calculator.rb

class Calculator
  def doubler(number)
    number * 2
  end
  
  def runner(number)
    yield(number)
  end
  
  def input(number, operation)
    runner(number, &method(operation))
  end
end

# pry(main)> calculator = Calculator.new
# => #<Calculator:0x007fc3432884e0>
# pry(main)> calculator.input(6, :doubler)
# => 12