author | hoelzl |
Wed, 02 Apr 2014 18:35:01 +0200 | |
changeset 56369 | 2704ca85be98 |
parent 52537 | 4b5941730bd8 |
child 56685 | 535d59d4ed12 |
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 } }