Hi,
i want to propose two new primitives for LuaTeX:
- The existing `\luafunction` has some similarities to `\count`, `\dimen`, `\skip`. Especially for most use cases, you will have to allocate a number, but there is no equivalent to `\countdef` etc.
I think LuaTeX would benefit from `\luafunctiondef`, such that e.g. `\luafunctiondef\something1` would define `\something`, such that `\something` is equivalent to `\luafunction1`.
What is the difference to creating a regular macro? This would allow `\something` to be expandable in a single step, which is especially important for emulating primitives from other engines with lua code.
- Additionally it would be useful to allow "expandable temporary macro definitions". So for example
\scantexmacro#1#2\stop{-#1-#2-}abc\stop def
would expand to
-a-bc-def
This allows using the TeX macro argument parser inside expandable macros, especially when the delimiter can change. For example if you implement a property list as `\@key key1\@value value1\@key key2\@value value2...`, you can create an expandable macro to ge the value of key `#2` without requiring recursive calls with
\def\propget#1#2{%
\scantexmacro##1\@key#2\@value##2\@key##3\stop{%
##2%
}#1\@key#2\@value\@key\stop
}
Another use-case would be implementingan expandable version of functionality similar to the expl3 `\seq_map_inline:Nn`.
What do think? Is there any chance to see something like this in LuaTeX?
I attached a first implementation as patch against the current experimental branch.
Best regards
Marcel Krüger
