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Replacing string with its length in Regex

by Brovnik (Hermit)
on Jul 27, 2001 at 20:25 UTC ( #100355=perlquestion: print w/ replies, xml ) Need Help??
Brovnik has asked for the wisdom of the Perl Monks concerning the following question:

I have a sub which converts e.g.
_________XX_X_XX_________ => 2,1,2 __________XXXXX__________ => 5 ____XXXX___XXX__XXXXX____ => 4,3,5
Spec: output is comma separated list of run lengths of the 'X' parts.

The sub is :

sub template { my $r = shift; $r =~ s/^_+//; $r =~ s/_+$//; $r =~ s/_+/_/g; return join ',', map { length($_) } split(/_/,$r); }
Is there a Regex way of doing the last line ?
I'd like to be able to do e.g.
But this if course doesn't do what I need.

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Re: Replacing string with its length in Regex
by japhy (Canon) on Jul 27, 2001 at 20:40 UTC
    You can execute code in the right-hand side of a substitution, by supplying the /e modifier.
    s/(X+)/length $1/eg;

    Jeff japhy Pinyan: Perl, regex, and perl hacker.
    s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;

Re: Replacing string with its length in Regex
by bikeNomad (Priest) on Jul 27, 2001 at 20:34 UTC
    Why not just:

    my $s = s/_*(X+)_*/length($1) . ','/ge; $s =~ s/,$//;
      even simpler:
      $r =~ s/(^_+|_+$)//g; $r =~ s/_+/,/g; $r =~ s/(X+)/length$1/ge;

Re: Replacing string with its length in Regex
by merlyn (Sage) on Jul 27, 2001 at 22:00 UTC
      Not homework honest.

      It is part of a Nonogram Solver/manipulator. This sub is part of the file loader. I know that nonogram solvers have been given as homework in other places, and I wrote one in C++ some time ago, but thought I would rebuild it in Perl for fun.

      This site gives more on Nonograms (also know as Paint by Numbers).

        Wow, so there is a name for the puzzles in picross! I take it the idea is to generate the number hints to a puzzle from an ascii bitmap?

        'The fickle fascination of and Everlasting God' - Billy Corgan, The Smashing Pumpkins

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