arrow-fx-stm/arrow.fx.stm/STM/update

update

open fun <K, V> TMap<K, V>.update(k: K, fn: (V) -> V)

Update a value at a key if it exists.

import arrow.fx.stm.TMap
import arrow.fx.stm.atomically

suspend fun main() {
  //sampleStart
  val tmap = TMap.new<Int, String>()
  val result = atomically {
    tmap[2] = "Hello"
    tmap.update(2) { it.reversed() }
    tmap[2]
  }
  //sampleEnd
  println("Result $result")
}