From: "David A. Black" <dblack@...>
Date: 2009-01-25T04:58:52+09:00
Subject: Re: how to find the position of each match within a string

Hi --

On Sun, 25 Jan 2009, Li Chen wrote:

>
> Hi all,
>
> I have  a small script to find a match. If a match is found I need to
> print its position within the string. I try the String#index but it only
> returns the first match. Any idea?
>
> Thanks,
>
> Li
>
> C:\Documents and Settings\chen73\My Documents\Ruby\bin>irb
> irb(main):001:0> "ello-hello".scan('e') do |match|
> irb(main):002:1*     p "ello-hello".index(match)
> irb(main):003:1> end
> 0
> 0
> => "ello-hello"

You can examine the $~ global MatchData object, in a couple of ways:

irb(main):003:0> "ello-hello".scan('e') do |match|
irb(main):004:1*   p $~.pre_match.size
irb(main):005:1> end
0
6
=> "ello-hello"
irb(main):006:0> "ello-hello".scan('e') do |match|
irb(main):007:1*   p $~.offset(0)[0]
irb(main):008:1> end
0
6
=> "ello-hello

(And there may be more I'm not thinking of.)


David

-- 
David A. Black / Ruby Power and Light, LLC
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