class Calc
	attr_reader :sum
 
  def initialize
  	@operation = nil
  	@sum = 0
  end
 
  def plus
  	@operation = ->(a,b){ a + b }
  	self
  end
 
  def minus
  	@operation = ->(a,b){ a - b }
  	self
  end
 
  def times
  	@operation = ->(a,b){ a * b }
  	self
  end
 
  def divided_by
  	@operation = ->(a,b){ a.fdiv(b) }
  	self
  end
 
  def one
  	operate(1)
  	self
  end
 
  def two
  	operate(2)
  	self
  end
 
  def three
  	operate(3)
  	self
  end
 
  def to_s
  	@sum
  end
 
  def inspect
  	@sum
  end
 
  private
 
  def operate(value)
  	if @operation
      @sum = @operation.(@sum, value)
  	  @operation = nil
  	else
  	  @sum = value
  	 end
  end
end
 
p Calc.new.one.plus.two
p Calc.new.one.minus.two.divided_by.three

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