author | blanchet |
Wed, 24 Sep 2014 15:45:55 +0200 | |
changeset 58425 | 246985c6b20b |
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 }