gistfile1.rb

if RUBY_VERSION < '1.8.7'
 class Array
   alias original_index index
   def index *args

     if args.length > 0
       return original_index(*args)
     else
        pos = nil
        each_with_index do |element, i|
          if yield(element)
            return i
          end
        end
       return nil
     end
    end
  end
end