How to prevent last period in captions from appearing in the list of figures?

Question

Is there any simple way of removing the last character of an argument to a command (or environment)? I'm looking for a simple way to remove the punctuation mark from a caption when it appears in the contents list without having to write the same caption twice.

Answer 1

If you are using the caption package, you can use the option textformat=period which will add a period to the caption itself but not to the list entry, e.g.:

\documentclass{article}
\usepackage[textformat=period]{caption}

\begin{document}

\listoffigures

\begin{figure}
  \centering
  \fbox{\(\sin^2x+\cos^2x\equiv1\)}
  \caption{An identity}
\end{figure}

\end{document}

Answer 2

The safest way, in my opinion, is to use a command for the final period:

...
\DeclareRobustCommand{\captionperiod}{.}
...
\begin{document}
...
\begingroup
\renewcommand{\captionperiod}{}
\listoffigures
\listoftables
... % other lists
\endgroup
...
\begin{figure}
...
\caption{A caption\captionperiod}
\end{figure}
...
\end{document}

In this way you have a precise control on what you type.

Answer 3

Ideal task for luatex

\def\removelast#1{\directlua{tex.print((string.gsub([==[#1]==], ".$", "")))}}

\removelast{What punctuation?}

\bye

You can easily make it more robust and remove the last character only if it is a punctuation.

Answer 4

Another solution is to patch \@caption, using tools provided by the etoolbox and xstring packages:

\documentclass{article}

\usepackage{etoolbox}
\usepackage{xstring}

\makeatletter
\patchcmd{\@caption}{%
  \ignorespaces#2%
}{%
  \protecting{\noexpandarg\StrGobbleRight}{\ignorespaces#2}{1}%
}{}{}
\makeatother

\begin{document}

\listoffigures

\begin{figure}
  \centering
  \fbox{\(\sin^2x+\cos^2x\equiv1\)}
  \caption{A \emph{very important} identity!}
\end{figure}

\end{document}

The resulting output is:

Note that you must patch \@memold@caption instead of \@caption if you use the memoir document class without the hyperref package. Furthermore, the patch might have to be adapted if the caption package were used. However, as follows from the answer and the comment of Axel Sommerfeldt, a patch is actually not needed in this case since the caption package allows to configure the format of the caption text anyway.