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Background: I'be been reading the PGF manual (keys section) and today the TeX Book just arrived in the mail and just started reading chapter 7 (How TeX reads what you type) -- feeling like Mickey Mouse in "The Sorcerers Apprentice".

I want (but this is not the question) to do a routine that does something like that:

 input: a,b ; c,d ; e,f. output: a\nodepart{b} && c\nodepart{d} && e\nodepart{f}\\

My idea was to use the PGF parser to read the input. If I were using the languages I know (old Basic, Python, Maple script) I would save intermediary results in a variable but for what I understood so far LaTeX/TeX/ and TikZ/PGF do not work in this way. There is no string manipulation routines. I know we can store stuff into pgf keys. Before you stop reading I better ask my questions:

  1. Are there any examples of (LaTeX/TeX/ and TikZ/PGF) code that reads some input of variable lenght possibly more than ten and spits some other code?
  2. With the example above in mind, which references should I read to be able to implement the routine in an efficient way?

Post-script:

  1. Reading the suggested tags, I just learn about the LaTeX parse package, will check it also.
  2. @egreg: The ultimate goal will be to define a bimatrix environment in TikZ to display two-player games in normal form. The idea is to create outputs similar to this http://www.maths.lse.ac.uk/Personal/stengel/bimatrixgame/example.pdf but with the intuitive and human-like language we see in TikZ constructs.
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    In How do I split a string? you have other pointers Commented May 12, 2014 at 15:47
  • @JLDiaz: Thanks! Please correct me if I am wrong. The accepted answer to the question you mentioned works only if the input has a fixed number of parts but the second answer does the job, right? Commented May 12, 2014 at 15:55
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    Yes, the second one uses some low-level tricks to adapt itself to an arbitrary number of words. You can have fun trying to understand this solution armed with your new book of spells :-) Commented May 12, 2014 at 16:00
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    It's important to know where and how you want to use this. Can you make an example? Commented May 12, 2014 at 16:16
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    You may be able to use any of the options listed in How to iterate over a comma separated list? Commented May 12, 2014 at 16:31

2 Answers 2

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This is an adaptation of the second answer of the question How do I split a string? to your problem. It is not exactly what you want, but it can help to get you on the way.

\documentclass[a4paper]{article} \makeatletter \def\processArg#1,#2{% #1 nodepart #2 } \def\myutil@empty{} \def\severalparts#1;#2\@nil{% \def\NextArg{#2}% \processArg#1% \ifx\myutil@empty\NextArg \let\next\@gobble \else XX \fi \next#2\@nil }% \def\ProcessString#1{% \let\next\severalparts \next#1;\@nil % }% \makeatother \begin{document} \ProcessString{a,b;c,d;e,f} \end{document}

This the pdf output:

Result

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  • @SergioParreiras And, as Mickey the sorcercer learned the hard way, always remember to include a termination condition in your loops. Otherwise, infinite expansion will lead to overflow :-) Commented May 13, 2014 at 8:19
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If you are willing to slightly change the input format a simpler solution is to use \foreach:

enter image description here

Notes:

  • This may or may not work for you depending on your particular application.
  • The intermediate step using an \edef allows this to be used with a string, or a macro defined string. See TikZ \foreach loop with macro-defined list for more details.

Code:

\documentclass[a4paper]{article} \usepackage{tikz} \newcommand*{\ProcessString}[1]{% \edef\StringToProcess{#1}% \foreach \x/\y in \StringToProcess {% \x\ nodepart \{\y\} XX }% }% \newcommand*{\MyStrings}{x/y,w/u,1/2}% \begin{document} \ProcessString{a/b,c/d,e/f} \bigskip \ProcessString{\MyStrings} \end{document}
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    Why \StringToProcess intermediate variable? You can use \foreach ... in {#1}. There are unknown caveats? Commented May 12, 2014 at 16:52
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    @JLDiaz: The intermediate step is useful as you can use it with a direct string, or a string defined via a macro. See updated solution. Commented May 12, 2014 at 16:58
  • @PeterGrill: Neat! But is there a way we can have the characters \ and { in the output? That is: a\nodepart{b} instead of a nodepart b? Commented May 12, 2014 at 17:03
  • @SergioParreiras: Sure, just add a \{ and \}. Have updated solution. However, as I warned in the solution, this may or may not work for you depending on the actual application. Commented May 12, 2014 at 17:12
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    @Sergio I haven't tested, but try saying \string\nodepart or \cs{nodepart} in place of the plain nodepart. Commented May 12, 2014 at 17:14

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