scala闭包与柯里化

闭包

var factor = 3
val multiplier = (i:Int) => i * factor //返回值依赖外部的变量factor
//"="号右边是作为fun的函数体的函数，它的返回值取决于fun的局部变量
def fun(x: Int) = (y: Int) => x * y //fun: fun[](val x: Int) => Int => Int
//上边可以写成柯里化形式
def fun(x: Int)(y: Int) = x * y //fun: fun[](val x: Int)(val y: Int) => Int
fun(2)(3) //6

柯里化(curring)

//原始多参数
def sum(x:Int,y:Int) = x + y

//变换成接收一个参数
def first(x:Int) = (y:Int) => x + y //first: first[](val x: Int) => Int => Int

//调用方式1
val second=first(1) //second: Int => Int = <function1>
second(2) //res0: Int = 3
//调用方式2
first(1)(2)

//方式2的调用比较简洁，所以**方法**也可以定义成与此一致的方式
def sum(x:Int)(y:Int) = x + y //sum: sum[](val x: Int)(val y: Int) => Int
sum(1)(2) //res0: Int = 3