# Force expansion of counter value in command argument

In the following MWE I would like to expand both \envnum as well as \itemnum while passing them to \cmdwithexpandedargs but only the first one got expanded. Note the different output between \wlog and \printcmd, this still intrigues me.



The \wlog output "1.a - 1.b - 2.a - 2.b - 2.c" is what I want, but it is not what \printcmd gives: "1c - 1c - 2c - 2c - 2c". I'm accepting LaTeX3 (expl3) solutions here, if required!

Replay

The difference is because you aren't expanding \itemnum when passing it to \cmdwithexpandedargs, but \wlog fully expands its argument.

You can do it more efficiently:

\documentclass{letter}

\newcounter{nenv}
\newcommand\printcmd{}

\makeatletter
\newenvironment{test}{%
\stepcounter{nenv}%
\let\olditem\item
\renewcommand\item{%
\olditem
\xdef\printcmd{\printcmd\arabic{nenv}\alph{enumi} - }%
\wlog{\arabic{nenv}.\alph{enumi}}%
}%
\begin{enumerate}%
}{\end{enumerate}}
\makeatother

\begin{document}
\begin{test}
\item one
\item two
\end{test}
\begin{test}
\item one
\item two
\item three
\end{test}
\printcmd
\end{document}



No need to do separate \xdef (global is actually useless and could simply be \edef).

In the log file you find

1.a
1.b
2.a
2.b
2.c



You need to expand not only \envnum, but also \itemnum. That means the one line got revised to \expandafter\expandafter\expandafter\cmdwithexpandedargs\expandafter\expandafter\expandafter{\expandafter\envnum\itemnum}. After the first round of expansion, \itemnum is expanded leaving what you started with, \expandafter\cmdwithexpandedargs\expandafter{\envnum\itemnum}. This second round expands \envnum and you are good to go.

\documentclass{letter}

\newcounter{nenv}
\newcommand\printcmd{}

\makeatletter
\newcommand\cmdwithexpandedargs[1]{%
\[email protected]@macro\printcmd{#1 - }
}
\makeatother

\newenvironment{test}{%
\stepcounter{nenv}%
\let\olditem\item
\renewcommand\item{%
\olditem
\xdef\envnum{\arabic{nenv}}%
\xdef\itemnum{\alph{enumi}}%
\wlog{\envnum.\itemnum}
\expandafter\expandafter\expandafter\cmdwithexpandedargs\expandafter\expandafter\expandafter{\expandafter\envnum\itemnum}%
}%
\begin{enumerate}%
}{\end{enumerate}}

\begin{document}
\begin{test}
\item one
\item two
\end{test}
\begin{test}
\item one
\item two
\item three
\end{test}
\printcmd
\end{document}



AFTERNOTE

I got some magic code from Christian Tellechea:

% CODE FROM CHRISTIAN TELLECHEA
\makeatletter
\def\expandtimes(#1)#2#{\[email protected]@i(#1){#2}}
\def\[email protected]@i(#1)#2#3{%
\ifnum#1>0 \expandafter\[email protected]\else\expandafter\[email protected]\fi
{\expandafter\[email protected]\expandafter{\expandafter\expandtimes\expandafter(\number%
\numexpr#1-1)#2}}{#2}{#3}%
}
\long\def\[email protected]#1#2{#1}
\long\def\[email protected]#1#2{#2}
\long\def\[email protected]#1#2{#2{#1}}
\long\def\[email protected]#1#2{\expandafter\[email protected]\expandafter{#2}{#1}}
\makeatother
%



that, if added to the preamble, would allow the multi-expansion syntax to be condensed to

\expandtimes(3)\cmdwithexpandedargs{\expandafter\envnum\itemnum}



to achieve the same result.

Category: macros Time: 2016-07-28 Views: 0

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