end
+    end
+    s = 'return '..s
+    local chunk,err = utils.load(s,'tbl','t',{})
+    if not chunk then return nil,err end
+    local global_env = save_global_env()
+    local ok,ret = pcall(chunk)
+    restore_global_env(global_env)
+    if ok then return ret
+    else
+        return nil,ret
+    end
+end
+
+--- Read a Lua chunk.
+-- @string s Lua code.
+-- @tab[opt] env environment used to run the code, empty by default.
+-- @bool[opt] paranoid abort loading if any looping constructs a found in the code
+-- and disable string methods.
+-- @return the environment in case of success or `nil` and syntax or runtime error
+-- if something went wrong.
+function pretty.load (s, env, paranoid)
+    env = env or {}
+    if paranoid then
+        local tok = lexer.lua(s)
+        for t,v in tok do
+            if t == 'keyword'
+                and (v == 'for' or v == 'repeat' or v == 'function' or v == 'goto')
+            then
+                return nil,"looping not allowed"
+            end
+        end
+    end
+    local chunk,err = utils.load(s,'tbl','t',env)
+    if not chunk then return nil,err end
+    local global_env = paranoid and save_global_env()
+    local ok,err = pcall(chunk)
+    restore_global_env(global_env)
+    if not ok then return nil,err end
+    return env
+end
+
+local function quote_if_necessary (v)
+    if not v then return ''
+    else
+        --AAS
+        if v:find ' ' then v = quote_string(v) end
+    end
+    return v
+end
+
+local keywords
+
+local function is_identifier (s)
+    return type(s) == 'string' and s:find('^[%a_][%w_]*$') and not keywords[s]
+end
+
+local function quote (s)
+    if type(s) == 'table' then
+        return pretty.write(s,'')
+    else
+        --AAS
+        return quote_string(s)-- ('%q'):format(tostring(s))
+    end
+end
+
+local function index (numkey,key)
+    --AAS
+    if not numkey then
+        key = quote(key)
+         key = key:find("^%[") and (" " .. key .. " ") or key
+    end
+    return '['..key..']'
+end
+
+
+--- Create a string representation of a Lua table.
+-- This function never fails, but may complain by returning an
+-- extra value. Normally puts out one item per line, using
+-- the provided indent; set the second parameter to an empty string
+-- if you want output on one line.
+--
+-- *NOTE:* this is NOT a serialization function, not a full blown
+-- debug function. Checkout out respectively the
+-- [serpent](https://github.com/pkulchenko/serpent)
+-- or [inspect](https://github.com/kikito/inspect.lua)
+-- Lua modules for that if you need them.
+-- @tab tbl Table to serialize to a string.
+-- @string[opt] space The indent to use.
+-- Defaults to two spaces; pass an empty string for no indentation.
+-- @bool[opt] not_clever Pass `true` for plain output, e.g `{['key']=1}`.
+-- Defaults to `false`.
+-- @return a string
+-- @return an optional error message
+function pretty.write (tbl,space,not_clever)
+    if type(tbl) ~= 'table' then
+        local res = tostring(tbl)
+        if type(tbl) == 'string' then return quote(tbl) end
+        return res, 'not a table'
+    end
+    if not keywords then
+        keywords = lexer.get_keywords()
+    end
+    local set = ' = '
+    if space == '' then set = '=' end
+    space = space or '  '
+    local lines = {}
+    local line = ''
+    local tables = {}
+
+
+    local function put(s)
+        if #s > 0 then
+            line = line..s
+        end
+    end
+
+    local function putln (s)
+        if #line > 0 then
+            line = line..s
+            append(lines,line)
+            line = ''
+        else
+            append(lines,s)
+        end
+    end
+
+    local function eat_last_comma ()
+        local n = #lines
+        local lastch = lines[n]:sub(-1,-1)
+        if lastch == ',' then
+            lines[n] = lines[n]:sub(1,-2)
+        end
+    end
+
+
+    -- safe versions for iterators since 5.3+ honors metamethods that can throw
+    -- errors
+    local ipairs = function(t)
+        local i = 0
+        local ok, v
+        local getter = function() return t[i] end
+        return function()
+                i = i + 1
+                ok, v = pcall(getter)
+                if v == nil or not ok then return end
+                return i, t[i]
+            end
+    end
+    local pairs = function(t)
+        local k, v, ok
+        local getter = function() return next(t, k) end
+        return function()
+                ok, k, v = pcall(getter)
+                if not ok then return end
+                return k, v
+            end
+    end
+
+    local writeit
+    writeit = function (t,oldindent,indent)
+        local tp = type(t)
+        if tp ~= 'string' and  tp ~= 'table' then
+            putln(quote_if_necessary(tostring(t))..',')
+        elseif tp == 'string' then
+            -- if t:find('\n') then
+            --     putln('[[\n'..t..']],')
+            -- else
+            --     putln(quote(t)..',')
+            -- end
+            --AAS
+            putln(quote_string(t) ..",")
+        elseif tp == 'table' then
+            if tables[t] then
+                putln('<cycle>,')
+                return
+            end
+            tables[t] = true
+            local newindent = indent..space
+            putln('{')
+            local used = {}
+            if not not_clever then
+                for i,val in ipairs(t) do
+                    put(indent)
+                    writeit(val,indent,newindent)
+                    used[i] = true
+                end
+            end
+            local ordered_keys = {}
+            for k,v in pairs(t) do
+               if type(k) ~= 'number' then
+                  ordered_keys[#ordered_keys + 1] = k
+               end
+            end
+            table.sort(ordered_keys, function (a, b)
+                if type(a) == type(b)  and type(a) == 'string' then
+                    return a < b
+                end
+                return type(a) == 'boolean' or (type(b) ~= 'boolean' and type(a) == 'table')
+            end)
+            local function write_entry (key, val)
+                local tkey = type(key)
+                local numkey = tkey == 'number'
+                if not_clever then
+                    key = tostring(key)
+                    put(indent..index(numkey,key)..set)
+                    writeit(val,indent,newindent)
+                else
+                    if not numkey or not used[key] then -- non-array indices
+                        if tkey ~= 'string' then
+                            key = tostring(key)
+                        end
+                        if numkey or not is_identifier(key) then
+                            key = index(numkey,key)
+                        end
+                        put(indent..key..set)
+                        writeit(val,indent,newindent)
+                    end
+                end
+            end
+            for i = 1, #ordered_keys do
+                local key = ordered_keys[i]
+                local val = t[key]
+                write_entry(key, val)
+            end
+            for key,val in pairs(t) do
+               if type(key) == 'number' then
+                  write_entry(key, val)
+               end
+            end
+            tables[t] = nil
+            eat_last_comma()
+            putln(oldindent..'},')
+        else
+            putln(tostring(t)..',')
+        end
+    end
+    writeit(tbl,'',space)
+    eat_last_comma()
+    return concat(lines,#space > 0 and '\n' or '')
+end
+
+--- Dump a Lua table out to a file or stdout.
+-- @tab t The table to write to a file or stdout.
+-- @string[opt] filename File name to write too. Defaults to writing
+-- to stdout.
+function pretty.dump (t, filename)
+    if not filename then
+        print(pretty.write(t))
+        return true
+    else
+        return utils.writefile(filename, pretty.write(t))
+    end
+end
+
+--- Dump a series of arguments to stdout for debug purposes.
+-- This function is attached to the module table `__call` method, to make it
+-- extra easy to access. So the full:
+--
+--     print(require("pl.pretty").write({...}))
+--
+-- Can be shortened to:
+--
+--     require"pl.pretty" (...)
+--
+-- Any `nil` entries will be printed as `"<nil>"` to make them explicit.
+-- @param ... the parameters to dump to stdout.
+-- @usage
+-- -- example debug output
+-- require"pl.pretty" ("hello", nil, "world", { bye = "world", true} )
+--
+-- -- output:
+-- {
+--   ["arg 1"] = "hello",
+--   ["arg 2"] = "<nil>",
+--   ["arg 3"] = "world",
+--   ["arg 4"] = {
+--     true,
+--     bye = "world"
+--   }
+-- }
+function pretty.debug(...)
+    local n = select("#", ...)
+    local t = { ... }
+    for i = 1, n do
+        local value = t[i]
+        if value == nil then
+            value = "<nil>"
+        end
+        t[i] = nil
+        t["arg " .. i] = value
+    end
+
+    print(pretty.write(t))
+    return true
+end
+
+
+local memp,nump = {'B','KiB','MiB','GiB'},{'','K','M','B'}
+
+local function comma (val)
+    local thou = math.floor(val/1000)
+    if thou > 0 then return comma(thou)..','.. tostring(val % 1000)
+    else return tostring(val) end
+end
+
+--- Format large numbers nicely for human consumption.
+-- @number num a number.
+-- @string[opt] kind one of `'M'` (memory in `KiB`, `MiB`, etc.),
+-- `'N'` (postfixes are `'K'`, `'M'` and `'B'`),
+-- or `'T'` (use commas as thousands separator), `'N'` by default.
+-- @int[opt] prec number of digits to use for `'M'` and `'N'`, `1` by default.
+function pretty.number (num,kind,prec)
+    local fmt = '%.'..(prec or 1)..'f%s'
+    if kind == 'T' then
+        return comma(num)
+    else
+        local postfixes, fact
+        if kind == 'M' then
+            fact = 1024
+            postfixes = memp
+        else
+            fact = 1000
+            postfixes = nump
+        end
+        local div = fact
+        local k = 1
+        while num >= div and k <= #postfixes do
+            div = div * fact
+            k = k + 1
+        end
+        div = div / fact
+        if k > #postfixes then k = k - 1; div = div/fact end
+        if k > 1 then
+            return fmt:format(num/div,postfixes[k] or 'duh')
+        else
+            return num..postfixes[1]
+        end
+    end
+end
+
+return setmetatable(pretty, {
+    __call = function(self, ...)
+        return self.debug(...)
+    end
+})
+
+end,
+
+["pl.seq"] = function()
+--------------------
+-- Module: 'pl.seq'
+--------------------
+--- Manipulating iterators as sequences.
+-- See @{07-functional.md.Sequences|The Guide}
+--
+-- Dependencies: `pl.utils`, `pl.types`, `debug`
+-- @module pl.seq
+
+local next,assert,pairs,tonumber,type,setmetatable = next,assert,pairs,tonumber,type,setmetatable
+local strfind,format = string.find,string.format
+local mrandom = math.random
+local tsort,tappend = table.sort,table.insert
+local io = io
+local utils = require 'pl.utils'
+local callable = require 'pl.types'.is_callable
+local function_arg = utils.function_arg
+local assert_arg = utils.assert_arg
+local debug = require 'debug'
+
+local seq = {}
+
+-- given a number, return a function(y) which returns true if y > x
+-- @param x a number
+function seq.greater_than(x)
+  return function(v)
+    return tonumber(v) > x
+  end
+end
+
+-- given a number, returns a function(y) which returns true if y < x
+-- @param x a number
+function seq.less_than(x)
+  return function(v)
+    return tonumber(v) < x
+  end
+end
+
+-- given any value, return a function(y) which returns true if y == x
+-- @param x a value
+function seq.equal_to(x)
+  if type(x) == "number" then
+    return function(v)
+      return tonumber(v) == x
+    end
+  else
+    return function(v)
+      return v == x
+    end
+  end
+end
+
+--- given a string, return a function(y) which matches y against the string.
+-- @param s a string
+function seq.matching(s)
+  return function(v)
+     return strfind(v,s)
+  end
+end
+
+local nexti
+
+--- sequence adaptor for a table.   Note that if any generic function is
+-- passed a table, it will automatically use seq.list()
+-- @param t a list-like table
+-- @usage sum(list(t)) is the sum of all elements of t
+-- @usage for x in list(t) do...end
+function seq.list(t)
+  assert_arg(1,t,'table')
+  if not nexti then
+    nexti = ipairs{}
+  end
+  local key,value = 0
+  return function()
+    key,value = nexti(t,key)
+    return value
+  end
+end
+
+--- return the keys of the table.
+-- @param t an arbitrary table
+-- @return iterator over keys
+function seq.keys(t)
+  assert_arg(1,t,'table')
+  local key
+  return function()
+    key = next(t,key)
+    return key
+  end
+end
+
+local list = seq.list
+local function default_iter(iter)
+  if type(iter) == 'table' then return list(iter)
+  else return iter end
+end
+
+seq.iter = default_iter
+
+--- create an iterator over a numerical range. Like the standard Python function xrange.
+-- @param start a number
+-- @param finish a number greater than start
+function seq.range(start,finish)
+  local i = start - 1
+  return function()
+      i = i + 1
+      if i > finish then return nil
+      else return i end
+  end
+end
+
+-- count the number of elements in the sequence which satisfy the predicate
+-- @param iter a sequence
+-- @param condn a predicate function (must return either true or false)
+-- @param optional argument to be passed to predicate as second argument.
+-- @return count
+function seq.count(iter,condn,arg)
+  local i = 0
+  seq.foreach(iter,function(val)
+        if condn(val,arg) then i = i + 1 end
+  end)
+  return i
+end
+
+--- return the minimum and the maximum value of the sequence.
+-- @param iter a sequence
+-- @return minimum value
+-- @return maximum value
+function seq.minmax(iter)
+  local vmin,vmax = 1e70,-1e70
+  for v in default_iter(iter) do
+    v = tonumber(v)
+    if v < vmin then vmin = v end
+    if v > vmax then vmax = v end
+  end
+  return vmin,vmax
+end
+
+--- return the sum and element count of the sequence.
+-- @param iter a sequence
+-- @param fn an optional function to apply to the values
+function seq.sum(iter,fn)
+  local s = 0
+  local i = 0
+  for v in default_iter(iter) do
+    if fn then v = fn(v) end
+    s = s + v
+    i = i + 1
+  end
+  return s,i
+end
+
+--- create a table from the sequence. (This will make the result a List.)
+-- @param iter a sequence
+-- @return a List
+-- @usage copy(list(ls)) is equal to ls
+-- @usage copy(list {1,2,3}) == List{1,2,3}
+function seq.copy(iter)
+    local res,k = {},1
+    for v in default_iter(iter) do
+        res[k] = v
+        k = k + 1
+    end
+    setmetatable(res, require('pl.List'))
+    return res
+end
+
+--- create a table of pairs from the double-valued sequence.
+-- @param iter a double-valued sequence
+-- @param i1 used to capture extra iterator values
+-- @param i2 as with pairs & ipairs
+-- @usage copy2(ipairs{10,20,30}) == {{1,10},{2,20},{3,30}}
+-- @return a list-like table
+function seq.copy2 (iter,i1,i2)
+    local res,k = {},1
+    for v1,v2 in iter,i1,i2 do
+        res[k] = {v1,v2}
+        k = k + 1
+    end
+    return res
+end
+
+--- create a table of 'tuples' from a multi-valued sequence.
+-- A generalization of copy2 above
+-- @param iter a multiple-valued sequence
+-- @return a list-like table
+function seq.copy_tuples (iter)
+    iter = default_iter(iter)
+    local res = {}
+    local row = {iter()}
+    while #row > 0 do
+        tappend(res,row)
+        row = {iter()}
+    end
+    return res
+end
+
+--- return an iterator of random numbers.
+-- @param n the length of the sequence
+-- @param l same as the first optional argument to math.random
+-- @param u same as the second optional argument to math.random
+-- @return a sequence
+function seq.random(n,l,u)
+  local rand
+  assert(type(n) == 'number')
+  if u then
+     rand = function() return mrandom(l,u) end
+  elseif l then
+     rand = function() return mrandom(l) end
+  else
+     rand = mrandom
+  end
+
+  return function()
+     if n == 0 then return nil
+     else
+       n = n - 1
+       return rand()
+     end
+  end
+end
+
+--- return an iterator to the sorted elements of a sequence.
+-- @param iter a sequence
+-- @param comp an optional comparison function (comp(x,y) is true if x < y)
+function seq.sort(iter,comp)
+    local t = seq.copy(iter)
+    tsort(t,comp)
+    return list(t)
+end
+
+--- return an iterator which returns elements of two sequences.
+-- @param iter1 a sequence
+-- @param iter2 a sequence
+-- @usage for x,y in seq.zip(ls1,ls2) do....end
+function seq.zip(iter1,iter2)
+    iter1 = default_iter(iter1)
+    iter2 = default_iter(iter2)
+    return function()
+        return iter1(),iter2()
+    end
+end
+
+--- Makes a table where the key/values are the values and value counts of the sequence.
+-- This version works with 'hashable' values like strings and numbers.
+-- `pl.tablex.count_map` is more general.
+-- @param iter a sequence
+-- @return a map-like table
+-- @return a table
+-- @see pl.tablex.count_map
+function seq.count_map(iter)
+    local t = {}
+    local v
+    for s in default_iter(iter) do
+        v = t[s]
+        if v then t[s] = v + 1
+        else t[s] = 1 end
+    end
+    return setmetatable(t, require('pl.Map'))
+end
+
+-- given a sequence, return all the unique values in that sequence.
+-- @param iter a sequence
+-- @param returns_table true if we return a table, not a sequence
+-- @return a sequence or a table; defaults to a sequence.
+function seq.unique(iter,returns_table)
+    local t = seq.count_map(iter)
+    local res,k = {},1
+    for key in pairs(t) do res[k] = key; k = k + 1 end
+    table.sort(res)
+    if returns_table then
+        return res
+    else
+        return list(res)
+    end
+end
+
+--- print out a sequence iter with a separator.
+-- @param iter a sequence
+-- @param sep the separator (default space)
+-- @param nfields maximum number of values per line (default 7)
+-- @param fmt optional format function for each value
+function seq.printall(iter,sep,nfields,fmt)
+  local write = io.write
+  if not sep then sep = ' ' end
+  if not nfields then
+      if sep == '\n' then nfields = 1e30
+      else nfields = 7 end
+  end
+  if fmt then
+    local fstr = fmt
+    fmt = function(v) return format(fstr,v) end
+  end
+  local k = 1
+  for v in default_iter(iter) do
+     if fmt then v = fmt(v) end
+     if k < nfields then
+       write(v,sep)
+       k = k + 1
+    else
+       write(v,'\n')
+       k = 1
+    end
+  end
+  write '\n'
+end
+
+-- return an iterator running over every element of two sequences (concatenation).
+-- @param iter1 a sequence
+-- @param iter2 a sequence
+function seq.splice(iter1,iter2)
+  iter1 = default_iter(iter1)
+  iter2 = default_iter(iter2)
+  local iter = iter1
+  return function()
+    local ret = iter()
+    if ret == nil then
+      if iter == iter1 then
+        iter = iter2
+        return iter()
+      else return nil end
+   else
+       return  ret
+   end
+ end
+end
+
+--- return a sequence where every element of a sequence has been transformed
+-- by a function. If you don't supply an argument, then the function will
+-- receive both values of a double-valued sequence, otherwise behaves rather like
+-- tablex.map.
+-- @param fn a function to apply to elements; may take two arguments
+-- @param iter a sequence of one or two values
+-- @param arg optional argument to pass to function.
+function seq.map(fn,iter,arg)
+    fn = function_arg(1,fn)
+    iter = default_iter(iter)
+    return function()
+        local v1,v2 = iter()
+        if v1 == nil then return nil end
+        return fn(v1,arg or v2) or false
+    end
+end
+
+--- filter a sequence using a predicate function.
+-- @param iter a sequence of one or two values
+-- @param pred a boolean function; may take two arguments
+-- @param arg optional argument to pass to function.
+function seq.filter (iter,pred,arg)
+    pred = function_arg(2,pred)
+    return function ()
+        local v1,v2
+        while true do
+            v1,v2 = iter()
+            if v1 == nil then return nil end
+            if pred(v1,arg or v2) then return v1,v2 end
+        end
+    end
+end
+
+--- 'reduce' a sequence using a binary function.
+-- @func fn a function of two arguments
+-- @param iter a sequence
+-- @param initval optional initial value
+-- @usage seq.reduce(operator.add,seq.list{1,2,3,4}) == 10
+-- @usage seq.reduce('-',{1,2,3,4,5}) == -13
+function seq.reduce (fn,iter,initval)
+   fn = function_arg(1,fn)
+   iter = default_iter(iter)
+   local val = initval or iter()
+   if val == nil then return nil end
+   for v in iter do
+       val = fn(val,v)
+   end
+   return val
+end
+
+--- take the first n values from the sequence.
+-- @param iter a sequence of one or two values
+-- @param n number of items to take
+-- @return a sequence of at most n items
+function seq.take (iter,n)
+    iter = default_iter(iter)
+    return function()
+        if n < 1 then return end
+        local val1,val2 = iter()
+        if not val1 then return end
+        n = n - 1
+        return val1,val2
+    end
+end
+
+--- skip the first n values of a sequence
+-- @param iter a sequence of one or more values
+-- @param n number of items to skip
+function seq.skip (iter,n)
+    n = n or 1
+    for i = 1,n do
+        if iter() == nil then return list{} end
+    end
+    return iter
+end
+
+--- a sequence with a sequence count and the original value.
+-- enum(copy(ls)) is a roundabout way of saying ipairs(ls).
+-- @param iter a single or double valued sequence
+-- @return sequence of (i,v), i = 1..n and v is from iter.
+function seq.enum (iter)
+    local i = 0
+    iter = default_iter(iter)
+    return function  ()
+        local val1,val2 = iter()
+        if not val1 then return end
+        i = i + 1
+        return i,val1,val2
+    end
+end
+
+--- map using a named method over a sequence.
+-- @param iter a sequence
+-- @param name the method name
+-- @param arg1 optional first extra argument
+-- @param arg2 optional second extra argument
+function seq.mapmethod (iter,name,arg1,arg2)
+    iter = default_iter(iter)
+    return function()
+        local val = iter()
+        if not val then return end
+        local fn = val[name]
+        if not fn then error(type(val).." does not have method "..name) end
+        return fn(val,arg1,arg2)
+    end
+end
+
+--- a sequence of (last,current) values from another sequence.
