7

I am using the package algorithm2e. When using comments like this

\documentclass[11pt,a4paper,twoside,openright]{book}
\usepackage[algochapter,linesnumbered,ruled,lined,boxed]{algorithm2e}
\begin{document}
\begin{algorithm}
    \tcp{not aligned comment}
    \If(\tcp*[h]{comment next to if}){constraint}{ 
         c  \tcp*[l]{bla}
         $d = \min \{c,e\}$ \tcp*[l]{minimum}
    }      

\end{algorithm}
\end{document}

the result is

// not aligned comment
if constraint then // comment next to if 
   c; // bla
   d = min{c,e}; // minimum
end

I would like to have the comments aligned, that is

// not aligned comment
if constraint then       // comment next to if
   c;                    // bla
   d = min{c,e};         // minimum
end

I only found an answer for the package algorithmicx: Algpseudocode (algorithmicx) package comments.

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0

2 Answers 2

Reset to default
3

This flushes them right, padded to the longest comment, so the // line up. It takes a couple of runs to get the measuring. I added some $ to avoid errors that were generated when I tried your MWE.

enter image description here

\documentclass{article}
\usepackage{algorithm2e}

\makeatletter
\newdimen\commentwd
\let\oldtcp\tcp
\def\tcp*[#1]#2{% only support one style for simplicity
\setbox0\hbox{#2}%
\ifdim\wd\z@>\commentwd\global\commentwd\wd\z@\fi
\oldtcp*[r]{\leavevmode\hbox to \commentwd{\box0\hfill}}}

\let\oldalgorithm\algorithm
\def\algorithm{\oldalgorithm
\global\commentwd\z@
\expandafter\ifx\csname commentwd@\romannumeral\csname c@\algocf@float\endcsname\endcsname\relax\else
\global\commentwd\csname commentwd@\romannumeral\csname c@\algocf@float\endcsname\endcsname
\fi
}
\let\oldendalgorithm\endalgorithm
\def\endalgorithm{\oldendalgorithm
\immediate\write\@auxout{\gdef\expandafter\string\csname commentwd@\romannumeral\csname c@\algocf@float\endcsname\endcsname{%
\the\commentwd}}}

\begin{document}
\begin{algorithm}
    c  \tcp*[l]{bla}
    $d = \min \{c,e\}$ \tcp*[l]{minimum}
\end{algorithm}
\end{document}
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4
  • Unfortunately, now a normal command like \tcp{comment} throws an error. Is it possible to also use regular comments? Edited my question.
    – Jana
    Nov 20, 2012 at 18:05
  • easiest is to change \def\tcp*[#1]#2 to \def\mytcp*[#1]#2 or some such then use \mytcp.
    – David Carlisle
    Nov 20, 2012 at 18:43
  • This does not work with if-statements, and the font is not the same.
    – Jana
    Nov 20, 2012 at 19:30
  • Ive never used the package just based on your mwe, so don't know about if statement markup, The code I posted does nothing with fonts, oh you might prefer to replace \box0 by #2 if the tcp command changes font.
    – David Carlisle
    Nov 20, 2012 at 20:33
5

Here's a solution I'm using with algorithm2e. The idea is to use right-aligned comments (\tcp*[r]), and put them in a box of fixed length \commentWidth. The important stuff is wrapped in an "aligned comment" macro \atcp for ease of use.

\documentclass[11pt,a4paper,twoside,openright]{book}
\usepackage[algochapter,linesnumbered,ruled,lined,boxed]{algorithm2e}
\begin{document}

\newlength{\commentWidth}
\setlength{\commentWidth}{7cm}
\newcommand{\atcp}[1]{\tcp*[r]{\makebox[\commentWidth]{#1\hfill}}}

\begin{algorithm}
    \tcp{not aligned comment}
    \If(\tcp*[h]{comment next to if}){constraint}{ 
         c  \atcp{bla}
         $d = \min \{c,e\}$ \atcp{minimum}
    }      

\end{algorithm}
\end{document}

This results in:

n ima

I do not know how to align comments after if-style blocks, though.

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2
  • You can align the if-style comments by using your own \atcp function instead of \tcp*.
    – Freddie R
    Jun 17, 2020 at 12:25
  • This is perfect! Note that the [r] option after \tcp* will automatically insert a newline; So, either omit \; from lines ending with the comment, or remove [r], to avoid double-newlines.
    – MRule
    Oct 19, 2022 at 17:56

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