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

algorithmscommentshorizontal alignment

I will to align comments in another column, package algorithm.
(Similar question: Faulty right alignment for comments in algorithmic package), but I will to become that result:

enter image description here

\usepackage{algorithm,algorithmic}
\renewcommand{\algorithmiccomment}[1]{\bgroup\hfill//~#1\egroup}

[...]

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

Best Answer

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}
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