[Tex/LaTex] Nested block comments

comments

Is there any way to get nestable block comments in LaTeX? I am using the comment package to get block comments, but nesting one comment inside another with \begin{comment}...\begin{comment}...\end{comment}...\end{comment} doesn't seem to work. (I get an error "\begin{document} ended by \end{comment}".)

When writing and revising papers, it would be useful to me to be able to comment out arbitrary blocks of text, even if they already have commented-out blocks within them.

I'm aware that there are editor-based solutions. What I'm asking is if there is a way to do this within the source of my LaTeX document.

Best Answer

I suggest a wrapper command, that uses the block which should be commented as an argument and 'drops it into the trash bin'.

\newcommand{\mycomment}[1]{% }%

\mycomment{%

Other stuff...
}%

This works as long as the commented block follows correct LaTeX syntax, i.e. no unclosed right } or something similar, however, in such cases, compilation will fail eventually without the comment anyway.

Related Solutions

[Tex/LaTex] Are comments safely hidden once the document is compiled

The answer to your question is two fold:

Yes, comments are ignored when compiling and the text of a comment is irrecoverable from the final document.

However, no. It is often possible to tell where / how long the comments in the source were. For instance, take the following senario:

Line 1
Line 2

vs.

Line 1%
Line 2

In the compiled output, the newline character after Line 1 in the first example is treated as whitespace and converted to a space, so the output reads Line 1 Line 2. However, in the second example, the comment character comments out the whitespace, so the final compiled output reads Line 1Line 2. While this example doesn't leak any information itself, it does show how easy it is for comments to modify the structure of a TeX document in ways that you wouldn't expect.

While I doubt this is relevant to your use case, it does make it possible to get some information about where comments were, and sometimes how long they were, so it might be good to think through your questions / answers to make sure you're not leaking any information in this manner (that being said, are your students likely to think it through this far?).

EDIT: Saw right after posting that someone beat me to it. Sorry for the redundant info.

[Tex/LaTex] texcl, escapeinside, and single character comments, with listings package

You need to use morecomment to add the sequences ;; and ;;;:

Sample output

\documentclass{article}

\usepackage{listings}

\begin{document}

\lstset{%
  comment=[l];,morecomment=[l];;,morecomment=[l];;;,
  texcl=true,
  escapeinside={;@}{\^^M},
  numbers=left
}
\begin{lstlisting}
  ;;; top level \LaTeX
  (defun foo (x) 
    ;; in body
    (let ((y (+ x 1))) ; on line $y=x+1$
      y)) ;@ \label{code:y}
\end{lstlisting}
A reference to line~\ref{code:y}
\end{document}

Best Answer

Related Solutions

[Tex/LaTex] Are comments safely hidden once the document is compiled

[Tex/LaTex] texcl, escapeinside, and single character comments, with listings package

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