calc1.mirah

interface IOperator do
  def run(x:int, y:int)
    returns int
  end 
end

class Add
  implements IOperator

  def run(x:int, y:int)
    returns int
    
    x + y
  end
end

class Sub
  implements IOperator

  def run(x:int, y:int)
    returns int
    
    x - y
  end
end

class Operators
  def add
    Add.new
  end
  
  def sub
    Sub.new
  end
end

def calculate(op:IOperator)
  op.run(4, 20)
end

ops = Operators.new

puts calculate ops.add

puts calculate ops.sub