# Commenting a single line comments the whole block

So there are paragraphs in my document, and even if I try to comment a single line using % I find that all the rest of the paragraph is also commented. I know this since the color changes to grey (using TeX Studio 2.5.2). What is the solution? I don't think I need the comment package.

• A % comment character tells TeX to skip everything from that until the next "newline" character (\n in C programming notation). So if your paragraph is written on a single line, without any hard returns, then the comment character will cause it all to be ignored. Many of us use a new line for each sentence in TeX documents. – musarithmia May 29 '15 at 21:27
• But we would need a small example document that we could test in order to know for sure. – musarithmia May 29 '15 at 21:27
• You probably have the paragraph types on a single line, yet TeX Studio wraps the lines to the screen. You can insert manual line-breaks (without leaving a blank line) and it would allow you to comment out specific "lines" in a regular paragraph. – Werner May 29 '15 at 21:43
• IMO, Opt.2 from @cptnjtk's answer should suite your requirements. However, please see my comment to that answer before using Opt.2. I use such a command often in my work to comment out specific lines/ blocks from paragraphs. – Amar May 30 '15 at 1:15

All of the comments under the question are correct. TeXstudio wraps lines that go beyond the width of the viewing window. This is what allows you to type a full paragraph on a single line, and when putting in comments, it is treated as a single line. Take a look at the line wrap example image below.

One solution I often use is to put a newline after every sentence in a paragraph as follows:

\documentclass[10pt,a4paper]{article}
\begin{document}
Tractography refers to the three-dimensional modeling technique for visually display neural tracts.
%
The source data for tractography comes from diffusion tensor imaging (DTI) and magnetic resonance imaging (MRI).
%
By employing analysis techniques (including image analysis) on this source data, neural tracts can be identified throughout the brain.
%
These neural tracts are encoded as a series of line segments.

Tractography is used for multiple purposes.
%
First, surgeons use tractography in conjunction with anatomical knowledge to plan surgeries around critical motor neurons for actions such as speech or movement.
%
While this usage often does not require real-time analysis, the timelines between
acquiring data and analysis by the surgeon is typically on the order of days.
%
Neuroscience researchers use tractography data in a different way: to create maps of the human brain.
%
In this case, the analysis has no real-time component, and analysis techniques taking longer periods are acceptable.
\end{document}


Writing documents like this makes it very easy to add, edit, or remove sentences, and does not cause the comment issue that you are seeing.

Option 2 If you do not want to restructure your paragraphs as in the above example and must comment them in place, you could define a comment command: \newcommand{\comment}[1]{\ignorespaces}

This allows you to comment a single sentence in a block paragraph, when % would comment the entire remainder of the block. Notice how these paragraphs run off on one line; that is what was tripping TeXstudio up.

\documentclass[10pt,a4paper]{article}
\newcommand{\comment}[1]{\ignorespaces} % corrected!
\begin{document}
Tractography is used for multiple purposes.\comment{First, surgeons use tractography in conjunction with anatomical knowledge to plan surgeries around critical motor neurons for actions such as speech or movement.} While this usage often does not require real-time analysis, the timelines between acquiring data and analysis by the surgeon is typically on the order of days. Neuroscience researchers use tractography data in a different way: to create maps of the human brain. In this case, the analysis has no real-time component, and analysis techniques taking longer periods are acceptable.

Tractography is used for multiple purposes. %First, surgeons use tractography in conjunction with anatomical knowledge to plan surgeries around critical motor neurons for actions such as speech or movement. While this usage often does not require real-time analysis, the timelines between acquiring data and analysis by the surgeon is typically on the order of days. Neuroscience researchers use tractography data in a different way: to create maps of the human brain. In this case, the analysis has no real-time component, and analysis techniques taking longer periods are acceptable.

\end{document}


Option 3 This option will allow you to have comment style highlighting around the new comment environment. The environment declaration is: \newenvironment{hashed}[1]{\ignorespaces}{\ignorespacesafterend}

To enable hightlighting in TeXstudio go to "Options->Configure Texstudio..." and add the command "hashed" to "Custom Highlighting" and set the "Type of Environment" to "comment" as follows:

It can be used as follows (notice the comment style highlighting):

This may not be the cleanest method, but custom environemnts are the only way that I know to add custom highlighting to TeXstudio.

• You are correct about the space, if you put a space after the period before the comment command like: abc. \comment{...}. If there is not space though, you are good to go. Thanks for pointy this out though! – cptnjtk May 30 '15 at 6:55
• Usually, as one types a paragraph, it is by habit that we put a <space> after ending any sentence with a period. I'd personally find it very odd to see a paragraph that runs continuously without any spaces separating the periods (for that matter, other punctuation marks like ; , : as well) and the start of a new sentence! Please note, that if you use this macro (as suggested above) within a line, it WILL add a trailing space! For more explanation, please see my answer given below. – Amar May 30 '15 at 7:18
• While this is a correct solution, as I marked, it has the disadvantage that the commented block now doesn't have specific highlighting since TeX Studio expects comments to start with % and not with \comment. I looked into the highlighting section in the options and it doesn't seem that I can add my own. Any ideas? – student1 May 30 '15 at 21:07
• Good point on the highlighting, this way of commenting does make visually parsing more difficult in TeXstudio. I have amended my answer with a third more involved option (not the cleanest but does work well), and it does let you have highlighting! Thanks to @Amar for the pointer on ignoring spaces. – cptnjtk May 30 '15 at 23:13

As @werner has already suggested (in his comment on your question), you can insert manual line-breaks (without leaving a blank line) and it would allow you to comment out specific lines in a regular paragraph.

Otherwise you can define a new macro which can selectively comment-out only the specific line or part of the targeted paragraph and if you use this method, you may continue to type your input text without worrying about manual line-breaks (of course, except when -- you want to leave intentional line-breaks to start a new line in your output or a manual line-break followed by a blank line to create a new paragraph in your output).

This macro can be defined as:

\newcommand{\hashed}[2]{#2}


OR as:

\newcommand{\hashed}[1]{\ignorespaces}


I would prefer the earlier than latter (for no specific reason whatsoever! It's just that I've been using the same for a while). Add either to your document preamble (before \begin{document}) and you can use it as:

The Red dragon was mighty \& strong. \hashed{His scales were stronger than any steel man has ever known!} His name was Shruikan.


Result for both these commands would look like this:

The Red dragon was mighty & strong.<space>His name was Shruikan.

As I have mentioned above in my comment on @cptnjtk's solution, if this macro was defined as suggested by @cptnjtk, i.e. --

\newcommand{\hashed}[1]{}


The above result would look like this:

The Red dragon was mighty & strong.<space><space>His name was Shruikan.

To avoid inserting such additional spaces, use either of the earlier mentioned macros.