(*  Title:      Pure/Isar/toplevel.ML

     Author:     Markus Wenzel, TU Muenchen

 Isabelle/Isar toplevel transactions.

 *)

 signature TOPLEVEL =

 sig

   exception UNDEF

   type state

   val theory_toplevel: theory -> state

   val toplevel: state

   val is_toplevel: state -> bool

   val is_theory: state -> bool

   val is_proof: state -> bool

   val is_skipped_proof: state -> bool

   val level: state -> int

   val presentation_context_of: state -> Proof.context

   val previous_context_of: state -> Proof.context option

   val context_of: state -> Proof.context

   val generic_theory_of: state -> generic_theory

   val theory_of: state -> theory

   val proof_of: state -> Proof.state

   val proof_position_of: state -> int

   val end_theory: Position.T -> state -> theory

   val pretty_context: state -> Pretty.T list

   val pretty_state: state -> Pretty.T list

   val string_of_state: state -> string

   val pretty_abstract: state -> Pretty.T

   type transition

   val empty: transition

   val name_of: transition -> string

   val pos_of: transition -> Position.T

   val type_error: transition -> string

   val name: string -> transition -> transition

   val position: Position.T -> transition -> transition

   val init_theory: (unit -> theory) -> transition -> transition

   val is_init: transition -> bool

   val modify_init: (unit -> theory) -> transition -> transition

   val exit: transition -> transition

   val keep: (state -> unit) -> transition -> transition

   val keep': (bool -> state -> unit) -> transition -> transition

   val keep_proof: (state -> unit) -> transition -> transition

   val ignored: Position.T -> transition

   val is_ignored: transition -> bool

   val malformed: Position.T -> string -> transition

   val generic_theory: (generic_theory -> generic_theory) -> transition -> transition

   val theory': (bool -> theory -> theory) -> transition -> transition

   val theory: (theory -> theory) -> transition -> transition

   val begin_local_theory: bool -> (theory -> local_theory) -> transition -> transition

   val end_local_theory: transition -> transition

   val open_target: (generic_theory -> local_theory) -> transition -> transition

   val close_target: transition -> transition

   val local_theory': (bool * Position.T) option -> (xstring * Position.T) option ->

     (bool -> local_theory -> local_theory) -> transition -> transition

   val local_theory: (bool * Position.T) option -> (xstring * Position.T) option ->

     (local_theory -> local_theory) -> transition -> transition

   val present_local_theory: (xstring * Position.T) option -> (state -> unit) ->

     transition -> transition

   val local_theory_to_proof': (bool * Position.T) option -> (xstring * Position.T) option ->

     (bool -> local_theory -> Proof.state) -> transition -> transition

   val local_theory_to_proof: (bool * Position.T) option -> (xstring * Position.T) option ->

     (local_theory -> Proof.state) -> transition -> transition

   val theory_to_proof: (theory -> Proof.state) -> transition -> transition

   val end_proof: (bool -> Proof.state -> Proof.context) -> transition -> transition

   val forget_proof: bool -> transition -> transition

   val proofs': (bool -> Proof.state -> Proof.state Seq.result Seq.seq) -> transition -> transition

   val proof': (bool -> Proof.state -> Proof.state) -> transition -> transition

   val proofs: (Proof.state -> Proof.state Seq.result Seq.seq) -> transition -> transition

   val proof: (Proof.state -> Proof.state) -> transition -> transition

   val actual_proof: (Proof_Node.T -> Proof_Node.T) -> transition -> transition

   val skip_proof: (unit -> unit) -> transition -> transition

   val skip_proof_open: transition -> transition

   val skip_proof_close: transition -> transition

   val exec_id: Document_ID.exec -> transition -> transition

   val setmp_thread_position: transition -> ('a -> 'b) -> 'a -> 'b

   val add_hook: (transition -> state -> state -> unit) -> unit

   val get_timing: transition -> Time.time

   val put_timing: Time.time -> transition -> transition

   val transition: bool -> transition -> state -> state * (exn * string) option

   val command_errors: bool -> transition -> state -> Runtime.error list * state option

   val command_exception: bool -> transition -> state -> state

   val reset_theory: state -> state option

   val reset_proof: state -> state option

   type result

   val join_results: result -> (transition * state) list

   val element_result: Keyword.keywords -> transition Thy_Syntax.element -> state -> result * state

 end;

 structure Toplevel: TOPLEVEL =

 struct

 (** toplevel state **)

 exception UNDEF = Runtime.UNDEF;