+--  This will return S(i-1),S(i) if given S(i)
+-- @param iter a sequence
+function seq.last (iter)
+    iter = default_iter(iter)
+    local val, l = iter(), nil
+    if val == nil then return list{} end
+    return function ()
+        val,l = iter(),val
+        if val == nil then return nil end
+        return val,l
+    end
+end
+
+--- call the function on each element of the sequence.
+-- @param iter a sequence with up to 3 values
+-- @param fn a function
+function seq.foreach(iter,fn)
+    fn = function_arg(2,fn)
+    for i1,i2,i3 in default_iter(iter) do fn(i1,i2,i3) end
+end
+
+---------------------- Sequence Adapters ---------------------
+
+local SMT
+
+local function SW (iter,...)
+    if callable(iter) then
+        return setmetatable({iter=iter},SMT)
+    else
+        return iter,...
+    end
+end
+
+
+-- can't directly look these up in seq because of the wrong argument order...
+local map,reduce,mapmethod = seq.map, seq.reduce, seq.mapmethod
+local overrides = {
+    map = function(self,fun,arg)
+        return map(fun,self,arg)
+    end,
+    reduce = function(self,fun,initval)
+        return reduce(fun,self,initval)
+    end
+}
+
+SMT = {
+    __index = function (tbl,key)
+        local fn = overrides[key] or seq[key]
+        if fn then
+            return function(sw,...) return SW(fn(sw.iter,...)) end
+        else
+            return function(sw,...) return SW(mapmethod(sw.iter,key,...)) end
+        end
+    end,
+    __call = function (sw)
+        return sw.iter()
+    end,
+}
+
+setmetatable(seq,{
+    __call = function(tbl,iter,extra)
+        if not callable(iter) then
+            if type(iter) == 'table' then iter = seq.list(iter)
+            else return iter
+            end
+        end
+        if extra then
+            return setmetatable({iter=function()
+                return iter(extra)
+            end},SMT)
+        else
+            return setmetatable({iter=iter},SMT)
+        end
+    end
+})
+
+--- create a wrapped iterator over all lines in the file.
+-- @param f either a filename, file-like object, or 'STDIN' (for standard input)
+-- @param ... for Lua 5.2 only, optional format specifiers, as in `io.read`.
+-- @return a sequence wrapper
+function seq.lines (f,...)
+    local iter,obj
+    if f == 'STDIN' then
+        f = io.stdin
+    elseif type(f) == 'string' then
+        iter,obj = io.lines(f,...)
+    elseif not f.read then
+        error("Pass either a string or a file-like object",2)
+    end
+    if not iter then
+        iter,obj = f:lines(...)
+    end
+    if obj then -- LuaJIT version returns a function operating on a file
+        local lines,file = iter,obj
+        iter = function() return lines(file) end
+    end
+    return SW(iter)
+end
+
+function seq.import ()
+    debug.setmetatable(function() end,{
+        __index = function(tbl,key)
+            local s = overrides[key] or seq[key]
+            if s then return s
+            else
+                return function(s,...) return seq.mapmethod(s,key,...) end
+            end
+        end
+    })
+end
+
+return seq
+
+end,
+
+["pl.Set"] = function()
+--------------------
+-- Module: 'pl.Set'
+--------------------
+--- A Set class.
+--
+--     > Set = require 'pl.Set'
+--     > = Set{'one','two'} == Set{'two','one'}
+--     true
+--     > fruit = Set{'apple','banana','orange'}
+--     > = fruit['banana']
+--     true
+--     > = fruit['hazelnut']
+--     nil
+--     > colours = Set{'red','orange','green','blue'}
+--     > = fruit,colours
+--     [apple,orange,banana]   [blue,green,orange,red]
+--     > = fruit+colours
+--     [blue,green,apple,red,orange,banana]
+--     [orange]
+--     > more_fruits = fruit + 'apricot'
+--     > = fruit*colours
+--    > =  more_fruits, fruit
+--    [banana,apricot,apple,orange]	[banana,apple,orange]
+--
+-- Dependencies: `pl.utils`, `pl.tablex`, `pl.class`, `pl.Map`, (`pl.List` if __tostring is used)
+-- @classmod pl.Set
+
+local tablex = require 'pl.tablex'
+local utils = require 'pl.utils'
+local array_tostring, concat = utils.array_tostring, table.concat
+local merge,difference = tablex.merge,tablex.difference
+local Map = require 'pl.Map'
+local class = require 'pl.class'
+local stdmt = utils.stdmt
+local Set = stdmt.Set
+
+-- the Set class --------------------
+class(Map,nil,Set)
+
+-- note: Set has _no_ methods!
+Set.__index = nil
+
+local function makeset (t)
+    return setmetatable(t,Set)
+end
+
+--- create a set. <br>
+-- @param t may be a Set, Map or list-like table.
+-- @class function
+-- @name Set
+function Set:_init (t)
+    t = t or {}
+    local mt = getmetatable(t)
+    if mt == Set or mt == Map then
+        for k in pairs(t) do self[k] = true end
+    else
+        for _,v in ipairs(t) do self[v] = true end
+    end
+end
+
+--- string representation of a set.
+-- @within metamethods
+function Set:__tostring ()
+    return '['..concat(array_tostring(Set.values(self)),',')..']'
+end
+
+--- get a list of the values in a set.
+-- @param self a Set
+-- @function Set.values
+-- @return a list
+Set.values = Map.keys
+
+--- map a function over the values of a set.
+-- @param self a Set
+-- @param fn a function
+-- @param ... extra arguments to pass to the function.
+-- @return a new set
+function Set.map (self,fn,...)
+    fn = utils.function_arg(1,fn)
+    local res = {}
+    for k in pairs(self) do
+        res[fn(k,...)] = true
+    end
+    return makeset(res)
+end
+
+--- union of two sets (also +).
+-- @param self a Set
+-- @param set another set
+-- @return a new set
+function Set.union (self,set)
+    return merge(self,set,true)
+end
+
+--- modifies '+' operator to allow addition of non-Set elements
+--- Preserves +/- semantics - does not modify first argument.
+local function setadd(self,other)
+    local mt = getmetatable(other)
+    if mt == Set or mt == Map then
+        return Set.union(self,other)
+    else
+        local new = Set(self)
+        new[other] = true
+        return new
+    end
+end
+
+--- union of sets.
+-- @within metamethods
+-- @function Set.__add
+
+Set.__add = setadd
+
+--- intersection of two sets (also *).
+-- @param self a Set
+-- @param set another set
+-- @return a new set
+-- @usage
+-- > s = Set{10,20,30}
+-- > t = Set{20,30,40}
+-- > = t
+-- [20,30,40]
+-- > = Set.intersection(s,t)
+-- [30,20]
+-- > = s*t
+-- [30,20]
+
+function Set.intersection (self,set)
+    return merge(self,set,false)
+end
+
+--- intersection of sets.
+-- @within metamethods
+-- @function Set.__mul
+Set.__mul = Set.intersection
+
+--- new set with elements in the set that are not in the other (also -).
+-- @param self a Set
+-- @param set another set
+-- @return a new set
+function Set.difference (self,set)
+    return difference(self,set,false)
+end
+
+--- modifies "-" operator to remove non-Set values from set.
+--- Preserves +/- semantics - does not modify first argument.
+local function setminus (self,other)
+    local mt = getmetatable(other)
+    if mt == Set or mt == Map then
+        return Set.difference(self,other)
+    else
+        local new = Set(self)
+        new[other] = nil
+        return new
+    end
+end
+
+--- difference of sets.
+-- @within metamethods
+-- @function Set.__sub
+Set.__sub = setminus
+
+-- a new set with elements in _either_ the set _or_ other but not both (also ^).
+-- @param self a Set
+-- @param set another set
+-- @return a new set
+function Set.symmetric_difference (self,set)
+    return difference(self,set,true)
+end
+
+--- symmetric difference of sets.
+-- @within metamethods
+-- @function Set.__pow
+Set.__pow = Set.symmetric_difference
+
+--- is the first set a subset of the second (also <)?.
+-- @param self a Set
+-- @param set another set
+-- @return true or false
+function Set.issubset (self,set)
+    for k in pairs(self) do
+        if not set[k] then return false end
+    end
+    return true
+end
+
+--- first set subset of second?
+-- @within metamethods
+-- @function Set.__lt
+Set.__lt = Set.issubset
+
+--- is the set empty?.
+-- @param self a Set
+-- @return true or false
+function Set.isempty (self)
+    return next(self) == nil
+end
+
+--- are the sets disjoint? (no elements in common).
+-- Uses naive definition, i.e. that intersection is empty
+-- @param s1 a Set
+-- @param s2 another set
+-- @return true or false
+function Set.isdisjoint (s1,s2)
+    return Set.isempty(Set.intersection(s1,s2))
+end
+
+--- size of this set (also # for 5.2).
+-- @param s a Set
+-- @return size
+-- @function Set.len
+Set.len = tablex.size
+
+--- cardinality of set (5.2).
+-- @within metamethods
+-- @function Set.__len
+Set.__len = Set.len
+
+--- equality between sets.
+-- @within metamethods
+function Set.__eq (s1,s2)
+    return Set.issubset(s1,s2) and Set.issubset(s2,s1)
+end
+
+return Set
+
+end,
+
+["pl.sip"] = function()
+--------------------
+-- Module: 'pl.sip'
+--------------------
+--- Simple Input Patterns (SIP).
+-- SIP patterns start with '$', then a
+-- one-letter type, and then an optional variable in curly braces.
+--
+--    sip.match('$v=$q','name="dolly"',res)
+--    ==> res=={'name','dolly'}
+--    sip.match('($q{first},$q{second})','("john","smith")',res)
+--    ==> res=={second='smith',first='john'}
+--
+-- Type names:
+--
+--    v     identifier
+--    i     integer
+--    f     floating-point
+--    q     quoted string
+--    ([{<  match up to closing bracket
+--
+-- See @{08-additional.md.Simple_Input_Patterns|the Guide}
+--
+-- @module pl.sip
+
+local loadstring = rawget(_G,'loadstring') or load
+local unpack = rawget(_G,'unpack') or rawget(table,'unpack')
+
+local append,concat = table.insert,table.concat
+local ipairs,type = ipairs,type
+local io,_G = io,_G
+local print,rawget = print,rawget
+
+local patterns = {
+    FLOAT = '[%+%-%d]%d*%.?%d*[eE]?[%+%-]?%d*',
+    INTEGER = '[+%-%d]%d*',
+    IDEN = '[%a_][%w_]*',
+    OPTION = '[%a_][%w_%-]*',
+}
+
+local function assert_arg(idx,val,tp)
+    if type(val) ~= tp then
+        error("argument "..idx.." must be "..tp, 2)
+    end
+end
+
+local sip = {}
+
+local brackets = {['<'] = '>', ['('] = ')', ['{'] = '}', ['['] = ']' }
+local stdclasses = {a=1,c=0,d=1,l=1,p=0,u=1,w=1,x=1,s=0}
+
+local function group(s)
+    return '('..s..')'
+end
+
+-- escape all magic characters except $, which has special meaning
+-- Also, un-escape any characters after $, so $( and $[ passes through as is.
+local function escape (spec)
+    return (spec:gsub('[%-%.%+%[%]%(%)%^%%%?%*]','%%%0'):gsub('%$%%(%S)','$%1'))
+end
+
+-- Most spaces within patterns can match zero or more spaces.
+-- Spaces between alphanumeric characters or underscores or between
+-- patterns that can match these characters, however, must match at least
+-- one space. Otherwise '$v $v' would match 'abcd' as {'abc', 'd'}.
+-- This function replaces continuous spaces within a pattern with either
+-- '%s*' or '%s+' according to this rule. The pattern has already
+-- been stripped of pattern names by now.
+local function compress_spaces(patt)
+    return (patt:gsub("()%s+()", function(i1, i2)
+        local before = patt:sub(i1 - 2, i1 - 1)
+        if before:match('%$[vifadxlu]') or before:match('^[^%$]?[%w_]$') then
+            local after = patt:sub(i2, i2 + 1)
+            if after:match('%$[vifadxlu]') or after:match('^[%w_]') then
+                return '%s+'
+            end
+        end
+        return '%s*'
+    end))
+end
+
+local pattern_map = {
+  v = group(patterns.IDEN),
+  i = group(patterns.INTEGER),
+  f = group(patterns.FLOAT),
+  o = group(patterns.OPTION),
+  r = '(%S.*)',
+  p = '([%a]?[:]?[\\/%.%w_]+)'
+}
+
+function sip.custom_pattern(flag,patt)
+    pattern_map[flag] = patt
+end
+
+--- convert a SIP pattern into the equivalent Lua string pattern.
+-- @param spec a SIP pattern
+-- @param options a table; only the <code>at_start</code> field is
+-- currently meaningful and ensures that the pattern is anchored
+-- at the start of the string.
+-- @return a Lua string pattern.
+function sip.create_pattern (spec,options)
+    assert_arg(1,spec,'string')
+    local fieldnames,fieldtypes = {},{}
+
+    if type(spec) == 'string' then
+        spec = escape(spec)
+    else
+        local res = {}
+        for i,s in ipairs(spec) do
+            res[i] = escape(s)
+        end
+        spec = concat(res,'.-')
+    end
+
+    local kount = 1
+
+    local function addfield (name,type)
+        name = name or kount
+        append(fieldnames,name)
+        fieldtypes[name] = type
+        kount = kount + 1
+    end
+
+    local named_vars = spec:find('{%a+}')
+
+    if options and options.at_start then
+        spec = '^'..spec
+    end
+    if spec:sub(-1,-1) == '$' then
+        spec = spec:sub(1,-2)..'$r'
+        if named_vars then spec = spec..'{rest}' end
+    end
+
+    local names
+
+    if named_vars then
+        names = {}
+        spec = spec:gsub('{(%a+)}',function(name)
+            append(names,name)
+            return ''
+        end)
+    end
+    spec = compress_spaces(spec)
+
+    local k = 1
+    local err
+    local r = (spec:gsub('%$%S',function(s)
+        local type,name
+        type = s:sub(2,2)
+        if names then name = names[k]; k=k+1 end
+        -- this kludge is necessary because %q generates two matches, and
+        -- we want to ignore the first. Not a problem for named captures.
+        if not names and type == 'q' then
+            addfield(nil,'Q')
+        else
+            addfield(name,type)
+        end
+        local res
+        if pattern_map[type] then
+            res = pattern_map[type]
+        elseif type == 'q' then
+            -- some Lua pattern matching voodoo; we want to match '...' as
+            -- well as "...", and can use the fact that %n will match a
+            -- previous capture. Adding the extra field above comes from needing
+            -- to accommodate the extra spurious match (which is either ' or ")
+            addfield(name,type)
+            res = '(["\'])(.-)%'..(kount-2)
+        else
+            local endbracket = brackets[type]
+            if endbracket then
+                res = '(%b'..type..endbracket..')'
+            elseif stdclasses[type] or stdclasses[type:lower()] then
+                res = '(%'..type..'+)'
+            else
+                err = "unknown format type or character class"
+            end
+        end
+        return res
+    end))
+
+    if err then
+        return nil,err
+    else
+        return r,fieldnames,fieldtypes
+    end
+end
+
+
+local function tnumber (s)
+    return s == 'd' or s == 'i' or s == 'f'
+end
+
+function sip.create_spec_fun(spec,options)
+    local fieldtypes,fieldnames
+    local ls = {}
+    spec,fieldnames,fieldtypes = sip.create_pattern(spec,options)
+    if not spec then return spec,fieldnames end
+    local named_vars = type(fieldnames[1]) == 'string'
+    for i = 1,#fieldnames do
+        append(ls,'mm'..i)
+    end
+    ls[1] = ls[1] or "mm1" -- behave correctly if there are no patterns
+    local fun = ('return (function(s,res)\n\tlocal %s = s:match(%q)\n'):format(concat(ls,','),spec)
+    fun = fun..'\tif not mm1 then return false end\n'
+    local k=1
+    for i,f in ipairs(fieldnames) do
+        if f ~= '_' then
+            local var = 'mm'..i
+            if tnumber(fieldtypes[f]) then
+                var = 'tonumber('..var..')'
+            elseif brackets[fieldtypes[f]] then
+                var = var..':sub(2,-2)'
+            end
+            if named_vars then
+                fun = ('%s\tres.%s = %s\n'):format(fun,f,var)
+            else
+                if fieldtypes[f] ~= 'Q' then -- we skip the string-delim capture
+                    fun = ('%s\tres[%d] = %s\n'):format(fun,k,var)
+                    k = k + 1
+                end
+            end
+        end
+    end
+    return fun..'\treturn true\nend)\n', named_vars
+end
+
+--- convert a SIP pattern into a matching function.
+-- The returned function takes two arguments, the line and an empty table.
+-- If the line matched the pattern, then this function returns true
+-- and the table is filled with field-value pairs.
+-- @param spec a SIP pattern
+-- @param options optional table; {at_start=true} ensures that the pattern
+-- is anchored at the start of the string.
+-- @return a function if successful, or nil,error
+function sip.compile(spec,options)
+    assert_arg(1,spec,'string')
+    local fun,names = sip.create_spec_fun(spec,options)
+    if not fun then return nil,names end
+    if rawget(_G,'_DEBUG') then print(fun) end
+    local chunk,err = loadstring(fun,'tmp')
+    if err then return nil,err end
+    return chunk(),names
+end
+
+local cache = {}
+
+--- match a SIP pattern against a string.
+-- @param spec a SIP pattern
+-- @param line a string
+-- @param res a table to receive values
+-- @param options (optional) option table
+-- @return true or false
+function sip.match (spec,line,res,options)
+    assert_arg(1,spec,'string')
+    assert_arg(2,line,'string')
+    assert_arg(3,res,'table')
+    if not cache[spec] then
+        cache[spec] = sip.compile(spec,options)
+    end
+    return cache[spec](line,res)
+end
+
+--- match a SIP pattern against the start of a string.
+-- @param spec a SIP pattern
+-- @param line a string
+-- @param res a table to receive values
+-- @return true or false
+function sip.match_at_start (spec,line,res)
+    return sip.match(spec,line,res,{at_start=true})
+end
+
+--- given a pattern and a file object, return an iterator over the results
+-- @param spec a SIP pattern
+-- @param f a file-like object.
+function sip.fields (spec,f)
+    assert_arg(1,spec,'string')
+    if not f then return nil,"no file object" end
+    local fun,err = sip.compile(spec)
+    if not fun then return nil,err end
+    local res = {}
+    return function()
+        while true do
+            local line = f:read()
+            if not line then return end
+            if fun(line,res) then
+                local values = res
+                res = {}
+                return unpack(values)
+            end
+        end
+    end
+end
+
+local read_patterns = {}
+
+--- register a match which will be used in the read function.
+-- @string spec a SIP pattern
+-- @func fun a function to be called with the results of the match
+-- @see read
+function sip.pattern (spec,fun)
+    assert_arg(1,spec,'string')
+    local pat,named = sip.compile(spec)
+    append(read_patterns,{pat=pat,named=named,callback=fun})
+end
+
+--- enter a loop which applies all registered matches to the input file.
+-- @param f a file-like object
+-- @array matches optional list of `{spec,fun}` pairs, as for `pattern` above.
+function sip.read (f,matches)
+    local owned,err
+    if not f then return nil,"no file object" end
+    if type(f) == 'string' then
+        f,err = io.open(f)
+        if not f then return nil,err end
+        owned = true
+    end
+    if matches then
+        for _,p in ipairs(matches) do
+            sip.pattern(p[1],p[2])
+        end
+    end
+    local res = {}
+    for line in f:lines() do
+        for _,item in ipairs(read_patterns) do
+            if item.pat(line,res) then
+                if item.callback then
+                    if item.named then
+                        item.callback(res)
+                    else
+                        item.callback(unpack(res))
+                    end
+                end
+                res = {}
+                break
+            end
+        end
+    end
+    if owned then f:close() end
+end
+
+return sip
+
+end,
+
+["pl.strict"] = function()
+--------------------
+-- Module: 'pl.strict'
+--------------------
+--- Checks uses of undeclared global variables.
+-- All global variables must be 'declared' through a regular assignment
+-- (even assigning `nil` will do) in a main chunk before being used
+-- anywhere or assigned to inside a function. Existing metatables `__newindex` and `__index`
+-- metamethods are respected.
+--
+-- You can set any table to have strict behaviour using `strict.module`. Creating a new
+-- module with `strict.closed_module` makes the module immune to monkey-patching, if
+-- you don't wish to encourage monkey business.
+--
+-- If the global `PENLIGHT_NO_GLOBAL_STRICT` is defined, then this module won't make the
+-- global environment strict - if you just want to explicitly set table strictness.
+--
+-- @module pl.strict
+
+require 'debug' -- for Lua 5.2
+local getinfo, error, rawset, rawget = debug.getinfo, error, rawset, rawget
+local strict = {}
+
+local function what ()
+    local d = getinfo(3, "S")
+    return d and d.what or "C"
+end
+
+--- make an existing table strict.
+-- @string[opt] name name of table
+-- @tab[opt] mod the table to protect - if `nil` then we'll return a new table
+-- @tab[opt] predeclared - table of variables that are to be considered predeclared.
