[Tex/LaTex] Align comments in algorithm with package algorithm2e

algorithm2ecommentshorizontal alignment

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.

Best Answer

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}

Related Solutions

[Tex/LaTex] How to avoid the number line for comments under algorithm2e

Here are no less than four ways to do it, maybe the second is preferable.

Use separate \KwData lines.
A new command \KwDataXX is defined that leaves space as if Data: is written, but without actually writing it.
Using an aligned environment; here, only one comment can be left to the right of the aligned block
using an align* environment with comments in the math block itself

Code:

\documentclass{article}
\usepackage[ruled,vlined]{algorithm2e}
\usepackage{amsmath,amssymb}
\usepackage{cprotect}%% only needed to have \verb work in \caption

\makeatletter
\algocf@newcommand{KwDataXX}[1]{%
  \sbox\algocf@inputbox{\hbox{\KwSty{Data}\algocf@typo: }}%
  \ifthenelse{\boolean{algocf@inoutnumbered}}{\relax}{\everypar={\relax}}%
  {\let\\\algocf@newinput\hspace{\wd\algocf@inputbox}\hangindent=\wd\algocf@inputbox\hangafter=\wd\algocf@inputbox#1\par}%
  \algocf@linesnumbered% reset the numbering of the lines
}
\makeatother

\begin{document}
\begin{algorithm}[!ht]
\LinesNumbered
\KwData{$\mathbf{X}\in \mathbb{R}^{i\times j}$            \tcp*{comment}}
\KwData{$p_x,p_y,p_z \in \mathbb{N}$                      \tcp*{comment}}
\KwData{$\alpha \in \mathbb{R}$                           \tcp*{comment}}
\KwResult{$\mathcal{X}\in \mathbb{R}^{i\times j\times k}$ \tcp*{comment}}
\cprotect\caption{algo -- separate \verb!\KwData! lines}
\label{alg:name}
\end{algorithm}

\begin{algorithm}[!ht]
\LinesNumbered
\KwData  {$\mathbf{X}\in \mathbb{R}^{i\times j}$          \tcp*{comment}}
\KwDataXX{$p_x,p_y,p_z \in \mathbb{N}$                    \tcp*{comment}}
\KwDataXX{$\alpha \in \mathbb{R}$                         \tcp*{comment}}
\KwResult{$\mathcal{X}\in \mathbb{R}^{i\times j\times k}$ \tcp*{comment}}
\cprotect\caption{algo2 -- using the new \verb!\KwDataXX! command}
\label{alg:name2}
\end{algorithm}

\begin{algorithm}[!ht]
\LinesNumbered
\DontPrintSemicolon
\KwData{%
  $\begin{aligned}
    \mathbf{X}  & \in \mathbb{R}^{i\times j}\\
    p_x,p_y,p_z & \in \mathbb{N}\\
    \alpha      & \in \mathbb{R}
  \end{aligned}$\tcp*{comment}
}
\KwResult{$\mathcal{X}\in \mathbb{R}^{i\times j\times k}$}
\cprotect\caption{algo3 -- using an \verb!aligned! environment, only one comment possible}
\label{alg:name3}
\end{algorithm}

\begin{algorithm}[!ht]
\LinesNumbered
\KwData{%
  \begin{align*}
    \mathbf{X}  & \in \mathbb{R}^{i\times j} && \text{comment}\\
    p_x,p_y,p_z & \in \mathbb{N} && \text{comment} \\
    \alpha      & \in \mathbb{R} && \text{comment}
  \end{align*}%
}
\KwResult{$\mathcal{X}\in \mathbb{R}^{i\times j\times k}$}
\cprotect\caption{algo4 -- using \verb!align*! with in-math comments}
\label{alg:name4}
\end{algorithm}
\end{document}

sample output

[Tex/LaTex] How to align comments in algorithm code

Here is an algorithmicx implementation:

enter image description here

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{algorithm,algcompatible,amssymb,amsmath}
\renewcommand{\COMMENT}[2][.5\linewidth]{%
  \leavevmode\hfill\makebox[#1][l]{//~#2}}
\algnewcommand\algorithmicto{\textbf{to}}
\algnewcommand\RETURN{\State \textbf{return} }
\begin{document}

