Functional way to mutate state inside higher order functions scala

Question

Consider the following code,

 1 var ip = ArrayBuffer[String]()
 2 ip += "1"
 3 println(ip)
 4 ip.clear()
 5 (1 to 10).foreach(ip += ("1"))
 6 println(ip)

Here in line no: 5 using variable ip inside higher order function results in exception. I do know using var is not advisable but I want to know how to use vars inside higher order functions. Or is there an alternative to mange state.

If you want to go the mutable route, just use a for loop: `for (_ <- 1 to 10) ip += "1"` — Lasf, Nov 12 '18 at 16:15

Terry Dactyl · Accepted Answer · 2018-11-12T16:34:03.717

3

The following works:

(1 to 10).foreach(_ => ip += "1")

foldLeft is more functional and you can dispense with mutable state:

(1 to 10).foldLeft(List.empty[String]){
  case (acc, _) => "1" :: acc
}

Output:

List[String] = List(1, 1, 1, 1, 1, 1, 1, 1, 1, 1)

edited Nov 12 '18 at 16:34

answered Nov 12 '18 at 16:28

Terry Dactyl

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https://stackoverflow.com/questions/38734007/behavior-of-scala-fold-in-parallel-collections – Terry Dactyl Nov 12 '18 at 17:05

Functional way to mutate state inside higher order functions scala

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