[regex-coach] alternations working differently in Regex Coach versus perl program.

Troy Peterson troypennpeterson at gmail.com
Sun Aug 2 18:35:50 UTC 2009 

 I am writing a regex to test for valid dates in YYYY-MM-DD format.

Using this regex in a perl test program I get positive results for all dates
for the next 365 days.

Regex Coach however failes to match some such as '2010-06-30'.  I assume
this is because of the  order of the alternations and the regex wanting to
match a sub-pattern as quickly as possible.  I can resolve the issue in The
Regex Coach by adding () around the month and year patterns.

I would like to know why there is a difference between my Perl program and
Regex Coach.  Could this be implementation dependent.  Both my program and
its output are below.

I tend to think that The Regex Coach got this right.

(?# regex in The Regex Coach)
*        [123456789]\d\d\d-                                           # year
*
*         (?:                                                      *
*            (?:0[13578]|10|12 -  [012][123456789]|10|20|30|31)  |      #
Months with 31 days*
*            (?:0[469]|11      -  [012][123456789]|10|20|30   )  |      #
Months with 30 days  *
*            (?:02             -  [012][12345678]||10|20|19   )         #
Febuary*
*         )*

### perl Test program
#!/iw-home/teamsite/iw-perl/bin/iwperl

use strict;
use warnings;
use Carp;
use Getopt::Long;
use Pod::Usage;
use Cwd;
use Date::Calc qw(:all);

my $dateregex = qr{
        [123456789]\d\d\d-                                           # year
         (?:
            (?:0[13578]|10|12 -  [012][123456789]|10|20|30|31)  |      #
Months with 31 days
            (?:0[469]|11      -  [012][123456789]|10|20|30   )  |      #
Months with 30 days
            (?:02             -  [012][12345678]||10|20|19   )         #
Febuary
         )
}smx;

sub testdate {
    my ($d) = (@_);
    print "$d";
    if ( $d =~ m{$dateregex}smx ) {
        print "okay\n";
    }
    else {
        print "\n";
        croak "broken";
    }
}

foreach my $d ( 1 .. 365 ) {
    my ( $year, $month, $day, $hour, $min, $sec, $doy, $dow, $dst ) =
      System_Clock();
    ( $year, $month, $day, $hour, $min, $sec ) =
      Add_Delta_DHMS( $year, $month, $day, '0', '0', '0', "$d", '0', '0',
'0' );

    my $td = sprintf( "%4d-%02d-%02d", $year, $month, $day );
    testdate("$td");

}
exit;


