Re: About xstring and ConTeXt

[Hans Hagen <j.hagen@xs4all.nl>]

On 7/8/2020 12:00 AM, Jairo A. del Rio wrote:
> Yep, now it finally works. Certainly it requires a few more lines. I was 
> going to rewrite some TikZ code which was too dependent on LaTeX and 
> xstring was the last stone on the shoe. Thank you a lot, Phelype and 
> Wolfgang (I didn't know about push/popmacro either and now it's in my 
> to-do readings).

We can have a module that takes care of some things, like

\usemodule[system-aliasing]

\registeralias\unexpanded\normalunexpanded  % preset
\registeralias\expanded  \normalexpanded    % preset

\registeraliasfile{rubish.tex}    % any file with that name
\registeraliasfile{generic/*.tex} % a bit more explicit

after which

\input rubish.tex
\input generic/foo.tex

(or whatever way it's loaded) will (hopefully) work ok. But as a module, 
not in the core, because we don't want additional overhead for third 
party stuff, but ok on user demand. Of course one cannot expect the 
context dev to keep a list of files that need such a treatment.

Hans

> Jairo :D
> 
> El mar., 7 de jul. de 2020 a la(s) 16:31, Phelype Oleinik 
> (phe.h.o1@gmail.com <mailto:phe.h.o1@gmail.com>) escribió:
> 
>     On Tue, Jul 7, 2020 at 6:21 PM Jairo A. del Rio
>     <jairoadelrio6@gmail.com <mailto:jairoadelrio6@gmail.com>> wrote:
>      >
>      > Thank, Wolfgang! Both methods work, but both fail with the
>     following example:
>      >
>      > \pushmacro\unexpanded
>      > \let\unexpanded\normalunexpanded
>      > \input xstring
>      > \popmacro\unexpanded
>      > \starttext
>      > \StrGobbleLeft{bcdef}{4}
>      > \stoptext
>      >
>      > The log says:
>      >
>      > tex error > tex error on line 6 in file ./tests.tex: ! This can't
>     happen (prefixed command)
>      >
>      >
>      > <argument> \unexpanded {
>      >
>      > f}
>      >
>      > \xs_execfirst #1#2->#1
>      >
>      > However, some others work.
> 
>     As I said, the internals of `xstring` still use \unexpanded which, after
>     you do \popmacro\unexpanded, will mean e-TeX's \protected, rather than
>     \unexpanded, which are quite different.  To be on the safe side, you'd
>     need to wrap every `xstring` command in
>          \pushmacro\unexpanded
>          \let\unexpanded\normalunexpanded
>          <xstring stuff>
>          \popmacro\unexpanded
>     to make sure that \unexpanded means what `xstring` expects.
> 
>     The *proper* way to make `xstring` work in ConTeXt would be something
>     like Circuitikz does:
>          \ifcsname normalunexpanded\endcsname
>            \let\pgfcircutil@unexpanded\normalunexpanded
>          \else
>            \let\pgfcircutil@unexpanded\unexpanded
>          \fi
>     then use \pgfcircutil@unexpanded in the code, which will always have the
>     same meaning.  That, of course, requires an update to `xstring`.
> 
>     Phelype
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