From: Dave Thomas <Dave@...>
Date: 2000-09-02T18:32:51+09:00
Subject: [ruby-talk:4743] Re: Possible regex bug?

"Conrad Schneiker" <schneiker@jump.net> writes:

> I guess I didn't read the docs carefully enough. The reason I didn't mention
> this was that I had presumed that Ruby's regular expressions were greedy by
> default, unless you explicitly indicated otherwise, just as I thought Perl's
> were. (I don't have my manuals and docs with me, so I haven't checked this,
> and could be wrong about that too. However, if Ruby and Perl do differ in
> this regard, is there a good reason for this?)


Perl:

     my @a = split(/,? */, "1.2, 3.4, 5.6/");
     print join(":", @a), "\n";

  ->
     1:.:2:3:.:4:5:.:6:/


Both Perl and Ruby' regular expressions _are_ greedy by
default. However, they're also lazy: they stop once they find the
first match.

Think of this case:

    "ooXXooXXXXXXXXX" =~ /X+/

You'd expect it to match the first set of X's. It doesn't say
"hmm.. I've found two X's, but maybe there's a string of 10 coming up, 
so I'll keep on looking."

It's exactly the same with these zero-length-matching patterns. _If_
is happens to come across a ',' followed by a space, it will greedily
eat it up. If it doesn't, and the match succeeds anyway, it's happy.


So, in this respect, Perl and Ruby do the same thing.


Regards


Dave