muzimuzhi/ltx-pkg-ntheorem-issues

Record issues/problems of latex package ntheorem

ltx-pkg-ntheorem-issues's Issues

Package option `thref` is incompatible with LaTeX2e 2023-06-01 or newer

From https://tex.stackexchange.com/a/654404.

LaTeX2e extended \label to five data, the one previously used by hyperref, see https://github.com/latex3/latex2e/pull/956.

For \label{key},

% before, in .aux
\newlabel{key}{{<label>}{<page>}}
% after
\newlabel{key}{{<label>}{<page>}{<label name>}{<Href>}{<reserved>}}

Missing braces in \item[{... #1 ...}]

• For macros not defined by xparse, one need to use \cmd[{... ] ...}] to reserve ] used in the optional argument.
• Inside the definition of a macro, if something is parsed as the opt-arg of another macro \cmdB, then \cmdB[{...}] is always recommended. This way, the code works either ... contains ] or not.
• Otherwise, more than one extra level of braces are required, see https://tex.stackexchange.com/a/17108.

In the example from linked answer,

\documentclass{article}
\usepackage{ntheorem}
\newtheorem{thm}{Theorem}

\begin{document}
\begin{thm}[{\cite[page 10]{ABC2011}}]
\end{thm}

\begin{thebibliography}{9}
  \bibitem{ABC2011} A bibitem.
\end{thebibliography}
\end{document}

the opt-arg of thm env acts as the #3 of \@opargbegintheorem, which is defined as

\gdef\th@plain{%
  \def\theorem@headerfont{\normalfont\bfseries}\itshape%
  \def\@begintheorem##1##2{%
      \item[\hskip\labelsep \theorem@headerfont ##1\ ##2.]}%
  \def\@opargbegintheorem##1##2##3{%
     \item[\hskip\labelsep \theorem@headerfont ##1\ ##2\ (##3).]}}

Here \begin{thm}[{\cite[page 10]{ABC2011}}] will expand to

\item[... \cite[page 10]{ABC2011} ...]

hence raises errors.

Short-term workaround would be:

\documentclass{article}
\usepackage{ntheorem}
\usepackage{regexpatch}

\newtheorem{thm}{Theorem}

\makeatletter
\regexpatchcmd*\th@plain
  {\c{item}\cO\[(.*?\cO)\]}
  {\c{item}\cO\[\cB\{\1\cE\}\cO\]}
  {}{\fail}
\makeatother

\begin{document}

\begin{thm}[{\cite[page 10]{ABC2011}}]
A theorem.
\end{thm}

\begin{thebibliography}{9}
  \bibitem{ABC2011} A bibitem.
\end{thebibliography}

\end{document}

Long-term fix is to use \item[{...}] throughout the ntheorem.sty.