Calculators

stateful_calc.rb

class StatefulCalculator
  def initialize
    @total = 0
  end
 
  def add(x)
    @total += x
    self
  end
  
  def sub(x)
    @total -= x
    self
  end
  
  def mul(x)
    @total *= x
    self
  end
  
  def div(denom)
    @total /= denom
    self
  end
  
  def result
    @total
  end
end

# stateful
c = StatefulCalculator.new
assert_equal 3, c.add(1).add(5).div(2).result()

stateless_calc.rb

module StatelessCalculator
  def add(x, y)
    x + y
  end
  
  def sub(x, y)
    x - y
  end
  
  def mul(x, y)
    x * y
  end
  
  def div(num, denom)
    num / denom
  end
  
  module_function :add, :sub, :mul, :div
end

# stateless
c = StatelessCalculator
assert_equal 3, c.div(c.add(1, 5), 2)