How to avoid parentheses + brackets in the title in amsthm when only using \cite?

Question

This is a follow-up to this question and this one. Basically, I would like to avoid the sequence ([...]) in theorem's optional arguments, as shown below:

To obtain this result, as suggested by this answer, I used the \patchcmd macro of the etoolbox package. However, I have to switch from \patchcmd{\thmhead}{(#3)}{#3}{}{} to \patchcmd{\thmhead}{#3}{(#3)}{}{} on every change, which is not very convenient for a large book with many theorems. Thus I was wondering whether a single command would be possible. Note that I am using the two forms \cite{} and \cite[]{}, which makes things a bit more complex.

\documentclass[10pt]{article}
\usepackage[]{amsmath, amssymb, amsthm}

\newtheorem{theorem}{Theorem}[section]
\usepackage{etoolbox}% http://ctan.org/pkg/etoolbox
\begin{document}
\section{Pythagoras' theorem}
\noindent Correct versions:
\begin{theorem}[Pythagoras]
  $a^2 + b^2 = c^2$.
\end{theorem}
\begin{theorem}[Pythagoras, \cite{Pythagoras}]
  $a^2 + b^2 = c^2$.
\end{theorem}
\begin{theorem}[Pythagoras, {\cite[p.\ 345]{Pythagoras}}]
  $a^2 + b^2 = c^2$.
\end{theorem}
\patchcmd{\thmhead}{(#3)}{#3}{}{}
\begin{theorem}[\cite{Pythagoras}]
  $a^2 + b^2 = c^2$.
\end{theorem}
\begin{theorem}[{\cite[p.\ 21]{Pythagoras}}]
  $a^2 + b^2 = c^2$.
\end{theorem}
\noindent To be avoided:
\patchcmd{\thmhead}{#3}{(#3)}{}{}
\begin{theorem}[\cite{Pythagoras}]
  $a^2 + b^2 = c^2$.
\end{theorem}
\begin{theorem}[{\cite[p.\ 21]{Pythagoras}}]
  $a^2 + b^2 = c^2$.
\end{theorem}
\begin{thebibliography}{HD}
\bibitem[1]{Pythagoras}
Pythagoras' theorem.
\end{thebibliography}
\end{document}

Why not just have the citation as the first thing within the theorem? This also has the added benefit of not having a strange bold full stop after non-bold text. — oliversm, Sep 09 '20 at 10:39
@oliversm one reason to use the optional argument is that it is printed in the List of Theorems (\listoftheorems). — Marijn, Sep 09 '20 at 14:49
@Marijn, Having something like a named theorem in the list of theorems is useful, but having a naked numeric citation I can't imagine being desirable in the list of theorems. — oliversm, Sep 09 '20 at 15:17
@oliversm Isn't the bold full stop the default behaviour of the optional argument (See Theorem 1.1) ? Anyway, your comment is not relevant to my question. — J.-E. Pin, Sep 09 '20 at 15:56

score 1 · Accepted Answer · answered Feb 10 '24 at 20:36

You can match the argument against a regular expression that represents \cite followed by zero or one occurrence of [...] and by {...}.

\documentclass[10pt]{article}
\usepackage[]{amsmath, amssymb, amsthm}
% see https://tex.stackexchange.com/a/17555/4427 for the parameters
\newtheoremstyle{jepinplain}
  {\topsep}   % ABOVESPACE
  {\topsep}   % BELOWSPACE
  {\itshape}  % BODYFONT
  {0pt}       % INDENT (empty value is the same as 0pt)
  {\bfseries} % HEADFONT
  {.}         % HEADPUNCT
  {5pt plus 1pt minus 1pt} % HEADSPACE
  {\thmname{#1}\thmnumber{ #2}\thmnote{{\normalfont\ \checkcite{#3}}}} % CUSTOM-HEAD-SPEC
\ExplSyntaxOn
\NewDocumentCommand{\checkcite}{m}
 {
  \regex_match:nnTF {\A \c{cite}(?:[[^]]])?{.} \Z} { #1 }
   {% only \cite
    #1
   }
   { (#1) }
 }
\ExplSyntaxOff
\theoremstyle{jepinplain}
\newtheorem{theorem}{Theorem}[section]
\begin{document}
\section{Pythagoras' theorem}
\noindent Correct versions:
\begin{theorem}
  $a^2 + b^2 = c^2$.
\end{theorem}
\begin{theorem}[Pythagoras]
  $a^2 + b^2 = c^2$.
\end{theorem}
\begin{theorem}[Pythagoras, \cite{Pythagoras}]
  $a^2 + b^2 = c^2$.
\end{theorem}
\begin{theorem}[Pythagoras, {\cite[p.\ 345]{Pythagoras}}]
  $a^2 + b^2 = c^2$.
\end{theorem}
\begin{theorem}[\cite{Pythagoras}]
  $a^2 + b^2 = c^2$.
\end{theorem}
\begin{theorem}[{\cite[p.\ 21]{Pythagoras}}]
  $a^2 + b^2 = c^2$.
\end{theorem}
\begin{thebibliography}{1}
\bibitem[1]{Pythagoras}
Pythagoras' theorem.
\end{thebibliography}
\end{document}

A new theorem style is better, unless you want to modify the standard \thmhead command.

score 0 · Answer 2 · answered May 16 '23 at 14:35

This question is a little old now, but I was addressing the same issue so thought I'd post how I did it. It would be nice to somehow be able to just flag whether parentheses should be added or not, but I worked around it manually.

Solution 0:

Leave the amendment in place permanently, and add your own parentheses.

\patchcmd{\thmhead}{(#3)}{#3}{}{}
\begin{theorem}[(Pythagoras)]
  $a^2 + b^2 = c^2$.
\end{theorem}
\begin{theorem}[(Pythagoras, \cite{Pythagoras})]
  $a^2 + b^2 = c^2$.
\end{theorem}
\begin{theorem}[\cite{Pythagoras}]
  $a^2 + b^2 = c^2$.
\end{theorem}

Of course, this loses part of the benefit of LaTeX macros, that you can redefine an appearance in one place and have it apply everywhere -- if you suddenly decide to bracket the theorem notes some other way, you'd have to go through and manually change them all. So a tiny improvement is:

Solution 1:

Define a macro.

\patchcmd{\thmhead}{(#3)}{#3}{}{}
\newcommand{\notewrap}[1]{(#1)}
\begin{theorem}[\notewrap{Pythagoras}]
  $a^2 + b^2 = c^2$.
\end{theorem}
\begin{theorem}[\notewrap{Pythagoras, \cite{Pythagoras}}]
  $a^2 + b^2 = c^2$.
\end{theorem}
\begin{theorem}[\cite{Pythagoras}]
  $a^2 + b^2 = c^2$.
\end{theorem}

How to avoid parentheses + brackets in the title in amsthm when only using \cite?

2 Answers2