+-- @return the given table, or a new table
+-- @usage
+-- local M = { hello = "world" }
+-- strict.module ("Awesome_Module", M, {
+--   Lua = true,  -- defines allowed keys
+-- })
+--
+-- assert(M.hello == "world")
+-- assert(M.Lua == nil)       -- access allowed, but has no value yet
+-- M.Lua = "Rocks"
+-- assert(M.Lua == "Rocks")
+-- M.not_allowed = "bad boy"  -- throws an error
+function strict.module (name,mod,predeclared)
+    local mt, old_newindex, old_index, old_index_type, global
+    if predeclared then
+        global = predeclared.__global
+    end
+    if type(mod) == 'table' then
+        mt = getmetatable(mod)
+        if mt and rawget(mt,'__declared') then return end -- already patched...
+    else
+        mod = {}
+    end
+    if mt == nil then
+        mt = {}
+        setmetatable(mod, mt)
+    else
+        old_newindex = mt.__newindex
+        old_index = mt.__index
+        old_index_type = type(old_index)
+    end
+    mt.__declared = predeclared or {}
+    mt.__newindex = function(t, n, v)
+        if old_newindex then
+            old_newindex(t, n, v)
+            if rawget(t,n)~=nil then return end
+        end
+        if not mt.__declared[n] then
+            if global then
+                local w = what()
+                if w ~= "main" and w ~= "C" then
+                    error("assign to undeclared global '"..n.."'", 2)
+                end
+            end
+            mt.__declared[n] = true
+        end
+        rawset(t, n, v)
+    end
+    mt.__index = function(t,n)
+        if not mt.__declared[n] and what() ~= "C" then
+            if old_index then
+                if old_index_type == "table" then
+                    local fallback = old_index[n]
+                    if fallback ~= nil then
+                        return fallback
+                    end
+                else
+                    local res = old_index(t, n)
+                    if res ~= nil then
+                        return res
+                    end
+                end
+            end
+            local msg = "variable '"..n.."' is not declared"
+            if name then
+                msg = msg .. " in '"..tostring(name).."'"
+            end
+            error(msg, 2)
+        end
+        return rawget(t, n)
+    end
+    return mod
+end
+
+--- make all tables in a table strict.
+-- So `strict.make_all_strict(_G)` prevents monkey-patching
+-- of any global table
+-- @tab T the table containing the tables to protect. Table `T` itself will NOT be protected.
+function strict.make_all_strict (T)
+    for k,v in pairs(T) do
+        if type(v) == 'table' and v ~= T then
+            strict.module(k,v)
+        end
+    end
+end
+
+--- make a new module table which is closed to further changes.
+-- @tab mod module table
+-- @string name module name
+function strict.closed_module (mod,name)
+    -- No clue to what this is useful for? see tests
+    -- Deprecate this and remove???
+    local M = {}
+    mod = mod or {}
+    local mt = getmetatable(mod)
+    if not mt then
+        mt = {}
+        setmetatable(mod,mt)
+    end
+    mt.__newindex = function(t,k,v)
+        M[k] = v
+    end
+    return strict.module(name,M)
+end
+
+if not rawget(_G,'PENLIGHT_NO_GLOBAL_STRICT') then
+    strict.module(nil,_G,{_PROMPT=true,_PROMPT2=true,__global=true})
+end
+
+return strict
+
+end,
+
+["pl.stringio"] = function()
+--------------------
+-- Module: 'pl.stringio'
+--------------------
+--- Reading and writing strings using file-like objects. <br>
+--
+--    f = stringio.open(text)
+--    l1 = f:read()  -- read first line
+--    n,m = f:read ('*n','*n') -- read two numbers
+--    for line in f:lines() do print(line) end -- iterate over all lines
+--    f = stringio.create()
+--    f:write('hello')
+--    f:write('dolly')
+--    assert(f:value(),'hellodolly')
+--
+-- See  @{03-strings.md.File_style_I_O_on_Strings|the Guide}.
+-- @module pl.stringio
+
+local unpack = rawget(_G,'unpack') or rawget(table,'unpack')
+local tonumber = tonumber
+local concat,append = table.concat,table.insert
+
+local stringio = {}
+
+-- Writer class
+local SW = {}
+SW.__index = SW
+
+local function xwrite(self,...)
+    local args = {...} --arguments may not be nil!
+    for i = 1, #args do
+        append(self.tbl,args[i])
+    end
+end
+
+function SW:write(arg1,arg2,...)
+    if arg2 then
+        xwrite(self,arg1,arg2,...)
+    else
+        append(self.tbl,arg1)
+    end
+end
+
+function SW:writef(fmt,...)
+    self:write(fmt:format(...))
+end
+
+function SW:value()
+    return concat(self.tbl)
+end
+
+function SW:__tostring()
+    return self:value()
+end
+
+function SW:close() -- for compatibility only
+end
+
+function SW:seek()
+end
+
+-- Reader class
+local SR = {}
+SR.__index = SR
+
+function SR:_read(fmt)
+    local i,str = self.i,self.str
+    local sz = #str
+    if i > sz then return nil end
+    local res
+    if fmt == '*l' or fmt == '*L' then
+        local idx = str:find('\n',i) or (sz+1)
+        res = str:sub(i,fmt == '*l' and idx-1 or idx)
+        self.i = idx+1
+    elseif fmt == '*a' then
+        res = str:sub(i)
+        self.i = sz
+    elseif fmt == '*n' then
+        local _,i2,idx
+        _,idx = str:find ('%s*%d+',i)
+        _,i2 = str:find ('^%.%d+',idx+1)
+        if i2 then idx = i2 end
+        _,i2 = str:find ('^[eE][%+%-]*%d+',idx+1)
+        if i2 then idx = i2 end
+        local val = str:sub(i,idx)
+        res = tonumber(val)
+        self.i = idx+1
+    elseif type(fmt) == 'number' then
+        res = str:sub(i,i+fmt-1)
+        self.i = i + fmt
+    else
+        error("bad read format",2)
+    end
+    return res
+end
+
+function SR:read(...)
+    if select('#',...) == 0 then
+        return self:_read('*l')
+    else
+        local res, fmts = {},{...}
+        for i = 1, #fmts do
+            res[i] = self:_read(fmts[i])
+        end
+        return unpack(res)
+    end
+end
+
+function SR:seek(whence,offset)
+    local base
+    whence = whence or 'cur'
+    offset = offset or 0
+    if whence == 'set' then
+        base = 1
+    elseif whence == 'cur' then
+        base = self.i
+    elseif whence == 'end' then
+        base = #self.str
+    end
+    self.i = base + offset
+    return self.i
+end
+
+function SR:lines(...)
+    local n, args = select('#',...)
+    if n > 0 then
+        args = {...}
+    end
+    return function()
+        if n == 0 then
+            return self:_read '*l'
+        else
+            return self:read(unpack(args))
+        end
+    end
+end
+
+function SR:close() -- for compatibility only
+end
+
+--- create a file-like object which can be used to construct a string.
+-- The resulting object has an extra `value()` method for
+-- retrieving the string value.  Implements `file:write`, `file:seek`, `file:lines`,
+-- plus an extra `writef` method which works like `utils.printf`.
+-- @usage f = create(); f:write('hello, dolly\n'); print(f:value())
+function stringio.create()
+    return setmetatable({tbl={}},SW)
+end
+
+--- create a file-like object for reading from a given string.
+-- Implements `file:read`.
+-- @string s The input string.
+-- @usage fs = open '20 10'; x,y = f:read ('*n','*n'); assert(x == 20 and y == 10)
+function stringio.open(s)
+    return setmetatable({str=s,i=1},SR)
+end
+
+function stringio.lines(s,...)
+    return stringio.open(s):lines(...)
+end
+
+return stringio
+
+end,
+
+["pl.stringx"] = function()
+--------------------
+-- Module: 'pl.stringx'
+--------------------
+--- Python-style extended string library.
+--
+-- see 3.6.1 of the Python reference.
+-- If you want to make these available as string methods, then say
+-- `stringx.import()` to bring them into the standard `string` table.
+--
+-- See @{03-strings.md|the Guide}
+--
+-- Dependencies: `pl.utils`
+-- @module pl.stringx
+local utils = require 'pl.utils'
+local string = string
+local find = string.find
+local type,setmetatable,ipairs = type,setmetatable,ipairs
+local error = error
+local gsub = string.gsub
+local rep = string.rep
+local sub = string.sub
+local reverse = string.reverse
+local concat = table.concat
+local append = table.insert
+local escape = utils.escape
+local ceil, max = math.ceil, math.max
+local assert_arg,usplit = utils.assert_arg,utils.split
+local lstrip
+
+local function assert_string (n,s)
+    assert_arg(n,s,'string')
+end
+
+local function non_empty(s)
+    return #s > 0
+end
+
+local function assert_nonempty_string(n,s)
+    assert_arg(n,s,'string',non_empty,'must be a non-empty string')
+end
+
+local function makelist(l)
+    return setmetatable(l, require('pl.List'))
+end
+
+local stringx = {}
+
+------------------
+-- String Predicates
+-- @section predicates
+
+--- does s only contain alphabetic characters?
+-- @string s a string
+function stringx.isalpha(s)
+    assert_string(1,s)
+    return find(s,'^%a+$') == 1
+end
+
+--- does s only contain digits?
+-- @string s a string
+function stringx.isdigit(s)
+    assert_string(1,s)
+    return find(s,'^%d+$') == 1
+end
+
+--- does s only contain alphanumeric characters?
+-- @string s a string
+function stringx.isalnum(s)
+    assert_string(1,s)
+    return find(s,'^%w+$') == 1
+end
+
+--- does s only contain spaces?
+-- @string s a string
+function stringx.isspace(s)
+    assert_string(1,s)
+    return find(s,'^%s+$') == 1
+end
+
+--- does s only contain lower case characters?
+-- @string s a string
+function stringx.islower(s)
+    assert_string(1,s)
+    return find(s,'^[%l%s]+$') == 1
+end
+
+--- does s only contain upper case characters?
+-- @string s a string
+function stringx.isupper(s)
+    assert_string(1,s)
+    return find(s,'^[%u%s]+$') == 1
+end
+
+local function raw_startswith(s, prefix)
+    return find(s,prefix,1,true) == 1
+end
+
+local function raw_endswith(s, suffix)
+    return #s >= #suffix and find(s, suffix, #s-#suffix+1, true) and true or false
+end
+
+local function test_affixes(s, affixes, fn)
+    if type(affixes) == 'string' then
+        return fn(s,affixes)
+    elseif type(affixes) == 'table' then
+        for _,affix in ipairs(affixes) do
+            if fn(s,affix) then return true end
+        end
+        return false
+    else
+        error(("argument #2 expected a 'string' or a 'table', got a '%s'"):format(type(affixes)))
+    end
+end
+
+--- does s start with prefix or one of prefixes?
+-- @string s a string
+-- @param prefix a string or an array of strings
+function stringx.startswith(s,prefix)
+    assert_string(1,s)
+    return test_affixes(s,prefix,raw_startswith)
+end
+
+--- does s end with suffix or one of suffixes?
+-- @string s a string
+-- @param suffix a string or an array of strings
+function stringx.endswith(s,suffix)
+    assert_string(1,s)
+    return test_affixes(s,suffix,raw_endswith)
+end
+
+--- Strings and Lists
+-- @section lists
+
+--- concatenate the strings using this string as a delimiter.
+-- Note that the arguments are reversed from `string.concat`.
+-- @string s the string
+-- @param seq a table of strings or numbers
+-- @usage stringx.join(' ', {1,2,3}) == '1 2 3'
+function stringx.join(s,seq)
+    assert_string(1,s)
+    return concat(seq,s)
+end
+
+--- Split a string into a list of lines.
+-- `"\r"`, `"\n"`, and `"\r\n"` are considered line ends.
+-- They are not included in the lines unless `keepends` is passed.
+-- Terminal line end does not produce an extra line.
+-- Splitting an empty string results in an empty list.
+-- @string s the string.
+-- @bool[opt] keep_ends include line ends.
+-- @return List of lines
+function stringx.splitlines(s, keep_ends)
+    assert_string(1, s)
+    local res = {}
+    local pos = 1
+    while true do
+        local line_end_pos = find(s, '[\r\n]', pos)
+        if not line_end_pos then
+            break
+        end
+
+        local line_end = sub(s, line_end_pos, line_end_pos)
+        if line_end == '\r' and sub(s, line_end_pos + 1, line_end_pos + 1) == '\n' then
+            line_end = '\r\n'
+        end
+
+        local line = sub(s, pos, line_end_pos - 1)
+        if keep_ends then
+            line = line .. line_end
+        end
+        append(res, line)
+
+        pos = line_end_pos + #line_end
+    end
+
+    if pos <= #s then
+        append(res, sub(s, pos))
+    end
+    return makelist(res)
+end
+
+--- split a string into a list of strings using a delimiter.
+-- @function split
+-- @string s the string
+-- @string[opt] re a delimiter (defaults to whitespace)
+-- @int[opt] n maximum number of results
+-- @return List
+-- @usage #(stringx.split('one two')) == 2
+-- @usage stringx.split('one,two,three', ',') == List{'one','two','three'}
+-- @usage stringx.split('one,two,three', ',', 2) == List{'one','two,three'}
+function stringx.split(s,re,n)
+    assert_string(1,s)
+    local plain = true
+    if not re then -- default spaces
+        s = lstrip(s)
+        plain = false
+    end
+    local res = usplit(s,re,plain,n)
+    if re and re ~= '' and
+       find(s,re,-#re,true) and
+       (n or math.huge) > #res then
+        res[#res+1] = ""
+    end
+    return makelist(res)
+end
+
+--- replace all tabs in s with tabsize spaces. If not specified, tabsize defaults to 8.
+-- Tab stops will be honored.
+-- @string s the string
+-- @int tabsize[opt=8] number of spaces to expand each tab
+-- @return expanded string
+-- @usage stringx.expandtabs('\tone,two,three', 4)   == '    one,two,three'
+-- @usage stringx.expandtabs('  \tone,two,three', 4) == '    one,two,three'
+function stringx.expandtabs(s,tabsize)
+    assert_string(1,s)
+    tabsize = tabsize or 8
+    return (s:gsub("([^\t\r\n]*)\t", function(before_tab)
+        return before_tab .. (" "):rep(tabsize - #before_tab % tabsize)
+    end))
+end
+
+--- Finding and Replacing
+-- @section find
+
+local function _find_all(s,sub,first,last,allow_overlap)
+    first = first or 1
+    last = last or #s
+    if sub == '' then return last+1,last-first+1 end
+    local i1,i2 = find(s,sub,first,true)
+    local res
+    local k = 0
+    while i1 do
+        if last and i2 > last then break end
+        res = i1
+        k = k + 1
+        if allow_overlap then
+            i1,i2 = find(s,sub,i1+1,true)
+        else
+            i1,i2 = find(s,sub,i2+1,true)
+        end
+    end
+    return res,k
+end
+
+--- find index of first instance of sub in s from the left.
+-- @string s the string
+-- @string sub substring
+-- @int[opt] first first index
+-- @int[opt] last last index
+-- @return start index, or nil if not found
+function stringx.lfind(s,sub,first,last)
+    assert_string(1,s)
+    assert_string(2,sub)
+    local i1, i2 = find(s,sub,first,true)
+
+    if i1 and (not last or i2 <= last) then
+        return i1
+    else
+        return nil
+    end
+end
+
+--- find index of first instance of sub in s from the right.
+-- @string s the string
+-- @string sub substring
+-- @int[opt] first first index
+-- @int[opt] last last index
+-- @return start index, or nil if not found
+function stringx.rfind(s,sub,first,last)
+    assert_string(1,s)
+    assert_string(2,sub)
+    return (_find_all(s,sub,first,last,true))
+end
+
+--- replace up to n instances of old by new in the string s.
+-- If n is not present, replace all instances.
+-- @string s the string
+-- @string old the target substring
+-- @string new the substitution
+-- @int[opt] n optional maximum number of substitutions
+-- @return result string
+function stringx.replace(s,old,new,n)
+    assert_string(1,s)
+    assert_string(2,old)
+    assert_string(3,new)
+    return (gsub(s,escape(old),new:gsub('%%','%%%%'),n))
+end
+
+--- count all instances of substring in string.
+-- @string s the string
+-- @string sub substring
+-- @bool[opt] allow_overlap allow matches to overlap
+-- @usage
+-- assert(stringx.count('banana', 'ana') == 1)
+-- assert(stringx.count('banana', 'ana', true) == 2)
+function stringx.count(s,sub,allow_overlap)
+    assert_string(1,s)
+    local _,k = _find_all(s,sub,1,false,allow_overlap)
+    return k
+end
+
+--- Stripping and Justifying
+-- @section strip
+
+local function _just(s,w,ch,left,right)
+    local n = #s
+    if w > n then
+        if not ch then ch = ' ' end
+        local f1,f2
+        if left and right then
+            local rn = ceil((w-n)/2)
+            local ln = w - n - rn
+            f1 = rep(ch,ln)
+            f2 = rep(ch,rn)
+        elseif right then
+            f1 = rep(ch,w-n)
+            f2 = ''
+        else
+            f2 = rep(ch,w-n)
+            f1 = ''
+        end
+        return f1..s..f2
+    else
+        return s
+    end
+end
+
+--- left-justify s with width w.
+-- @string s the string
+-- @int w width of justification
+-- @string[opt=' '] ch padding character
+-- @usage stringx.ljust('hello', 10, '*') == '*****hello'
+function stringx.ljust(s,w,ch)
+    assert_string(1,s)
+    assert_arg(2,w,'number')
+    return _just(s,w,ch,true,false)
+end
+
+--- right-justify s with width w.
+-- @string s the string
+-- @int w width of justification
+-- @string[opt=' '] ch padding character
+-- @usage stringx.rjust('hello', 10, '*') == 'hello*****'
+function stringx.rjust(s,w,ch)
+    assert_string(1,s)
+    assert_arg(2,w,'number')
+    return _just(s,w,ch,false,true)
+end
+
+--- center-justify s with width w.
+-- @string s the string
+-- @int w width of justification
+-- @string[opt=' '] ch padding character
+-- @usage stringx.center('hello', 10, '*') == '**hello***'
+function stringx.center(s,w,ch)
+    assert_string(1,s)
+    assert_arg(2,w,'number')
+    return _just(s,w,ch,true,true)
+end
+
+local function _strip(s,left,right,chrs)
+    if not chrs then
+        chrs = '%s'
+    else
+        chrs = '['..escape(chrs)..']'
+    end
+    local f = 1
+    local t
+    if left then
+        local i1,i2 = find(s,'^'..chrs..'*')
+        if i2 >= i1 then
+            f = i2+1
+        end
+    end
+    if right then
+        if #s < 200 then
+            local i1,i2 = find(s,chrs..'*$',f)
+            if i2 >= i1 then
+                t = i1-1
+            end
+        else
+            local rs = reverse(s)
+            local i1,i2 = find(rs, '^'..chrs..'*')
+            if i2 >= i1 then
+                t = -i2-1
+            end
+        end
+    end
+    return sub(s,f,t)
+end
+
+--- trim any whitespace on the left of s.
+-- @string s the string
+-- @string[opt='%s'] chrs default any whitespace character,
+--  but can be a string of characters to be trimmed
+function stringx.lstrip(s,chrs)
+    assert_string(1,s)
+    return _strip(s,true,false,chrs)
+end
+lstrip = stringx.lstrip
+
+--- trim any whitespace on the right of s.
+-- @string s the string
+-- @string[opt='%s'] chrs default any whitespace character,
+--  but can be a string of characters to be trimmed
+function stringx.rstrip(s,chrs)
+    assert_string(1,s)
+    return _strip(s,false,true,chrs)
+end
+
+--- trim any whitespace on both left and right of s.
+-- @string s the string
+-- @string[opt='%s'] chrs default any whitespace character,
+--  but can be a string of characters to be trimmed
+function stringx.strip(s,chrs)
+    assert_string(1,s)
+    return _strip(s,true,true,chrs)
+end
+
+--- Partioning Strings
+-- @section partioning
+
+--- split a string using a pattern. Note that at least one value will be returned!
+-- @string s the string
+-- @string[opt='%s'] re a Lua string pattern (defaults to whitespace)
+-- @return the parts of the string
+-- @usage  a,b = line:splitv('=')
+-- @see utils.splitv
+function stringx.splitv(s,re)
+    assert_string(1,s)
+    return utils.splitv(s,re)
+end
+
+-- The partition functions split a string using a delimiter into three parts:
+-- the part before, the delimiter itself, and the part afterwards
+local function _partition(p,delim,fn)
+    local i1,i2 = fn(p,delim)
+    if not i1 or i1 == -1 then
+        return p,'',''
+    else
+        if not i2 then i2 = i1 end
+        return sub(p,1,i1-1),sub(p,i1,i2),sub(p,i2+1)
+    end
+end
+
+--- partition the string using first occurance of a delimiter
+-- @string s the string
+-- @string ch delimiter
+-- @return part before ch
+-- @return ch
+-- @return part after ch
+-- @usage {stringx.partition('a,b,c', ','))} == {'a', ',', 'b,c'}
+-- @usage {stringx.partition('abc', 'x'))} == {'abc', '', ''}
+function stringx.partition(s,ch)
+    assert_string(1,s)
+    assert_nonempty_string(2,ch)
+    return _partition(s,ch,stringx.lfind)
+end
+
+--- partition the string p using last occurance of a delimiter
+-- @string s the string
+-- @string ch delimiter
+-- @return part before ch
+-- @return ch
+-- @return part after ch
+-- @usage {stringx.rpartition('a,b,c', ','))} == {'a,b', ',', 'c'}
+-- @usage {stringx.rpartition('abc', 'x'))} == {'', '', 'abc'}
+function stringx.rpartition(s,ch)
+    assert_string(1,s)
+    assert_nonempty_string(2,ch)
+    local a,b,c = _partition(s,ch,stringx.rfind)
+    if a == s then -- no match found
+        return c,b,a
+    end
+    return a,b,c
+end
+
+--- return the 'character' at the index.
