author | wenzelm |
Mon, 28 Nov 2011 22:18:19 +0100 | |
changeset 45667 | 546d78f0d81f |
parent 45243 | 27466646a7a3 |
child 45673 | cd41e3903fbf |
permissions | -rw-r--r-- |
/* Title: Pure/Concurrent/counter.scala Module: Library 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 } class Counter private { private var count: Counter.ID = 0 def apply(): Counter.ID = synchronized { require(count > java.lang.Long.MIN_VALUE) count -= 1 count } }