[Tex/LaTex] algorithm2e command \procedure already defined

algorithm2ealgorithmsincompatibility

I included algorithm2e and start getting error message of "algorithm2e.sty command\procedure already defined." Here are the list of packages in my latex file

\documentclass[useAMS,usenatbib]{coin.cls}
\def\bSig\mathbf{\Sigma}
\newcommand{\VS}{V\&S}
\newcommand{\tr}{\mbox{tr}}

%\usepackage[figuresright]{rotating}
\usepackage[vlined,ruled,linesnumbered, algo2e]{algorithm2e}
\usepackage{multirow}
\usepackage{graphicx}
\usepackage{float}
\usepackage{hyperref}
\usepackage{wrapfig}
\usepackage{caption}
\usepackage{subcaption}
\usepackage{stfloats}

Best Answer

If you're referring to coin.cls that forms part of the Computational Intelligence group at Dalhousie University's Department of Computer Science, then the solution is fairly straight-forward if you want to keep using algorithm2e: set the \procedure and \endprocedure macros to \relax.

% https://projects.cs.dal.ca/ci/latex/template-files/coin.cls
\documentclass{coin}

\let\procedure\relax
\let\endprocedure\relax
\usepackage[algo2e]{algorithm2e}

\begin{document}

\begin{algorithm2e}[H]
  \SetAlgoLined
  \KwData{this text}
  \KwResult{how to write algorithm with \LaTeX2e }
  initialization\;
  \While{not at end of this document}{
    read current\;
    \eIf{understand}{
      go to next section\;
      current section becomes this one\;
    }{
      go back to the beginning of current section\;
    }
  }
  \caption{How to write algorithms}
\end{algorithm2e}

\end{document}

So if you're not going use these theorem-like structures, then there shouldn't be any other conflict.

Both the algorithm and procedure environments are predefined inside the coin document class as theorems:

\newtheorem{algorithm}{Algorithm}%[theorem]
%...
\newtheorem{procedure}{Procedure}%[section]

The algorithm environment definition is avoided by using the algo2e option of algorithm2e, which creates an algorithm2e float rather than algorithm.

Related Solutions

[Tex/LaTex] algorithm2e, function, procedure, \par, error

This is explained in page 17 of the documentation (talking about the procedure environment, but the same remark applies to function):

the syntax of the \caption command is restricted as follow: you MUST put a name followed by 2 braces like this Name(). You can put arguments inside the braces and text after. If no argument is given, the braces will be removed in the title.

A complete example:

\documentclass{article}
\usepackage[boxed]{algorithm2e}

\begin{document}

\begin{function}
    $x \gets x$\;
    \caption{Identity()}
\end{function}

\end{document}

enter image description here

[Tex/LaTex] algorithm2e Command \algorithm already defined

Since the algorithm and algorithm2e packages both define an algorithm environment, simply loading both with no extra precaution will cause a name clash like you experienced.

However, you can still use both packages (if you really need both), but you need to pass the option algo2e to algorithm:

\usepackage[algo2e]{algorithm2e}

This option changes the name of the environment algorithm from the algorithm2e package into algorithm2e and so avoids the conflict with the package which already define an algorithm environment; the option also changes the command name for the list of algorithms to \listofalgorithmes.