如何在 algpseudocode 中将注释左对齐？

Question

我怎样才能让这些评论左对齐？
像这样？

\documentclass{article}
\usepackage{algorithm,algpseudocode}
\begin{document}

\begin{algorithm}
  \caption{Euclid’s algorithm}\label{euclid}
  \begin{algorithmic}[1]
    \Procedure{Euclid}{$a,b$}\Comment{The g.c.d. of a and b}
      \State $r\gets a\bmod b$
      \While{$r\not=0$}\Comment{We have the answer if r is 0}
        \State $a\gets b$
        \State $b\gets r$
        \State $r\gets a\bmod b$
      \EndWhile\label{euclidendwhile}
      \State \textbf{return} $b$ \Comment{The gcd is b}
    \EndProcedure
  \end{algorithmic}
\end{algorithm}

\end{document}

Answer 1

\documentclass{article}
\usepackage{algorithm}
\usepackage{algpseudocode}
\newlength{\commentlen}
\begin{document}

\begin{algorithm}
  \caption{Euclid’s algorithm}\label{euclid}
  \setlength{\commentlen}{30ex}
  \begin{algorithmic}[1]
    \Procedure{Euclid}{$a,b$}\Comment{\makebox[\commentlen][l]{The g.c.d. of a and b}}
      \State $r\gets a\bmod b$
      \While{$r\not=0$}\Comment{\makebox[\commentlen][l]{We have the answer if r is 0}}
        \State $a\gets b$
        \State $b\gets r$
        \State $r\gets a\bmod b$
      \EndWhile\label{euclidendwhile}
      \State \textbf{return} $b$ \Comment{\makebox[\commentlen][l]{The gcd is b}}
    \EndProcedure
  \end{algorithmic}
\end{algorithm}

\end{document}

Answer 2

您可以在第一次运行时测量注释，并将最宽的注释保存在辅助文件中。在下一次运行时，注释将排版在所需宽度的框中。

\documentclass{article}
\usepackage{algorithm,algpseudocode}

\makeatletter
\newlength{\comment@width}

\renewcommand{\Comment}[1]{%
  \sbox0{#1}% measure
  \ifdim\wd0>\comment@width
    \setlength{\comment@width}{\wd0}%
  \fi
  \ifcsname comment@\arabic{algorithm}@width\endcsname
    \algorithmiccomment{\makebox[\csname comment@\thealgorithm @width\endcsname][l]{#1}}%
  \else
    \algorithmiccomment{#1}%
  \fi
}
\AtBeginEnvironment{algorithmic}{\setlength{\comment@width}{0pt}}
\AtEndEnvironment{algorithmic}{%
  \immediate\write\@auxout{%
    \string\algcommentwidth{\thealgorithm}{\the\comment@width}%
  }%
}
\newcommand{\algcommentwidth}[2]{%
  \global\@namedef{comment@#1@width}{#2}%
}
\makeatother


\begin{document}

\begin{algorithm}
\caption{Euclid’s algorithm}\label{euclid}

\begin{algorithmic}[1]
  \Procedure{Euclid}{$a,b$}\Comment{The g.c.d. of a and b}
  \State $r\gets a\bmod b$
  \While{$r\not=0$}\Comment{We have the answer if r is 0}
    \State $a\gets b$
    \State $b\gets r$
    \State $r\gets a\bmod b$
  \EndWhile\label{euclidendwhile}
  \State \textbf{return} $b$ \Comment{The gcd is b}
  \EndProcedure
\end{algorithmic}

\end{algorithm}

\begin{algorithm}
\caption{Euclid’s algorithm}\label{euclid2}

\begin{algorithmic}[1]
  \Procedure{Euclid}{$a,b$}\Comment{aaa bbb}
  \State $r\gets a\bmod b$
  \While{$r\not=0$}\Comment{ccc}
    \State $a\gets b$
    \State $b\gets r$
    \State $r\gets a\bmod b$
  \EndWhile
  \State \textbf{return} $b$ \Comment{ddd}
  \EndProcedure
\end{algorithmic}

\end{algorithm}

\end{document}

我利用这个事实\Comment只是和的别名\algorithmiccomment，所以我可以重新定义前者，并使用后者进行实际排版。