Can I comment a block of lines in an MATLAB file using /* ... */ as I can in C?
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I understand that in MATLAB we can comment line by line using % but this is troublesome, especially if I have a whole group of lines that I want to comment out temporarily. Is there anyway we can 'block' comment, like in 'C' where we can use /* at the beginning of a block of comments and */ at the the end of the block?
Accepted Answer
MathWorks Support Team
on 18 Oct 2021
Edited: MathWorks Support Team
on 18 Oct 2021
You can comment out a block of code in MATLAB using the block comment operators, %{ and %}. The %{ and %} operators must appear alone on the lines that immediately precede and follow the block of code that you want to comment out. Do not include any other text on these lines.
For example:
a = magic(3);
%{
sum(a)
diag(a)
sum(diag(a))
%}
sum(diag(fliplr(a)))
You also can comment out a block of code by selecting the code, going to the Editor or Live Editor tab, and pressing the comment button: 
Alternatively, you can type Ctrl+R.
To uncomment the selected lines code, press the uncomment button: 
Alternatively, you can type Ctrl+Shift+R.
For more information about adding comments to code, see:
5 Comments
Patrik Ek
on 13 May 2014
Is it also possible to comment part of a code on a line with this?
Walter Roberson
on 7 Apr 2017
One trick: on a source line, everything after a ... (that is not in a string) is treated as comments.
Steven Lord
on 9 Apr 2021
That is correct. From the documentation "To comment out multiple lines of code, use the block comment operators, %{ and %}. The %{ and %} operators must appear alone on the lines that immediately precede and follow the block of help text. Do not include any other text on these lines."
Rik
on 9 Apr 2021
(working from memory):
I believe adding whitespace is fine as well, but I haven't checked if that only allows space, or if other whitespace characters are also allowed. One of the many exceptions I needed to handle to strip comments from code.
Walter Roberson
on 10 Apr 2021
Edited: MathWorks Support Team
on 4 May 2023
Testing only single characters immediately after the %{ the ones that do not interrupt the meaning as comment are:
- 9 (tab)
- 10 (newline)
- 11 (vertical tab)
- 12 (form feed)
- 13 (carriage return)
- 32 (space)
This excludes a number of Unicode spacing characters such as No-Break Space and Zero-Width No-Break Space; https://jkorpela.fi/chars/spaces.html
More Answers (1)
Gaganjyoti Baishya
on 21 Jun 2020
0 votes
Yeah it can be easily done. Instead of /* use %{
and instead of */ use %}
1 Comment
Walter Roberson
on 9 Apr 2021
C and C++ permit /* */ to appear in the middle of a line and the rest of the line after the */ will be executed for them. MATLAB requires that %{ and %} be on lines by tthemselves .
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