[NTG-context] About xstring and ConTeXt

Phelype Oleinik phe.h.o1 at gmail.com
Tue Jul 7 23:30:49 CEST 2020

On Tue, Jul 7, 2020 at 6:21 PM Jairo A. del Rio <jairoadelrio6 at 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
    <xstring stuff>
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 at unexpanded\normalunexpanded
      \let\pgfcircutil at unexpanded\unexpanded
then use \pgfcircutil at unexpanded in the code, which will always have the
same meaning.  That, of course, requires an update to `xstring`.


More information about the ntg-context mailing list