How do I find the last occurrence of a match using regexp in MATLAB?

2013 8 15
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If I have the following string in MATLAB:
str = '/* This is a comment */ int x; /* sectionEndExample */';
How do I find the last comment that contains sectionEndExample? I have tried the following:
expr = ['^.*/\*.*sectionEndExample.*\*/'];
sectionEndIdx1 = regexp(str, expr);
But this always returns the sectionEndIdx1 as 1. I am looking in the documentation and have so far played around with the lookAround options. However, I can't figure out a way to do it in MATLAB :(

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Azzi Abdelmalek
Azzi Abdelmalek 2013-8-15
if you knpw the comment sectionEndExample, why are you looking for it?
Or do you want to find the last comment between * ?
Swati Tiwari
Swati Tiwari 2013-8-16
I apologize for not framing the question correctly. I want to be able to find the last comment in the line. I believe I could get this by tweaking the regular expression. But, my efforts have been in vain.

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Azzi Abdelmalek
Azzi Abdelmalek 2013-8-16

1 个投票

str = '/* This is a comment */ int x; /* sectionEndExample */';
pattern='(/)\*[\w\s]+\*(/)';
[sectionEndIdx1,debut,fin] = regexp(str, pattern,'match','start','end');
sectionEndIdx1=sectionEndIdx1{end}
start_comment=debut(end)
end_comment=fin(end)

更多回答（3 个）

Cedric
Cedric 2013-8-15
编辑：Cedric 2013-8-15

2 个投票

Is it what you want? If so, we can work a bit to improve it (in particular for allowing stars in the comment if relevant, which are not allowed with this pattern).
>> regexp(str, '[^\*]+(?=\*/$)', 'match')
ans =
' sectionEndExample '
Azzi Abdelmalek
Azzi Abdelmalek 2013-8-15

2 个投票

str = '/* This is a comment */ int x; /* sectionEndExample */';
pattern='(?<=/\*)[\w\s]+(?=\*/)';
sectionEndIdx1 = regexp(str, pattern,'match');
sectionEndIdx1=sectionEndIdx1{end}

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Cedric
Cedric 2013-8-15
编辑：Cedric 2013-8-16
This solution is better than mine if there can be code (EDIT: or anything) after the last comment.
Azzi Abdelmalek
Azzi Abdelmalek 2013-8-15
You are right, even a space will make a problem.
Swati Tiwari
Swati Tiwari 2013-8-16
Thank you very much for all your help. Really appreciate it. To rephrase the question, I wish to get the start position and the end position of the comment (including the starting '/*' and the ending '*/' that contains the string 'sectionEndExample'.

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Swati Tiwari
Swati Tiwari 2013-8-16

0 个投票

Thank you all. I also figured out a way to do it!
str = '/* This is a sectionEndExample comment */ int x; /* sectionEndExample */';
pattern='/\*[^\*]*sectionEndExample[^\*]*\*/';
sectionEndIdx1 = regexp(str, pattern,'match')
This will find all the comments with the string sectionEndExample.

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Swati Tiwari
Swati Tiwari 2013-8-16
编辑：Azzi Abdelmalek 2013-8-16
Here, I divided the string into three parts:
1. (anything but a *)* sectionEndExample (anything but a *)*
2. The start comment identifier /*
3. The end comment identifier

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