Legacy implementation of strtrim prior to R2016a

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sst
sst 2016-8-30
编辑： Guillaume 2016-8-31
It looks like strtrim changed in R2016a to not trim significant whitespace characters. However, I have a need for a legacy implementation. Is it possible to provide one that works in R2016a, but also trims significant whitespace characters?

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Guillaume
Guillaume 2016-8-30
regexp(yourstring, '(?<=^\W*)\w.*?(?=\W*$)', 'match', 'once')
should do the trick
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sst
sst 2016-8-31
The first implementation using regexp turned out to be the fastest alternative approach, though still well over ten times slower than the built-in strtrim. I was really hoping TMW would have provided a 'legacy' option for strtrim, like they did for functions like ismember, union, and intersect :)
Guillaume
Guillaume 2016-8-31
编辑：Guillaume 2016-8-31
First of all, I made a mistake in the regex, it should have been \s instead of \W and \S instead of \w (yes upper and lower case should be swapped as well), so:
regexp(yourstring, '(?<=^\s*)\S.*?(?=\s*$)', 'match', 'once')
This will not speed up the regex, the slow down is probably caused by the non-greedy all capturing star .*? followed by the greedy capturing \s*, which causes a lot of backtracking.
However, this regex will do the same and should be significantly faster:
regexp(yourstring, '(?<=^\s*)\S.*\S(?=\s*$)', 'match', 'once')
As for a legacy option for strtrim, this is something you would have to ask Mathworks through a service request.

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