2

When I'm trying to load data for tikz's \foreach using \input, or later with \directlua I noticed that it is not splited.

    \foreach \a / \n in {\directlua{tex.sprint("a/b")}}
      {\a}

Can I (and how) force it to be parsed correctly?

results in enter image description here

Mico
  • 506,678
majkrzak
  • 143
  • It is not about what https://tex.stackexchange.com/questions/283274/reading-the-data-to-iterate-over-with-foreach-from-a-file is about. This question refers to macro expansion in foreach environment – majkrzak Nov 13 '20 at 08:49

3 Answers3

3

You have to expand \directlua before \foreach scans the argument. This could be done with the \expanded primitive:

\documentclass[]{article}

\usepackage[]{tikz}


\begin{document}
\expanded{\unexpanded{\foreach \a / \n in }{\directlua{tex.sprint("a/b")}}}
  {\a\ and \n}


\end{document}
Skillmon
  • 60,462
  • I thought so, but applied \expanded in wrong place. thx – majkrzak Nov 12 '20 at 16:03
  • @majkrzak note that this won't work with \input. LaTeX's \input isn't expandable, and while the primitive is (which one can access with \@@input), I couldn't make this work with \foreach. – Skillmon Nov 12 '20 at 16:05
2

This is what I use for when I want to foreach over a file content (not sure, but probably copied from Reading the data to iterate over with \foreach from a file):

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{pgffor}
\begin{filecontents}[overwrite]{mylist.txt}
    a/b, 1/2,
    c/d
\end{filecontents}
\usepackage{catchfile}
\newcommand\loaddata[1]{\CatchFileDef\loadeddata{#1}{\endlinechar=-1}}
\begin{document}
    \loaddata{mylist.txt}
    \foreach \one/\two in \loadeddata {\one--\two\par}
\end{document}

enter image description here

Rmano
  • 40,848
  • 3
  • 64
  • 125
2

You can use the patch provided below to provide an expand list option to fully expand the list before use.

\documentclass{article}
\usepackage{pgffor}
\begin{document}
\foreach [expand list=true] \a / \n in {\directlua{tex.sprint("a/b")}} {
    \a
}
\end{document}

diff --git a/tex/generic/pgf/utilities/pgffor.code.tex b/tex/generic/pgf/utilities/pgffor.code.tex
index cdb77b31..65b62b8c 100644
--- a/tex/generic/pgf/utilities/pgffor.code.tex
+++ b/tex/generic/pgf/utilities/pgffor.code.tex
@@ -79,10 +79,13 @@
     \fi%
 }

+\def\pgffor@expand@list@true{\let\pgffor@expand@list\edef}
+\def\pgffor@expand@list@false{\let\pgffor@expand@list\def}
 \def\pgffor@macro@list#1{%
   \expandafter\pgffor@normal@list\expandafter{#1}}
 \def\pgffor@normal@list#1{%


    

  • \def\pgffor@values{#1, \pgffor@stop,}%
    • 



    

  • \pgffor@expand@list\pgffor@values{#1}%
    • 

  • \expandafter\def\expandafter\pgffor@values\expandafter{\pgffor@values, \pgffor@stop,}%
\ifx\pgffor@values\pgffor@emptyvalues
  \def\pgffor@values{\pgffor@stop,}%
\fi%
    • 



@@ -619,6 +622,9 @@
     count/.code=\pgffor@count@parse#1\pgffor@stop,
     parse/.is if=pgffor@assign@parse,
     parse/.default=false,


    

  • expand list/.is if=pgffor@expand@list@,
    • 

  • expand list/.default=true,
    • 

  • expand list=false,
    • 



}


\def\pgffor@assign@parse#1{%

Instead of patching your PGF installation (which will be overriden by the next update anyway), you can also include the necessary definitions in your document directly.

\documentclass{article}
\usepackage{pgffor}

\makeatletter
\def\pgffor@expand@list@true{\let\pgffor@expand@list\edef}
\def\pgffor@expand@list@false{\let\pgffor@expand@list\def}
\def\pgffor@normal@list#1{%
  \pgffor@expand@list\pgffor@values{#1}%
  \expandafter\def\expandafter\pgffor@values\expandafter{\pgffor@values, \pgffor@stop,}%
  \ifx\pgffor@values\pgffor@emptyvalues
    \def\pgffor@values{\pgffor@stop,}%
  \fi%
  \let\pgffor@body=\pgfutil@empty%
  \global\pgffor@continuetrue%
  \pgffor@collectbody}
\makeatother


\pgfqkeys{/pgf/foreach}{
  expand list/.is if=pgffor@expand@list@,
  expand list/.default=true,
  expand list=false,
}


\begin{document}
\foreach [expand list=true] \a / \n in {\directlua{tex.sprint("a/b")}} {
  \a
}
\end{document}
Henri Menke
  • 109,596
  • thx! Is this change going to be included in upcoming release of pgf? Will it woek with \input or its primitive \@@input? – majkrzak Nov 13 '20 at 20:24
  • @majkrzak The patch would have to be applied to your PGF installation. I've added another section to the answer on how to backport the feature to your document without patching. – Henri Menke Nov 13 '20 at 20:30