author | desharna |
Fri, 11 Jul 2025 10:12:01 +0200 | |
changeset 82825 | 5e9c9f2c2cd8 |
parent 68804 | cbde6e3b132b |
permissions | -rw-r--r-- |
(* Title: Pure/Concurrent/counter.ML Author: Makarius Synchronized counter for unique identifiers > 0. NB: ML ticks forwards, JVM ticks backwards. *) signature COUNTER = sig val make: unit -> unit -> int end; structure Counter: COUNTER = struct fun make () = let val counter = Synchronized.var "counter" 0; fun next () = Synchronized.change_result counter (fn i => let val k = i + 1; val n = if Thread_Data.is_virtual then 2 * k + 1 else 2 * k; in (n, k) end); in next end; end;