 (* datatype node *)

 datatype node =

   Theory of generic_theory * Proof.context option

     (*theory with presentation context*) |

   Proof of Proof_Node.T * ((Proof.context -> generic_theory) * generic_theory)

     (*proof node, finish, original theory*) |

   Skipped_Proof of int * (generic_theory * generic_theory);

     (*proof depth, resulting theory, original theory*)

 val theory_node = fn Theory (gthy, _) => SOME gthy | _ => NONE;

 val proof_node = fn Proof (prf, _) => SOME prf | _ => NONE;

 val skipped_proof_node = fn Skipped_Proof _ => true | _ => false;

 fun cases_node f _ (Theory (gthy, _)) = f gthy

   | cases_node _ g (Proof (prf, _)) = g (Proof_Node.current prf)

   | cases_node f _ (Skipped_Proof (_, (gthy, _))) = f gthy;

 val context_node = cases_node Context.proof_of Proof.context_of;

 (* datatype state *)

 datatype state = State of node option * node option;  (*current, previous*)

 fun theory_toplevel thy = State (SOME (Theory (Context.Theory thy, NONE)), NONE);

 val toplevel = State (NONE, NONE);

 fun is_toplevel (State (NONE, _)) = true

   | is_toplevel _ = false;

 fun level (State (NONE, _)) = 0

   | level (State (SOME (Theory _), _)) = 0

   | level (State (SOME (Proof (prf, _)), _)) = Proof.level (Proof_Node.current prf)

   | level (State (SOME (Skipped_Proof (d, _)), _)) = d + 1;   (*different notion of proof depth!*)

 fun str_of_state (State (NONE, SOME (Theory (Context.Theory thy, _)))) =

       "at top level, result theory " ^ quote (Context.theory_name thy)

   | str_of_state (State (NONE, _)) = "at top level"

   | str_of_state (State (SOME (Theory (Context.Theory _, _)), _)) = "in theory mode"

   | str_of_state (State (SOME (Theory (Context.Proof _, _)), _)) = "in local theory mode"

   | str_of_state (State (SOME (Proof _), _)) = "in proof mode"

   | str_of_state (State (SOME (Skipped_Proof _), _)) = "in skipped proof mode";

 (* current node *)

 fun node_of (State (NONE, _)) = raise UNDEF

   | node_of (State (SOME node, _)) = node;

 fun is_theory state = not (is_toplevel state) andalso is_some (theory_node (node_of state));

 fun is_proof state = not (is_toplevel state) andalso is_some (proof_node (node_of state));

 fun is_skipped_proof state = not (is_toplevel state) andalso skipped_proof_node (node_of state);

 fun node_case f g state = cases_node f g (node_of state);

 fun presentation_context_of state =

   (case try node_of state of

     SOME (Theory (_, SOME ctxt)) => ctxt

   | SOME node => context_node node

   | NONE => raise UNDEF);

 fun previous_context_of (State (_, NONE)) = NONE

   | previous_context_of (State (_, SOME prev)) = SOME (context_node prev);

 val context_of = node_case Context.proof_of Proof.context_of;

 val generic_theory_of = node_case I (Context.Proof o Proof.context_of);

 val theory_of = node_case Context.theory_of Proof.theory_of;

 val proof_of = node_case (fn _ => error "No proof state") I;

 fun proof_position_of state =

   (case node_of state of

     Proof (prf, _) => Proof_Node.position prf

   | _ => ~1);

 fun end_theory _ (State (NONE, SOME (Theory (Context.Theory thy, _)))) = thy

   | end_theory pos (State (NONE, _)) = error ("Bad theory" ^ Position.here pos)

   | end_theory pos (State (SOME _, _)) = error ("Unfinished theory" ^ Position.here pos);

