I'm not sure if my mind is twisted enough! I can follow how Jairo's answer
works, and that does what I need it to, but it's not as clear to me what
the last two TeX-only approaches are doing at a low level.

Perhaps more importantly, I should clarify that for my purposes, the
\MyOuter macro is the \currentbtxrighttext macro, which is defined in a
separate module that I'd prefer not to modify. I want to be able to detect
and parse the parameters of a \loc macro that a user can specify in a
citation as follows:

```
\cite[lefttext={See}, righttext={\loc[vol=8,p=223] for further
details}][clementinehomilies]
```

Because the locator parameters may need to be parenthesized or formatted
differently depending on the category of the bibliography entry, they
should be typeset separately from the plain part of the righttext. This is
why I'd like to be able to parse the parameters and then expand the \loc
macro itself as empty when the righttext is typeset.

Joey

On Tue, Nov 16, 2021 at 4:19 PM Hans Hagen via ntg-context <
ntg-context@ntg.nl> wrote:

> On 11/16/2021 9:09 PM, Jairo A. del Rio via ntg-context wrote:
> > If I understand it correctly, you may need something like this...?
> >
> > % Protection is key
> > \protected\def\inner[#1]{\empty}
> > % \outer is (or was) already defined in \CONTEXT
> > % Please use another name
> > \def\Outer{\inner[123] and \inner[some text] etc.}
> > \startluacode
> > local implement = interfaces.implement
> > local argument = tokens.scanners.argument
> > local function parseinner()
> >    local r = {}
> >    local str = argument()
> >    str = str:gsub("\\inner%s*(%b[])",function(s)r[#r+1] =
> s:sub(2,#s-1)end)
> >    context(table.concat(r," ")) -- Change " " by another spacer if needed
> > end
> > implement{name = "parseinner", public = true, actions = parseinner}
> > \stopluacode
> > \starttext
> > \parseinner{\Outer}
> > \stoptext
> >
> > However, this will only work with very simple cases (no nesting, etc.).
> > Hope this helps.
> well, if we start talking weird code ...
>
> \starttext
>
> \tolerant\def\MyInnerOuter#1\MyInner[#2]#3\MyDone\ignorearguments{#2}
>
> \def\MyOuter#1{\MyInnerOuter#1\MyDone\ignorearguments}
>
> whatever: \MyOuter{\MyInner[oeps]}\par
> whatever: \MyOuter{\InnerMy[oeps]}\par
>
> \edef\ItWorksA{\MyOuter{\MyInner[oeps]}}
> \edef\ItWorksB{\MyOuter{\InnerMy[oeps]}}
>
> whatever: \meaningless\ItWorksA\par
> whatever: \meaningless\ItWorksB\par
>
> \stoptext
>
> (1) we're tolerant so no problem when no match
> (2) the ignore hack quits scanning because tex will keep looking
>
> it's pretty fast and needs no lua magic, only a twisted mind
>
> Hans
>
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