From: Robert Klemme <bob.news@...>
Date: 2004-08-19T17:15:54+09:00
Subject: Re: Regexp scanning with MatchData (Re: multiple regexp matches)


"Austin Ziegler" <halostatue@gmail.com> schrieb im Newsbeitrag
news:9e7db911040818075512cd5a01@mail.gmail.com...
> On Wed, 18 Aug 2004 19:31:01 +0900, Robert Klemme <bob.news@gmx.net>
wrote:
> > "Austin Ziegler" <halostatue@gmail.com> schrieb im Newsbeitrag
> > news:9e7db91104081713254f2eb39e@mail.gmail.com...
> >> str = '<span id="1"> <span> ...</span> </span> '
> >> re = /(<(\/?)span> )/i
> >>
> >> str.scan(re)
> >> # => [["<span> ", ""], ["</span> ", "/"], ["</span> ", "/"]]
> >>
> >> matches = []
> >> str.scan(re) do
> >>   matches << Regexp.last_match
> >> end
> >>
> >> matches.each do |match|
> >>   match.captures.each_with_index do |capture, ii|
> >>     soff, eoff = match.offset(ii + 1)
> >>     puts %Q("#{capture}" #{soff} .. #{eoff})
> >>   end
> >> end
> > While that works, isn't it ridiculous that one has to resort to a
> > class method ("Regexp.last_match")? I mean, there should rather be
> > something like
> >
> > /o/.each( "foo" ) do |md|
> >   # md is MatchData
> > end
>
> There's a simple solution, and I'll probably open an RCR about this
> if others agree with it. String#scan, #sub, and #gsub should yield
> MatchData objects, not Strings. There are probably others, but those
> are the ones that come to mind. This *will* break some code,
> unfortunately, but that can be mitigated by adding #to_str. IMO,
> this will make #gsub much easier to deal with, as you won't have to
> resort to either Regexp.last_match or $[0-9] variables to be able to
> work with captures. My Regexp.last_match call only presumes that
> Regexp.last_match is actually threadsafe, whereas we know that the
> ugly Perlish $ variables are threadsafe. I think this is an
> acceptable level of incompatibility because of the use of #to_str
> and the amount of flexibility that would be gained. As far as I
> know, it wouldn't require *that* big a change, because for
> Regexp.last_match to work, there must still be a MatchData object
> *somewhere*.
>
> What do you think?

I like the functionality very much, but I'd prefer to *not* change the
behavior of String#scan, #sub, and #gsub.  I'd rather have Regexp#scan(str,
&block), Regexp#sub(str, replace=nil, &block) and Regexp#gsub(str,
replace=nil, &block) that yield MatchData if there is a block.  There might
be other names but since the behavior is quite similar to those methods in
String these names are propably good.  The only drawback I can see is that
they might cause confusion ("Which were the ones that yielded MatchData?"),
but IMHO people can cope with this - especially since old behavior does not
change.  (Personally I would find it easy to remember that Regexp <->
MatchData and String <-> String or Array of String.)

Kind regards

    robert