author | wenzelm |
Sun, 02 Jul 2023 19:05:59 +0200 | |
changeset 78243 | 0e221a8128e4 |
parent 75393 | 87ebf5a50283 |
permissions | -rw-r--r-- |
/* Title: Pure/Concurrent/counter.scala Author: Makarius Synchronized counter for unique identifiers < 0. NB: ML ticks forwards, JVM ticks backwards. */ package isabelle object Counter { type ID = Long def make(): Counter = new Counter } final class Counter private { private var count: Counter.ID = 0 def apply(): Counter.ID = synchronized { require(count > Long.MinValue, "counter overflow") count -= 1 count } override def toString: String = count.toString }