(UNNAMED) generator expression like Python in Ruby

gistfile1.rb

#!/usr/bin/env ruby
# -*- coding: utf-8 -*-
$VERBOSE = true
=begin
Maybe usable as generator expression in Python
requires ruby1.9 or facets ( >= 2.9.1 )
=end

if RUBY_VERSION < '1.9'
  require 'rubygems'
  require 'facets/enumerator'
end

module Enumerable
  def _unnamed_enum_compact_map &blk
    Enumerator.new{|y|
      self.each{|e|
        res = blk.call e
        y.yield res unless res.nil?
      }
    }
  end
end

if __FILE__ == $PROGRAM_NAME
                                               #mapper    #predicate
  enum = (1..100)._unnamed_enum_compact_map{|x| x**2   if x.odd?    }
  p enum.next #=> 1
  p enum.next #=> 9
  p enum.take( 5 ) #=> [1, 9, 25, 49, 81]

  #case maybe that doesn't work as you expect.
  #if an item is mapped into nil by the mapper,
  #it's omitted even the predicate returns true.
  enum = %w/ruby perl python php javascript/._unnamed_enum_compact_map{|s|
    #mapper      #predicate
    s =~ /p/ if s.length > 3
  }
  p enum.next #=> 0 ( *p*erl: not nil, the value of '"ruby" =~ /p/' )
  p enum.next #=> 0 ( *p*yhon )
  #'php' was omitted because '"php".length > 3' is false
  p enum.next #=> 8 ( javascri*p*t )
end