\begin{algorithm}
  \caption{$\text{function}(n : \mathbb{N}_0) : \mathbb{N}_0$}\label{algo1}
  \begin{algorithmic}[1]
    \REQUIRE $n \in \mathbb{N}_0$
    \STATE $\text{result} \leftarrow 0 : \mathbb{N}_0$
    \STATE $\text{temp} \leftarrow 1 : \mathbb{N}_0$
    \FOR{$i \leftarrow 0$ \algorithmicto{} $n-1$} \COMMENT{$n$ Durchläufe}
      \FOR{$j \leftarrow i$ \algorithmicto{} $i$}
        \STATE $\text{temp} \leftarrow \text{temp} \cdot 2$ \COMMENT{Multiplikation}
      \ENDFOR
      \STATE $\text{result} \leftarrow \text{result} + \text{temp}$ \COMMENT{Addition}
      \STATE $\text{temp} \leftarrow 1$
    \ENDFOR
    \RETURN $\text{result}$
  \end{algorithmic}
\end{algorithm}
\end{document}

\COMMENT[<len>]{<stuff>} is reformatted to put the comment <stuff> in a box of width <len> (default is .5\linewidth) flush right. You can adjust this to your liking.

A pure algorithmic implementation is somewhat different:

\usepackage{letltxmacro}

\newlength{\commentindent}
\setlength{\commentindent}{.5\textwidth}
\makeatletter
\renewcommand{\algorithmiccomment}[1]{\unskip\hfill\makebox[\commentindent][l]{//~#1}\par}
\LetLtxMacro{\oldalgorithmic}{\algorithmic}
\renewcommand{\algorithmic}[1][0]{%
  \oldalgorithmic[#1]%
  \renewcommand{\ALC@com}[1]{%
    \ifnum\pdfstrcmp{##1}{default}=0\else\algorithmiccomment{##1}\fi}%
}
\makeatother

It uses e-TeX (for the string comparison), but that can be changed. The reason for the difference in implementation is mainly because of the way loops are handled in algorithmic - the comment is inserted as an optional argument to the loop structure. As such, it's difficult to allow another optional argument for the length parameter as above in the algorithmicx implementation. The work-around is to define a length \commentindent that handles this in a similar way the optional argument would handle things.

Here's a full implementation, with the same output:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{algorithm,algorithmic,amssymb,amsmath,letltxmacro}
\newlength{\commentindent}
\setlength{\commentindent}{.5\textwidth}
\makeatletter
\renewcommand{\algorithmiccomment}[1]{\unskip\hfill\makebox[\commentindent][l]{//~#1}\par}
\LetLtxMacro{\oldalgorithmic}{\algorithmic}
\renewcommand{\algorithmic}[1][0]{%
  \oldalgorithmic[#1]%
  \renewcommand{\ALC@com}[1]{%
    \ifnum\pdfstrcmp{##1}{default}=0\else\algorithmiccomment{##1}\fi}%
}
\makeatother

\begin{document}

\begin{algorithm}
  \caption{$\text{function}(n : \mathbb{N}_0) : \mathbb{N}_0$}\label{algo1}
  \begin{algorithmic}[1]
    \REQUIRE $n \in \mathbb{N}_0$
    \STATE $\text{result} \leftarrow 0 : \mathbb{N}_0$
    \STATE $\text{temp} \leftarrow 1 : \mathbb{N}_0$
    \FOR[$n$ Durchläufe]{$i \leftarrow 0$ \TO $n-1$}
      \FOR{$j \leftarrow i$ \TO $i$}
        \STATE $\text{temp} \leftarrow \text{temp} \cdot 2$ \COMMENT{Multiplikation}
      \ENDFOR
      \STATE $\text{result} \leftarrow \text{result} + \text{temp}$ \COMMENT{Addition}
      \STATE $\text{temp} \leftarrow 1$
    \ENDFOR
    \RETURN $\text{result}$
  \end{algorithmic}
\end{algorithm}
\end{document}

Best Answer

Related Solutions

[Tex/LaTex] How to avoid the number line for comments under algorithm2e

[Tex/LaTex] How to align comments in algorithm code

Related Question