+-- @string s the string
+-- @int idx an index (can be negative)
+-- @return a substring of length 1 if successful, empty string otherwise.
+function stringx.at(s,idx)
+    assert_string(1,s)
+    assert_arg(2,idx,'number')
+    return sub(s,idx,idx)
+end
+
+--- Miscelaneous
+-- @section misc
+
+--- return an iterator over all lines in a string
+-- @string s the string
+-- @return an iterator
+-- @usage
+-- local line_no = 1
+-- for line in stringx.lines(some_text) do
+--   print(line_no, line)
+--   line_no = line_no + 1
+-- end
+function stringx.lines(s)
+    assert_string(1,s)
+    if not s:find '\n$' then s = s..'\n' end
+    return s:gmatch('([^\n]*)\n')
+end
+
+--- inital word letters uppercase ('title case').
+-- Here 'words' mean chunks of non-space characters.
+-- @string s the string
+-- @return a string with each word's first letter uppercase
+-- @usage stringx.title("hello world") == "Hello World")
+function stringx.title(s)
+    assert_string(1,s)
+    return (s:gsub('(%S)(%S*)',function(f,r)
+        return f:upper()..r:lower()
+    end))
+end
+
+stringx.capitalize = stringx.title
+
+local ellipsis = '...'
+local n_ellipsis = #ellipsis
+
+--- Return a shortened version of a string.
+-- Fits string within w characters. Removed characters are marked with ellipsis.
+-- @string s the string
+-- @int w the maxinum size allowed
+-- @bool tail true if we want to show the end of the string (head otherwise)
+-- @usage ('1234567890'):shorten(8) == '12345...'
+-- @usage ('1234567890'):shorten(8, true) == '...67890'
+-- @usage ('1234567890'):shorten(20) == '1234567890'
+function stringx.shorten(s,w,tail)
+    assert_string(1,s)
+    if #s > w then
+        if w < n_ellipsis then return ellipsis:sub(1,w) end
+        if tail then
+            local i = #s - w + 1 + n_ellipsis
+            return ellipsis .. s:sub(i)
+        else
+            return s:sub(1,w-n_ellipsis) .. ellipsis
+        end
+    end
+    return s
+end
+
+--- Utility function that finds any patterns that match a long string's an open or close.
+-- Note that having this function use the least number of equal signs that is possible is a harder algorithm to come up with.
+-- Right now, it simply returns the greatest number of them found.
+-- @param s The string
+-- @return 'nil' if not found. If found, the maximum number of equal signs found within all matches.
+local function has_lquote(s)
+    local lstring_pat = '([%[%]])(=*)%1'
+    local equals, new_equals, _
+    local finish = 1
+    repeat
+        _, finish, _, new_equals = s:find(lstring_pat, finish)
+        if new_equals then
+            equals = max(equals or 0, #new_equals)
+        end
+    until not new_equals
+
+    return equals
+end
+
+--- Quote the given string and preserve any control or escape characters, such that reloading the string in Lua returns the same result.
+-- @param s The string to be quoted.
+-- @return The quoted string.
+function stringx.quote_string(s)
+    assert_string(1,s)
+    -- Find out if there are any embedded long-quote sequences that may cause issues.
+    -- This is important when strings are embedded within strings, like when serializing.
+    -- Append a closing bracket to catch unfinished long-quote sequences at the end of the string.
+    local equal_signs = has_lquote(s .. "]")
+
+    -- Note that strings containing "\r" can't be quoted using long brackets
+    -- as Lua lexer converts all newlines to "\n" within long strings.
+    if (s:find("\n") or equal_signs) and not s:find("\r") then
+        -- If there is an embedded sequence that matches a long quote, then
+        -- find the one with the maximum number of = signs and add one to that number.
+        equal_signs = ("="):rep((equal_signs or -1) + 1)
+        -- Long strings strip out leading newline. We want to retain that, when quoting.
+        if s:find("^\n") then s = "\n" .. s end
+        local lbracket, rbracket =
+            "[" .. equal_signs .. "[",
+            "]" .. equal_signs .. "]"
+        s = lbracket .. s .. rbracket
+    else
+        -- Escape funny stuff. Lua 5.1 does not handle "\r" correctly.
+        s = ("%q"):format(s):gsub("\r", "\\r")
+    end
+    return s
+end
+
+function stringx.import()
+    utils.import(stringx,string)
+end
+
+return stringx
+
+end,
+
+["pl.tablex"] = function()
+--------------------
+-- Module: 'pl.tablex'
+--------------------
+--- Extended operations on Lua tables.
+--
+-- See @{02-arrays.md.Useful_Operations_on_Tables|the Guide}
+--
+-- Dependencies: `pl.utils`, `pl.types`
+-- @module pl.tablex
+local utils = require ('pl.utils')
+local types = require ('pl.types')
+local getmetatable,setmetatable,require = getmetatable,setmetatable,require
+local tsort,append,remove = table.sort,table.insert,table.remove
+local min = math.min
+local pairs,type,unpack,select,tostring = pairs,type,utils.unpack,select,tostring
+local function_arg = utils.function_arg
+local assert_arg = utils.assert_arg
+
+local tablex = {}
+
+-- generally, functions that make copies of tables try to preserve the metatable.
+-- However, when the source has no obvious type, then we attach appropriate metatables
+-- like List, Map, etc to the result.
+local function setmeta (res,tbl,pl_class)
+    local mt = getmetatable(tbl) or pl_class and require('pl.' .. pl_class)
+    return mt and setmetatable(res, mt) or res
+end
+
+local function makelist(l)
+    return setmetatable(l, require('pl.List'))
+end
+
+local function makemap(m)
+    return setmetatable(m, require('pl.Map'))
+end
+
+local function complain (idx,msg)
+    error(('argument %d is not %s'):format(idx,msg),3)
+end
+
+local function assert_arg_indexable (idx,val)
+    if not types.is_indexable(val) then
+        complain(idx,"indexable")
+    end
+end
+
+local function assert_arg_iterable (idx,val)
+    if not types.is_iterable(val) then
+        complain(idx,"iterable")
+    end
+end
+
+local function assert_arg_writeable (idx,val)
+    if not types.is_writeable(val) then
+        complain(idx,"writeable")
+    end
+end
+
+--- copy a table into another, in-place.
+-- @within Copying
+-- @tab t1 destination table
+-- @tab t2 source (actually any iterable object)
+-- @return first table
+function tablex.update (t1,t2)
+    assert_arg_writeable(1,t1)
+    assert_arg_iterable(2,t2)
+    for k,v in pairs(t2) do
+        t1[k] = v
+    end
+    return t1
+end
+
+--- total number of elements in this table.
+-- Note that this is distinct from `#t`, which is the number
+-- of values in the array part; this value will always
+-- be greater or equal. The difference gives the size of
+-- the hash part, for practical purposes. Works for any
+-- object with a __pairs metamethod.
+-- @tab t a table
+-- @return the size
+function tablex.size (t)
+    assert_arg_iterable(1,t)
+    local i = 0
+    for k in pairs(t) do i = i + 1 end
+    return i
+end
+
+--- make a shallow copy of a table
+-- @within Copying
+-- @tab t an iterable source
+-- @return new table
+function tablex.copy (t)
+    assert_arg_iterable(1,t)
+    local res = {}
+    for k,v in pairs(t) do
+        res[k] = v
+    end
+    return res
+end
+
+local function cycle_aware_copy(t, cache)
+    if type(t) ~= 'table' then return t end
+    if cache[t] then return cache[t] end
+    assert_arg_iterable(1,t)
+    local res = {}
+    cache[t] = res
+    local mt = getmetatable(t)
+    for k,v in pairs(t) do
+        k = cycle_aware_copy(k, cache)
+        v = cycle_aware_copy(v, cache)
+        res[k] = v
+    end
+    setmetatable(res,mt)
+    return res
+end
+
+--- make a deep copy of a table, recursively copying all the keys and fields.
+-- This supports cycles in tables; cycles will be reproduced in the copy.
+-- This will also set the copied table's metatable to that of the original.
+-- @within Copying
+-- @tab t A table
+-- @return new table
+function tablex.deepcopy(t)
+    return cycle_aware_copy(t,{})
+end
+
+local abs = math.abs
+
+local function cycle_aware_compare(t1,t2,ignore_mt,eps,cache)
+    if cache[t1] and cache[t1][t2] then return true end
+    local ty1 = type(t1)
+    local ty2 = type(t2)
+    if ty1 ~= ty2 then return false end
+    -- non-table types can be directly compared
+    if ty1 ~= 'table' then
+        if ty1 == 'number' and eps then return abs(t1-t2) < eps end
+        return t1 == t2
+    end
+    -- as well as tables which have the metamethod __eq
+    local mt = getmetatable(t1)
+    if not ignore_mt and mt and mt.__eq then return t1 == t2 end
+    for k1 in pairs(t1) do
+        if t2[k1]==nil then return false end
+    end
+    for k2 in pairs(t2) do
+        if t1[k2]==nil then return false end
+    end
+    cache[t1] = cache[t1] or {}
+    cache[t1][t2] = true
+    for k1,v1 in pairs(t1) do
+        local v2 = t2[k1]
+        if not cycle_aware_compare(v1,v2,ignore_mt,eps,cache) then return false end
+    end
+    return true
+end
+
+--- compare two values.
+-- if they are tables, then compare their keys and fields recursively.
+-- @within Comparing
+-- @param t1 A value
+-- @param t2 A value
+-- @bool[opt] ignore_mt if true, ignore __eq metamethod (default false)
+-- @number[opt] eps if defined, then used for any number comparisons
+-- @return true or false
+function tablex.deepcompare(t1,t2,ignore_mt,eps)
+    return cycle_aware_compare(t1,t2,ignore_mt,eps,{})
+end
+
+--- compare two arrays using a predicate.
+-- @within Comparing
+-- @array t1 an array
+-- @array t2 an array
+-- @func cmp A comparison function; `bool = cmp(t1_value, t2_value)`
+-- @return true or false
+-- @usage
+-- assert(tablex.compare({ 1, 2, 3 }, { 1, 2, 3 }, "=="))
+--
+-- assert(tablex.compare(
+--    {1,2,3, hello = "world"},  -- fields are not compared!
+--    {1,2,3}, function(v1, v2) return v1 == v2 end)
+function tablex.compare (t1,t2,cmp)
+    assert_arg_indexable(1,t1)
+    assert_arg_indexable(2,t2)
+    if #t1 ~= #t2 then return false end
+    cmp = function_arg(3,cmp)
+    for k = 1,#t1 do
+        if not cmp(t1[k],t2[k]) then return false end
+    end
+    return true
+end
+
+--- compare two list-like tables using an optional predicate, without regard for element order.
+-- @within Comparing
+-- @array t1 a list-like table
+-- @array t2 a list-like table
+-- @param cmp A comparison function (may be nil)
+function tablex.compare_no_order (t1,t2,cmp)
+    assert_arg_indexable(1,t1)
+    assert_arg_indexable(2,t2)
+    if cmp then cmp = function_arg(3,cmp) end
+    if #t1 ~= #t2 then return false end
+    local visited = {}
+    for i = 1,#t1 do
+        local val = t1[i]
+        local gotcha
+        for j = 1,#t2 do
+            if not visited[j] then
+                local match
+                if cmp then match = cmp(val,t2[j]) else match = val == t2[j] end
+                if match then
+                    gotcha = j
+                    break
+                end
+            end
+        end
+        if not gotcha then return false end
+        visited[gotcha] = true
+    end
+    return true
+end
+
+
+--- return the index of a value in a list.
+-- Like string.find, there is an optional index to start searching,
+-- which can be negative.
+-- @within Finding
+-- @array t A list-like table
+-- @param val A value
+-- @int idx index to start; -1 means last element,etc (default 1)
+-- @return index of value or nil if not found
+-- @usage find({10,20,30},20) == 2
+-- @usage find({'a','b','a','c'},'a',2) == 3
+function tablex.find(t,val,idx)
+    assert_arg_indexable(1,t)
+    idx = idx or 1
+    if idx < 0 then idx = #t + idx + 1 end
+    for i = idx,#t do
+        if t[i] == val then return i end
+    end
+    return nil
+end
+
+--- return the index of a value in a list, searching from the end.
+-- Like string.find, there is an optional index to start searching,
+-- which can be negative.
+-- @within Finding
+-- @array t A list-like table
+-- @param val A value
+-- @param idx index to start; -1 means last element,etc (default `#t`)
+-- @return index of value or nil if not found
+-- @usage rfind({10,10,10},10) == 3
+function tablex.rfind(t,val,idx)
+    assert_arg_indexable(1,t)
+    idx = idx or #t
+    if idx < 0 then idx = #t + idx + 1 end
+    for i = idx,1,-1 do
+        if t[i] == val then return i end
+    end
+    return nil
+end
+
+
+--- return the index (or key) of a value in a table using a comparison function.
+--
+-- *NOTE*: the 2nd return value of this function, the value returned
+-- by the comparison function, has a limitation that it cannot be `false`.
+-- Because if it is, then it indicates the comparison failed, and the
+-- function will continue the search. See examples.
+-- @within Finding
+-- @tab t A table
+-- @func cmp A comparison function
+-- @param arg an optional second argument to the function
+-- @return index of value, or nil if not found
+-- @return value returned by comparison function (cannot be `false`!)
+-- @usage
+-- -- using an operator
+-- local lst = { "Rudolph", true, false, 15 }
+-- local idx, cmp_result = tablex.rfind(lst, "==", "Rudolph")
+-- assert(idx == 1)
+-- assert(cmp_result == true)
+--
+-- local idx, cmp_result = tablex.rfind(lst, "==", false)
+-- assert(idx == 3)
+-- assert(cmp_result == true)       -- looking up 'false' works!
+--
+-- -- using a function returning the value looked up
+-- local cmp = function(v1, v2) return v1 == v2 and v2 end
+-- local idx, cmp_result = tablex.rfind(lst, cmp, "Rudolph")
+-- assert(idx == 1)
+-- assert(cmp_result == "Rudolph")  -- the value is returned
+--
+-- -- NOTE: this fails, since 'false' cannot be returned!
+-- local idx, cmp_result = tablex.rfind(lst, cmp, false)
+-- assert(idx == nil)               -- looking up 'false' failed!
+-- assert(cmp_result == nil)
+function tablex.find_if(t,cmp,arg)
+    assert_arg_iterable(1,t)
+    cmp = function_arg(2,cmp)
+    for k,v in pairs(t) do
+        local c = cmp(v,arg)
+        if c then return k,c end
+    end
+    return nil
+end
+
+--- return a list of all values in a table indexed by another list.
+-- @tab tbl a table
+-- @array idx an index table (a list of keys)
+-- @return a list-like table
+-- @usage index_by({10,20,30,40},{2,4}) == {20,40}
+-- @usage index_by({one=1,two=2,three=3},{'one','three'}) == {1,3}
+function tablex.index_by(tbl,idx)
+    assert_arg_indexable(1,tbl)
+    assert_arg_indexable(2,idx)
+    local res = {}
+    for i = 1,#idx do
+        res[i] = tbl[idx[i]]
+    end
+    return setmeta(res,tbl,'List')
+end
+
+--- apply a function to all values of a table.
+-- This returns a table of the results.
+-- Any extra arguments are passed to the function.
+-- @within MappingAndFiltering
+-- @func fun A function that takes at least one argument
+-- @tab t A table
+-- @param ... optional arguments
+-- @usage map(function(v) return v*v end, {10,20,30,fred=2}) is {100,400,900,fred=4}
+function tablex.map(fun,t,...)
+    assert_arg_iterable(1,t)
+    fun = function_arg(1,fun)
+    local res = {}
+    for k,v in pairs(t) do
+        res[k] = fun(v,...)
+    end
+    return setmeta(res,t)
+end
+
+--- apply a function to all values of a list.
+-- This returns a table of the results.
+-- Any extra arguments are passed to the function.
+-- @within MappingAndFiltering
+-- @func fun A function that takes at least one argument
+-- @array t a table (applies to array part)
+-- @param ... optional arguments
+-- @return a list-like table
+-- @usage imap(function(v) return v*v end, {10,20,30,fred=2}) is {100,400,900}
+function tablex.imap(fun,t,...)
+    assert_arg_indexable(1,t)
+    fun = function_arg(1,fun)
+    local res = {}
+    for i = 1,#t do
+        res[i] = fun(t[i],...) or false
+    end
+    return setmeta(res,t,'List')
+end
+
+--- apply a named method to values from a table.
+-- @within MappingAndFiltering
+-- @string name the method name
+-- @array t a list-like table
+-- @param ... any extra arguments to the method
+-- @return a `List` with the results of the method (1st result only)
+-- @usage
+-- local Car = {}
+-- Car.__index = Car
+-- function Car.new(car)
+--   return setmetatable(car or {}, Car)
+-- end
+-- Car.speed = 0
+-- function Car:faster(increase)
+--   self.speed = self.speed + increase
+--   return self.speed
+-- end
+--
+-- local ferrari = Car.new{ name = "Ferrari" }
+-- local lamborghini = Car.new{ name = "Lamborghini", speed = 50 }
+-- local cars = { ferrari, lamborghini }
+--
+-- assert(ferrari.speed == 0)
+-- assert(lamborghini.speed == 50)
+-- tablex.map_named_method("faster", cars, 10)
+-- assert(ferrari.speed == 10)
+-- assert(lamborghini.speed == 60)
+function tablex.map_named_method (name,t,...)
+    utils.assert_string(1,name)
+    assert_arg_indexable(2,t)
+    local res = {}
+    for i = 1,#t do
+        local val = t[i]
+        local fun = val[name]
+        res[i] = fun(val,...)
+    end
+    return setmeta(res,t,'List')
+end
+
+--- apply a function to all values of a table, in-place.
+-- Any extra arguments are passed to the function.
+-- @func fun A function that takes at least one argument
+-- @tab t a table
+-- @param ... extra arguments passed to `fun`
+-- @see tablex.foreach
+function tablex.transform (fun,t,...)
+    assert_arg_iterable(1,t)
+    fun = function_arg(1,fun)
+    for k,v in pairs(t) do
+        t[k] = fun(v,...)
+    end
+end
+
+--- generate a table of all numbers in a range.
+-- This is consistent with a numerical for loop.
+-- @int start  number
+-- @int finish number
+-- @int[opt=1] step  make this negative for start < finish
+function tablex.range (start,finish,step)
+    local res
+    step = step or 1
+    if start == finish then
+        res = {start}
+    elseif (start > finish and step > 0) or (finish > start and step < 0) then
+        res = {}
+    else
+        local k = 1
+        res = {}
+        for i=start,finish,step do res[k]=i; k=k+1 end
+    end
+    return makelist(res)
+end
+
+--- apply a function to values from two tables.
+-- @within MappingAndFiltering
+-- @func fun a function of at least two arguments
+-- @tab t1 a table
+-- @tab t2 a table
+-- @param ... extra arguments
+-- @return a table
+-- @usage map2('+',{1,2,3,m=4},{10,20,30,m=40}) is {11,22,23,m=44}
+function tablex.map2 (fun,t1,t2,...)
+    assert_arg_iterable(1,t1)
+    assert_arg_iterable(2,t2)
+    fun = function_arg(1,fun)
+    local res = {}
+    for k,v in pairs(t1) do
+        res[k] = fun(v,t2[k],...)
+    end
+    return setmeta(res,t1,'List')
+end
+
+--- apply a function to values from two arrays.
+-- The result will be the length of the shortest array.
+-- @within MappingAndFiltering
+-- @func fun a function of at least two arguments
+-- @array t1 a list-like table
+-- @array t2 a list-like table
+-- @param ... extra arguments
+-- @usage imap2('+',{1,2,3,m=4},{10,20,30,m=40}) is {11,22,23}
+function tablex.imap2 (fun,t1,t2,...)
+    assert_arg_indexable(2,t1)
+    assert_arg_indexable(3,t2)
+    fun = function_arg(1,fun)
+    local res,n = {},math.min(#t1,#t2)
+    for i = 1,n do
+        res[i] = fun(t1[i],t2[i],...)
+    end
+    return res
+end
+
+--- 'reduce' a list using a binary function.
+-- @func fun a function of two arguments
+-- @array t a list-like table
+-- @array memo optional initial memo value. Defaults to first value in table.
+-- @return the result of the function
+-- @usage reduce('+',{1,2,3,4}) == 10
+function tablex.reduce (fun,t,memo)
+    assert_arg_indexable(2,t)
+    fun = function_arg(1,fun)
+    local n = #t
+    if n == 0 then
+        return memo
+    end
+    local res = memo and fun(memo, t[1]) or t[1]
+    for i = 2,n do
+        res = fun(res,t[i])
+    end
+    return res
+end
+
+--- apply a function to all elements of a table.
+-- The arguments to the function will be the value,
+-- the key and _finally_ any extra arguments passed to this function.
+-- Note that the Lua 5.0 function table.foreach passed the _key_ first.
+-- @within Iterating
+-- @tab t a table
+-- @func fun a function on the elements; `function(value, key, ...)`
+-- @param ... extra arguments passed to `fun`
+-- @see tablex.transform
+function tablex.foreach(t,fun,...)
+    assert_arg_iterable(1,t)
+    fun = function_arg(2,fun)
+    for k,v in pairs(t) do
+        fun(v,k,...)
+    end
+end
+
+--- apply a function to all elements of a list-like table in order.
+-- The arguments to the function will be the value,
+-- the index and _finally_ any extra arguments passed to this function
+-- @within Iterating
+-- @array t a table
+-- @func fun a function with at least one argument
+-- @param ... optional arguments
+function tablex.foreachi(t,fun,...)
+    assert_arg_indexable(1,t)
+    fun = function_arg(2,fun)
+    for i = 1,#t do
+        fun(t[i],i,...)
+    end
+end
+
+--- Apply a function to a number of tables.
