From: Robert Klemme <shortcutter@...>
Date: 2008-12-07T21:23:44+09:00
Subject: Re: Proximity searches in Ruby


I played a bit around and came up with a more involved version which 
works with arbitrary numbers of words but still fits into a few lines of 
code.  Another advantage is that it identifies character positions with 
matches in the text.  Note that this allows a maximum distance between 
the first and the last word of (distance * (words - 1)).  It could be 
modified pretty easily (with an additional method in Array) to keep 
*all* words within distance.

Have fun

	robert


#!/bin/env ruby

# search words in arbitrary order where
# pairs of words have a max distance between
# them
ProximitySearchData = Struct.new :word, :wpos, :spos

def proximity_search(text, distance, *words)
   sdata = words.map {|w| ProximitySearchData.new w.downcase}

   wpos = 0

   text.scan %r{\w+}i do |match|
     match = match.downcase
     pos = $`.length

     sdata.each do |sd|
       if sd.word == match
	sd.spos = pos
	sd.wpos = wpos
	break :change
       end
     end == :change and
     sdata.all? {|sd| sd.wpos} and
     sdata.
       sort_by {|sd| sd.wpos}.
       each_cons(2).
       all? {|sd1,sd2| sd2.wpos - sd1.wpos <= distance} and
     yield *sdata.map {|sd| sd.spos}

     wpos += 1
   end
end

text = <<EOT
Hello world, how are you today? I said "Hello"
to the other guy but he would not answer although
all the world could hear me.
EOT

proximity_search text, 3, "hello", "World" do |a,b|
   printf "Found at char positions %3d and %3d\n", a, b
end