in reply to Regexp for alphabetical order match within the string

Do you really need it to be a regex?

# $str defined elsewhere
print "Is alphabetical\n" 
    if( $str eq join '', sort split //, $str );

[download]

----
I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
-- Schemer

: () { :|:& };:

Note: All code is untested, unless otherwise stated

Replies are listed 'Best First'.
Re: Re: Regexp for alphabetical order match within the string
by sauoq (Abbot) on Oct 30, 2003 at 19:09 UTC

    You can avoid the sort for an O(N) solution: 

    sub is_alphabetical {
    my @c = split //, shift;
    ord($c[$_]) >= ord($c[$_ - 1]) or return 0 for 1 .. $#c;
    return 1;
}

    [download]

    Update: Yes, my use of ord() is unnecessary. Thanks tlhf++.

    Edit: Added a missing my.

    -sauoq
"My two cents aren't worth a dime.";
[reply]
[d/l]
[select]
      Elegent solution, tho the ords are needless. 
      sub is_alphabetical {
    my @c = split //, shift;
    $c[$_] ge $c[$_-1] or return 0 for 1..$#c;
    return 1;
}

      [download]

      tlhf
      (Everyone forgets about ge and le ^_^)

[reply]
[d/l]
[select]

      ++, but the original post obviously allows non-alphabetical chars in the string, and their orders are not considered. A small improvement to meet the original requirement:

      $str = "aBcD12ef7812g";
print is_alphabetical($str);

sub is_alphabetical {
    (my $str = lc(shift)) =~ s/([^a-z])//g;
    my @c = split //, $str;
    $c[$_] ge $c[$_ - 1] or return 0 for 1 .. $#c;
    return 1;
}

      [download]
[reply]
[d/l]
        Re: s/([^a-z])//g:
        Please, tr/a-z//dc is feeling unloved.
[reply]
[d/l]
[select]
        but the original post obviously allows non-alphabetical chars in the string, and their orders are not considered.

        Actually, the regular expression in the original post did not match any non-alphabetic or even uppercase characters. (Okay, as the original wasn't anchored, I guess it did permit such characters in the string, but then it didn't deal with more than a single group of characters. And beyond that it matched the empty string.)

        I intentionally neglected those questions as I didn't feel they were really specified.

        -sauoq
"My two cents aren't worth a dime.";
[reply]
Re: Re: Regexp for alphabetical order match within the string
by asarih (Hermit) on Oct 30, 2003 at 19:37 UTC
    But this won't take case into consideration, would it? "Ba" is not really alphabetical in my book.
[reply]
      For case-insensitivity just throw an lc before the shift.
[reply]
[d/l]
[select]

In Section Seekers of Perl Wisdom