regex maching unique character set

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

Hi,

This question might have been asked a million times, but here it is.

I want a regex to fail if there is:

1. A character not in the set

2. A character twice in the set

f.e.
The list of characters 'ABCDEF', than it should return false if.
ABDA
ABXD
AABB

But true if
ABC
A
DEFA

I now worked around with a map or grep, but I think it should be doable in a single regex. The sequence of characters doesn't matter

Thanks for your help
---------------------------
Dr. Mark Ceulemans
Senior Consultant
IT Masters, Belgium

Comment on regex maching unique character set

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Re: regex maching unique character set by Corion (Patriarch) on Jan 30, 2003 at 11:31 UTC
You want to use a backreference for the "twice" part. I punted on the "not in the set" part, and used an alternation for that. So my regex is really two parts : `/([$set]).\1/ # Look if there is any repetition or /[^$set]/ # Look if there is any unallowed character # Which combines to /([$set]).\1\|[^$set]/` [download] . Here's my test code : `my $set = "ABCDEF"; for (<DATA>) { chomp; print "$_ vs. $set : ", $_ =~ m!([$set]).*\1\|[^$set]! ? "Yes" : "No" +, "\n"; }; __DATA__ A B C ACX ABC AA BB` [download] `perl -MHTTP::Daemon -MHTTP::Response -MLWP::Simple -e ' ; # The $d = new HTTP::Daemon and fork and getprint $d->url and exit;#spider ($c = $d->accept())->get_request(); $c->send_response( new #in the HTTP::Response(200,$_,$_,qq(Just another Perl hacker\n))); ' # web` [download]	[reply] [d/l] [select]
Re: regex maching unique character set by broquaint (Abbot) on Jan 30, 2003 at 11:35 UTC
This should do it `use strict; my $cc = "ABCDEF"; my @false = qw(ABDA ABXD AABB); my @true = qw(ABC A DEFA); for(@false,@true) { my $res = /[^$cc] \| ([$cc]) [$cc]* \1/x ? "no" : "yes"; print "$_: $res\n"; } __output__ ABDA: no ABXD: no AABB: no ABC: yes A: yes DEFA: yes` [download] HTH `_________ broquaint`	[reply] [d/l]