* These combinators only make sense if the operator (function or predicate) applied to the list of operands takes considerable time. The overhead of scheduling is significantly higher than just traversing the list of operands sequentially.
* The order of operator application is non-deterministic. Watch out for operators that have side-effects or raise exceptions!
*)
signature PAR_LIST = sig valmap': {name: string, sequential: bool} -> ('a -> 'b) -> 'a list -> 'b list val map_independent: ('a -> 'b) -> 'a list -> 'b list valmap: ('a -> 'b) -> 'a list -> 'b list val get_some: ('a -> 'b option) -> 'a list -> 'b option val find_some: ('a -> bool) -> 'a list -> 'a option valexists: ('a -> bool) -> 'a list -> bool val forall: ('a -> bool) -> 'a list -> bool end;
structure Par_List: PAR_LIST = struct
fun managed_results {name, sequential} f xs = if sequential orelse not (Future.relevant xs) thenmap (Exn.capture f) xs else
Future.forked_results
{name = if name = ""then"Par_List.map"else name, deps = []}
(map (fn x => fn () => f x) xs);
funmap' params f xs = Par_Exn.release_first (managed_results params f xs); funmap f = map' {name = "", sequential = false} f; fun map_independent f = map (Exn.result f) #> Par_Exn.release_all;
fun get_some f xs = let
exception FOUND of'b; val results =
managed_results {name = "Par_List.get_some", sequential = false}
(fn x => (case f x of NONE => () | SOME y => raise FOUND y)) xs; in
(case get_first (fn Exn.Exn (FOUND res) => SOME res | _ => NONE) results of
NONE => (Par_Exn.release_first results; NONE)
| some => some) end;
fun find_some P = get_some (fn x => if P x then SOME x else NONE);
funexists P = is_some o find_some P; fun forall P = not o exists (not o P);
end;
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