10

Consider the following MWE which writes the word "Cat" to a file.

\documentclass{article} \usepackage{amsmath} \begin{document} \newwrite\datei \immediate\openout\datei=Beispiel.txt \begin{align*} a+b &=c \\ \immediate\write\datei{Cat} c+d &= 88+ 9 \end{align*} \end{document}

Actually, this writes the word "Cat" twice (I have more complicated examples, where it is written four times).

  1. Can I determine how many times is an align processed?

  2. Can I somehow ensure that the writing command is only called once?

Improve this question

1 Answer 1

Reset to default
7

amsmath uses the conditional \ifmeasuring@ which is true in the first steps when things are measured and false during the "typesetting step". So you can say

\makeatletter \newcommand{\alignwrite}[2]{% \ifmeasuring@\else \write#1{#2}% \fi} \makeatother

and \immediate\alignwrite\datei{Cat} will be executed only on the "typesetting step".

Here's the complete example:

\documentclass{article} \usepackage{amsmath} \makeatletter \newcommand{\alignwrite}[2]{% \ifmeasuring@\else \write#1{#2}% \fi} \makeatother \begin{document} \newwrite\datei \immediate\openout\datei=Beispiel.txt \begin{align*} a+b &=c \\ \immediate\write\datei{Cat} c+d &= 88+ 9 \end{align*} \begin{align*} a+b &=c \\ \immediate\alignwrite\datei{Dog} c+d &= 88+ 9 \end{align*} \end{document}

The contents of Beispiel.txt is

Cat Cat Dog

This uses the fact that \immediate which is not followed by \write or \closeout is ignored, but it expands the following token to see what really follows.

Improve this answer
2
  • Can I rely on \ifmeasuring@ being false everywhere OUTSIDE a math environment? Then I could include your \alignwrite in commands which can be used everywhere in the document. Commented Mar 30, 2013 at 9:19
  • @JFMeier amsmath always does \begingroup\measuring@true, so the conditional is set to true inside a group (and no \global is used in this context). So you should be safe. Commented Mar 30, 2013 at 10:28

You must log in to answer this question.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.