+-- A more general version of map
+-- The result is a table containing the result of applying that function to the
+-- ith value of each table. Length of output list is the minimum length of all the lists
+-- @within MappingAndFiltering
+-- @func fun a function of n arguments
+-- @tab ... n tables
+-- @usage mapn(function(x,y,z) return x+y+z end, {1,2,3},{10,20,30},{100,200,300}) is {111,222,333}
+-- @usage mapn(math.max, {1,20,300},{10,2,3},{100,200,100}) is    {100,200,300}
+-- @param fun A function that takes as many arguments as there are tables
+function tablex.mapn(fun,...)
+    fun = function_arg(1,fun)
+    local res = {}
+    local lists = {...}
+    local minn = 1e40
+    for i = 1,#lists do
+        minn = min(minn,#(lists[i]))
+    end
+    for i = 1,minn do
+        local args,k = {},1
+        for j = 1,#lists do
+            args[k] = lists[j][i]
+            k = k + 1
+        end
+        res[#res+1] = fun(unpack(args))
+    end
+    return res
+end
+
+--- call the function with the key and value pairs from a table.
+-- The function can return a value and a key (note the order!). If both
+-- are not nil, then this pair is inserted into the result: if the key already exists, we convert the value for that
+-- key into a table and append into it. If only value is not nil, then it is appended to the result.
+-- @within MappingAndFiltering
+-- @func fun A function which will be passed each key and value as arguments, plus any extra arguments to pairmap.
+-- @tab t A table
+-- @param ... optional arguments
+-- @usage pairmap(function(k,v) return v end,{fred=10,bonzo=20}) is {10,20} _or_ {20,10}
+-- @usage pairmap(function(k,v) return {k,v},k end,{one=1,two=2}) is {one={'one',1},two={'two',2}}
+function tablex.pairmap(fun,t,...)
+    assert_arg_iterable(1,t)
+    fun = function_arg(1,fun)
+    local res = {}
+    for k,v in pairs(t) do
+        local rv,rk = fun(k,v,...)
+        if rk then
+            if res[rk] then
+                if type(res[rk]) == 'table' then
+                    table.insert(res[rk],rv)
+                else
+                    res[rk] = {res[rk], rv}
+                end
+            else
+                res[rk] = rv
+            end
+        else
+            res[#res+1] = rv
+        end
+    end
+    return res
+end
+
+local function keys_op(i,v) return i end
+
+--- return all the keys of a table in arbitrary order.
+-- @within Extraction
+--  @tab t A table
+function tablex.keys(t)
+    assert_arg_iterable(1,t)
+    return makelist(tablex.pairmap(keys_op,t))
+end
+
+local function values_op(i,v) return v end
+
+--- return all the values of the table in arbitrary order
+-- @within Extraction
+--  @tab t A table
+function tablex.values(t)
+    assert_arg_iterable(1,t)
+    return makelist(tablex.pairmap(values_op,t))
+end
+
+local function index_map_op (i,v) return i,v end
+
+--- create an index map from a list-like table. The original values become keys,
+-- and the associated values are the indices into the original list.
+-- @array t a list-like table
+-- @return a map-like table
+function tablex.index_map (t)
+    assert_arg_indexable(1,t)
+    return makemap(tablex.pairmap(index_map_op,t))
+end
+
+local function set_op(i,v) return true,v end
+
+--- create a set from a list-like table. A set is a table where the original values
+-- become keys, and the associated values are all true.
+-- @array t a list-like table
+-- @return a set (a map-like table)
+function tablex.makeset (t)
+    assert_arg_indexable(1,t)
+    return setmetatable(tablex.pairmap(set_op,t),require('pl.Set'))
+end
+
+--- combine two tables, either as union or intersection. Corresponds to
+-- set operations for sets () but more general. Not particularly
+-- useful for list-like tables.
+-- @within Merging
+-- @tab t1 a table
+-- @tab t2 a table
+-- @bool dup true for a union, false for an intersection.
+-- @usage merge({alice=23,fred=34},{bob=25,fred=34}) is {fred=34}
+-- @usage merge({alice=23,fred=34},{bob=25,fred=34},true) is {bob=25,fred=34,alice=23}
+-- @see tablex.index_map
+function tablex.merge (t1,t2,dup)
+    assert_arg_iterable(1,t1)
+    assert_arg_iterable(2,t2)
+    local res = {}
+    for k,v in pairs(t1) do
+        if dup or t2[k] then res[k] = v end
+    end
+    if dup then
+      for k,v in pairs(t2) do
+        res[k] = v
+      end
+    end
+    return setmeta(res,t1,'Map')
+end
+
+--- the union of two map-like tables.
+-- If there are duplicate keys, the second table wins.
+-- @tab t1 a table
+-- @tab t2 a table
+-- @treturn tab
+-- @see tablex.merge
+function tablex.union(t1, t2)
+    return tablex.merge(t1, t2, true)
+end
+
+--- the intersection of two map-like tables.
+-- @tab t1 a table
+-- @tab t2 a table
+-- @treturn tab
+-- @see tablex.merge
+function tablex.intersection(t1, t2)
+    return tablex.merge(t1, t2, false)
+end
+
+--- a new table which is the difference of two tables.
+-- With sets (where the values are all true) this is set difference and
+-- symmetric difference depending on the third parameter.
+-- @within Merging
+-- @tab s1 a map-like table or set
+-- @tab s2 a map-like table or set
+-- @bool symm symmetric difference (default false)
+-- @return a map-like table or set
+function tablex.difference (s1,s2,symm)
+    assert_arg_iterable(1,s1)
+    assert_arg_iterable(2,s2)
+    local res = {}
+    for k,v in pairs(s1) do
+        if s2[k] == nil then res[k] = v end
+    end
+    if symm then
+        for k,v in pairs(s2) do
+            if s1[k] == nil then res[k] = v end
+        end
+    end
+    return setmeta(res,s1,'Map')
+end
+
+--- A table where the key/values are the values and value counts of the table.
+-- @array t a list-like table
+-- @func cmp a function that defines equality (otherwise uses ==)
+-- @return a map-like table
+-- @see seq.count_map
+function tablex.count_map (t,cmp)
+    assert_arg_indexable(1,t)
+    local res,mask = {},{}
+    cmp = function_arg(2,cmp or '==')
+    local n = #t
+    for i = 1,#t do
+        local v = t[i]
+        if not mask[v] then
+            mask[v] = true
+            -- check this value against all other values
+            res[v] = 1  -- there's at least one instance
+            for j = i+1,n do
+                local w = t[j]
+                local ok = cmp(v,w)
+                if ok then
+                    res[v] = res[v] + 1
+                    mask[w] = true
+                end
+            end
+        end
+    end
+    return makemap(res)
+end
+
+--- filter an array's values using a predicate function
+-- @within MappingAndFiltering
+-- @array t a list-like table
+-- @func pred a boolean function
+-- @param arg optional argument to be passed as second argument of the predicate
+function tablex.filter (t,pred,arg)
+    assert_arg_indexable(1,t)
+    pred = function_arg(2,pred)
+    local res,k = {},1
+    for i = 1,#t do
+        local v = t[i]
+        if pred(v,arg) then
+            res[k] = v
+            k = k + 1
+        end
+    end
+    return setmeta(res,t,'List')
+end
+
+--- return a table where each element is a table of the ith values of an arbitrary
+-- number of tables. It is equivalent to a matrix transpose.
+-- @within Merging
+-- @usage zip({10,20,30},{100,200,300}) is {{10,100},{20,200},{30,300}}
+-- @array ... arrays to be zipped
+function tablex.zip(...)
+    return tablex.mapn(function(...) return {...} end,...)
+end
+
+local _copy
+function _copy (dest,src,idest,isrc,nsrc,clean_tail)
+    idest = idest or 1
+    isrc = isrc or 1
+    local iend
+    if not nsrc then
+        nsrc = #src
+        iend = #src
+    else
+        iend = isrc + min(nsrc-1,#src-isrc)
+    end
+    if dest == src then -- special case
+        if idest > isrc and iend >= idest then -- overlapping ranges
+            src = tablex.sub(src,isrc,nsrc)
+            isrc = 1; iend = #src
+        end
+    end
+    for i = isrc,iend do
+        dest[idest] = src[i]
+        idest = idest + 1
+    end
+    if clean_tail then
+        tablex.clear(dest,idest)
+    end
+    return dest
+end
+
+--- copy an array into another one, clearing `dest` after `idest+nsrc`, if necessary.
+-- @within Copying
+-- @array dest a list-like table
+-- @array src a list-like table
+-- @int[opt=1] idest where to start copying values into destination
+-- @int[opt=1] isrc where to start copying values from source
+-- @int[opt=#src] nsrc number of elements to copy from source
+function tablex.icopy (dest,src,idest,isrc,nsrc)
+    assert_arg_indexable(1,dest)
+    assert_arg_indexable(2,src)
+    return _copy(dest,src,idest,isrc,nsrc,true)
+end
+
+--- copy an array into another one.
+-- @within Copying
+-- @array dest a list-like table
+-- @array src a list-like table
+-- @int[opt=1] idest where to start copying values into destination
+-- @int[opt=1] isrc where to start copying values from source
+-- @int[opt=#src] nsrc number of elements to copy from source
+function tablex.move (dest,src,idest,isrc,nsrc)
+    assert_arg_indexable(1,dest)
+    assert_arg_indexable(2,src)
+    return _copy(dest,src,idest,isrc,nsrc,false)
+end
+
+function tablex._normalize_slice(self,first,last)
+  local sz = #self
+  if not first then first=1 end
+  if first<0 then first=sz+first+1 end
+  -- make the range _inclusive_!
+  if not last then last=sz end
+  if last < 0 then last=sz+1+last end
+  return first,last
+end
+
+--- Extract a range from a table, like  'string.sub'.
+-- If first or last are negative then they are relative to the end of the list
+-- eg. sub(t,-2) gives last 2 entries in a list, and
+-- sub(t,-4,-2) gives from -4th to -2nd
+-- @within Extraction
+-- @array t a list-like table
+-- @int first An index
+-- @int last An index
+-- @return a new List
+function tablex.sub(t,first,last)
+    assert_arg_indexable(1,t)
+    first,last = tablex._normalize_slice(t,first,last)
+    local res={}
+    for i=first,last do append(res,t[i]) end
+    return setmeta(res,t,'List')
+end
+
+--- set an array range to a value. If it's a function we use the result
+-- of applying it to the indices.
+-- @array t a list-like table
+-- @param val a value
+-- @int[opt=1] i1 start range
+-- @int[opt=#t] i2 end range
+function tablex.set (t,val,i1,i2)
+    assert_arg_indexable(1,t)
+    i1,i2 = i1 or 1,i2 or #t
+    if types.is_callable(val) then
+        for i = i1,i2 do
+            t[i] = val(i)
+        end
+    else
+        for i = i1,i2 do
+            t[i] = val
+        end
+    end
+end
+
+--- create a new array of specified size with initial value.
+-- @int n size
+-- @param val initial value (can be `nil`, but don't expect `#` to work!)
+-- @return the table
+function tablex.new (n,val)
+    local res = {}
+    tablex.set(res,val,1,n)
+    return res
+end
+
+--- clear out the contents of a table.
+-- @array t a list
+-- @param istart optional start position
+function tablex.clear(t,istart)
+    istart = istart or 1
+    for i = istart,#t do remove(t) end
+end
+
+--- insert values into a table.
+-- similar to `table.insert` but inserts values from given table `values`,
+-- not the object itself, into table `t` at position `pos`.
+-- @within Copying
+-- @array t the list
+-- @int[opt] position (default is at end)
+-- @array values
+function tablex.insertvalues(t, ...)
+    assert_arg(1,t,'table')
+    local pos, values
+    if select('#', ...) == 1 then
+        pos,values = #t+1, ...
+    else
+        pos,values = ...
+    end
+    if #values > 0 then
+        for i=#t,pos,-1 do
+            t[i+#values] = t[i]
+        end
+        local offset = 1 - pos
+        for i=pos,pos+#values-1 do
+            t[i] = values[i + offset]
+        end
+    end
+    return t
+end
+
+--- remove a range of values from a table.
+-- End of range may be negative.
+-- @array t a list-like table
+-- @int i1 start index
+-- @int i2 end index
+-- @return the table
+function tablex.removevalues (t,i1,i2)
+    assert_arg(1,t,'table')
+    i1,i2 = tablex._normalize_slice(t,i1,i2)
+    for i = i1,i2 do
+        remove(t,i1)
+    end
+    return t
+end
+
+local _find
+_find = function (t,value,tables)
+    for k,v in pairs(t) do
+        if v == value then return k end
+    end
+    for k,v in pairs(t) do
+        if not tables[v] and type(v) == 'table' then
+            tables[v] = true
+            local res = _find(v,value,tables)
+            if res then
+                res = tostring(res)
+                if type(k) ~= 'string' then
+                    return '['..k..']'..res
+                else
+                    return k..'.'..res
+                end
+            end
+        end
+    end
+end
+
+--- find a value in a table by recursive search.
+-- @within Finding
+-- @tab t the table
+-- @param value the value
+-- @array[opt] exclude any tables to avoid searching
+-- @return a fieldspec, e.g. 'a.b' or 'math.sin'
+-- @usage search(_G,math.sin,{package.path}) == 'math.sin'
+function tablex.search (t,value,exclude)
+    assert_arg_iterable(1,t)
+    local tables = {[t]=true}
+    if exclude then
+        for _,v in pairs(exclude) do tables[v] = true end
+    end
+    return _find(t,value,tables)
+end
+
+--- return an iterator to a table sorted by its keys
+-- @within Iterating
+-- @tab t the table
+-- @func f an optional comparison function (f(x,y) is true if x < y)
+-- @usage for k,v in tablex.sort(t) do print(k,v) end
+-- @return an iterator to traverse elements sorted by the keys
+function tablex.sort(t,f)
+    local keys = {}
+    for k in pairs(t) do keys[#keys + 1] = k end
+    tsort(keys,f)
+    local i = 0
+    return function()
+        i = i + 1
+        return keys[i], t[keys[i]]
+    end
+end
+
+--- return an iterator to a table sorted by its values
+-- @within Iterating
+-- @tab t the table
+-- @func f an optional comparison function (f(x,y) is true if x < y)
+-- @usage for k,v in tablex.sortv(t) do print(k,v) end
+-- @return an iterator to traverse elements sorted by the values
+function tablex.sortv(t,f)
+    f = function_arg(2, f or '<')
+    local keys = {}
+    for k in pairs(t) do keys[#keys + 1] = k end
+    tsort(keys,function(x, y) return f(t[x], t[y]) end)
+    local i = 0
+    return function()
+        i = i + 1
+        return keys[i], t[keys[i]]
+    end
+end
+
+--- modifies a table to be read only.
+-- This only offers weak protection. Tables can still be modified with
+-- `table.insert` and `rawset`.
+--
+-- *NOTE*: for Lua 5.1 length, pairs and ipairs will not work, since the
+-- equivalent metamethods are only available in Lua 5.2 and newer.
+-- @tab t the table
+-- @return the table read only (a proxy).
+function tablex.readonly(t)
+    local mt = {
+        __index=t,
+        __newindex=function(t, k, v) error("Attempt to modify read-only table", 2) end,
+        __pairs=function() return pairs(t) end,
+        __ipairs=function() return ipairs(t) end,
+        __len=function() return #t end,
+        __metatable=false
+    }
+    return setmetatable({}, mt)
+end
+
+return tablex
+
+end,
+
+["pl.template"] = function()
+--------------------
+-- Module: 'pl.template'
+--------------------
+--- A template preprocessor.
+-- Originally by [Ricki Lake](http://lua-users.org/wiki/SlightlyLessSimpleLuaPreprocessor)
+--
+-- There are two rules:
+--
+--  * lines starting with # are Lua
+--  * otherwise, `$(expr)` is the result of evaluating `expr`
+--
+-- Example:
+--
+--    #  for i = 1,3 do
+--       $(i) Hello, Word!
+--    #  end
+--    ===>
+--    1 Hello, Word!
+--    2 Hello, Word!
+--    3 Hello, Word!
+--
+-- Other escape characters can be used, when the defaults conflict
+-- with the output language.
+--
+--    > for _,n in pairs{'one','two','three'} do
+--    static int l_${n} (luaState *state);
+--    > end
+--
+-- See  @{03-strings.md.Another_Style_of_Template|the Guide}.
+--
+-- Dependencies: `pl.utils`
+-- @module pl.template
+
+local utils = require 'pl.utils'
+
+local append,format,strsub,strfind,strgsub = table.insert,string.format,string.sub,string.find,string.gsub
+
+local APPENDER = "\n__R_size = __R_size + 1; __R_table[__R_size] = "
+
+local function parseDollarParen(pieces, chunk, exec_pat, newline)
+    local s = 1
+    for term, executed, e in chunk:gmatch(exec_pat) do
+        executed = '('..strsub(executed,2,-2)..')'
+        append(pieces, APPENDER..format("%q", strsub(chunk,s, term - 1)))
+        append(pieces, APPENDER..format("__tostring(%s or '')", executed))
+        s = e
+    end
+    local r
+    if newline then
+        r = format("%q", strgsub(strsub(chunk,s),"\n",""))
+    else
+        r = format("%q", strsub(chunk,s))
+    end
+    if r ~= '""' then
+        append(pieces, APPENDER..r)
+    end
+end
+
+local function parseHashLines(chunk,inline_escape,brackets,esc,newline)
+    local exec_pat = "()"..inline_escape.."(%b"..brackets..")()"
+
+    local esc_pat = esc.."+([^\n]*\n?)"
+    local esc_pat1, esc_pat2 = "^"..esc_pat, "\n"..esc_pat
+    local  pieces, s = {"return function()\nlocal __R_size, __R_table, __tostring = 0, {}, __tostring", n = 1}, 1
+    while true do
+        local _, e, lua = strfind(chunk,esc_pat1, s)
+        if not e then
+            local ss
+            ss, e, lua = strfind(chunk,esc_pat2, s)
+            parseDollarParen(pieces, strsub(chunk,s, ss), exec_pat, newline)
+            if not e then break end
+        end
+        if strsub(lua, -1, -1) == "\n" then lua = strsub(lua, 1, -2) end
+        append(pieces, "\n"..lua)
+        s = e + 1
+    end
+    append(pieces, "\nreturn __R_table\nend")
+
+    -- let's check for a special case where there is nothing to template, but it's
+    -- just a single static string
+    local short = false
+    if (#pieces == 3) and (pieces[2]:find(APPENDER, 1, true) == 1) then
+        pieces = { "return " .. pieces[2]:sub(#APPENDER+1,-1) }
+        short = true
+    end
+    -- if short == true, the generated function will not return a table of strings,
+    -- but a single string
+    return table.concat(pieces), short
+end
+
+local template = {}
+
+--- expand the template using the specified environment.
+-- This function will compile and render the template. For more performant
+-- recurring usage use the two step approach by using `compile` and `ct:render`.
+-- There are six special fields in the environment table `env`
+--
+--   * `_parent`: continue looking up in this table (e.g. `_parent=_G`).
+--   * `_brackets`: bracket pair that wraps inline Lua expressions,  default is '()'.
+--   * `_escape`: character marking Lua lines, default is '#'
+--   * `_inline_escape`: character marking inline Lua expression, default is '$'.
+--   * `_chunk_name`: chunk name for loaded templates, used if there
+--     is an error in Lua code. Default is 'TMP'.
+--   * `_debug`: if truthy, the generated code will be printed upon a render error
+--
+-- @string str the template string
+-- @tab[opt] env the environment
+-- @return `rendered template + nil + source_code`, or `nil + error + source_code`. The last
+-- return value (`source_code`) is only returned if the debug option is used.
+function template.substitute(str,env)
+    env = env or {}
+    local t, err = template.compile(str, {
+        chunk_name = rawget(env,"_chunk_name"),
+        escape = rawget(env,"_escape"),
+        inline_escape = rawget(env,"_inline_escape"),
+        inline_brackets = rawget(env,"_brackets"),
+        newline = nil,
+        debug = rawget(env,"_debug")
+    })
+    if not t then return t, err end
+
+    return t:render(env, rawget(env,"_parent"), rawget(env,"_debug"))
+end
+
+--- executes the previously compiled template and renders it.
+-- @function ct:render
+-- @tab[opt] env the environment.
+-- @tab[opt] parent continue looking up in this table (e.g. `parent=_G`).
+-- @bool[opt] db if thruthy, it will print the code upon a render error
+-- (provided the template was compiled with the debug option).
+-- @return `rendered template + nil + source_code`, or `nil + error + source_code`. The last return value
+-- (`source_code`) is only returned if the template was compiled with the debug option.
+-- @usage
+-- local ct, err = template.compile(my_template)
+-- local rendered , err = ct:render(my_env, parent)
+local render = function(self, env, parent, db)
+    env = env or {}
+    if parent then  -- parent is a bit silly, but for backward compatibility retained
+        setmetatable(env, {__index = parent})
+    end
+    setmetatable(self.env, {__index = env})
+
+    local res, out = xpcall(self.fn, debug.traceback)
+    if not res then
+        if self.code and db then print(self.code) end
+        return nil, out, self.code
+    end
+    return table.concat(out), nil, self.code
+end
+
+--- compiles the template.
+-- Returns an object that can repeatedly be rendered without parsing/compiling
+-- the template again.
+-- The options passed in the `opts` table support the following options:
+--
+--   * `chunk_name`: chunk name for loaded templates, used if there
+--     is an error in Lua code. Default is 'TMP'.
+--   * `escape`: character marking Lua lines, default is '#'
+--   * `inline_escape`: character marking inline Lua expression, default is '$'.
+--   * `inline_brackets`: bracket pair that wraps inline Lua expressions, default is '()'.
