Monkey patch to provide Cartesian product of enumerables in ruby.

enumerable_product.rb

module Enumerable

  def self.product(first, *rest)
    return enum_for(__method__, first, *rest) unless block_given?
    if rest.empty?
      first.each do |v0|
        yield [v0]
      end
    else
      enum_for_rest = product(*rest)
      first.each do |v0|
        enum_for_rest.each do |vs|
          yield [v0, *vs]
        end
      end
    end
    nil
  end

  def enum_product(first, *rest, &block)
    Enumerable.product(self, first, *rest, &block)
  end

end