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

I expect the string "1" to match the following regex but it doesn't.

my $str = "1";

if ($str =~ m/-?\p{Nd}/){
   print "Matches\n";
else {
   print "Doesn't match\n";
}

[download]

I am using Perl v5.10.0

Replies are listed 'Best First'.
Re: Simple regex should match number
by repellent (Priest) on Feb 01, 2012 at 07:41 UTC
    Really weird, looks like a bug:
    use Test::More;

ok( 1 =~ m/\p{Nd}/ );
ok( 1 =~ m/^-?\p{Nd}/ );
ok( 1 =~ m/-?\p{Nd}+/ );

ok( 1 =~ m/-?\p{Nd}/ );
ok( 1 =~ m/-*\p{Nd}/ );
ok( 1 =~ m/x?\p{Nd}/ );
ok( 1 =~ m/x?y?\p{Nd}/ );

done_testing();

__END__
ok 1
ok 2
ok 3
not ok 4
#   Failed test at ./t.pl line 16.
not ok 5
#   Failed test at ./t.pl line 17.
not ok 6
#   Failed test at ./t.pl line 18.
not ok 7
#   Failed test at ./t.pl line 19.
1..7
# Looks like you failed 4 tests of 7.

    [download]

    $ perl -v

This is perl, v5.10.0 built for darwin-thread-multi-2level

    [download]
[reply]
[d/l]
[select]
      That's a known bug, and, AFAIK, fixed in 5.14.0. It's certainly fixed in 5.14.2.
[reply]
Re: Simple regex should match number
by davido (Cardinal) on Feb 01, 2012 at 07:25 UTC

    According to what I've read in perlretut (or at least how I interpret it), \p{Nd} says match a non-digit. Maybe you want \P{Nd} which is "Match anything that is NOT a non-digit (double negative equals a positive). But that's a rather convoluted way of saying \p{Digit} or \p{IsDigit}.I haven't tested, so I'll leave that to you to decide which works best.

    Update: I guess I should have tested. :) It does match for me. ...and now I'll have to re-read the paragraph in perlretut. Perl 5.14.2. (And I see now that I did misread: \p{Nd} is indeed an affirmative, and \P{Nd} matches non-digit. So I do get a match, and you don't... we're back to square one. Move on to the next response. ;)


    Dave

[reply]
[d/l]
[select]
Re: Simple regex should match number
by Anonymous Monk on Feb 01, 2012 at 07:58 UTC
    Yup, it works in 5.14.1 but doesn't work in 5.12.2 
    my $str = "1";
if ($str =~ m/-?\p{Nd}/){
   print "Matches\n";
} else {
   print "Doesn't match\n";
}
__END__
Doesn't match

    [download]

    What does work in 5.12.2 (and I assume 5.10) is adding a quantifier, say m/-?\p{Nd}{1}/

[reply]
[d/l]
[select]
[reply]
[d/l]
[select]
Re: Simple regex should match number
by JavaFan (Canon) on Feb 01, 2012 at 11:52 UTC
    Known bug. Upgrade to 5.14.
[reply]

      Thanks. How do you find the bugs per release. I'm looking at http://rt.perl.org/rt3/Public and its one longggg list.

[reply]
        Other than rt.perl.org, I don't think anyone keeps official records. Note that noone knows all the bugs -- not every bug gets discovered or reported.
[reply]

Back to Seekers of Perl Wisdom