Scala是否可以像Scheme的“count”一样在函数中隐藏状态，因为它也有闭包？

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英文:

Can scala hide state in function like scheme's "count" since it have closure too?

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！

英文:

《The scheme programming language》4th:

  1. (define count
  2.  (let ([next 0])
  3.   (lambda ()
  4.    (let ([v next])
  5.     (set! next (+ next 1))
  6.     v))))

it hide state in the count using the closure,aovid the “global variable”。It seems scala support closure too,so how to do this in scala?Thanks!

答案1

得分: 2

Sure, here are the translated code snippets:

Scala Code:

  1. 你是指
  3. ```scala
  4. val count: () => Int = {
  5. //def count(): Int
  6.   var next = 0
  7.   () => {
  8.     val v = next
  9.     next += 1
  10.     v
  11.   }
  12. }

吗？

  2. Functional Programming Style:
  3. ```scala
  4. FP风格的话会是
  5. ```scala
  6. def count(): Int = {
  7.   def loop(next: Int, v: Int): Int = v
  8.   val next = 0
  9.   loop(next + 1, next)
  10. }
  2. Please note that the code is presented in a translated form, as requested.
  4. <details>
  5. <summary>英文:</summary>
  7. Do you mean
  9. ```scala
  10. val count: () =&gt; Int = {
  11. //def count(): Int
  12.   var next = 0
  13.   () =&gt; {
  14.     val v = next
  15.     next += 1
  16.     v
  17.   }
  18. }

?

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

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

FP style would be

  1. def count(): Int = {
  2.   def loop(next: Int, v: Int): Int = v
  3.   val next = 0
  4.   loop(next + 1, next)
  5. }

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

huangapple
  • 本文由 发表于 2023年4月17日 15:33:51
  • 转载请务必保留本文链接：https://go.coder-hub.com/76032684.html
  • scala
  • scheme
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