+--   * `newline`: string to replace newline characters, default is `nil` (not replacing newlines).
+--   * `debug`: if truthy, the generated source code will be retained within the compiled template object, default is `nil`.
+--
+-- @string str the template string
+-- @tab[opt] opts the compilation options to use
+-- @return template object, or `nil + error + source_code`
+-- @usage
+-- local ct, err = template.compile(my_template)
+-- local rendered , err = ct:render(my_env, parent)
+function template.compile(str, opts)
+    opts = opts or {}
+    local chunk_name = opts.chunk_name or 'TMP'
+    local escape = opts.escape or '#'
+    local inline_escape = opts.inline_escape or '$'
+    local inline_brackets = opts.inline_brackets or '()'
+
+    local code, short = parseHashLines(str,inline_escape,inline_brackets,escape,opts.newline)
+    local env = { __tostring = tostring }
+    local fn, err = utils.load(code, chunk_name,'t',env)
+    if not fn then return nil, err, code end
+
+    if short then
+        -- the template returns a single constant string, let's optimize for that
+        local constant_string = fn()
+        return {
+            fn = fn(),
+            env = env,
+            render = function(self) -- additional params can be ignored
+                -- skip the metatable magic and error handling in the render
+                -- function above for this special case
+                return constant_string, nil, self.code
+            end,
+            code = opts.debug and code or nil,
+        }
+    end
+
+    return {
+        fn = fn(),
+        env = env,
+        render = render,
+        code = opts.debug and code or nil,
+    }
+end
+
+return template
+
+end,
+
+["pl.test"] = function()
+--------------------
+-- Module: 'pl.test'
+--------------------
+--- Useful test utilities.
+--
+--    test.asserteq({1,2},{1,2}) -- can compare tables
+--    test.asserteq(1.2,1.19,0.02) -- compare FP numbers within precision
+--    T = test.tuple -- used for comparing multiple results
+--    test.asserteq(T(string.find(" me","me")),T(2,3))
+--
+-- Dependencies: `pl.utils`, `pl.tablex`, `pl.pretty`, `pl.path`, `debug`
+-- @module pl.test
+
+local tablex = require 'pl.tablex'
+local utils = require 'pl.utils'
+local pretty = require 'pl.pretty'
+local path = require 'pl.path'
+local type,unpack,pack = type,utils.unpack,utils.pack
+local clock = os.clock
+local debug = require 'debug'
+local io = io
+
+local function dump(x)
+    if type(x) == 'table' and not (getmetatable(x) and getmetatable(x).__tostring) then
+        return pretty.write(x,' ',true)
+    elseif type(x) == 'string' then
+        return '"'..x..'"'
+    else
+        return tostring(x)
+    end
+end
+
+local test = {}
+
+---- error handling for test results.
+-- By default, this writes to stderr and exits the program.
+-- Re-define this function to raise an error and/or redirect output
+function test.error_handler(file,line,got_text, needed_text,msg)
+    local err = io.stderr
+    err:write(path.basename(file)..':'..line..': assertion failed\n')
+    err:write("got:\t",got_text,'\n')
+    err:write("needed:\t",needed_text,'\n')
+    utils.quit(1,msg or "these values were not equal")
+end
+
+local function complain (x,y,msg,where)
+    local i = debug.getinfo(3 + (where or 0))
+    test.error_handler(i.short_src,i.currentline,dump(x),dump(y),msg)
+end
+
+--- general test complain message.
+-- Useful for composing new test functions (see tests/tablex.lua for an example)
+-- @param x a value
+-- @param y value to compare first value against
+-- @param msg message
+-- @param where extra level offset for errors
+-- @function complain
+test.complain = complain
+
+--- like assert, except takes two arguments that must be equal and can be tables.
+-- If they are plain tables, it will use tablex.deepcompare.
+-- @param x any value
+-- @param y a value equal to x
+-- @param eps an optional tolerance for numerical comparisons
+-- @param where extra level offset
+function test.asserteq (x,y,eps,where)
+    local res = x == y
+    if not res then
+        res = tablex.deepcompare(x,y,true,eps)
+    end
+    if not res then
+        complain(x,y,nil,where)
+    end
+end
+
+--- assert that the first string matches the second.
+-- @param s1 a string
+-- @param s2 a string
+-- @param where extra level offset
+function test.assertmatch (s1,s2,where)
+    if not s1:match(s2) then
+        complain (s1,s2,"these strings did not match",where)
+    end
+end
+
+--- assert that the function raises a particular error.
+-- @param fn a function or a table of the form {function,arg1,...}
+-- @param e a string to match the error against
+-- @param where extra level offset
+function test.assertraise(fn,e,where)
+    local ok, err
+    if type(fn) == 'table' then
+        ok, err = pcall(unpack(fn))
+    else
+        ok, err = pcall(fn)
+    end
+    if ok or err:match(e)==nil then
+        complain (err,e,"these errors did not match",where)
+    end
+end
+
+--- a version of asserteq that takes two pairs of values.
+-- <code>x1==y1 and x2==y2</code> must be true. Useful for functions that naturally
+-- return two values.
+-- @param x1 any value
+-- @param x2 any value
+-- @param y1 any value
+-- @param y2 any value
+-- @param where extra level offset
+function test.asserteq2 (x1,x2,y1,y2,where)
+    if x1 ~= y1 then complain(x1,y1,nil,where) end
+    if x2 ~= y2 then complain(x2,y2,nil,where) end
+end
+
+-- tuple type --
+
+local tuple_mt = {
+    unpack = unpack
+}
+tuple_mt.__index = tuple_mt
+
+function tuple_mt.__tostring(self)
+    local ts = {}
+    for i=1, self.n do
+        local s = self[i]
+        ts[i] = type(s) == 'string' and ('%q'):format(s) or tostring(s)
+    end
+    return 'tuple(' .. table.concat(ts, ', ') .. ')'
+end
+
+function tuple_mt.__eq(a, b)
+    if a.n ~= b.n then return false end
+    for i=1, a.n do
+        if a[i] ~= b[i] then return false end
+    end
+    return true
+end
+
+function tuple_mt.__len(self)
+    return self.n
+end
+
+--- encode an arbitrary argument list as a tuple.
+-- This can be used to compare to other argument lists, which is
+-- very useful for testing functions which return a number of values.
+-- Unlike regular array-like tables ('sequences') they may contain nils.
+-- Tuples understand equality and know how to print themselves out.
+-- The # operator is defined to be the size, irrespecive of any nils,
+-- and there is an `unpack` method.
+-- @usage asserteq(tuple( ('ab'):find 'a'), tuple(1,1))
+function test.tuple(...)
+    return setmetatable(pack(...), tuple_mt)
+end
+
+--- Time a function. Call the function a given number of times, and report the number of seconds taken,
+-- together with a message.  Any extra arguments will be passed to the function.
+-- @string msg a descriptive message
+-- @int n number of times to call the function
+-- @func fun the function
+-- @param ... optional arguments to fun
+function test.timer(msg,n,fun,...)
+    local start = clock()
+    for i = 1,n do fun(...) end
+    utils.printf("%s: took %7.2f sec\n",msg,clock()-start)
+end
+
+return test
+
+end,
+
+["pl.text"] = function()
+--------------------
+-- Module: 'pl.text'
+--------------------
+--- Text processing utilities.
+--
+-- This provides a Template class (modeled after the same from the Python
+-- libraries, see string.Template). It also provides similar functions to those
+-- found in the textwrap module.
+--
+-- See  @{03-strings.md.String_Templates|the Guide}.
+--
+-- Calling `text.format_operator()` overloads the % operator for strings to give Python/Ruby style formated output.
+-- This is extended to also do template-like substitution for map-like data.
+--
+--    > require 'pl.text'.format_operator()
+--    > = '%s = %5.3f' % {'PI',math.pi}
+--    PI = 3.142
+--    > = '$name = $value' % {name='dog',value='Pluto'}
+--    dog = Pluto
+--
+-- Dependencies: `pl.utils`, `pl.types`
+-- @module pl.text
+
+local gsub = string.gsub
+local concat,append = table.concat,table.insert
+local utils = require 'pl.utils'
+local bind1,usplit,assert_arg = utils.bind1,utils.split,utils.assert_arg
+local is_callable = require 'pl.types'.is_callable
+local unpack = utils.unpack
+
+local text = {}
+
+
+local function makelist(l)
+    return setmetatable(l, require('pl.List'))
+end
+
+local function lstrip(str)  return (str:gsub('^%s+',''))  end
+local function strip(str)  return (lstrip(str):gsub('%s+$','')) end
+local function split(s,delim)  return makelist(usplit(s,delim)) end
+
+local function imap(f,t,...)
+    local res = {}
+    for i = 1,#t do res[i] = f(t[i],...) end
+    return res
+end
+
+local function _indent (s,sp)
+    local sl = split(s,'\n')
+    return concat(imap(bind1('..',sp),sl),'\n')..'\n'
+end
+
+--- indent a multiline string.
+-- @param s the string
+-- @param n the size of the indent
+-- @param ch the character to use when indenting (default ' ')
+-- @return indented string
+function text.indent (s,n,ch)
+    assert_arg(1,s,'string')
+    assert_arg(2,n,'number')
+    return _indent(s,string.rep(ch or ' ',n))
+end
+
+--- dedent a multiline string by removing any initial indent.
+-- useful when working with [[..]] strings.
+-- @param s the string
+-- @return a string with initial indent zero.
+function text.dedent (s)
+    assert_arg(1,s,'string')
+    local sl = split(s,'\n')
+    local _,i2 = (#sl>0 and sl[1] or ''):find('^%s*')
+    sl = imap(string.sub,sl,i2+1)
+    return concat(sl,'\n')..'\n'
+end
+
+--- format a paragraph into lines so that they fit into a line width.
+-- It will not break long words, so lines can be over the length
+-- to that extent.
+-- @param s the string
+-- @param width the margin width, default 70
+-- @return a list of lines (List object)
+-- @see pl.List
+function text.wrap (s,width)
+    assert_arg(1,s,'string')
+    width = width or 70
+    s = s:gsub('\n',' ')
+    local i,nxt = 1
+    local lines,line = {}
+    while i < #s do
+        nxt = i+width
+        if s:find("[%w']",nxt) then -- inside a word
+            nxt = s:find('%W',nxt+1) -- so find word boundary
+        end
+        line = s:sub(i,nxt)
+        i = i + #line
+        append(lines,strip(line))
+    end
+    return makelist(lines)
+end
+
+--- format a paragraph so that it fits into a line width.
+-- @param s the string
+-- @param width the margin width, default 70
+-- @return a string
+-- @see wrap
+function text.fill (s,width)
+    return concat(text.wrap(s,width),'\n') .. '\n'
+end
+
+local Template = {}
+text.Template = Template
+Template.__index = Template
+setmetatable(Template, {
+    __call = function(obj,tmpl)
+        return Template.new(tmpl)
+    end})
+
+function Template.new(tmpl)
+    assert_arg(1,tmpl,'string')
+    local res = {}
+    res.tmpl = tmpl
+    setmetatable(res,Template)
+    return res
+end
+
+local function _substitute(s,tbl,safe)
+    local subst
+    if is_callable(tbl) then
+        subst = tbl
+    else
+        function subst(f)
+            local s = tbl[f]
+            if not s then
+                if safe then
+                    return f
+                else
+                    error("not present in table "..f)
+                end
+            else
+                return s
+            end
+        end
+    end
+    local res = gsub(s,'%${([%w_]+)}',subst)
+    return (gsub(res,'%$([%w_]+)',subst))
+end
+
+--- substitute values into a template, throwing an error.
+-- This will throw an error if no name is found.
+-- @param tbl a table of name-value pairs.
+function Template:substitute(tbl)
+    assert_arg(1,tbl,'table')
+    return _substitute(self.tmpl,tbl,false)
+end
+
+--- substitute values into a template.
+-- This version just passes unknown names through.
+-- @param tbl a table of name-value pairs.
+function Template:safe_substitute(tbl)
+    assert_arg(1,tbl,'table')
+    return _substitute(self.tmpl,tbl,true)
+end
+
+--- substitute values into a template, preserving indentation. <br>
+-- If the value is a multiline string _or_ a template, it will insert
+-- the lines at the correct indentation. <br>
+-- Furthermore, if a template, then that template will be subsituted
+-- using the same table.
+-- @param tbl a table of name-value pairs.
+function Template:indent_substitute(tbl)
+    assert_arg(1,tbl,'table')
+    if not self.strings then
+        self.strings = split(self.tmpl,'\n')
+    end
+    -- the idea is to substitute line by line, grabbing any spaces as
+    -- well as the $var. If the value to be substituted contains newlines,
+    -- then we split that into lines and adjust the indent before inserting.
+    local function subst(line)
+        return line:gsub('(%s*)%$([%w_]+)',function(sp,f)
+            local subtmpl
+            local s = tbl[f]
+            if not s then error("not present in table "..f) end
+            if getmetatable(s) == Template then
+                subtmpl = s
+                s = s.tmpl
+            else
+                s = tostring(s)
+            end
+            if s:find '\n' then
+                s = _indent(s,sp)
+            end
+            if subtmpl then return _substitute(s,tbl)
+            else return s
+            end
+        end)
+    end
+    local lines = imap(subst,self.strings)
+    return concat(lines,'\n')..'\n'
+end
+
+------- Python-style formatting operator ------
+-- (see <a href="http://lua-users.org/wiki/StringInterpolation">the lua-users wiki</a>) --
+
+function text.format_operator()
+
+    local format = string.format
+
+    -- a more forgiving version of string.format, which applies
+    -- tostring() to any value with a %s format.
+    local function formatx (fmt,...)
+        local args = {...}
+        local i = 1
+        for p in fmt:gmatch('%%.') do
+            if p == '%s' and type(args[i]) ~= 'string' then
+                args[i] = tostring(args[i])
+            end
+            i = i + 1
+        end
+        return format(fmt,unpack(args))
+    end
+
+    local function basic_subst(s,t)
+        return (s:gsub('%$([%w_]+)',t))
+    end
+
+    -- Note this goes further than the original, and will allow these cases:
+    -- 1. a single value
+    -- 2. a list of values
+    -- 3. a map of var=value pairs
+    -- 4. a function, as in gsub
+    -- For the second two cases, it uses $-variable substituion.
+    getmetatable("").__mod = function(a, b)
+        if b == nil then
+            return a
+        elseif type(b) == "table" and getmetatable(b) == nil then
+            if #b == 0 then -- assume a map-like table
+                return _substitute(a,b,true)
+            else
+                return formatx(a,unpack(b))
+            end
+        elseif type(b) == 'function' then
+            return basic_subst(a,b)
+        else
+            return formatx(a,b)
+        end
+    end
+end
+
+return text
+
+end,
+
+["pl.types"] = function()
+--------------------
+-- Module: 'pl.types'
+--------------------
+---- Dealing with Detailed Type Information
+
+-- Dependencies `pl.utils`
+-- @module pl.types
+
+local utils = require 'pl.utils'
+local math_ceil = math.ceil
+local assert_arg = utils.assert_arg
+local types = {}
+
+--- is the object either a function or a callable object?.
+-- @param obj Object to check.
+function types.is_callable (obj)
+    return type(obj) == 'function' or getmetatable(obj) and getmetatable(obj).__call and true
+end
+
+--- is the object of the specified type?.
+-- If the type is a string, then use type, otherwise compare with metatable.
+--
+-- NOTE: this function is imported from `utils.is_type`.
+-- @param obj An object to check
+-- @param tp The expected type
+-- @function is_type
+-- @see utils.is_type
+types.is_type = utils.is_type
+
+local fileMT = getmetatable(io.stdout)
+
+--- a string representation of a type.
+-- For tables and userdata with metatables, we assume that the metatable has a `_name`
+-- field. If the field is not present it will return 'unknown table' or
+-- 'unknown userdata'.
+-- Lua file objects return the type 'file'.
+-- @param obj an object
+-- @return a string like 'number', 'table', 'file' or 'List'
+function types.type (obj)
+    local t = type(obj)
+    if t == 'table' or t == 'userdata' then
+        local mt = getmetatable(obj)
+        if mt == fileMT then
+            return 'file'
+        elseif mt == nil then
+            return t
+        else
+            -- TODO: the "unknown" is weird, it should just return the type
+            return mt._name or "unknown "..t
+        end
+    else
+        return t
+    end
+end
+
+--- is this number an integer?
+-- @param x a number
+-- @raise error if x is not a number
+-- @return boolean
+function types.is_integer (x)
+    return math_ceil(x)==x
+end
+
+--- Check if the object is "empty".
+-- An object is considered empty if it is:
+--
+-- - `nil`
+-- - a table without any items (key-value pairs or indexes)
+-- - a string with no content ("")
+-- - not a nil/table/string
+-- @param o The object to check if it is empty.
+-- @param ignore_spaces If the object is a string and this is true the string is
+-- considered empty if it only contains spaces.
+-- @return `true` if the object is empty, otherwise a falsy value.
+function types.is_empty(o, ignore_spaces)
+    if o == nil then
+        return true
+    elseif type(o) == "table" then
+        return next(o) == nil
+    elseif type(o) == "string" then
+        return o == "" or (not not ignore_spaces and (not not o:find("^%s+$")))
+    else
+        return true
+    end
+end
+
+local function check_meta (val)
+    if type(val) == 'table' then return true end
+    return getmetatable(val)
+end
+
+--- is an object 'array-like'?
+-- An object is array like if:
+--
+-- - it is a table, or
+-- - it has a metatable with `__len` and `__index` methods
+--
+-- NOTE: since `__len` is 5.2+, on 5.1 is usually returns `false` for userdata
+-- @param val any value.
+-- @return `true` if the object is array-like, otherwise a falsy value.
+function types.is_indexable (val)
+    local mt = check_meta(val)
+    if mt == true then return true end
+    return mt and mt.__len and mt.__index and true
+end
+
+--- can an object be iterated over with `pairs`?
+-- An object is iterable if:
+--
+-- - it is a table, or
+-- - it has a metatable with a `__pairs` meta method
+--
+-- NOTE: since `__pairs` is 5.2+, on 5.1 is usually returns `false` for userdata
+-- @param val any value.
+-- @return `true` if the object is iterable, otherwise a falsy value.
+function types.is_iterable (val)
+    local mt = check_meta(val)
+    if mt == true then return true end
+    return mt and mt.__pairs and true
+end
+
+--- can an object accept new key/pair values?
+-- An object is iterable if:
+--
+-- - it is a table, or
+-- - it has a metatable with a `__newindex` meta method
+--
+-- @param val any value.
+-- @return `true` if the object is writeable, otherwise a falsy value.
+function types.is_writeable (val)
+    local mt = check_meta(val)
+    if mt == true then return true end
+    return mt and mt.__newindex and true
+end
+
+-- Strings that should evaluate to true.   -- TODO: add on/off ???
+local trues = { yes=true, y=true, ["true"]=true, t=true, ["1"]=true }
+-- Conditions types should evaluate to true.
+local true_types = {
+    boolean=function(o, true_strs, check_objs) return o end,
+    string=function(o, true_strs, check_objs)
+        o = o:lower()
+        if trues[o] then
+            return true
+        end
+        -- Check alternative user provided strings.
+        for _,v in ipairs(true_strs or {}) do
+            if type(v) == "string" and o == v:lower() then
+                return true
+            end
+        end
+        return false
+    end,
+    number=function(o, true_strs, check_objs) return o ~= 0 end,
+    table=function(o, true_strs, check_objs) if check_objs and next(o) ~= nil then return true end return false end
+}
+--- Convert to a boolean value.
+-- True values are:
+--
+-- * boolean: true.
+-- * string: 'yes', 'y', 'true', 't', '1' or additional strings specified by `true_strs`.
+-- * number: Any non-zero value.
+-- * table: Is not empty and `check_objs` is true.
+-- * everything else: Is not `nil` and `check_objs` is true.
+--
+-- @param o The object to evaluate.
+-- @param[opt] true_strs optional Additional strings that when matched should evaluate to true. Comparison is case insensitive.
+-- This should be a List of strings. E.g. "ja" to support German.
+-- @param[opt] check_objs True if objects should be evaluated.
+-- @return true if the input evaluates to true, otherwise false.
+function types.to_bool(o, true_strs, check_objs)
+    local true_func
+    if true_strs then
+        assert_arg(2, true_strs, "table")
+    end
+    true_func = true_types[type(o)]
+    if true_func then
+        return true_func(o, true_strs, check_objs)
+    elseif check_objs and o ~= nil then
+        return true
+    end
+    return false
+end
+
+
+return types
+
+end,
+
+["pl.url"] = function()
+--------------------
+-- Module: 'pl.url'
+--------------------
+--- Python-style URL quoting library.
+--
+-- @module pl.url
+
+local url = {}
+
+local function quote_char(c)
+    return string.format("%%%02X", string.byte(c))
+end
+
+--- Quote the url, replacing special characters using the '%xx' escape.
+-- @string s the string
+-- @bool quote_plus Also escape slashes and replace spaces by plus signs.
+-- @return The quoted string, or if `s` wasn't a string, just plain unaltered `s`.
+function url.quote(s, quote_plus)
+    if type(s) ~= "string" then
+        return s
+    end
+
+    s = s:gsub("\n", "\r\n")
+    s = s:gsub("([^A-Za-z0-9 %-_%./])", quote_char)
+    if quote_plus then
+        s = s:gsub(" ", "+")
+        s = s:gsub("/", quote_char)
+    else
+        s = s:gsub(" ", "%%20")
+    end
+
+    return s
+end
+
+local function unquote_char(h)
+    return string.char(tonumber(h, 16))
+end
+
+--- Unquote the url, replacing '%xx' escapes and plus signs.
+-- @string s the string
+-- @return The unquoted string, or if `s` wasn't a string, just plain unaltered `s`.
