author | bulwahn |
Thu, 07 Jul 2011 23:33:14 +0200 | |
changeset 43704 | 47b0be18ccbe |
parent 43660 | bfc0bb115fa1 |
child 45243 | 27466646a7a3 |
permissions | -rw-r--r-- |
/* Title: Pure/Concurrent/counter.scala Author: Makarius Synchronized counter for unique identifiers < 0. NB: ML ticks forwards, JVM ticks backwards. */ package isabelle object Counter { type ID = Long } class Counter { private var count: Counter.ID = 0 def apply(): Counter.ID = synchronized { require(count > java.lang.Long.MIN_VALUE) count -= 1 count } }