Ruby Array's subtract method which subtracts the values of the elements not the elements themselves

ruby array #subtract

# Ruby Array's "-" (minus) method removes elements from the receiver which exist in the parameter Array

[5, 6, 1] - [2, 3, 5]

# => [6, 1]

# this #subtract method will subtract the value of the parameter Array from the value of the receiver Array, defined by the actual index.
# type mismatch, Nil, and different Array length are not handled

class Array
  def subtract(other_ary)
    self.map.with_index {|v, i| v-other_ary[i]}
  end  
end