Help to solve a regexp problem

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Kouichi C. Nakamura
编辑： Stephen23 2016-7-8
I'm trying to capture comment block in a string (char array). Regular expression '%.*(\n|$)' captures string from % to the end of the line.
regexp(sprintf(' %%this is a comment'),'%.*(\n|$)','match')
ans =
cell
'% this is a comment'
However, what I want to do is to capture multiple incidence of comment blocks in a char array. The above expression only captures the first one, failing to match '% and this'.
regexp(sprintf(' %%this is a comment\n %%and this\n'),'%.*(\n|$)','match')
ans =
cell
'% this is a comment…'
Could somebody help me about this?
  2 个评论
Stephen23
Stephen23 2016-7-8
编辑：Stephen23 2016-7-8
To make writing regular expressions easier, you might like to try using my FEX submission that lets you interactively write and develop regular expressions:
https://www.mathworks.com/matlabcentral/fileexchange/48930-interactive-regular-expression-maker
Simply run it to open the interactive figure, then enter your data string, and start playing around with the regular expression. The figure will update and show you the regexp outputs as you change the regular expression. This makes it fast and easy to try different regular expressions, and to check how changes affect the outputs.
PS: This page is very useful too. Lots of information, but worth reading and referring to:
http://www.mathworks.com/help/matlab/matlab_prog/regular-expressions.html
Kouichi C. Nakamura
Kouichi C. Nakamura 2016-7-8
This looks really interesting. I'll surely give it a try. I could help me a lot. Thanks!

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per isakson
per isakson 2016-7-8
Test this
>> str = sprintf(' %%this is a comment\n %%and this\n');
>> cac = regexp( str, '[ ]*%[^\n]+', 'match' )
cac =
' % this is a comment' ' % and this'
>> whos cac
Name Size Bytes Class Attributes
cac 1x2 294 cell
  2 个评论
Kouichi C. Nakamura
Kouichi C. Nakamura 2016-7-8
Thanks a lot. Yours included leading spaces (maybe I was not clear enough about what I want to catch), but '%[^\n]+' successfully did the job!
>> cac = regexp(str, '%[^\n]+', 'match' )
cac =
1×2 cell array
'% this is a comment' '% and this'
Guillaume
Guillaume 2016-7-8
Note that your regular expression would have worked if you'd used the non-greedy *?:
regexp(sprintf(' %%this is a comment\n %%and this\n'),'%.*?(\n|$)','match')
Nonetheless, per's expression is probably more efficient.

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