author | wenzelm |
Mon, 27 Feb 2012 17:13:25 +0100 | |
changeset 46712 | 8650d9a95736 |
parent 45673 | cd41e3903fbf |
child 52537 | 4b5941730bd8 |
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 apply(): 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 } }