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

Question

《The scheme programming language》4th:

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

Answer 1

Do you mean

val count: () => Int = {
//def count(): Int
  var next = 0
  () => {
    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