Problem with foreach loop through parameters

Question

I have a problem with foreach loop. When I pass parameters as list with '/' used as separator it works really well. However when any element in that list is defined with \def the separator seems to not work and the strings are concatenated.

\newcommand{\testme}[1]{
\foreach \aa/\bb in {#1} { 
    |\aa| |\bb| \newline
    }
}
\def\testmedef{{xyz}/{XYZ}}
\testme{
    {abc}/{CDE},
    \testmedef%
}

Result:

|abc|CDE|
|xyz/XYZ|xyz/XYZ|

Thank you for your kind help!

(if you want to read more, this is special case 4 of my question verbatim - Why can't I use inside the argument of ? - TeX - LaTeX Stack Exchange , where the outer macro does not expand the inner one) ■ — user202729, Jul 13 '22 at 01:40
There's also a TikZ specific solution
which is probably the best in this case as long as the inner content is unexpandable https://tex.stackexchange.com/a/648813/250119 ■ Or use ExpandArgs pstricks - How do I have to invoke \expandafter for a macro with multiple arguments? - TeX - LaTeX Stack Exchange — user202729, Jul 13 '22 at 01:41
Side note, you're using % at exactly the wrong locations. See symbols - What is the use of percent signs (%) at the end of lines? (Why is my macro creating extra space?) - TeX - LaTeX Stack Exchange and the linked question — user202729, Jul 13 '22 at 01:43

ljguo · Accepted Answer · 2022-07-13T01:52:03.507

1

you can call:

\newcommand{\testme}[1]{
\foreach \aa/\bb in {#1} { 
    |\aa| |\bb| \newline
    }
}
\def\testmedef{{xyz}/{XYZ}}
\ExplSyntaxOn
  \cs_set_eq:NN \expandx \exp_args:Nx
\ExplSyntaxOff
\def\testmedef{{xyz}/{XYZ}}
\expandx\testme{abc/CDE,\testmedef}

edited Jul 13 '22 at 01:52

answered Jul 13 '22 at 01:39

ljguo

1,213
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12

Wrong order. OP's def is the second item – user202729 Jul 13 '22 at 01:42
Thank you, the \expandx worked magic. Now if I only knew what does it do :) – goki Jul 13 '22 at 02:26
@goki Documentation of that particular one is in interface3.pdf; in general there is macros - Where do I find out how a command/environment is defined? - TeX - LaTeX Stack Exchange – user202729 Jul 13 '22 at 02:28

Problem with foreach loop through parameters

1 Answers1