author | wenzelm |
Wed, 12 Mar 2025 11:39:00 +0100 | |
changeset 82265 | 4b875a4c83b0 |
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;