Swift嵌套函数

    可以将函数定义在其他函数中，成为嵌套函数

    func caculate(opr : String) ->(Int,Int) ->Int {

                func add(a : Int, b : Int) -> Int {

                    return a + b

}

                func sub(a : Int,b : Int) -> Int {

                    return a - b

}

                var result : (Int,Int) -> Int

                switch opr{

                    case "+":

                        result = add

                    case "-":

                        result = sub

                    default: 

                        result = add

}

                  return result

}

        let f1 :(Int,Int)->Int = caculate("+")

         println(f1(1,2))

        let f2 :(Int,Int)->Int = caculate("-")

            println(f2(10,2))