Jot it down

Usage scenarios of "=>" in scala

I have always been confused about the use of "=>" in scala, and I don't know what it means. Today, its usage scenarios are listed as follows, and I hope to discuss them together.

1. Indicates the return type of the function (Function Type)

    scala> def double(x: Int): Int = x*2
    double: (x: Int)Int
    //定义一个函数变量:	
    scala> var x : (Int) => Int = double
    x: Int => Int = <function1>
    //调用
    scala> x(2)
    res1: Int = 4
   

The type of function double is (x: Int) => Int or Int => Int. The left side is the parameter type, and the right side is the method return value type.
Note:  When the function has only one parameter, the parentheses enclosing the function parameters in the function type can be omitted.

1. Anonymous function

    //通过匿名函数定义一个函数变量xx
    scala> var xx = (x: Int) => x + 1
    xx: Int => Int = <function1>
    //给一个高阶函数，传递一个函数：
    scala> val newList = List(1,2,3).map { (x: Int) => x * 2 }
    newList: List[Int] = List(2, 4, 6)
   

Anonymous function definition, the left side is the parameter, the right side is the function implementation body (x: Int)=>{}