On Tue, Jul 7, 2020 at 6:21 PM Jairo A. del Rio <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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