Re: Regexp cleanup

[Laurent Hoeltgen]

On 07/03/2013 09:57 PM, PhilipNienhuis wrote:
> Rik-4 wrote
> > 7/3/13
> >
> > All,
> >
> > Does anyone know if the following expression is legal in Matlab?
> >
> > [S, E, TE, M, T, NM, SP] = regexp ("John Davis\nRogers, James",
> > '(?
> > <first>
> > \w+)\s+(?
> > <last>
> > \w+)|(?
> > <last>
> > \w+),\s+(?
> > <first>
> > \w+)')
> >
> > The issue is with the repeated use of a named capture buffer across an
> > alternation operator.  PCRE, which we use underneath for regular
> > expressions, does not support non-unique capture names in a pattern.
> > Octave currently works around this by renaming the capture buffers.
> > However, the logic at the far end to parse the output of PCRE and return
> > results to Octave is very complex and creaky.  I re-wrote the back end
> > routine in util/regexp.cc and I can now, at least, follow what the code is
> > doing.  The re-write also solves the following existing bugs (I said it
> > was
> > creaky).
> >
> > 38778: wrong return value for regexp
> > 38616: memory leak
> > 38149: wrong tokens returned
> >
> > So, depending on what Matlab does, would it be okay to drop support for
> > this esoterica?  I'm pretty tired of trying to work it out at this point.
> >
> > --Rik
> Matlab r2013b prerelease does (after changing double quote to single quote,
> and removing empty lines):
>
> > > [S, E, TE, M, T, NM, SP] = regexp ('John Davis\nRogers, James',
> > > '(?<first>\w+)\s+(?<last>\w+)|(?<last>\w+),\s+(?<first>\w+)')
> S =
>       1    12
> E =
>      10    25
> TE =
>      [2x2 double]    [2x2 double]
> M =
>      'John Davis'    'nRogers, James'
> T =
>      {1x2 cell}    {1x2 cell}
> NM =
> 1x2 struct array with fields:
>      first
>      last
> SP =
>      ''    '\'    ''
> ...so it seems Matlab thinks this is valid.
>
> Philip
>
>
>
> --
> View this message in context: 
> http://octave.1599824.n4.nabble.com/Regexp-cleanup-tp4655163p4655172.html
> Sent from the Octave - Maintainers mailing list archive at Nabble.com.

Hi,

Matlab R2012a returns the same result as above.

Regards,
Laurent