Scala無狀態函數

Question

我在做什麼錯？舉例來說，這應該返回10：

{ val (get, set) = getAndSet (5); set (10); get() } 

---

val getAndSet : Int => (() => Int, Int => Unit) = { 
var s : Int = 0 
val get :() => Int =() => { 
    val z = s; 
    s = s + 1; 
    z 
} 
val set : Int => Unit = (x:Int) => { 
    s = x 
} 
x => (get, set) 
} 

Answer 1

夫婦的錯誤：

• n不存在，則可能意味着s。
• 最後一行應該是x => (get, set)，儘管您沒有以任何方式使用x。

這裏是你的代碼的至少修改過的版本。由於你沒有使用x的作品

val getAndSet: Int => (() => Int, Int => Unit) = { 
    var s: Int = 0 
    val get :() => Int =() => { 
    val z = s; 
    s = s + 1; 
    z 
    } 
    val set : Int => Unit = (x:Int) => { 
    s = x 
    } 
    x => (get, set) 
} 

，則可以選擇做

val getAndSet: Int => (() => Int, Int => Unit) = _ => { 
    var s: Int = 0 
    val get :() => Int =() => { 
    val z = s; 
    s = s + 1; 
    z 
    } 
    val set : Int => Unit = (x:Int) => { 
    s = x 
    } 
    (get, set) 
}