+function url.unquote(s)
+    if type(s) ~= "string" then
+        return s
+    end
+
+    s = s:gsub("+", " ")
+    s = s:gsub("%%(%x%x)", unquote_char)
+    s = s:gsub("\r\n", "\n")
+
+    return s
+end
+
+return url
+
+end,
+
+["pl.utils"] = function()
+--------------------
+-- Module: 'pl.utils'
+--------------------
+--- Generally useful routines.
+-- See  @{01-introduction.md.Generally_useful_functions|the Guide}.
+--
+-- Dependencies: `pl.compat`, all exported fields and functions from
+-- `pl.compat` are also available in this module.
+--
+-- @module pl.utils
+local format = string.format
+local compat = require 'pl.compat'
+local stdout = io.stdout
+local append = table.insert
+local _unpack = table.unpack  -- always injected by 'compat'
+
+local is_windows = compat.is_windows
+local err_mode = 'default'
+local raise
+local operators
+local _function_factories = {}
+
+
+local utils = { _VERSION = "1.11.0" }
+for k, v in pairs(compat) do utils[k] = v  end
+
+--- Some standard patterns
+-- @table patterns
+utils.patterns = {
+    FLOAT = '[%+%-%d]%d*%.?%d*[eE]?[%+%-]?%d*', -- floating point number
+    INTEGER = '[+%-%d]%d*',                     -- integer number
+    IDEN = '[%a_][%w_]*',                       -- identifier
+    FILE = '[%a%.\\][:%][%w%._%-\\]*',          -- file
+}
+
+
+--- Standard meta-tables as used by other Penlight modules
+-- @table stdmt
+-- @field List the List metatable
+-- @field Map the Map metatable
+-- @field Set the Set metatable
+-- @field MultiMap the MultiMap metatable
+utils.stdmt = {
+    List = {_name='List'},
+    Map = {_name='Map'},
+    Set = {_name='Set'},
+    MultiMap = {_name='MultiMap'},
+}
+
+
+--- pack an argument list into a table.
+-- @param ... any arguments
+-- @return a table with field `n` set to the length
+-- @function utils.pack
+-- @see compat.pack
+-- @see utils.npairs
+-- @see utils.unpack
+utils.pack = table.pack  -- added here to be symmetrical with unpack
+
+--- unpack a table and return its contents.
+--
+-- NOTE: this implementation differs from the Lua implementation in the way
+-- that this one DOES honor the `n` field in the table `t`, such that it is 'nil-safe'.
+-- @param t table to unpack
+-- @param[opt] i index from which to start unpacking, defaults to 1
+-- @param[opt] t index of the last element to unpack, defaults to `t.n` or `#t`
+-- @return multiple return values from the table
+-- @function utils.unpack
+-- @see compat.unpack
+-- @see utils.pack
+-- @see utils.npairs
+-- @usage
+-- local t = table.pack(nil, nil, nil, 4)
+-- local a, b, c, d = table.unpack(t)   -- this `unpack` is NOT nil-safe, so d == nil
+--
+-- local a, b, c, d = utils.unpack(t)   -- this is nil-safe, so d == 4
+function utils.unpack(t, i, j)
+    return _unpack(t, i or 1, j or t.n or #t)
+end
+
+--- print an arbitrary number of arguments using a format.
+-- Output will be sent to `stdout`.
+-- @param fmt The format (see `string.format`)
+-- @param ... Extra arguments for format
+function utils.printf(fmt, ...)
+    utils.assert_string(1, fmt)
+    utils.fprintf(stdout, fmt, ...)
+end
+
+--- write an arbitrary number of arguments to a file using a format.
+-- @param f File handle to write to.
+-- @param fmt The format (see `string.format`).
+-- @param ... Extra arguments for format
+function utils.fprintf(f,fmt,...)
+    utils.assert_string(2,fmt)
+    f:write(format(fmt,...))
+end
+
+do
+    local function import_symbol(T,k,v,libname)
+        local key = rawget(T,k)
+        -- warn about collisions!
+        if key and k ~= '_M' and k ~= '_NAME' and k ~= '_PACKAGE' and k ~= '_VERSION' then
+            utils.fprintf(io.stderr,"warning: '%s.%s' will not override existing symbol\n",libname,k)
+            return
+        end
+        rawset(T,k,v)
+    end
+
+    local function lookup_lib(T,t)
+        for k,v in pairs(T) do
+            if v == t then return k end
+        end
+        return '?'
+    end
+
+    local already_imported = {}
+
+    --- take a table and 'inject' it into the local namespace.
+    -- @param t The table (table), or module name (string), defaults to this `utils` module table
+    -- @param T An optional destination table (defaults to callers environment)
+    function utils.import(t,T)
+        T = T or _G
+        t = t or utils
+        if type(t) == 'string' then
+            t = require (t)
+        end
+        local libname = lookup_lib(T,t)
+        if already_imported[t] then return end
+        already_imported[t] = libname
+        for k,v in pairs(t) do
+            import_symbol(T,k,v,libname)
+        end
+    end
+end
+
+--- return either of two values, depending on a condition.
+-- @param cond A condition
+-- @param value1 Value returned if cond is truthy
+-- @param value2 Value returned if cond is falsy
+function utils.choose(cond, value1, value2)
+    return cond and value1 or value2
+end
+
+--- convert an array of values to strings.
+-- @param t a list-like table
+-- @param[opt] temp (table) buffer to use, otherwise allocate
+-- @param[opt] tostr custom tostring function, called with (value,index). Defaults to `tostring`.
+-- @return the converted buffer
+function utils.array_tostring (t,temp,tostr)
+    temp, tostr = temp or {}, tostr or tostring
+    for i = 1,#t do
+        temp[i] = tostr(t[i],i)
+    end
+    return temp
+end
+
+
+
+--- is the object of the specified type?
+-- If the type is a string, then use type, otherwise compare with metatable
+-- @param obj An object to check
+-- @param tp String of what type it should be
+-- @return boolean
+-- @usage utils.is_type("hello world", "string")   --> true
+-- -- or check metatable
+-- local my_mt = {}
+-- local my_obj = setmetatable(my_obj, my_mt)
+-- utils.is_type(my_obj, my_mt)  --> true
+function utils.is_type (obj,tp)
+    if type(tp) == 'string' then return type(obj) == tp end
+    local mt = getmetatable(obj)
+    return tp == mt
+end
+
+
+
+--- an iterator with indices, similar to `ipairs`, but with a range.
+-- This is a nil-safe index based iterator that will return `nil` when there
+-- is a hole in a list. To be safe ensure that table `t.n` contains the length.
+-- @tparam table t the table to iterate over
+-- @tparam[opt=1] integer i_start start index
+-- @tparam[opt=t.n or #t] integer i_end end index
+-- @tparam[opt=1] integer step step size
+-- @treturn integer index
+-- @treturn any value at index (which can be `nil`!)
+-- @see utils.pack
+-- @see utils.unpack
+-- @usage
+-- local t = utils.pack(nil, 123, nil)  -- adds an `n` field when packing
+--
+-- for i, v in utils.npairs(t, 2) do  -- start at index 2
+--   t[i] = tostring(t[i])
+-- end
+--
+-- -- t = { n = 3, [2] = "123", [3] = "nil" }
+function utils.npairs(t, i_start, i_end, step)
+  step = step or 1
+  if step == 0 then
+    error("iterator step-size cannot be 0", 2)
+  end
+  local i = (i_start or 1) - step
+  i_end = i_end or t.n or #t
+  if step < 0 then
+    return function()
+      i = i + step
+      if i < i_end then
+        return nil
+      end
+      return i, t[i]
+    end
+
+  else
+    return function()
+      i = i + step
+      if i > i_end then
+        return nil
+      end
+      return i, t[i]
+    end
+  end
+end
+
+
+
+--- Error handling
+-- @section Error-handling
+
+--- assert that the given argument is in fact of the correct type.
+-- @param n argument index
+-- @param val the value
+-- @param tp the type
+-- @param verify an optional verification function
+-- @param msg an optional custom message
+-- @param lev optional stack position for trace, default 2
+-- @return the validated value
+-- @raise if `val` is not the correct type
+-- @usage
+-- local param1 = assert_arg(1,"hello",'table')  --> error: argument 1 expected a 'table', got a 'string'
+-- local param4 = assert_arg(4,'!@#$%^&*','string',path.isdir,'not a directory')
+--      --> error: argument 4: '!@#$%^&*' not a directory
+function utils.assert_arg (n,val,tp,verify,msg,lev)
+    if type(val) ~= tp then
+        error(("argument %d expected a '%s', got a '%s'"):format(n,tp,type(val)),lev or 2)
+    end
+    if verify and not verify(val) then
+        error(("argument %d: '%s' %s"):format(n,val,msg),lev or 2)
+    end
+    return val
+end
+
+--- process a function argument.
+-- This is used throughout Penlight and defines what is meant by a function:
+-- Something that is callable, or an operator string as defined by <code>pl.operator</code>,
+-- such as '>' or '#'. If a function factory has been registered for the type, it will
+-- be called to get the function.
+-- @param idx argument index
+-- @param f a function, operator string, or callable object
+-- @param msg optional error message
+-- @return a callable
+-- @raise if idx is not a number or if f is not callable
+function utils.function_arg (idx,f,msg)
+    utils.assert_arg(1,idx,'number')
+    local tp = type(f)
+    if tp == 'function' then return f end  -- no worries!
+    -- ok, a string can correspond to an operator (like '==')
+    if tp == 'string' then
+        if not operators then operators = require 'pl.operator'.optable end
+        local fn = operators[f]
+        if fn then return fn end
+        local fn, err = utils.string_lambda(f)
+        if not fn then error(err..': '..f) end
+        return fn
+    elseif tp == 'table' or tp == 'userdata' then
+        local mt = getmetatable(f)
+        if not mt then error('not a callable object',2) end
+        local ff = _function_factories[mt]
+        if not ff then
+            if not mt.__call then error('not a callable object',2) end
+            return f
+        else
+            return ff(f) -- we have a function factory for this type!
+        end
+    end
+    if not msg then msg = " must be callable" end
+    if idx > 0 then
+        error("argument "..idx..": "..msg,2)
+    else
+        error(msg,2)
+    end
+end
+
+
+--- assert the common case that the argument is a string.
+-- @param n argument index
+-- @param val a value that must be a string
+-- @return the validated value
+-- @raise val must be a string
+-- @usage
+-- local val = 42
+-- local param2 = utils.assert_string(2, val) --> error: argument 2 expected a 'string', got a 'number'
+function utils.assert_string (n, val)
+    return utils.assert_arg(n,val,'string',nil,nil,3)
+end
+
+--- control the error strategy used by Penlight.
+-- This is a global setting that controls how `utils.raise` behaves:
+--
+-- - 'default': return `nil + error` (this is the default)
+-- - 'error': throw a Lua error
+-- - 'quit': exit the program
+--
+-- @param mode either 'default', 'quit'  or 'error'
+-- @see utils.raise
+function utils.on_error (mode)
+    mode = tostring(mode)
+    if ({['default'] = 1, ['quit'] = 2, ['error'] = 3})[mode] then
+      err_mode = mode
+    else
+      -- fail loudly
+      local err = "Bad argument expected string; 'default', 'quit', or 'error'. Got '"..tostring(mode).."'"
+      if err_mode == 'default' then
+        error(err, 2)  -- even in 'default' mode fail loud in this case
+      end
+      raise(err)
+    end
+end
+
+--- used by Penlight functions to return errors. Its global behaviour is controlled
+-- by `utils.on_error`.
+-- To use this function you MUST use it in conjunction with `return`, since it might
+-- return `nil + error`.
+-- @param err the error string.
+-- @see utils.on_error
+-- @usage
+-- if some_condition then
+--   return utils.raise("some condition was not met")  -- MUST use 'return'!
+-- end
+function utils.raise (err)
+    if err_mode == 'default' then
+        return nil, err
+    elseif err_mode == 'quit' then
+        return utils.quit(err)
+    else
+        error(err, 2)
+    end
+end
+raise = utils.raise
+
+
+
+--- File handling
+-- @section files
+
+--- return the contents of a file as a string
+-- @param filename The file path
+-- @param is_bin open in binary mode
+-- @return file contents
+function utils.readfile(filename,is_bin)
+    local mode = is_bin and 'b' or ''
+    utils.assert_string(1,filename)
+    local f,open_err = io.open(filename,'r'..mode)
+    if not f then return raise (open_err) end
+    local res,read_err = f:read('*a')
+    f:close()
+    if not res then
+        -- Errors in io.open have "filename: " prefix,
+        -- error in file:read don't, add it.
+        return raise (filename..": "..read_err)
+    end
+    return res
+end
+
+--- write a string to a file
+-- @param filename The file path
+-- @param str The string
+-- @param is_bin open in binary mode
+-- @return true or nil
+-- @return error message
+-- @raise error if filename or str aren't strings
+function utils.writefile(filename,str,is_bin)
+    local mode = is_bin and 'b' or ''
+    utils.assert_string(1,filename)
+    utils.assert_string(2,str)
+    local f,err = io.open(filename,'w'..mode)
+    if not f then return raise(err) end
+    local ok, write_err = f:write(str)
+    f:close()
+    if not ok then
+        -- Errors in io.open have "filename: " prefix,
+        -- error in file:write don't, add it.
+        return raise (filename..": "..write_err)
+    end
+    return true
+end
+
+--- return the contents of a file as a list of lines
+-- @param filename The file path
+-- @return file contents as a table
+-- @raise error if filename is not a string
+function utils.readlines(filename)
+    utils.assert_string(1,filename)
+    local f,err = io.open(filename,'r')
+    if not f then return raise(err) end
+    local res = {}
+    for line in f:lines() do
+        append(res,line)
+    end
+    f:close()
+    return res
+end
+
+--- OS functions
+-- @section OS-functions
+
+--- execute a shell command and return the output.
+-- This function redirects the output to tempfiles and returns the content of those files.
+-- @param cmd a shell command
+-- @param bin boolean, if true, read output as binary file
+-- @return true if successful
+-- @return actual return code
+-- @return stdout output (string)
+-- @return errout output (string)
+function utils.executeex(cmd, bin)
+    local outfile = os.tmpname()
+    local errfile = os.tmpname()
+
+    if is_windows and not outfile:find(':') then
+        outfile = os.getenv('TEMP')..outfile
+        errfile = os.getenv('TEMP')..errfile
+    end
+    cmd = cmd .. " > " .. utils.quote_arg(outfile) .. " 2> " .. utils.quote_arg(errfile)
+
+    local success, retcode = utils.execute(cmd)
+    local outcontent = utils.readfile(outfile, bin)
+    local errcontent = utils.readfile(errfile, bin)
+    os.remove(outfile)
+    os.remove(errfile)
+    return success, retcode, (outcontent or ""), (errcontent or "")
+end
+
+--- Quote and escape an argument of a command.
+-- Quotes a single (or list of) argument(s) of a command to be passed
+-- to `os.execute`, `pl.utils.execute` or `pl.utils.executeex`.
+-- @param argument (string or table/list) the argument to quote. If a list then
+-- all arguments in the list will be returned as a single string quoted.
+-- @return quoted and escaped argument.
+-- @usage
+-- local options = utils.quote_arg {
+--     "-lluacov",
+--     "-e",
+--     "utils = print(require('pl.utils')._VERSION",
+-- }
+-- -- returns: -lluacov -e 'utils = print(require('\''pl.utils'\'')._VERSION'
+function utils.quote_arg(argument)
+    if type(argument) == "table" then
+        -- encode an entire table
+        local r = {}
+        for i, arg in ipairs(argument) do
+            r[i] = utils.quote_arg(arg)
+        end
+
+        return table.concat(r, " ")
+    end
+    -- only a single argument
+    if is_windows then
+        if argument == "" or argument:find('[ \f\t\v]') then
+            -- Need to quote the argument.
+            -- Quotes need to be escaped with backslashes;
+            -- additionally, backslashes before a quote, escaped or not,
+            -- need to be doubled.
+            -- See documentation for CommandLineToArgvW Windows function.
+            argument = '"' .. argument:gsub([[(\*)"]], [[%1%1\"]]):gsub([[\+$]], "%0%0") .. '"'
+        end
+
+        -- os.execute() uses system() C function, which on Windows passes command
+        -- to cmd.exe. Escape its special characters.
+        return (argument:gsub('["^<>!|&%%]', "^%0"))
+    else
+        if argument == "" or argument:find('[^a-zA-Z0-9_@%+=:,./-]') then
+            -- To quote arguments on posix-like systems use single quotes.
+            -- To represent an embedded single quote close quoted string ('),
+            -- add escaped quote (\'), open quoted string again (').
+            argument = "'" .. argument:gsub("'", [['\'']]) .. "'"
+        end
+
+        return argument
+    end
+end
+
+--- error out of this program gracefully.
+-- @param[opt] code The exit code, defaults to -`1` if omitted
+-- @param msg The exit message will be sent to `stderr` (will be formatted with the extra parameters)
+-- @param ... extra arguments for message's format'
+-- @see utils.fprintf
+-- @usage utils.quit(-1, "Error '%s' happened", "42")
+-- -- is equivalent to
+-- utils.quit("Error '%s' happened", "42")  --> Error '42' happened
+function utils.quit(code, msg, ...)
+    if type(code) == 'string' then
+        utils.fprintf(io.stderr, code, msg, ...)
+        io.stderr:write('\n')
+        code = -1 -- TODO: this is odd, see the test. Which returns 255 as exit code
+    elseif msg then
+        utils.fprintf(io.stderr, msg, ...)
+        io.stderr:write('\n')
+    end
+    os.exit(code, true)
+end
+
+
+--- String functions
+-- @section string-functions
+
+--- escape any Lua 'magic' characters in a string
+-- @param s The input string
+function utils.escape(s)
+    utils.assert_string(1,s)
+    return (s:gsub('[%-%.%+%[%]%(%)%$%^%%%?%*]','%%%1'))
+end
+
+--- split a string into a list of strings separated by a delimiter.
+-- @param s The input string
+-- @param re optional A Lua string pattern; defaults to '%s+'
+-- @param plain optional If truthy don't use Lua patterns
+-- @param n optional maximum number of elements (if there are more, the last will remian un-split)
+-- @return a list-like table
+-- @raise error if s is not a string
+-- @see splitv
+function utils.split(s,re,plain,n)
+    utils.assert_string(1,s)
+    local find,sub,append = string.find, string.sub, table.insert
+    local i1,ls = 1,{}
+    if not re then re = '%s+' end
+    if re == '' then return {s} end
+    while true do
+        local i2,i3 = find(s,re,i1,plain)
+        if not i2 then
+            local last = sub(s,i1)
+            if last ~= '' then append(ls,last) end
+            if #ls == 1 and ls[1] == '' then
+                return {}
+            else
+                return ls
+            end
+        end
+        append(ls,sub(s,i1,i2-1))
+        if n and #ls == n then
+            ls[#ls] = sub(s,i1)
+            return ls
+        end
+        i1 = i3+1
+    end
+end
+
+--- split a string into a number of return values.
+-- Identical to `split` but returns multiple sub-strings instead of
+-- a single list of sub-strings.
+-- @param s the string
+-- @param re A Lua string pattern; defaults to '%s+'
+-- @param plain don't use Lua patterns
+-- @param n optional maximum number of splits
+-- @return n values
+-- @usage first,next = splitv('user=jane=doe','=', false, 2)
+-- assert(first == "user")
+-- assert(next == "jane=doe")
+-- @see split
+function utils.splitv (s,re, plain, n)
+    return _unpack(utils.split(s,re, plain, n))
+end
+
+
+--- Functional
+-- @section functional
+
+
+--- 'memoize' a function (cache returned value for next call).
+-- This is useful if you have a function which is relatively expensive,
+-- but you don't know in advance what values will be required, so
+-- building a table upfront is wasteful/impossible.
+-- @param func a function of at least one argument
+-- @return a function with at least one argument, which is used as the key.
+function utils.memoize(func)
+    local cache = {}
+    return function(k)
+        local res = cache[k]
+        if res == nil then
+            res = func(k)
+            cache[k] = res
+        end
+        return res
+    end
+end
+
+
+--- associate a function factory with a type.
+-- A function factory takes an object of the given type and
+-- returns a function for evaluating it
+-- @tab mt metatable
+-- @func fun a callable that returns a function
+function utils.add_function_factory (mt,fun)
+    _function_factories[mt] = fun
+end
+
+local function _string_lambda(f)
+    if f:find '^|' or f:find '_' then
+        local args,body = f:match '|([^|]*)|(.+)'
+        if f:find '_' then
+            args = '_'
+            body = f
+        else
+            if not args then return raise 'bad string lambda' end
+        end
+        local fstr = 'return function('..args..') return '..body..' end'
+        local fn,err = utils.load(fstr)
+        if not fn then return raise(err) end
+        fn = fn()
+        return fn
+    else
+        return raise 'not a string lambda'
+    end
+end
+
+
+--- an anonymous function as a string. This string is either of the form
+-- '|args| expression' or is a function of one argument, '_'
+-- @param lf function as a string
+-- @return a function
+-- @function utils.string_lambda
+-- @usage
+-- string_lambda '|x|x+1' (2) == 3
+-- string_lambda '_+1' (2) == 3
+utils.string_lambda = utils.memoize(_string_lambda)
+
+
+--- bind the first argument of the function to a value.
+-- @param fn a function of at least two values (may be an operator string)
+-- @param p a value
+-- @return a function such that f(x) is fn(p,x)
+-- @raise same as @{function_arg}
+-- @see func.bind1
+-- @usage local function f(msg, name)
+--   print(msg .. " " .. name)
+-- end
+--
+-- local hello = utils.bind1(f, "Hello")
+--
+-- print(hello("world"))     --> "Hello world"
+-- print(hello("sunshine"))  --> "Hello sunshine"
+function utils.bind1 (fn,p)
+    fn = utils.function_arg(1,fn)
+    return function(...) return fn(p,...) end
+end
+
+
+--- bind the second argument of the function to a value.
