[Tex/LaTex] Comment package not working

comments

I have added the package \usepackage{comment} in my .tex file. But when I am adding \begin{comment} and \end{comment} it is not commenting the text I want to comment. What to do?

Best Answer

I have attempted to reproduce this problem, and have only been able to come up with only one way to do that. And that is to have the following after the comment package is included:

\renewenvironment{comment}{}{}

So, if you un-comment this line the MWE below, you get the behavior you describe. With it commented, the text in red and blue does NOT show up in the output. So, check your preamble add see if there is something else that is redefining the behavior of the comment environment.

If you have another way of reproducing this behaviour, please add a MWE.

Note:

As @Ignasi commented, the \begin{comment} and \end{comment} need to be their own line with nothing else on that line (except for possibly trailing white space such as tabs). No space before the \end{comment} is allowed. Even a comment % character seems to results in:

Runaway argument? ! File ended while scanning use of \next. \par

Code:

\documentclass{article}
\usepackage{xcolor}
\usepackage{lipsum}
\usepackage{comment}

%\renewenvironment{comment}{}{}%

\begin{document}
\lipsum[1]
\begin{comment}         
    \textcolor{red}{This text should NOT be displayed.}
\end{comment}    
\lipsum[2]
\begin{comment} 
    \textcolor{blue}{This text should NOT be displayed.} 
\end{comment}    
\lipsum[3]
\end{document}

Related Solutions

[Tex/LaTex] \newenvironment issues with environment comment

The memoir class has a facility just for that:

\newcomment{marked}
\commentson{marked}
%\commentsoff{marked}

It's sufficient to uncomment the third line to exclude the contents of all marked environments. Look at page 284 of memoir's documentation.

For the environment form of a colored background box:

\newsavebox{\coloredbgbox}
\newenvironment{yellowbox}
  {\begin{lrbox}{\coloredbgbox}\begin{minipage}{0.8\textwidth}}
  {\end{minipage}\end{lrbox}%
   \begin{center}\colorbox{yellow}{\usebox{\coloredbgbox}}\end{center}}

With this definition, you can write

\begin{yellowbox}
Text to be produced on a yellow background as wide as 80\%
of the normal line width.
\end{yellowbox}

However, it's better to split different topics into different questions.

[Tex/LaTex] Comment out lines without using % and comment enviroment

If your input files all have the same form, that is some lines starting with \\ and an empty line after them, you can do by temporarily redefining \\ and changing the command for inputting the exercises:

\newcommand{\exeinput}[1]{%
  \let\latexdoublebackslash\\
  \ifprolog\let\\\showprolog\else\let\\\hideprolog\fi
  \input{#1}}

\def\showprolog#1\par{%
  \def\\{\par\noindent}% redefine `\\` to end lines
  \par\noindent
  #1% print the lines
  \par % end the last line
  \let\\\latexdoublebackslash}

\def\hideprolog#1\par{\let\\\latexdoublebackslash} % throw away the prolog lines

\newif\ifprolog

So you can say

\exeinput{exercise.435.tex}

and if you set \prologtrue also the prolog lines will be printed.

However this would spectacularly fail if there's not an empty line between the prolog and the main contents, so a special markup is probably the best strategy. For instance, if your exercise files have the form

\startprolog
\\ is the  exercise.435.tex % is the name of the file
\\ 1.84 ex. 127 page notes  % is the source of exercise etc
\stopprolog

\begin{exercise}    
. . . 
\end{exercise}

you can say

\newif\ifprolog
\long\def\startprolog#1\stopprolog{%
  \ifprolog
    \par
    \begingroup
    \let\\\par
    \color{red}\small #1
    \par\medskip
    \endgroup
  \fi}

and so

\input{exercise.435.tex}

will print the exercise without the prolog unless you set \prologtrue. The advantages are that you risk nothing if the prolog is not separated from the contents and that it's possible to reformat freely the prolog when you want to print it (maybe as a marginal note, for instance).