Formatting comments in LaTeX's algorithmic environment

Question

I want to typeset an algorithm in LaTeX. I'm using the algorithmic package and environment to do so. Everything is working great except when I add comments (using \\COMMENT), they are output immediately after the statements. I would like for all the comments to be aligned (and offset from the statements). Is there an easy way to do so?

"Reproducing" the PDF output in HTML's pre, I want:

if condition then
   something         # comment 1
else
   something else    # comment 2

rather than

if condition then
   something  # comment 1
else
   something else  # comment 2

Answer 1

I would do it like this:

\usepackage{eqparbox}
\renewcommand{\algorithmiccomment}[1]{\hfill\eqparbox{COMMENT}{\# #1}}

Note 1: two document compilations are necessary to determine the maximum width of the comment.

Note 2: obviously, this only works for single line comments that aren't too long.

---

Following on from this idea, here's a complete example in the same sort of way, but also providing a command to have comments that break over lines:

\documentclass{amsbook}
\usepackage{algorithmic,eqparbox,array}
\renewcommand\algorithmiccomment[1]{%
  \hfill\#\ \eqparbox{COMMENT}{#1}%
}
\newcommand\LONGCOMMENT[1]{%
  \hfill\#\ \begin{minipage}[t]{\eqboxwidth{COMMENT}}#1\strut\end{minipage}%
}
\begin{document}
\begin{algorithmic} 
\STATE do nothing \COMMENT{huh?} 
\end{algorithmic}
\begin{algorithmic} 
\STATE do something \LONGCOMMENT{this is a comment broken over lines} 
\end{algorithmic}
\begin{algorithmic} 
\STATE do something else \COMMENT{this is another comment} 
\end{algorithmic}
\end{document}

Answer 2

if condition then
   something        \hspace{2in} # comment 1
else
   something else   \hfill # comment 2

I'm not sure if the hspace and hfill will work inside an environment. I assume that they will. \\hfill will set the comments flush right, while \\hspace{space} will give you that much space between your text. good luck.

Answer 3

If you want own indentions for different algorithms, you could do this by including the counter in the redefinition of the comment commands. Here is an example:

\documentclass{amsbook}
\usepackage{algorithmicx,algorithm,eqparbox,array}

\algrenewcommand{\algorithmiccomment}[1]{\hfill// \eqparbox{COMMENT\thealgorithm}{#1}}
\algnewcommand{\LongComment}[1]{\hfill// \begin{minipage}[t]{\eqboxwidth{COMMENT\thealgorithm}}#1\strut\end{minipage}}

\begin{document}
\begin{algorithm}
\begin{algorithmic}
\State{do nothing}\Comment{huh?}
\end{algorithmic}
\caption{Test Alg}
\end{algorithm}

\begin{algorithm}
\begin{algorithmic}
\State{do something} \LongComment{this is a comment broken over lines}
\State{do something else} \Comment{this is another comment}
\end{algorithmic}
\caption{Other Alg}
\end{algorithm}
\end{document}