[Tex/LaTex] No numbers when using capt-of’s \captionof for listings

Question

I'm trying to use \captionof{lstlisting}{Pseudo Code} to obtain a listing with its normal caption "Listing 1. Pseudo Code", in an IEEEtran document.

I want caption of instead of the caption= because I want to add comments next to the code, and the caption to span above both code and comments.

Here's a MCVR:

\documentclass[10pt,journal,compsoc]{IEEEtran}

\usepackage{listings}
\usepackage{capt-of}

\makeatletter
% the 3 caption packages caption.sty, ltcaption.sty, newfloat.sty contain:
\providecommand*\ext@lstlisting{lol}%
\makeatother

\begin{document}

\begin{figure}
    \centering%
    \captionof{lstlisting}{pseudo code with comments}
    \begin{minipage}[t]{0.40\textwidth}
        \begin{lstlisting}[label=code]
code here
        \end{lstlisting}
    \end{minipage}%
    \hspace{1em}%
    \begin{minipage}[t]{0.45\textwidth}
        Some comments here
    \end{minipage}
\end{figure}

Reference Listing~\ref{code} in text.

\end{document}

This gets me nearly what I want, except the number does not appear: I get "Listing. Pseudo Code", however the references work fine.

I get an undefined control sequence from ext@lstlisting which I had to define manually for the file to compile.

The whole ordeal works fine if I load caption instead of capt-of however IEEEtrans guidelines warn:

Axel Sommerfeldt's caption.sty [will] override IEEEtran.cls' handling of captions and this will result in non-IEEE style figure/table captions.

And indeed, using this package changes the Table and Figure captions' style, so I need to not use this package (which makes this question different from this similar one that uses caption).

How can I work around this and get the listing numbers with \captionof{lstlisting}{}?

Answer 1

The command \captionof from capt-of is not as sophisticated as the \captionof command from caption package.

It uses \caption internally, which needs the \@captype to be defined being lstlisting but also \fnum@lstlisting, which is not properly defined then.

A redefinition of \fnum@lstlisting as (say) Listing~\thelstlisting cures the problem.

\documentclass[10pt,journal,compsoc]{IEEEtran}


\usepackage{capt-of}
\usepackage{listings}

\makeatletter

% the 3 caption packages caption.sty, ltcaption.sty, newfloat.sty contain:
 \AtBeginDocument{%
  \providecommand*\ext@lstlisting{lol}%
  \renewcommand{\fnum@lstlisting}{\lstlistingname\nobreakspace\thelstlisting}
 }
\makeatother

\begin{document}
\begin{figure}
  \centering%
   \captionof{lstlisting}{pseudo code with comments}
   \begin{minipage}[t]{0.40\textwidth}
    \begin{lstlisting}[label=code]
code here
\end{lstlisting}
\end{minipage}%
\hspace{1em}%
\begin{minipage}[t]{0.45\textwidth}
  Some comments here
\end{minipage}
\end{figure}

Reference Listing~\ref{code} in text.

\end{document}