From: Zach Dennis <zdennis@...>
Date: 2004-08-18T05:52:34+09:00
Subject: Re: multiple regexp matches

Ah...thanks for the clarification David. I was mistaken.

Sorry for the confusion Kevin.

Zach

David A. Black wrote:

>Hi --
>
>On Wed, 18 Aug 2004, Zach Dennis wrote:
>
>  
>
>>According to rdoc you are mistaken.
>>
>>I also think you are mistaken:
>>
>>#!/usr/bin/ruby
>>t = "This is my 1 text"
>>
>>re = /([^\s]*\s).*(\d)(\s.)/
>>md = re.match( t );
>>puts md.offset(0);
>>puts ""
>>puts md.offset( 1 );
>>puts ""
>>puts md.offset( 2 );
>>puts ""
>>puts md.offset( 3 );
>>
>>
>>It returns the correct offsets of the matches. offset(0) being the whole 
>>regex, offset(1) does the first subexpression, offset(2) does the second 
>>subexpression. It works.
>>    
>>
>
>The problem is that Kevin wanted to scan a string more than once with
>the same regex:
>
>  str = "abc abc abc"
>  re = /(\w+)/    # not /(\w+) (\w+) (\w+)/
>
>re will scan against str three times.  The difficulty is getting hold
>of the offsets of all the matches from all three times, in relation to
>the total length of the string.  
>
>Someone will probably post a simple or elegant solution; in the
>meantime, here's mine:
>
>  def find_offsets(str,re)
>    offsets = []
>    first = 0
>    of = [0,0]
>
>    loop do
>      break unless m = re.match(str[first..-1])
>      break if m.captures.empty?
>      m.captures.each_with_index do |c,i|
>	of = m.offset(i+1)
>	res = [c, [of[0]+first, of[1]+first ]]
>	yield res if block_given?
>	offsets << res
>      end
>      first += of[0]
>    end
>
>    offsets
>  end
>
>  # Little test:
>
>  str = '<span id="1"> <span>...</span> </span>'
>  re = /(<(\/?)span>)/i
>
>  puts str
>  (str.size/9).times { print "0123456789" }
>  puts; puts
>
>  find_offsets(str,re).each do |capture, (start, stop)|
>    puts "\"#{capture}\" starts at #{start}, ends at #{stop}"
>  end
>
>  # Output:
>  <span id="1"> <span>...</span> </span>
>  0123456789012345678901234567890123456789
>
>  "<span>" starts at 14, ends at 20
>  "" starts at 15, ends at 15
>  "</span>" starts at 23, ends at 30
>  "/" starts at 24, ends at 25
>  "</span>" starts at 31, ends at 38
>  "/" starts at 32, ends at 33
>
>
>David
>
>  
>