From: Kevin Howe <khowe@...>
Date: 2004-08-18T06:46:00+09:00
Subject: Re: multiple regexp matches

Awesome that works great thank you. I have to wonder why Ruby doesn't have
this built in, it's simple enough to add a method that returns a list of
MatchData objects as follows:

class MultiRegexp < Regexp
    def matches(str)
        str.scan(self) do
          yield Regexp.last_match
        end
    end
end

str = '<span id="1"> <span>...</span> </span>'
re = MultiRegexp.new('(<(\/?)span>)', true)
re.matches(str) { |i|
    capture = i.captures[0]
    start,stop = i.offset(0)
    puts "\"#{capture}\" starts at #{start}, ends at #{stop}"
}

An even nicer alternative would be to add a Regexp::MULTIMATCH constant:

str = '<span id="1"> <span>...</span> </span>'
re = Regexp.new('(<(\/?)span>)', Regexp::MULTIMATCH)
matches = re.match(str)

Just a thought :)


"Zach Dennis" <zdennis@mktec.com> wrote in message
news:41226FE4.4060108@mktec.com...
> 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
> >
> >
> >
>
>
>