Question on s///eg

dragonchild has asked for the wisdom of the Perl Monks concerning the following question:

I've got the following code. The idea is to convert an array representing a bitmap to a string representing the range of that bitmap. So, (1,1,0,1,1,1,0) would convert to "0-1,3-5". (In my code, I'm converting from 0-base to 1-base using the map.)

my @channels = (1, 1, 0, 1, 1, 1, 0);
my $val = join ',', map { $_ + 1 } grep { $channels[$_] } 0 .. $#chann
+els;

$val =~ s/(\d+),(\d+)/$1+1 == $2 ? "$1-$2" : "$1,$2"/eg;

print $val, $/;
[download]

Unfortunately, the regex only works if my set-bits are only in pairs. If I put the triple 1,1,1 (as above), it only works for the first pair. In addition, (1,1,1,0,1,1,0) converts to "1-2,3,5,6", which totally boggles me.

Help?

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Comment on Question on s///eg Download Code

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(Ovid) Re: Question on s///eg by Ovid (Cardinal) on Feb 27, 2002 at 17:19 UTC
Assuming you're using 5.6.0 or greater, you can use a range generator that japhy put together: List-to-Range generation. The rest should just be details :) `my @channels = (1, 1, 0, 1, 1, 1, 0); my @vals = map { $_ + 1 } grep { $channels[$_] } 0 .. $#channels; my $val = num2range( @vals ); print $val, $/; sub num2range { local $_ = join ',' => sort { $a <=> $b } @_; s/(?<!\d)(\d+)(?:,((??{$++1})))+(?!\d)/$1-$+/g; return $_; }` [download] Cheers, Ovid Join the Perlmonks Setiathome Group or just click on the the link and check out our stats.	[reply] [d/l]
Re: Question on s///eg by japhy (Canon) on Feb 27, 2002 at 17:46 UTC
Well, since I love regexes, I'll help out... `$bitmap =~ s{ (1 (?: ,1 )* ) # match 1 or 1,1 or 1,1,1,... \| ,? (0 (?: ,0 )* ) # match 0 or 0,0 or 0,0,0,... }{ # evil tr/// bug with $<DIGITS> my ($one, $zero) = ($1, $2); ++$i; if ($zero) { $i += $zero =~ tr/,//; ""; } else { if (my $c = $one =~ tr/,//) { "$i-" . ($i += $c) } else { $i } } }xge;` [download] _____________________________________________________ Jeff`[japhy]`Pinyan: Perl, regex, and perl hacker, who'd like a (from-home) job `s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;`	[reply] [d/l]
Re: Question on s///eg by particle (Vicar) on Feb 27, 2002 at 17:25 UTC
by the way, for long lists, you should probably be using vec. it will save you a lot of memory. ~Particle ;Þ	[reply]
Re: Question on s///eg by PrakashK (Pilgrim) on Feb 27, 2002 at 17:27 UTC
Here's some not so thouroughly tested code: `my @channels = (1, 1, 0, 1, 1, 1, 0); my $str = join "", @channels; my @range; push @range, join "-", ($-[0], $+[0]-1) while $str =~ m/(1+)/g; print join ",", @range;` [download] prints `0-1,3-5` /prakash Update: I must add that this may not work for perl versions older than 5.6.0.	[reply] [d/l] [select]
Re: Question on s///eg by zengargoyle (Deacon) on Feb 27, 2002 at 22:59 UTC
I've forgotten where this came from, but it could be helpful. `$n="1,2,3,4,9,10,11,12,14,16,17,18"; $n =~ s{ (?<!\d) (\d+) (?: , ( (??{ 1 + $+ }) ) )+ }{$1-$+}gx; print "$n\n"; $ perl cool_regex.pl 1-4,9-12,14,16-18` [download]	[reply] [d/l]
Re: Re: Question on s///eg by japhy (Canon) on Feb 27, 2002 at 23:01 UTC
That's mine, from Snippets. But you can feel free to use it! _____________________________________________________ Jeff`[japhy]`Pinyan: Perl, regex, and perl hacker, who'd like a (from-home) job `s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;`	[reply]
Re: Re: Re: Question on s///eg by zengargoyle (Deacon) on Feb 27, 2002 at 23:18 UTC
In my head, almost all my regex's are from japhy. moment of silence...	[reply]
Re: Question on s///eg by Sweeper (Pilgrim) on Feb 28, 2002 at 06:51 UTC
Maybe you could take a look at Mastering Algorithms in Perl page 228, or install Steven McDougall's module `Set::IntSpan`. (I have done the former, maybe I will try the latter sometime).	[reply]