##OUTPUT
2009-08-03okay
2009-08-04okay
2009-08-05okay
2009-08-06okay
2009-08-07okay
2009-08-08okay
2009-08-09okay
2009-08-10okay
2009-08-11okay
2009-08-12okay
2009-08-13okay
2009-08-14okay
2009-08-15okay
2009-08-16okay
2009-08-17okay
2009-08-18okay
2009-08-19okay
2009-08-20okay
2009-08-21okay
2009-08-22okay
2009-08-23okay
2009-08-24okay
2009-08-25okay
2009-08-26okay
2009-08-27okay
2009-08-28okay
2009-08-29okay
2009-08-30okay
2009-08-31okay
2009-09-01okay
2009-09-02okay
2009-09-03okay
2009-09-04okay
2009-09-05okay
2009-09-06okay
2009-09-07okay
2009-09-08okay
2009-09-09okay
2009-09-10okay
2009-09-11okay
2009-09-12okay
2009-09-13okay
2009-09-14okay
2009-09-15okay
2009-09-16okay
2009-09-17okay
2009-09-18okay
2009-09-19okay
2009-09-20okay
2009-09-21okay
2009-09-22okay
2009-09-23okay
2009-09-24okay
2009-09-25okay
2009-09-26okay
2009-09-27okay
2009-09-28okay
2009-09-29okay
2009-09-30okay
2009-10-01okay
2009-10-02okay
2009-10-03okay
2009-10-04okay
2009-10-05okay
2009-10-06okay
2009-10-07okay
2009-10-08okay
2009-10-09okay
2009-10-10okay
2009-10-11okay
2009-10-12okay
2009-10-13okay
2009-10-14okay
2009-10-15okay
2009-10-16okay
2009-10-17okay
2009-10-18okay
2009-10-19okay
2009-10-20okay
2009-10-21okay
2009-10-22okay
2009-10-23okay
2009-10-24okay
2009-10-25okay
2009-10-26okay
2009-10-27okay
2009-10-28okay
2009-10-29okay
2009-10-30okay
2009-10-31okay
2009-11-01okay
2009-11-02okay
2009-11-03okay
2009-11-04okay
2009-11-05okay
2009-11-06okay
2009-11-07okay
2009-11-08okay
2009-11-09okay
2009-11-10okay
2009-11-11okay
2009-11-12okay
2009-11-13okay
2009-11-14okay
2009-11-15okay
2009-11-16okay
2009-11-17okay
2009-11-18okay
2009-11-19okay
2009-11-20okay
2009-11-21okay
2009-11-22okay
2009-11-23okay
2009-11-24okay
2009-11-25okay
2009-11-26okay
2009-11-27okay
2009-11-28okay
2009-11-29okay
2009-11-30okay
2009-12-01okay
2009-12-02okay
2009-12-03okay
2009-12-04okay
2009-12-05okay
2009-12-06okay
2009-12-07okay
2009-12-08okay
2009-12-09okay
2009-12-10okay
2009-12-11okay
2009-12-12okay
2009-12-13okay
2009-12-14okay
2009-12-15okay
2009-12-16okay
2009-12-17okay
2009-12-18okay
2009-12-19okay
2009-12-20okay
2009-12-21okay
2009-12-22okay
2009-12-23okay
2009-12-24okay
2009-12-25okay
2009-12-26okay
2009-12-27okay
2009-12-28okay
2009-12-29okay
2009-12-30okay
2009-12-31okay
2010-01-01okay
2010-01-02okay
2010-01-03okay
2010-01-04okay
2010-01-05okay
2010-01-06okay
2010-01-07okay
2010-01-08okay
2010-01-09okay
2010-01-10okay
2010-01-11okay
2010-01-12okay
2010-01-13okay
2010-01-14okay
2010-01-15okay
2010-01-16okay
2010-01-17okay
2010-01-18okay
2010-01-19okay
2010-01-20okay
2010-01-21okay
2010-01-22okay
2010-01-23okay
2010-01-24okay
2010-01-25okay
2010-01-26okay
2010-01-27okay
2010-01-28okay
2010-01-29okay
2010-01-30okay
2010-01-31okay
2010-02-01okay
2010-02-02okay
2010-02-03okay
2010-02-04okay
2010-02-05okay
2010-02-06okay
2010-02-07okay
2010-02-08okay
2010-02-09okay
2010-02-10okay
2010-02-11okay
2010-02-12okay
2010-02-13okay
2010-02-14okay
2010-02-15okay
2010-02-16okay
2010-02-17okay
2010-02-18okay
2010-02-19okay
2010-02-20okay
2010-02-21okay
2010-02-22okay
2010-02-23okay
2010-02-24okay
2010-02-25okay
2010-02-26okay
2010-02-27okay
2010-02-28okay
2010-03-01okay
2010-03-02okay
2010-03-03okay
2010-03-04okay
2010-03-05okay
2010-03-06okay
2010-03-07okay
2010-03-08okay
2010-03-09okay
2010-03-10okay
2010-03-11okay
2010-03-12okay
2010-03-13okay
2010-03-14okay
2010-03-15okay
2010-03-16okay
2010-03-17okay
2010-03-18okay
2010-03-19okay
2010-03-20okay
2010-03-21okay
2010-03-22okay
2010-03-23okay
2010-03-24okay
2010-03-25okay
2010-03-26okay
2010-03-27okay
2010-03-28okay
2010-03-29okay
2010-03-30okay
2010-03-31okay
2010-04-01okay
2010-04-02okay
2010-04-03okay
2010-04-04okay
2010-04-05okay
2010-04-06okay
2010-04-07okay
2010-04-08okay
2010-04-09okay
2010-04-10okay
2010-04-11okay
2010-04-12okay
2010-04-13okay
2010-04-14okay
2010-04-15okay
2010-04-16okay
2010-04-17okay
2010-04-18okay
2010-04-19okay
2010-04-20okay
2010-04-21okay
2010-04-22okay
2010-04-23okay
2010-04-24okay
2010-04-25okay
2010-04-26okay
2010-04-27okay
2010-04-28okay
2010-04-29okay
2010-04-30okay
2010-05-01okay
2010-05-02okay
2010-05-03okay
2010-05-04okay
2010-05-05okay
2010-05-06okay
2010-05-07okay
2010-05-08okay
2010-05-09okay
2010-05-10okay
2010-05-11okay
2010-05-12okay
2010-05-13okay
2010-05-14okay
2010-05-15okay
2010-05-16okay
2010-05-17okay
2010-05-18okay
2010-05-19okay
2010-05-20okay
2010-05-21okay
2010-05-22okay
2010-05-23okay
2010-05-24okay
2010-05-25okay
2010-05-26okay
2010-05-27okay
2010-05-28okay
2010-05-29okay
2010-05-30okay
2010-05-31okay
2010-06-01okay
2010-06-02okay
2010-06-03okay
2010-06-04okay
2010-06-05okay
2010-06-06okay
2010-06-07okay
2010-06-08okay
2010-06-09okay
2010-06-10okay
2010-06-11okay
2010-06-12okay
2010-06-13okay
2010-06-14okay
2010-06-15okay
2010-06-16okay
2010-06-17okay
2010-06-18okay
2010-06-19okay
2010-06-20okay
2010-06-21okay
2010-06-22okay
2010-06-23okay
2010-06-24okay
2010-06-25okay
2010-06-26okay
2010-06-27okay
2010-06-28okay
2010-06-29okay
2010-06-30okay
2010-07-01okay
2010-07-02okay
2010-07-03okay
2010-07-04okay
2010-07-05okay
2010-07-06okay
2010-07-07okay
2010-07-08okay
2010-07-09okay
2010-07-10okay
2010-07-11okay
2010-07-12okay
2010-07-13okay
2010-07-14okay
2010-07-15okay
2010-07-16okay
2010-07-17okay
2010-07-18okay
2010-07-19okay
2010-07-20okay
2010-07-21okay
2010-07-22okay
2010-07-23okay
2010-07-24okay
2010-07-25okay
2010-07-26okay
2010-07-27okay
2010-07-28okay
2010-07-29okay
2010-07-30okay
2010-07-31okay
2010-08-01okay
2010-08-02okay
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