scala的apply方法

scala中的 apply 方法有着不同的含义, 对于函数来说该方法意味着调用function本身, 以下说明摘自Programming in Scala, 3rd Edition

Every function value is an instance of some class that extends one of several FunctionN traits in package scala, such as Function0 for functions with no parameters, Function1 for functions with one parameter, and so on. Each FunctionN trait has an apply method used to invoke the function.

在Scala语言中, 函数也是对象, 每一个对象都是scala.FunctionN(1-22)的实例, 其中N是函数参数的数量, 例如我们定义一个函数并复制给一个变量:

scala> val f = (x: Int) => x + 1
f: Int => Int = <function1>