 (* print state *)

 fun pretty_context state =

   (case try node_of state of

     NONE => []

   | SOME node =>

       let

         val gthy =

           (case node of

             Theory (gthy, _) => gthy

           | Proof (_, (_, gthy)) => gthy

           | Skipped_Proof (_, (gthy, _)) => gthy);

         val lthy = Context.cases (Named_Target.theory_init) I gthy;

       in Local_Theory.pretty lthy end);

 fun pretty_state state =

   (case try node_of state of

     NONE => []

   | SOME (Theory _) => []

   | SOME (Proof (prf, _)) => Proof.pretty_state (Proof_Node.current prf)

   | SOME (Skipped_Proof (d, _)) => [Pretty.str ("skipped proof: depth " ^ string_of_int d)]);

 val string_of_state = pretty_state #> Pretty.chunks #> Pretty.string_of;

 fun pretty_abstract state = Pretty.str ("<Isar " ^ str_of_state state ^ ">");

 val _ = ML_system_pp (fn _ => fn _ => Pretty.to_polyml o pretty_abstract);

 (** toplevel transitions **)

 (* node transactions -- maintaining stable checkpoints *)

 exception FAILURE of state * exn;

 local

 fun reset_presentation (Theory (gthy, _)) = Theory (gthy, NONE)

   | reset_presentation node = node;

 in

 fun apply_transaction f g node =

   let

     val cont_node = reset_presentation node;

     val context = cases_node I (Context.Proof o Proof.context_of) cont_node;

     fun state_error e nd = (State (SOME nd, SOME node), e);

     val (result, err) =

       cont_node

       |> Runtime.controlled_execution (SOME context) f

       |> state_error NONE

       handle exn => state_error (SOME exn) cont_node;

   in

     (case err of

       NONE => tap g result

     | SOME exn => raise FAILURE (result, exn))

   end;

 val exit_transaction =

   apply_transaction

     (fn Theory (Context.Theory thy, _) => Theory (Context.Theory (Theory.end_theory thy), NONE)

       | node => node) (K ())

   #> (fn State (node', _) => State (NONE, node'));

 end;

 (* primitive transitions *)

 datatype trans =

   Init of unit -> theory |               (*init theory*)

   Exit |                                 (*formal exit of theory*)

   Keep of bool -> state -> unit |        (*peek at state*)

   Transaction of (bool -> node -> node) * (state -> unit);  (*node transaction and presentation*)

 local

 fun apply_tr _ (Init f) (State (NONE, _)) =

       State (SOME (Theory (Context.Theory (Runtime.controlled_execution NONE f ()), NONE)), NONE)

   | apply_tr _ Exit (State (SOME (state as Theory (Context.Theory _, _)), _)) =

       exit_transaction state

   | apply_tr int (Keep f) state =

       Runtime.controlled_execution (try generic_theory_of state) (fn x => tap (f int) x) state

   | apply_tr int (Transaction (f, g)) (State (SOME state, _)) =

       apply_transaction (fn x => f int x) g state

   | apply_tr _ _ _ = raise UNDEF;

 fun apply_union _ [] state = raise FAILURE (state, UNDEF)

   | apply_union int (tr :: trs) state =

       apply_union int trs state

         handle Runtime.UNDEF => apply_tr int tr state

           | FAILURE (alt_state, UNDEF) => apply_tr int tr alt_state

           | exn as FAILURE _ => raise exn

           | exn => raise FAILURE (state, exn);

 in

 fun apply_trans int trs state = (apply_union int trs state, NONE)

   handle FAILURE (alt_state, exn) => (alt_state, SOME exn) | exn => (state, SOME exn);

 end;

 (* datatype transition *)

 datatype transition = Transition of

  {name: string,              (*command name*)

   pos: Position.T,           (*source position*)

   timing: Time.time,         (*prescient timing information*)

   trans: trans list};        (*primitive transitions (union)*)

 fun make_transition (name, pos, timing, trans) =

   Transition {name = name, pos = pos, timing = timing, trans = trans};

 fun map_transition f (Transition {name, pos, timing, trans}) =

   make_transition (f (name, pos, timing, trans));

 val empty = make_transition ("", Position.none, Time.zeroTime, []);

