From: Brian Candler <b.candler@...>
Date: 2009-04-30T16:07:53+09:00
Subject: Re: Random Access using IO#pos in code blocks

Robert Klemme wrote:
> String#scan is likely faster than manually matching portions with
> #match.  In both versions of Ruby you can do this to get the
> /character/ offset:
> 
> irb(main):001:0> s=%{foo bar baz}
> => "foo bar baz"
> irb(main):002:0> s.scan(/\w+/) { p $`.length }
> 0
> 4
> 8
> => "foo bar baz"

Well, my guess is that would be *less* efficient for large paragraphs, 
since $` forces allocation of a new string containing all the text from 
the start to the current point. But that reminds me, there is a global 
variable containing a MatchData object: $~

So you can write:

irb(main):001:0> s=%{foo bar baz}
=> "foo bar baz"
irb(main):002:0> s.scan(/\w+/) { p $~.begin(0) }
0
4
8
=> "foo bar baz"

Regards,

Brian.
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