Re: behavior of regexp ( ) function

[David Bateman]

Soren Hauberg wrote:
> ons, 28 01 2009 kl. 21:20 +0100, skrev David Bateman:
>   
> > John W. Eaton wrote:
> >     
> > > I'm not sure whether this is a bug.  But it is apparently incompatible
> > > behavior.  I don't know what the fix is, but I looked at the
> > > octregexp_list function, and it is correctly matching the first "20"
> > > and moving idx forward to 2 (the position of the next character in the
> > > string).  But then the next call to pcre_exec is matching zero or more
> > > of anything not TAB and returning a zero-length substring starting and
> > > ending at idx == 2.  So then ovector[1] <= ovector[0] and execution
> > > breaks out of the loop.
> > >   
> > >       
> > I no longer have easy to matlab so can someone run the commands
> >
> > a = sprintf("20\t50\tcelcius\t80");
> > b = sprintf("20\t50\t\t80");
> > regexp(a, '[^\t]+', 'match')
> > regexp(b, '[^\t]+', 'match')
> > regexp(a, '[^\t]*', 'match')
> > regexp(b, '[^\t]*', 'match')
> >
> > on matlab and send the results? Its not clear from your message John if 
> > the behavior described by Daniel is the right  one.
> >     
>
>   
> > > a = sprintf('20\t50\tcelcius\t80');
> > > b = sprintf('20\t50\t\t80');
> > > regexp(a, '[^\t]+', 'match')
> > >       
>
> ans = 
>
>     '20'    '50'    'celcius'    '80'
>
>   
> > > regexp(b, '[^\t]+', 'match')
> > >       
>
> ans = 
>
>     '20'    '50'    '80'
>
>   
> > > regexp(a, '[^\t]*', 'match')
> > >       
>
> ans = 
>
>     '20'    '50'    'celcius'    '80'
>
>   
> > > regexp(b, '[^\t]*', 'match')
> > >       
>
> ans = 
>
>     '20'    '50'    '80'
>
> Soren
>
>
>   
Thanks Soren and Benjamin, I believe the attached patch will do the 
right thing though I'm not sure why PCRE wants to return a zero length 
match for a pattern like "[^\t]*". Best just to ignore such matches 
rather than make them abort the search for matches as the code 
previously did. Patch pushed and attached

D.


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