Re: [FWP] counting in REs

[Rich Morin <rdm@cfcl.com>]

At 12:43 PM -0400 9/8/99, Ronald J Kimball wrote:
>That fails on the same string I presented for David's regex:
>'--a--a--a--a--' because it requires adjacent 'a's.
>
>    $string =~       /^[^a]*(a[^a]*a[^a]*)*$/ &&
>    $string =~ /^[^b]*b[^b]*(b[^b]*b[^b]*)*$/

No, it doesn't.  For instance, it passes ' a b a ' just fine.

OTOH, your test string ('--a--a--a--a--') does not meet the criteria
for the question, as it does not contain an odd number of 'b's.

-r

P.S.  To help us all read from the same page, here is a simple test
       harness I hacked up:

for (;;) {
   print 'Next? ';
   $string = <>;
   chop $string;
   if ($string =~       /^[^a]*(a[^a]*a[^a]*)*$/ &&
       $string =~ /^[^b]*b[^b]*(b[^b]*b[^b]*)*$/) {
     print "pass ($string)\n\n";
   } else {
     print "fail ($string)\n\n";
   }
}
--
Rich Morin:          rdm@cfcl.com, +1 650-873-7841, http://www.ptf.com/~rdm
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