instance_evalをつかって加算器をつくってみた。

Accumulator.rb

   Accumulator

  attr_reader :result

  def initialize
    @result = 0
  end
  
  def add(a, b)
    return @result += a + b
  end

  def sub(a, b)
    return @result += a - b
  end

  def times(a, b)
    return @result += a * b
  end

  def div(a, b)
    return @result += a / b
  end

  def mod(a, b)
    return @result += a % b
  end

  def calc(&proc)
    instance_eval(&proc)
  end
  
end

main.rb

a = Accumulator.new

a.calc do
  add(1, 1)
  sub(0, 2)
  times(4, 4)
  div(4, 4)
  mod(7, 3)

  puts result
end