ruby [계산기]

class Calculation
  # [1] ---------------------------------------------
  def initialize()
    @left_value  = 0
    @right_value = 0
  end
  # [2] ---------------------------------------------
  def dataInsert_method()
    print("left_value input:    ")
    @left_value = gets.chomp().to_i # very important
    print("right_value input:    ")
    @right_value = gets.chomp().to_i # very important
  end
  # [3] ---------------------------------------------
  def summation_method()
    printf("%d + %d = %d \n",
           @left_value, @right_value, @left_value + @right_value)
  end
  # [4] ---------------------------------------------
  def subtraction_method()
    printf("%d - %d = %d \n",
           @left_value, @right_value, @left_value - @right_value)
  end
  # [5] ---------------------------------------------
  def multiplication_method()
    printf("%d x %d = %d \n",
          @left_value,  @right_value, @left_value * @right_value)
  end
  # [6] ---------------------------------------------
  def dividen_method()
    printf("%d / %d = %.2f \n",# very important
           @left_value,  @right_value, Float(@left_value) / Float(@right_value))
  end
  # [7] ---------------------------------------------
  def remainder_method()
    printf("%d mod %d = %d \n",# very important
           @left_value,  @right_value, @left_value % @right_value)
  end
end

# ------------------------------main()------------------------------------------
study = Calculation.new # very important
study.dataInsert_method()
study.summation_method()
study.subtraction_method()
study.multiplication_method()
study.dividen_method()
study.remainder_method()