On 11/16/2021 8:22 PM, Joey McCollum via ntg-context wrote:
As the subject of this question suggests, this is really more of a
question about expansion control (a topic that is still a bit obscure to
me). Suppose I have a macro \inner that expects a single argument or an
assignment of parameters in brackets. For my purposes, I don't want this
macro to do anything when it is typeset, so I'll just define it as empty:
```
\def\inner[#1]\empty
```
Now suppose I have another macro \outer that invokes this macro with
some specific input and sets some plain text after it:
```
\def\outer{\inner[123] etc.}
```
What I'd like to do is parse the argument of \inner in \outer. I was
hoping that a string search in Lua would work, but I'm not having any
luck. A minimal (non)-working example is included below:
```
\def\inner[#1]\empty
\def\outer{\inner[123] etc.}
\startluacode
local userdata = userdata or {}
function userdata.parseinner(str)
local innerparams = ""
if string.find(str, "\\inner(%b[])") then
i, j = string.find(str, "\\inner(%b[])")
innerparams = string.sub(str, i+1, j-1) -- we just want the
content inside the brackets
end
context(innerparams)
return
end
\stopluacode
\def\parseinner#1{\ctxlua{userdata.parseinner([==[#1]==])}}
\starttext
Testing:\blank
\parseinner{\outer}
\stoptext
```
My problem is that when I pass \outer to the \parseinner macro, it gets
fully expanded, so there isn't anything left to match "\\inner%b[]". Is
there a way to expand \outer when I pass it to the \parseinner macro
without also expanding the \inner macro inside it? Or is there some
other preferred way of doing this?
One can always abuse native tex:
\starttext
\def\MyOuter#1%
{\beginlocalcontrol % hides the next
\let\Indeed\empty
\def\MyInner[##1]{\gdef\Indeed{##1}}%
\setbox\scratchbox\hpack{#1}%
\endlocalcontrol % but only if needed
\Indeed}
whatever: \MyOuter{\MyInner[oeps]}%
\edef\ItWorks{\MyOuter{\MyInner[oeps]}}
whatever: \meaningless\ItWorks
\stoptext
--
-----------------------------------------------------------------
Hans Hagen | PRAGMA ADE
Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------
___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the
Wiki!
maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage : http://www.pragma-ade.nl / http://context.aanhet.net
archive : https://bitbucket.org/phg/context-mirror/commits/
wiki : http://contextgarden.net
___________________________________________________________________________________
