[latex3-commits] [git/LaTeX3-latex3-latex3] master: Support for command replacement in text expansion (ba6af7823)

[Joseph Wright]

Repository : https://github.com/latex3/latex3
On branch  : master
Link       : https://github.com/latex3/latex3/commit/ba6af782390809cf2f53fda9d59b15837e4a1652

>---------------------------------------------------------------

commit ba6af782390809cf2f53fda9d59b15837e4a1652
Author: Joseph Wright <joseph.wright at morningstar2.co.uk>
Date:   Wed Jan 22 11:56:27 2020 +0000

    Support for command replacement in text expansion
    
    This is mainly needed for textcomp-like commands:
    \T1-cmd, etc. otherwise loop infinitely.


>---------------------------------------------------------------

ba6af782390809cf2f53fda9d59b15837e4a1652
 l3kernel/CHANGELOG.md |  3 +++
 l3kernel/l3text.dtx   | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 67 insertions(+), 1 deletion(-)

diff --git a/l3kernel/CHANGELOG.md b/l3kernel/CHANGELOG.md
index 151ab19ad..73f8acdd5 100644
--- a/l3kernel/CHANGELOG.md
+++ b/l3kernel/CHANGELOG.md
@@ -7,6 +7,9 @@ this project uses date-based 'snapshot' version identifiers.
 
 ## [Unreleased]
 
+### Added
+- Support for command replacement in text expansion
+
 ### Changed
 - Require key values for numerical key types (dim, int, etc.) (see #661)
 
diff --git a/l3kernel/l3text.dtx b/l3kernel/l3text.dtx
index 4cc60dcf5..bcc77afe5 100644
--- a/l3kernel/l3text.dtx
+++ b/l3kernel/l3text.dtx
@@ -77,6 +77,19 @@
 %   expansion
 % \end{function}
 %
+% \begin{function}[added = 2020-01-22]
+%   {
+%     \text_declare_expand_equivalent:Nn ,
+%     \text_declare_expand_equivalent:cn
+%   }
+%   \begin{syntax}
+%     \cs{text_declare_expand_equivalent:Nn} \meta{cmd} \Arg{replacement}
+%   \end{syntax}
+%   Declares that the \meta{replacement} tokens should be used whenever the
+%   \meta{cmd} (a single token) is encountered. The \meta{replacement} tokens
+%   should be expandable.
+% \end{function}
+%
 % \subsection{Case changing}
 %
 % \begin{function}[EXP, added = 2019-11-20]
@@ -522,6 +535,8 @@
 %   }
 % \begin{macro}[EXP]{\@@_expand_protect:nN}
 % \begin{macro}[EXP]{\@@_expand_protect:Nw}
+% \begin{macro}[EXP]{\@@_expand_replace:N}
+% \begin{macro}[EXP]{\@@_expand_replace:n}
 % \begin{macro}[EXP]{\@@_expand_cs_expand:N}
 %   After precautions against |&| tokens, start a simple loop: that of
 %   course means that \enquote{text} cannot contain the two recursion
@@ -834,7 +849,7 @@
   {
     \str_if_eq:nnTF {#1} { \protect }
       { \@@_expand_protect:N }
-      { \@@_expand_cs_expand:N #1 }
+      { \@@_expand_replace:N #1 }
   }
 \cs_new:Npn \@@_expand_protect:N #1
   {
@@ -855,6 +870,25 @@
     \@@_expand_loop:w
   }
 %    \end{macrocode}
+%   See if there is a dedicated replacement, and if there is, insert it.
+%    \begin{macrocode}
+\cs_new:Npn \@@_expand_replace:N #1
+  {
+    \bool_lazy_and:nnTF
+      { \cs_if_exist_p:c { l_@@_expand_ \token_to_str:N #1 _tl } }
+      {
+        \bool_lazy_or_p:nn
+          { \token_if_cs_p:N #1 }
+          { \token_if_active_p:N #1 }
+      }
+      {
+        \exp_args:Nv \@@_expand_replace:n
+          { l_@@_expand_ \token_to_str:N #1 _tl }
+      }
+      { \@@_expand_cs_expand:N #1 }
+  }
+\cs_new:Npn \@@_expand_replace:n #1 { \@@_expand_loop:w #1 }
+%    \end{macrocode}
 %   Finally, expand any macros which can be: this then loops back around to
 %   deal with what they produce.
 %    \begin{macrocode}
@@ -893,6 +927,35 @@
 % \end{macro}
 % \end{macro}
 %
+% \begin{macro}
+%   {
+%     \text_declare_expand_equivalent:Nn ,
+%     \text_declare_expand_equivalent:cn
+%   }
+%  Create equivalents to allow replacement. 
+%    \begin{macrocode}
+\cs_new_protected:Npn \text_declare_expand_equivalent:Nn #1#2
+  {
+    \tl_clear_new:c { l_@@_expand_ \token_to_str:N #1 _tl }
+    \tl_set:cn { l_@@_expand_ \token_to_str:N #1 _tl } {#2}
+  }
+\cs_generate_variant:Nn \text_declare_expand_equivalent:Nn { c }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}[EXP]{\@@_expand_textcomp:NN}
+%   Filter out \pkg{textcomp}-like commands.
+%    \begin{macrocode}
+%<*package>
+\cs_new:Npn \@@_expand_textcomp:NN #1#2 { \exp_not:n {#1} }
+\text_declare_expand_equivalent:cn { ?-cmd }  { \@@_expand_textcomp:NN }
+\text_declare_expand_equivalent:cn { T1-cmd }  { \@@_expand_textcomp:NN }
+\text_declare_expand_equivalent:cn { TS1-cmd } { \@@_expand_textcomp:NN }
+\text_declare_expand_equivalent:cn { TU-cmd }  { \@@_expand_textcomp:NN }
+%</package>
+%    \end{macrocode}
+% \end{macro}
+%
 %    \begin{macrocode}
 %</initex|package>
 %    \end{macrocode}