问题

《The scheme programming language》4th:

(define count
(let ([next 0])
(lambda ()
(let ([v next])
(set! next (+ next 1))
v))))

它使用闭包在count中隐藏状态，避免了“全局变量”。Scala似乎也支持闭包，那么在Scala中如何做到这一点呢？谢谢！

(define count
 (let ([next 0])
  (lambda ()
   (let ([v next])
    (set! next (+ next 1))
    v))))

答案1

得分: 2

Sure, here are the translated code snippets:

Scala Code:

你是指

```scala
val count: () => Int = {
//def count(): Int
  var next = 0
  () => {
    val v = next
    next += 1
    v
  }
}

吗？

Functional Programming Style:
```scala
FP风格的话会是
```scala
def count(): Int = {
  def loop(next: Int, v: Int): Int = v
  val next = 0
  loop(next + 1, next)
}

Please note that the code is presented in a translated form, as requested.

<details>
<summary>英文:</summary>

Do you mean

```scala
val count: () =&gt; Int = {
//def count(): Int
  var next = 0
  () =&gt; {
    val v = next
    next += 1
    v
  }
}

?

https://scastie.scala-lang.org/DmytroMitin/cFKKUqAjQaeFuBNos1OIvw

https://onecompiler.com/racket/3z5whfdkx

FP style would be

def count(): Int = {
  def loop(next: Int, v: Int): Int = v
  val next = 0
  loop(next + 1, next)
}

https://scastie.scala-lang.org/DmytroMitin/cFKKUqAjQaeFuBNos1OIvw/1