Automatically add a final period to a caption where there is none

Question

I tried to adapt the answer to Automatically add a final period if argument of '\paragraph' does not end with a punctuation character as a way to automatically add a period to a caption when there is none. For reasons I don't understand, this does not work out of the box. What is wrong (see Fig. 3)?

\documentclass{article}
\usepackage{graphicx}
\usepackage{caption}
\DeclareCaptionTextFormat{addpunct}{\maybeaddperiod{#1}}
\captionsetup{textformat=addpunct}
\ExplSyntaxOn
\NewDocumentCommand{\maybeaddperiod}{m}
 {
  \userninefourtwoninethree_maybeaddperiod:n { #1 }
 }
\cs_new_protected:Nn \userninefourtwoninethree_maybeaddperiod:n
 {
  \regex_match:nnTF { .*[!?.:] \Z } { #1 } { #1 } { #1. }
 }
\ExplSyntaxOff
\begin{document}
\begin{figure}[h]
  \centering
  \includegraphics[height=2cm]{example-image}
  \caption{This is an image}
\end{figure}
\begin{figure}[h]
  \centering
  \includegraphics[height=2cm]{example-image-a}
  \caption{This is image A}
\end{figure}
\begin{figure}[h]
  \centering
  \includegraphics[height=2cm]{example-image-b}
  \caption{This is image B.}
\end{figure}
\end{document}

score 6 · Answer 1 · answered May 15 '23 at 18:25

6

The following code shows how we can remove optional dot from the end of the argument of a macro and then we can add single period to the output. All is done only by TeX primitive commands.

\def\maybeaddperiod #1{\mbaddperiodA #1\empty.\empty\end}
\def\mbaddperiodA #1.\empty #2\end{#1.}
\maybeaddperiod{Text}        % prints: Text.
\maybeaddperiod{Foo. Bar.}   % prints: Foo. Bar.

answered May 15 '23 at 18:25

wipet

74,238

1

Thank you. This is a nice trick. It however adds an unwanted period when there is a punctation different from "."; e.g., \maybeaddperiod{Text!} produces Text!. – user94293 May 15 '23 at 21:49
1

@user94293 You can remove the !. and ?. pair from the argument by very similar trick. I leave this as an exercise for the reader. – wipet May 16 '23 at 03:44

egreg · Accepted Answer · 2023-05-15T20:24:33.813

If you add \tl_show:n{#1} in the code for \userninefourtwoninethree_maybeaddperiod:n, you will see that the first call shows

> \ignorespaces \caption@makeanchor {This is an image}.

For its purposes, caption wraps the actual caption text as an argument to \caption@makeanchor.

You see that the argument examined by \maybeaddperiod never ends with a period, but always with a }.

Change into

\cs_new_protected:Nn \userninefourtwoninethree_maybeaddperiod:n
 {
  \regex_match:nnTF { .*[\!\?\.\:] \} \Z } { #1 } { #1 } { #1. }
 }

Full example:

\documentclass{article}
\usepackage{graphicx}
\usepackage{caption}
\DeclareCaptionTextFormat{addpunct}{\maybeaddperiod{#1}}
\captionsetup{textformat=addpunct}
\ExplSyntaxOn
\NewDocumentCommand{\maybeaddperiod}{m}
 {
  \userninefourtwoninethree_maybeaddperiod:n { #1 }
 }
\cs_new_protected:Nn \userninefourtwoninethree_maybeaddperiod:n
 {
  \regex_match:nnTF { .*[!?.:] } \Z } { #1 } { #1 } { #1. }
 }
\ExplSyntaxOff
\begin{document}
\begin{figure}[h]
  \centering
  \includegraphics[height=2cm]{example-image}
  \caption{This is an image}
\end{figure}
\begin{figure}[h]
  \centering
  \includegraphics[height=2cm]{example-image-a}
  \caption{This is image A}
\end{figure}
\begin{figure}[h]
  \centering
  \includegraphics[height=2cm]{example-image-b}
  \caption{This is image B.}
\end{figure}
\end{document}

Automatically add a final period to a caption where there is none

2 Answers2