modular-restriction

class Array
  def sum
    inject(0) {|total,n| total + n }
  end
end

puts Array.new([1,2,3,4]).sum
puts [1,2,3,4].sum

module StickyFingaz
  class Array < ::Array
    def sum
      # I always keep one for myself
      inject(0) {|total,n| total + n } - 1
    end
  end
  puts Array.new([1,2,3,4]).sum
  puts [1,2,3,4].sum
end

module LazyFool
  class Array < ::Array
    def sum
      # You can teach a man to fish...
      lambda { inject(0) {|total,n| total + n } }
    end
  end
  
  puts Array.new([1,2,3,4]).sum
  puts [1,2,3,4].sum
end