From: Pistos Christou <jesusrubsyou.5.pistos@...>
Date: 2006-03-30T00:44:50+09:00
Subject: Re: Regexp gotcha

James H. wrote:
> Are you asking why we can write
> 
>   if match_result
> 
> as equivalent to
> 
>   if match_result != nil and match_result != false
> 
> ?

No, not at all.  :)  I'm just whining a bit that =~ can return both nil 
and false.  It's not that big a deal, but this is something that could 
catch unaware people who would follow down the same tracks as I did and 
assume match_result != nil would cover all the bases, when it doesn't.

Robert Klemme wrote:
> Personally I prefer to use /rx/ =~ str over str =~ /rx/ - to me this
> makes it clearer that the RX is the one that does the matching.  Just
> personal taste maybe but I think I also remember that that variant is a
> tad faster.

I didn't even realize this could be done :) (though I see now that it is 
documented, =~ being a synonym for Regexp#match).  If I lived in a 
vacuum for the last 15 years, and Ruby was the first and only 
programming language I ever learned, then I would have done it that way, 
too, from the very start.  :)  Alas, I came from [other languages and 
then] Perl, so it was just a carry over to continue using str =~ 
/regexp/.

FWIW, we still have the same problem:

irb(main):255:0> r1 =~ s
=> 0
irb(main):256:0> r2 =~ s
=> nil
irb(main):257:0> r3 =~ s
=> false

I've taken note that you say that r =~ s is faster.  I (or someone else) 
will have to do some benchmarking to see whether that's really true, and 
how much speed gain can be had.  Diakonos suffers when you use large and 
many regexps for syntax highlighting, so I'd be interested in anything 
that can speed that up.

Pistos

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