\ensuremath expansion fitting context

Question

I'm writing an elisp script to expand commands defined in the preamble to their definition. I need to do this replacements for my job and, also, to simplify the reading of math texts to a sight-impaired math student. I'm not the author of the documents. I'm a typesetter and my job is "to format" scientific papers.

E.g. if I have in the preamble:

\def\PA{\ensuremath{\mathrm{A}}}

I need to expand each instance of \PA in the document to its definition.

The way I do this is: In the elisp part of my script, in a while loop, I:

• search for a user-defined command (e.g., \COMMAND),
• insert "\writetotempfile\COMMAND" and compile,
• then I remove \writetotempfile

Thus I use the \writetotempfile command once at a time in the document, for every instance of user defined commands. Here \writetotempfile is the following code:

\newcommand{\writetotempfile}[1]
{#1\newwrite\tempfile%
\immediate\openout\tempfile=expandedCommand.tmp%
\immediate\write\tempfile{\unexpanded\expandafter{#1}}%
\immediate\closeout\tempfile}%

so, e.g., when I have

\writetotempfile\PA

that returns me the string "\ensuremath {\mathrm {A}}" in the expandedCommand.tmp file. My .tmp file is overwritten each time.

---

When I have \ensuremath in the definition I need to remove it and to expand the command fitting the context (e.g., in this case, $\mathrm{A}$ or simply \mathrm{A}). With some elisp regexp replacements I can clean the string to "\mathrm {A}" but it would be simpler to me if I could get the "$" or "not $" form of the expansion, fitting the context. That is, I need to get the $\mathrm{A}$ expansion in text (e.g. some text \PA some text) , and the \mathrm{A} expansion when I have $\PA$ (or \PA in math environments).

Some code may clarify my purpose:

\documentclass{article}

\usepackage{xspace}

\def\PA{\ensuremath{\mathrm{A}}\xspace}

\newcommand{\writetotempfile}[1]
{#1\newwrite\tempfile%
\immediate\openout\tempfile=expandedCommand.tmp%
\immediate\write\tempfile{\unexpanded\expandafter{#1}}%
\immediate\closeout\tempfile}

\begin{document}

\writetotempfile\PA   % to be expanded to $\mathrm{A}$

$\writetotempfile\PA$ % to be expanded to \mathrm{A}

\begin{equation}
\writetotempfile\PA   % to be expanded to \mathrm{A}
\begin{equation}

\end{document}

IMPORTANT! In the example above, I have 3 instance of \writetotempfile, but in reality I will use it once at a time.

Answer 1

You can redefine \ensuremath and \xspace during the \write.

One needs a protected write, though, which will produce \protect tokens.

\documentclass{article}

\usepackage{xspace}
\usepackage{xpatch}

\makeatletter
% from https://tex.stackexchange.com/a/229017/4427
% get a copy of \protected@write
\let\protected@iwrite\protected@write
% patch the copy to add \immediate
\xpatchcmd{\protected@iwrite}{\write}{\immediate\write}{}{}
%
\newcommand{\write@ensuremat}[1]{%
  \ifmmode#1\else$#1$\fi
}

\newwrite\tempfile % this must be outside the definition of \writetotempfile
\immediate\openout\tempfile=\jobname.tmp % I want all three occurrences
\newcommand{\writetotempfile}[1]{%
%  \immediate\openout\tempfile=\jobname.tmp
  \protected@iwrite\tempfile{\let\ensuremath\write@ensuremat\let\xspace\@empty}{#1}%
%  \immediate\closeout\tempfile
  #1%
}
\makeatother

\def\PA{\ensuremath{\mathrm{A}}\xspace}


\begin{document}

\writetotempfile\PA   % to be expanded to $\mathrm{A}$

$\writetotempfile\PA$ % to be expanded to \mathrm{A}

\begin{equation}
\writetotempfile\PA   % to be expanded to \mathrm{A}
\end{equation}

\end{document}

I moved the opening of the stream outside the macro, in order to show the effect in all three occurrences (and changed the file name not to clobber my files).

Here's the contents of the .tmp file:

$\protect \mathrm  {A}$
\protect \mathrm  {A}
\protect \mathrm  {A}

As you see, the first occurrence has the dollars, the other two don't.

Answer 2

I found a solution (that still needs some regexp replacement) with the \ifmmode command.

\newcommand{\writetotempfile}[1]
{#1\newwrite\tempfile%
\immediate\openout\tempfile=expandedCommand.tmp%
\ifmmode%
\immediate\write\tempfile{\unexpanded\expandafter{#1}}%
\else%
\immediate\write\tempfile{$\unexpanded\expandafter{#1}$}%
\fi%
\immediate\closeout\tempfile}

Now I have the $ in the right places so I have only to clean the code from the \ensuremath string.