Replacing string with its length in Regex

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
[download]

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);
}
[download]

Is there a Regex way of doing the last line ?
I'd like to be able to do e.g.

s/(X+)/length($1)/g;
[download]

But this if course doesn't do what I need.
--
Brovnik

Comment on Replacing string with its length in Regex Select or Download Code

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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;` [download] _____________________________________________________ Jeff `japhy` Pinyan: Perl, regex, and perl hacker. `s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;`	[reply] [d/l]
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; $s =~ s/,$//;` [download]	[reply] [d/l]
Re: Re: Replacing string with its length in Regex by petral (Curate) on Jul 29, 2001 at 12:28 UTC
even simpler: `$r =~ s/(^_+\|_+$)//g; $r =~ s/_+/,/g; $r =~ s/(X+)/length$1/ge;` [download] p	[reply] [d/l]
Re: Replacing string with its length in Regex by merlyn (Sage) on Jul 27, 2001 at 22:00 UTC
This smells a bit of being homework, but here's my answer: `sub template { return join ',', map length($_), shift =~ /(X+)/g; }` [download] -- Randal L. Schwartz, Perl hacker	[reply] [d/l]
Re: Re: Replacing string with its length in Regex by Brovnik (Hermit) on Jul 27, 2001 at 23:07 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). -- Brovnik	[reply]
Re: Re: Re: Replacing string with its length in Regex by Everlasting God (Beadle) on Jul 28, 2001 at 00:17 UTC
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	[reply]