src/Pure/par_tactical.ML

vacuous fact `TERM x`;

(*  Title:      Pure/par_tactical.ML
    Author:     Makarius

Parallel tacticals.
*)

signature BASIC_PAR_TACTICAL =
sig
  val PARALLEL_CHOICE: tactic list -> tactic
  val PARALLEL_GOALS: tactic -> tactic
  val PARALLEL_ALLGOALS: (int -> tactic) -> tactic
end;

signature PAR_TACTICAL =
sig
  include BASIC_PAR_TACTICAL
end;

structure Par_Tactical: PAR_TACTICAL =
struct

(* parallel choice of single results *)

fun PARALLEL_CHOICE tacs st =
  (case Par_List.get_some (fn tac => SINGLE tac st) tacs of
    NONE => Seq.empty
  | SOME st' => Seq.single st');


(* parallel refinement of non-schematic goal by single results *)

local

exception FAILED of unit;

fun retrofit st' =
  rotate_prems ~1 #>
  Thm.bicompose NONE {flatten = false, match = false, incremented = false}
      (false, Goal.conclude st', Thm.nprems_of st') 1;

in

fun PARALLEL_GOALS tac st =
  if not (Multithreading.enabled ()) orelse Thm.nprems_of st <= 1 then DETERM tac st
  else
    let val subgoals = map (Thm.adjust_maxidx_cterm ~1) (Drule.strip_imp_prems (Thm.cprop_of st)) in
      if exists (fn sg => Thm.maxidx_of_cterm sg >= 0) subgoals then DETERM tac st
      else
        let
          fun try_tac g =
            (case SINGLE tac g of
              NONE => raise FAILED ()
            | SOME g' => g');
          val results = Par_List.map (try_tac o Goal.init) subgoals;
        in EVERY (map retrofit (rev results)) st end
        handle FAILED () => Seq.empty
    end;

end;

val PARALLEL_ALLGOALS = PARALLEL_GOALS o ALLGOALS;

end;

structure Basic_Par_Tactical: BASIC_PAR_TACTICAL = Par_Tactical;
open Basic_Par_Tactical;