+-- @param fn a function of at least two values (may be an operator string)
+-- @param p a value
+-- @return a function such that f(x) is fn(x,p)
+-- @raise same as @{function_arg}
+-- @usage local function f(a, b, c)
+--   print(a .. " " .. b .. " " .. c)
+-- end
+--
+-- local hello = utils.bind1(f, "world")
+--
+-- print(hello("Hello", "!"))  --> "Hello world !"
+-- print(hello("Bye", "?"))    --> "Bye world ?"
+function utils.bind2 (fn,p)
+    fn = utils.function_arg(1,fn)
+    return function(x,...) return fn(x,p,...) end
+end
+
+
+
+
+--- Deprecation
+-- @section deprecation
+
+do
+  -- the default implementation
+  local deprecation_func = function(msg, trace)
+    if trace then
+      warn(msg, "\n", trace)  -- luacheck: ignore
+    else
+      warn(msg)  -- luacheck: ignore
+    end
+  end
+
+  --- Sets a deprecation warning function.
+  -- An application can override this function to support proper output of
+  -- deprecation warnings. The warnings can be generated from libraries or
+  -- functions by calling `utils.raise_deprecation`. The default function
+  -- will write to the 'warn' system (introduced in Lua 5.4, or the compatibility
+  -- function from the `compat` module for earlier versions).
+  --
+  -- Note: only applications should set/change this function, libraries should not.
+  -- @param func a callback with signature: `function(msg, trace)` both arguments are strings, the latter being optional.
+  -- @see utils.raise_deprecation
+  -- @usage
+  -- -- write to the Nginx logs with OpenResty
+  -- utils.set_deprecation_func(function(msg, trace)
+  --   ngx.log(ngx.WARN, msg, (trace and (" " .. trace) or nil))
+  -- end)
+  --
+  -- -- disable deprecation warnings
+  -- utils.set_deprecation_func()
+  function utils.set_deprecation_func(func)
+    if func == nil then
+      deprecation_func = function() end
+    else
+      utils.assert_arg(1, func, "function")
+      deprecation_func = func
+    end
+  end
+
+  --- raises a deprecation warning.
+  -- For options see the usage example below.
+  --
+  -- Note: the `opts.deprecated_after` field is the last version in which
+  -- a feature or option was NOT YET deprecated! Because when writing the code it
+  -- is quite often not known in what version the code will land. But the last
+  -- released version is usually known.
+  -- @param opts options table
+  -- @see utils.set_deprecation_func
+  -- @usage
+  -- warn("@on")   -- enable Lua warnings, they are usually off by default
+  --
+  -- function stringx.islower(str)
+  --   raise_deprecation {
+  --     source = "Penlight " .. utils._VERSION,                   -- optional
+  --     message = "function 'islower' was renamed to 'is_lower'", -- required
+  --     version_removed = "2.0.0",                                -- optional
+  --     deprecated_after = "1.2.3",                               -- optional
+  --     no_trace = true,                                          -- optional
+  --   }
+  --   return stringx.is_lower(str)
+  -- end
+  -- -- output: "[Penlight 1.9.2] function 'islower' was renamed to 'is_lower' (deprecated after 1.2.3, scheduled for removal in 2.0.0)"
+  function utils.raise_deprecation(opts)
+    utils.assert_arg(1, opts, "table")
+    if type(opts.message) ~= "string" then
+      error("field 'message' of the options table must be a string", 2)
+    end
+    local trace
+    if not opts.no_trace then
+      trace = debug.traceback("", 2):match("[\n%s]*(.-)$")
+    end
+    local msg
+    if opts.deprecated_after and opts.version_removed then
+      msg = (" (deprecated after %s, scheduled for removal in %s)"):format(
+        tostring(opts.deprecated_after), tostring(opts.version_removed))
+    elseif opts.deprecated_after then
+      msg = (" (deprecated after %s)"):format(tostring(opts.deprecated_after))
+    elseif opts.version_removed then
+      msg = (" (scheduled for removal in %s)"):format(tostring(opts.version_removed))
+    else
+      msg = ""
+    end
+
+    msg = opts.message .. msg
+
+    if opts.source then
+      msg = "[" .. opts.source .."] " .. msg
+    else
+      if msg:sub(1,1) == "@" then
+        -- in Lua 5.4 "@" prefixed messages are control messages to the warn system
+        error("message cannot start with '@'", 2)
+      end
+    end
+
+    deprecation_func(msg, trace)
+  end
+
+end
+
+
+return utils
+
+
+
+end,
+
+----------------------
+-- Modules part end --
+----------------------
+        }
+        if files[path] then
+            return files[path]
+        else
+            return origin_seacher(path)
+        end
+    end
+end
+---------------------------------------------------------
+----------------Auto generated code block----------------
+---------------------------------------------------------
+return require('pl.import_into')()
\ No newline at end of file


Property changes on: trunk/Master/texmf-dist/tex/luatex/penlight/penlight.lua
___________________________________________________________________
Added: svn:eol-style
## -0,0 +1 ##
+native
\ No newline at end of property
Added: trunk/Master/texmf-dist/tex/luatex/penlight/penlight.sty
===================================================================
--- trunk/Master/texmf-dist/tex/luatex/penlight/penlight.sty	                        (rev 0)
+++ trunk/Master/texmf-dist/tex/luatex/penlight/penlight.sty	2021-09-21 19:48:22 UTC (rev 60574)
@@ -0,0 +1,43 @@
+% Kale Ewasiuk (kalekje at gmail.com)
+% 2021-09-20
+%
+% Copyright (C) 2021 Kale Ewasiuk
+%
+% Permission is hereby granted, free of charge, to any person obtaining a copy
+% of this software and associated documentation files (the "Software"), to deal
+% in the Software without restriction, including without limitation the rights
+% to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+% copies of the Software, and to permit persons to whom the Software is
+% furnished to do so, subject to the following conditions:
+%
+% The above copyright notice and this permission notice shall be included in
+% all copies or substantial portions of the Software.
+%
+% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+% ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+% TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+% PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT
+% SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
+% ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+% ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+% OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
+% OR OTHER DEALINGS IN THE SOFTWARE.
+
+\ProvidesPackage{penlight}[2021-09-20]
+
+\RequirePackage{luapackageloader}
+
+\DeclareOption{pl}{\directlua{
+    pl = require('penlight')
+    __PENLIGHT__ = 'pl'
+}}
+\DeclareOption{penlight}{\directlua{
+    penlight = require('penlight')
+    __PENLIGHT__ = 'penlight'
+}}
+\DeclareOption{stringx}{\directlua{_G[__PENLIGHT__].stringx.import()}}
+\DeclareOption{format}{\directlua{_G[__PENLIGHT__].text.format_operator()}}
+\DeclareOption{func}{\directlua{_G[__PENLIGHT__].utils.import(__PENLIGHT__..'.func')}}
+\DeclareOption{extras}{\directlua{require('penlightextras')}}
+
+\ProcessOptions*\relax


Property changes on: trunk/Master/texmf-dist/tex/luatex/penlight/penlight.sty
___________________________________________________________________
Added: svn:eol-style
## -0,0 +1 ##
+native
\ No newline at end of property
Added: trunk/Master/texmf-dist/tex/luatex/penlight/penlightextras.lua
===================================================================
--- trunk/Master/texmf-dist/tex/luatex/penlight/penlightextras.lua	                        (rev 0)
+++ trunk/Master/texmf-dist/tex/luatex/penlight/penlightextras.lua	2021-09-21 19:48:22 UTC (rev 60574)
@@ -0,0 +1,413 @@
+-- requires penlight
+local pl = _G['penlight'] or _G['pl'] -- penlight for this namespace is pl
+local bind = bind or pl.func.bind
+
+function help_wrt(s1, s2) -- helpful printing, makes it easy to debug, s1 is object, s2 is note
+    local wrt = wrt or texio.write_nl
+    local wrt = wrt or print
+    s2 = s2 or ''
+    wrt('\nvvvvv '..s2)
+    if type(s1) == 'table' then
+        wrt(pl.pretty.write(s1))
+    else
+        wrt(tostring(s1))
+    end
+    wrt('^^^^^\n')
+end
+
+
+function prt_array2d(t)
+    for _, r in ipairs(t) do
+        local s = ''
+        for _, v in ipairs(r) do
+            s = s.. tostring(v)..', '
+        end
+        print(s)
+    end
+end
+
+-- -- -- -- --
+
+
+-- -- -- --  functions below are helpers for arrays and 2d
+
+local function compare_elements(a, b, op, ele)
+    op = op or pl.oper.gt
+    ele = ele or 1
+    return op(a[ele], b[ele])
+end
+
+local function comp_2ele_func(op, ele) -- make a 2 element comparison function,
+    --sort with function on element nnum
+    return bind(compare_elements, _1, _2, op, ele)
+end
+
+
+-- -- -- --
+
+local function check_index(ij, rc) -- converts array index to positive value if negative
+    if type(ij) ~= 'number' then
+        return 1
+    else
+        if ij < 0 then
+            ij = rc + ij + 1
+        elseif ij > rc then
+            ij = rc
+        end
+        return ij
+    end
+end
+local function check_slice(M, i1, j1, i2, j2) -- ensure a slice is valid; i.e. all positive numbers
+    r, c = pl.array2d.size(M)
+    i1 = check_index(i1, r)
+    i2 = check_index(i2, r)
+    j1 = check_index(j1, c)
+    j2 = check_index(j2, c)
+    return i1, j1, i2, j2
+end
+
+local function check_func(func)  -- check if a function is a PE, if so, make it a function
+    if type(func) ~= 'function' then
+        __func = I(func)
+    end
+    return __func
+end
+
+
+-- -- -- -- -- -- --
+-- -- -- --  functions below extend the array2d module
+
+
+local function map_slice1(func, L, i1, i2) -- map a function to a slice of an array, can use PlcExpr
+    i2 = i2 or i1
+    local len = #L
+    i1 = check_index(i1, len)
+    i2 = check_index(i2, len)
+    func = check_func(func)
+    for i in pl.seq.range(i1,i2) do
+            L[i] = func(L[i])
+        end
+   return L
+end
+
+local function map_slice2(func, M, i1, j1, i2, j2) -- map a function to a slice of a Matrix
+    i1, j1, i2, j2 = check_slice(M, i1, j1, i2, j2)
+    --for i,j in array2d.iter(M, true, i1, j1, i2, j2) do  --todo this did not work, penlight may have fixed this
+    func = check_func(func)
+    for i in pl.seq.range(i1,i2) do
+        for j in pl.seq.range(j1,j2) do
+            M[i][j] = func(M[i][j])
+        end
+    end
+   return M
+end
+
+local function map_columns(func, M, j1, j2) -- map function to columns of matrix
+    j2 = j2 or j1
+    return map_slice2(func, M, 1, j1, -1, j2)
+end
+
+local function map_rows(func, M, i1, i2) -- map function to rows of matrix
+    i2 = i2 or i1
+    return map_slice2(func, M, i1, 1, i2, -1)
+end
+
+
+-- -- -- -- -- -- -- --
+
+function sortOP(M, op, ele) -- sort a 2d array based on operator criteria, ele is column, ie sort on which element
+       M_new = {}
+        for row in pl.seq.sort(M, comp_2ele_func(op, ele)) do
+            M_new[#M_new+1] = row
+        end
+        return M_new
+end
+
+local function like(M1, v)
+    v = v or 0
+    r, c = pl.array2d.size(M1)
+    return pl.array2d.new(r,c,v)
+end
+
+function from_table(t) -- turns a labelled table to a 2d, label-free array
+    t_new = {}
+    for k, v in pairs(t) do
+        if type(v) == 'table' then
+            t_new_row = {k}
+            for _, v_ in ipairs(v) do
+                 t_new_row[#t_new_row+1] =  v_
+            end
+            t_new[#t_new+1] = t_new_row
+        else
+            t_new[#t_new+1] = {k, v}
+        end
+    end
+    return t_new
+end
+
+function toTeX(M, EL) --puts & between columns, can choose to end line with \\ if EL is true (end-line)
+    EL = EL or false
+    if EL then EL = '\\\\' else EL = '' end
+    return pl.array2d.reduce2(_1..EL.._2, _1..'&'.._2, M)..EL
+end
+
+-- -- -- -- -- -- --
+
+-- add to array2d module
+pl.array2d['map_columns'] = map_columns
+pl.array2d['map_rows'] = map_rows
+pl.array2d['map_slice2'] = map_slice2
+pl.array2d['map_slice1'] = map_slice1
+pl.array2d['from_table'] = from_table
+pl.array2d['toTeX'] = toTeX
+pl.array2d['sortOP'] = sortOP
+pl.array2d['like'] = like
+
+
+
+
+-- -- -- -- -- -- -- -- -- -- -- --  functions below extend the operator module
+
+local function strgt(a,b) return tostring(a) > tostring(b) end
+local function strlt(a,b) return tostring(a) < tostring(b) end
+pl.operator['strgt'] = strgt
+pl.operator['strlt'] = strlt
+
+
+
+
+
+local function gextract(s, pat) --extract a pattern from string, returns both
+    local s_extr = ''
+    local s_rem = s
+    for e in s:gmatch(pat) do
+        s_extr = s_extr..e
+        s_rem = s_rem:gsub(e,'')
+    end
+    return s_extr, s_rem
+end
+
+local function gfirst(s, t) -- get the first pattern found from a table of pattern
+    for _, pat in pairs(t) do
+        if string.find(s, pat) then
+            return pat
+        end
+    end
+end
+
+local function appif(S, W, B, O) --append W ord to S tring if B oolean true, otherwise O ther
+    --append Word to String
+    if B then --if b is true
+        S = S .. W
+    else --consider Other word
+        O = O or ''
+        S = S .. O
+    end
+    return S
+end
+
+local mt = getmetatable("") -- register functions with str
+mt.__index["gextract"] = gextract
+mt.__index["gfirst"] = gfirst
+mt.__index["app_if"] = appif
+
+
+function mod(a, b) -- math modulo, return remainder only
+    return a - (math.floor(a/b)*b)
+end
+
+function mod2(a) -- math modulo 2
+    return mod(a,2)
+end
+
+function hasval(x)  -- if something has value
+    -- todo check for Lists, other penlight objects
+    if (x == nil) or (x == false) or (x == 0) or (x == '') then
+        return false
+    elseif type(x) == 'table' then
+        if #x == 0 then
+            return false
+        else
+            return true
+        end
+    end
+    return true
+end
+
+
+
+
+-- testing here
+____zzz__ = [[
+function hasStrKey(T)
+    --checks if a Table contains a string-type key
+    local hasaStrKey = false
+    for k, v in pairs(T) do  --look through table pairs
+        if type(k) == "string" then  --if any string found, return true
+            hasaStrKey = true
+            break
+        end
+    end
+    return hasaStrKey
+end
+
+
+function any()
+    --todo go through table or list of args and return true of anything is something
+end
+
+function all()
+    --todo go through table or list of args and return true of anything is something
+end
+
+
+    --elseif x == {} then
+    --    return false
+
+n = nil
+b = false
+z = 0
+e = ''
+t = {}
+
+--s = 'a'
+--n = 1
+
+
+if is(nil) then
+    print('TRUE')
+else
+    print('FALSE')
+end
+
+--print({}=={})
+--print(0.0==0)
+
+
+]]
+
+
+
+
+
+
+
+
+
+
+
+-- Some simple and helpful LaTeX functions
+-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
+-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
+-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
+
+--Generic LuaLaTeX utilities for print commands or environments
+-- http://lua-users.org/wiki/SplitJoin -- todo read me!!
+__SKIP_TEX__ = __SKIP_TEX__ or false --if declared true before here, it will use regular print functions
+--                                       (for troubleshooting with texlua)
+
+-- xparse defaults
+_xTrue = '\\BooleanTrue '
+_xFalse = '\\BooleanFalse '
+_xNoValue = '-NoValue-'
+
+
+if not __SKIP_TEX__ then
+    prt = tex.sprint     --can print lists, but will NOT put new line between them
+    prtn = tex.print      --can print lists and will put new line. C-function not in Lua. think P rint R return
+    wrt = texio.write
+    wrtn = texio.write_nl
+else
+    prt = io.write
+    prtn = print --print with new line
+    wrt = io.write
+    wrtn = io.write_nl
+end
+
+function prtl(str) -- prints a literal string to latex, adds new line between them
+    for line in str:gmatch"[^\n]*" do  -- gets all characters up to a new line
+        prtn(line)
+    end
+end
+
+
+
+_NumBkts = 0
+function reset_bkt_cnt(n)
+     n = n or 0
+    _NumBkts = n
+end
+
+function add_bkt_cnt(n)
+     n = n or 1
+    _NumBkts = _NumBkts + n
+end
+
+function close_bkt_cnt()
+    local s = ('}'):rep(_NumBkts)
+    reset_bkt_cnt()
+    return s
+end
+
+
+
+
+
+
+
+
+--definition helpers -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
+-- todo add this
+
+local function defcmd_nest(cs) -- for option if you'd like your commands under  a parent ex. \csparent{var}
+    tex.print('\\gdef\\'..cs..'#1{\\csname '..var..'--#1--\\endcsname}')
+end
+
+
+local function defcmd(cs, val, nargs)
+    if (nargs == nil) or (args == 0) then
+        token.set_macro(cs, tostring(val), 'global')
+    else
+        local args = '#1'
+        tex.print('\\gdef\\'..cs..args..'{'..val..'}')
+        -- todo https://tex.stackexchange.com/questions/57551/create-a-capitalized-macro-token-using-csname
+        --    \expandafter\gdef\csname Two\endcsname#1#2{1:#1, two:#2} --todo do it like this
+    end
+end
+
+
+local function prvcmd(cs, val) -- provide command via lua
+   if token.is_defined(cs) then
+        tex.print('\\PackageWarning{YAMLvars}{Variable '..cs..' already defined, could not declare}{}')
+    else
+        defcmd(cs, val)
+    end
+end
+
+
+local function newcmd(cs, val) -- provide command via lua
+   if token.is_defined(cs) then
+        tex.print('\\PackageError{luadefs}{Command '..cs..' already defined}{}')
+    else
+        defcmd(cs, val)
+    end
+end
+
+local function renewcmd(cs, val) -- provide command via lua
+   if token.is_defined(cs) then
+        defcmd(cs, val)
+    else
+        tex.print('\\PackageError{luadefs}{Command '..cs..' already defined}{}')
+    end
+end
+
+local function deccmd(cs, def)
+    if def == nil then
+        prvcmd(cs, '\\PackageError{luadefs}{Command "'..cs..'" was declared and used but, not set}{}')
+    else
+        prvcmd(cs, def)
+    end
+end
+
+
+-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --


Property changes on: trunk/Master/texmf-dist/tex/luatex/penlight/penlightextras.lua
___________________________________________________________________
Added: svn:eol-style
## -0,0 +1 ##
+native
\ No newline at end of property
Modified: trunk/Master/tlpkg/bin/tlpkg-ctan-check
===================================================================
--- trunk/Master/tlpkg/bin/tlpkg-ctan-check	2021-09-21 19:46:31 UTC (rev 60573)
+++ trunk/Master/tlpkg/bin/tlpkg-ctan-check	2021-09-21 19:48:22 UTC (rev 60574)
@@ -595,7 +595,7 @@
     pdfpagediff pdfpages pdfpc pdfpc-movie pdfprivacy pdfreview
     pdfscreen pdfslide pdfsync
     pdftex-quiet pdftexcmds pdftricks pdftricks2 pdfx pdfxup
-    pecha pedigree-perl penrose perception perfectcut perltex
+    pecha pedigree-perl penlight penrose perception perfectcut perltex
     permute persian-bib
     petiteannonce petri-nets pfarrei pfdicons
     pgf pgf-blur pgf-cmykshadings pgf-pie

Modified: trunk/Master/tlpkg/libexec/ctan2tds
===================================================================
--- trunk/Master/tlpkg/libexec/ctan2tds	2021-09-21 19:46:31 UTC (rev 60573)
+++ trunk/Master/tlpkg/libexec/ctan2tds	2021-09-21 19:48:22 UTC (rev 60574)
@@ -2162,6 +2162,7 @@
  'pdfslide',    '\.jpg|\.sty|\.clo|\.cfg|meta.*\.pdf',
  'pdfx',        '\.(def|dfu|icc|xmp)$|(glyph|Profiles).*tex|pdfx\.sty|ICC_LIC',
  'pdfxup',	'(template\.tex|\.xup)$',
+ 'penlight',	'\.lua$|' . $standardtex,
  'petri-nets',  'pnets\.tex|pntext\.tex|\.sty|pndraw\.tex|pnversion\.tex|\.sty|pndraw\.tex',
  'profcollege',	'PfC.*\.tex|' . $standardtex,
  'pgf-blur',    'tikzlibraryshadows.blur.code.tex',

Modified: trunk/Master/tlpkg/tlpsrc/collection-luatex.tlpsrc
===================================================================
--- trunk/Master/tlpkg/tlpsrc/collection-luatex.tlpsrc	2021-09-21 19:46:31 UTC (rev 60573)
+++ trunk/Master/tlpkg/tlpsrc/collection-luatex.tlpsrc	2021-09-21 19:48:22 UTC (rev 60574)
@@ -62,6 +62,7 @@
 depend optex
 depend pdfarticle
 depend pdfextra
+depend penlight
 depend placeat
 depend plantuml
 depend pyluatex

Added: trunk/Master/tlpkg/tlpsrc/penlight.tlpsrc
===================================================================


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