Outputting internal at-macro via newcommand?

Question

Just noticed a somewhat strange behavior, when trying to show internal Latex @ commands from main document via \newcommand.

Consider the following MWE, where all instances of the internal macro ( \c@something) calls are already wrapped in \makeatletter/\makeatother:

\documentclass[10pt]{article}


% define internal at-macro
\makeatletter
\def\c@something{AAA}
\typeout{ == \c@something == }
\makeatother

% define a newcommand calling the at-macro
\newcommand{\mytest}{
\makeatletter
\c@something
\makeatother
}



\begin{document}


test

\mytest{}

\makeatletter
here \c@something
\makeatother


\end{document}

When I build the above with pdflatex, I get this:

... however, I would have expected something like:

test
AAA
here AAA

Can anyone explain why does the macro not get called/executed when put as part of \newcommand - and else looks ok called directly from the main body? (In other words, could I get its output as part of \newcommand at all?)

Answer 1

TeX converts characters to tokens when it first reads them. So when you do

\newcommand{\mytest}{
\makeatletter
\c@something
\makeatother
}

TeX 'sees' @ as an 'other' character, and the definition of \mytest is:

1. A space (as you have a new line with no % just after the opening {)
2. The token \makeatletter
3. The token \c
4. The 'other' character @
5. The 'letter' tokens 'something' (each separate)
6. The token \makeatother

What you wanted was

\makeatletter
\newcommand{\mytest}{%
  \c@somecommand
}
\makeatother

in which case the definition of \mytest is the single token \c@somecommand, exactly as for the \def case.