author | wenzelm |
Sun, 28 Feb 2016 21:20:51 +0100 | |
changeset 62459 | 7a5d88dd8cc9 |
parent 56685 | 535d59d4ed12 |
child 64370 | 865b39487b5d |
permissions | -rw-r--r-- |
/* Title: Pure/Concurrent/counter.scala Module: PIDE 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 > java.lang.Long.MIN_VALUE) count -= 1 count } override def toString: String = count.toString }