ruby make chain method
class SimpleMath
  def initialize
    @result = 0
  end
  #1 add function
  def add(val)
    @result += val
    self
  end
  #2 Subtract function
  def subtract(val)
    @result -= val
    self
  end
  def to_s
    @result
  end
end
newNumber = SimpleMath.new
p newNumber.add(2).add(2).subtract(1)
