From: Dossy <dossy@...>
Date: 2002-05-19T22:13:56+09:00
Subject: Re: Ruby regex question

On 2002.05.19, David Alan Black <dblack@candle.superlink.net> wrote:
> >    3086     # read header
> >    3087     my($line_count,$last_updated);
> >    3088     while (@lines) {
> >    3089         my $shift = shift(@lines);
> >    3090         last if $shift =~ /^\s*$/;
> >    3091         $shift =~ /^Line-Count:\s+(\d+)/ and $line_count = $1;
> >    3092         $shift =~ /^Last-Updated:\s+(.+)/ and $last_updated = $1;
> [...]
> >
> > Maybe this portion of CPAN.pm wasn't written by a Perl guru.
> 
> But in this example, the matches are indeed being checked, prior to
> saving $1.

True enough, we're relying on $line_count being undef from line 3087.
Gotta love Perl!

> > You are right though, that it is more common to find regex
> > success immediately with the regex evaluation.  Perhaps
> > it's because with Perl, you can't know if $1 is valid (applies
> > to the regex you just evaluated) _unless_ you test if the
> > regex succeeded, which _forces_ you to test for the regex
> > success.  Ruby doesn't force you to do this, so the only
> > reason for it to be a Ruby idiom is because it's a carry-over
> > from Perl.
> 
> I agree.  Of course there's nothing wrong with checking for the match,
> and there are situations where it's precisely what one wants to do.

Right.  When you're trying to match purely to see if a string matches
a regex, then of course, check it then.  But, when you're using regexes
to parse, let the objects downstream do the checking -- they have to
do it anyway, why duplicate code checking it twice?

Anyway, this thread is totally OT now.  ;-)

-- Dossy

-- 
Dossy Shiobara                       mail: dossy@panoptic.com 
Panoptic Computer Network             web: http://www.panoptic.com/ 
  "He realized the fastest way to change is to laugh at your own
    folly -- then you can let go and quickly move on." (p. 70)