2

I am writing an algorithm in LaTeX and I would like to remove the keyword "then" in the part of else if condition.

\documentclass{article}
\usepackage[noend]{algcompatible}

\begin{document}

\begin{algorithmic}
\If{c1}  
      \State{}
\ElsIf {c2}
      \State{}
\EndIf
\end{algorithmic}

\end{document}

I tried to add the following definition:

\algdef{SE}[ELSIF]{NoThenElseIf}{ElseIf}[1]{\algorithmicelsif\ #1}{\algorithmicelse\ \algorithmicif}%

and use it in the code.

 \NoThenElseIf {c2}
      \State{}

However, the compiler gives the following output:

! Undefined control sequence.
\ALG@text #1->\algorithmicelsif
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1 Answer 1

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3

Your code use resembles what is defined by algpseudocode, not algcompatible. However, the same process holds here (see end of post).

I first found the definition of \ElsIf within algpseudocode.sty:

\algdef{C}[IF]{IF}{ElsIf}[1]{\algorithmicelse\ \algorithmicif\ #1\ \algorithmicthen}

Then, I replicated it for a new command \NoThenElseIf:

\newcommand{\algorithmicelsif}{\textbf{elsif}}
\algdef{C}[IF]{IF}{NoThenElseIf}[1]{\algorithmicelsif\ #1}

enter image description here

\documentclass{article}

\usepackage[noend]{algpseudocode}

% Original definition of \ElsIf from
%   algpseudocode.sty (http://mirrors.ctan.org/macros/latex/contrib/algorithmicx/algpseudocode.sty)
% \algdef{C}[IF]{IF}{ElsIf}[1]{\algorithmicelse\ \algorithmicif\ #1\ \algorithmicthen}%

\newcommand{\algorithmicelsif}{\textbf{elsif}}
\algdef{C}[IF]{IF}{NoThenElseIf}[1]{\algorithmicelsif\ #1}

\begin{document}

\begin{algorithmic}
  \If{c1}  
    \State True branch
  \ElsIf{c2}
    \State Else true branch
  \NoThenElseIf{c3}
    \State No \textbf{then} true branch
  \EndIf
\end{algorithmic}

\end{document}

For algcompatible:

\algdef{C}[IF]{IF}{ELSIF}%
   [2][default]{\algorithmicelse\ \algorithmicif\ #2\ \algorithmicthen\ALG@compatcomm{#1}}%

This can be replaced with

\makeatletter
\newcommand{\algorithmicelsif}{\textbf{elsif}}
\algdef{C}[IF]{IF}{NOTHENELSIF}%
   [2][default]{\algorithmicelse\ \algorithmicif\ #2\ALG@compatcomm{#1}}%
\makeatother

Here's a complete minimal example:

\documentclass{article}

\usepackage[noend]{algcompatible}

% Original definition of \ELSIF from
%   algcompatible.sty (http://mirrors.ctan.org/macros/latex/contrib/algorithmicx/algcompatible.sty)
% \algdef{C}[IF]{IF}{ELSIF}%
%   [2][default]{\algorithmicelse\ \algorithmicif\ #2\ \algorithmicthen\ALG@compatcomm{#1}}%

\makeatletter
\newcommand{\algorithmicelsif}{\textbf{elsif}}
\algdef{C}[IF]{IF}{NOTHENELSIF}%
   [2][default]{\algorithmicelse\ \algorithmicif\ #2\ALG@compatcomm{#1}}%
\makeatother

\begin{document}

\begin{algorithmic}
  \IF{c1}  
    \STATE True branch
  \ELSIF{c2}
    \STATE Else true branch
  \NOTHENELSIF{c3}
    \STATE No \textbf{then} true branch
  \ENDIF
\end{algorithmic}

\end{document}
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  • 1
    @ Werner: Thank you very much for your fast and detailed explanation of the LaTeX background. What an excellent answer! Commented May 24, 2020 at 17:44

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