[luatex] token_filter

[Paul Isambert]

Arthur Reutenauer <arthur.reutenauer at normalesup.org> a écrit:
> > l.28 of your luaintercharnode.lua, you say:
> > 
> >     Why the hell can’t I index a table with a table?
> > 
> > Well, you can :)
> > 
> >     local t = { [{1, 1}] = emspace }
> >     t[{a = b}] = c
> 
>   Yes, but observe:
> 
> ---- cut before
> \directlua{ 
>   local function log(message)
>     texio.write_nl("term and log", message)
>   end
> 
>   local function say_if_node(n, label)
>     if node.is_node(n, label) then
>       log(label .. " is a node")
>     else
>       log(label .. " is NOT a node")
>     end
>   end
> 
>   local t = { }
>   local emspace = node.new(node.id('kern'), 1)
>   t[{ 1, 1 }] = emspace
>   t[1] = emspace
> 
>   say_if_node(emspace, "emspace")
>   say_if_node(t[{ 1, 1 }], "t[{ 1, 1 }]")
>   say_if_node(t[1], "t[1]")
> }
> ---- cut after
> 
> prints (amongst others):
> 
> ----
> emspace is a node
> t[{ 1, 1 }] is NOT a node
> t[1] is a node
> ----
> 
>   So something odd is happening when the table index is a table, which
> meant that in practice I couldn't use table as indexes there.
> 
>   With LuaTeX 0.70.2 from TeX Live 2012, haven't checked with 0.75.

That’s because you’re using two different tables, although they have
the same contents. What should be done is:

    local t, tindex = {}, {1, 1}
    ...
    t[tindex] = emspace
    ...
    say_if_node(t[tindex],  "t[{ 1, 1 }]")
    ...

Of course, that solution might not fit your goal.

Otherwise, I’m sure you could hack some metatable magic to the effect
that t[{1, 1}] always works.

Best,
Paul