Macro to be used in a \section command that has no effect in the table of contents

Question

I need a macro that is executed only in the main document (within a section title) and then disappears (for the table of contents).

A minimal example where this occurs is this:

\documentclass[12pt]{memoir}
\usepackage{fixltx2e}[2006/09/13]
\usepackage{times}
\usepackage[T1]{fontenc}
\usepackage{txfonts}


\begin{document}

\tableofcontents

\section{The only section}

Text.

\section{The only section [\textsl{continued}]}

More text.

\section{The only section [\textsl{continued\hspace{0.13ex}}]}

An attempted fix.

\end{document}

The first section title with "[continued]" in it is badly kerned. The manual adjustment (\hspace{0.13ex}) does the job, but it unfortunately leads to too much space in the table of contents. I would like the extra space to apply only to the actual section heading in the document's body. (I tried every conceivable combination of \/, \hspace, and \protect; nothing works.)

The culprit (what causes kerning to disappear) is clearly the loading of txfonts, which I need elsewhere in my document. (Yep, I need txfonts instead of newtxtext/newtxmath for an obscure reason having to do with font loading order I'd rather not get into, and circumventing the issue underlying that would be for another question anyways. And my sample code makes for a useful example.) If I omit txfonts, the problem disappears, meaning I don't need to insert a manual space in the first place. (This might point to another problem.)

Related:

• Is there a way of defining a command \nullifyifmoved{arg} that will normally act like its argument but act like a no-op if the macro is “moved”?
• Is there a way of defining a command which is automatically converted to a no-op after its first execution?

Answer 1

_{Added just for 'completeness'}

For this particular problem, you might use

\section[<stuff for the toc>]{<Actual section heading>}

Answer 2

A bit different approach: we write \dcorr to the .toc file, but we \let it \relax during the \tableofcontents:

\documentclass[12pt]{memoir}
\usepackage{fixltx2e}[2006/09/13]
\usepackage{times}
\usepackage[T1]{fontenc}
\usepackage{txfonts}

\DeclareRobustCommand{\dcorr}{\hspace*{0.13ex}}

\begin{document}

\begingroup
\let\dcorr\relax
\tableofcontents
\endgroup

\section{The only section}

Text.

\section{The only section [\textsl{continued}]}

More text.

\section{The only section [\textsl{continued}\dcorr]}
% If one keeps \dcorr within the \textsl macro,
% one needs either a larger value (0.23ex works)
% or one needs to put an italic correction (\/)
% at the beginning of the definition of \dcorr.

An attempted fix.

\end{document}

Answer 3

Like tohecz wrote: "this is sort-of a XY Problem". His answer solves the OP's real problem, but to answer the question for a "macro that is executed only the first time and then disappears":

\documentclass{article}

% method 1:
\newcommand{\mnc}{example%
  \renewcommand{\mnc}{}%
  }

% method 2:
\def\mnd{elpmaxe%
  \gdef\mnd{}%
  }

\begin{document}

A\mnc B\mnd C
% output: AexampleBelpmaxeC

D\mnc E\mnd F
% output: DEF

A\mnc B\mnd C
% output: ABC

\end{document}

(Put {} behind \mnc and \mnd if the respective spaces shall be preserved.)