String::Combination Package Bug?

b4swine has asked for the wisdom of the Perl Monks concerning the following question:

I used the String::Combination package, downloaded from the ActivePerl site, and got what appear so plainly like a bug that I believe I must be wrong somewhere in my understanding. The code

use String::Combination qw(combination);
my @comb = combination('12345678',8);
print "@comb[6..12]\n@comb[62..68]\n";
[download]

produces the output

23456781 32456781 34256781 34526781 34562781 34567281 34567821
23456781 32456781 34256781 34526781 34562781 34567281 34567821
[download]

As far as I see it, there should not be any repetitions. Am I misunderstanding something, or is this a bug?

Comment on String::Combination Package Bug? Select or Download Code

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Re: String::Combination Package Bug? by amarquis (Curate) on Jan 02, 2008 at 16:46 UTC
I downloaded String::Combination via ActiveState's PPM, and produced this behavior. I couldn't find the distro (or the author) on CPAN, but the documentation in the distro's POD seems to indicate that the combinations should be unique: "From a set of n elements, given an integer k, the algorithm calculates k! * n!/(k!(n-k)!) elements that are all the combinations of k elements from the set of n elements. " I believe Active's PPM just grabs "whatever will build" from CPAN, and doesn't do any other testing. Perhaps the C library that this module is the XS glue for is making assumptions about the machine it is running on? Edit: Forgot to mention, you can grab Algorithm::Combinatorics or Math::Combinatorics via PPM. Looking quickly, I'm thinking that they are overkill for your problem, but they are an option at least.	[reply]
Re: String::Combination Package Bug? by gamache (Friar) on Jan 02, 2008 at 16:38 UTC
I noticed a few strange things about String::Combination... It's not on CPAN, despite having been uploaded in 2004 It's remained at 0.01 since then Google is largely unaware of its presence	[reply]
Re^2: String::Combination Package Bug? by ysth (Canon) on Jan 03, 2008 at 08:03 UTC
It is on backpan (http://backpan.cpan.org/authors/id/D/DR/DREE/String-Combination-0.01.tar.gz ), for the curious. There's also a newer version, renamed as String-OrderedCombination. -- CollegeGear.com - more than just college gear (though, yes, we have college-branded teddy bears)	[reply]
Re: String::Combination Package Bug? by shmem (Chancellor) on Jan 02, 2008 at 17:21 UTC
Looks like a bug. `combination($str,$k)` returns each combination `($k-2)!` times. --shmem _($_=" "x(1<<5)."?\n".q·/)Oo. G°\ / /\_¯/(q / ---------------------------- \__(m.====·.(_("always off the crowd"))."· ");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}	[reply] [d/l] [select]
Re: String::Combination Package Bug? by Khen1950fx (Canon) on Jan 02, 2008 at 23:35 UTC
String::Combination worked for me. Try this: `#!/usr/bin/perl use strict; use warnings; use diagnostics; use String::Combination qw(combination); my @comp = combination('12345678', 8); print "@comp\n";` [download] It works with k integers 2 thru 8.	[reply] [d/l]
Re: String::Combination Package Bug? by Anonymous Monk on Jan 03, 2008 at 08:27 UTC
It seems DREE abandon/delete all his modules dree http://search.cpan.org/~DREE/ http://kobesearch.cpan.org/~DREE/ http://backpan.cpan.org/authors/id/D/DR/DREE/ http://www.nntp.perl.org/group/perl.modules/2002/05/msg11859.html http://search.cpan.org/~davidebe/ http://kobesearch.cpan.org/~davidebe/ http://backpan.perl.org/authors/id/D/DA/DAVIDEBE/	[reply]


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