 (* diagnostics *)

 fun name_of (Transition {name, ...}) = name;

 fun pos_of (Transition {pos, ...}) = pos;

 fun command_msg msg tr =

   msg ^ "command " ^ quote (Markup.markup Markup.keyword1 (name_of tr)) ^

     Position.here (pos_of tr);

 fun at_command tr = command_msg "At " tr;

 fun type_error tr = command_msg "Bad context for " tr;

 (* modify transitions *)

 fun name name = map_transition (fn (_, pos, timing, trans) =>

   (name, pos, timing, trans));

 fun position pos = map_transition (fn (name, _, timing, trans) =>

   (name, pos, timing, trans));

 fun add_trans tr = map_transition (fn (name, pos, timing, trans) =>

   (name, pos, timing, tr :: trans));

 val reset_trans = map_transition (fn (name, pos, timing, _) =>

   (name, pos, timing, []));

 (* basic transitions *)

 fun init_theory f = add_trans (Init f);

 fun is_init (Transition {trans = [Init _], ...}) = true

   | is_init _ = false;

 fun modify_init f tr = if is_init tr then init_theory f (reset_trans tr) else tr;

 val exit = add_trans Exit;

 val keep' = add_trans o Keep;

 fun present_transaction f g = add_trans (Transaction (f, g));

 fun transaction f = present_transaction f (K ());

 fun keep f = add_trans (Keep (fn _ => f));

 fun keep_proof f =

   keep (fn st =>

     if is_proof st then f st

     else if is_skipped_proof st then ()

     else warning "No proof state");

 fun ignored pos = empty |> name "<ignored>" |> position pos |> keep (fn _ => ());

 fun is_ignored tr = name_of tr = "<ignored>";

 fun malformed pos msg =

   empty |> name "<malformed>" |> position pos |> keep (fn _ => error msg);

 (* theory transitions *)

 fun generic_theory f = transaction (fn _ =>

   (fn Theory (gthy, _) => Theory (f gthy, NONE)

     | _ => raise UNDEF));

 fun theory' f = transaction (fn int =>

   (fn Theory (Context.Theory thy, _) =>

       let val thy' = thy

         |> Sign.new_group

         |> f int

         |> Sign.reset_group;

       in Theory (Context.Theory thy', NONE) end

     | _ => raise UNDEF));

 fun theory f = theory' (K f);

 fun begin_local_theory begin f = transaction (fn _ =>

   (fn Theory (Context.Theory thy, _) =>

         let

           val lthy = f thy;

           val gthy = if begin then Context.Proof lthy else Context.Theory (Named_Target.exit lthy);

           val _ =

             (case Local_Theory.pretty lthy of

               [] => ()

             | prts => Output.state (Pretty.string_of (Pretty.chunks prts)));

         in Theory (gthy, SOME lthy) end

     | _ => raise UNDEF));

 val end_local_theory = transaction (fn _ =>

   (fn Theory (Context.Proof lthy, _) => Theory (Context.Theory (Named_Target.exit lthy), SOME lthy)

     | _ => raise UNDEF));

 fun open_target f = transaction (fn _ =>

   (fn Theory (gthy, _) =>

         let val lthy = f gthy

         in Theory (Context.Proof lthy, SOME lthy) end

     | _ => raise UNDEF));

 val close_target = transaction (fn _ =>

   (fn Theory (Context.Proof lthy, _) =>

         (case try Local_Theory.close_target lthy of

           SOME ctxt' =>

             let

               val gthy' =

                 if can Local_Theory.assert ctxt'

                 then Context.Proof ctxt'

                 else Context.Theory (Proof_Context.theory_of ctxt');

             in Theory (gthy', SOME lthy) end

         | NONE => raise UNDEF)

     | _ => raise UNDEF));

 fun restricted_context (SOME (strict, scope)) =

       Proof_Context.map_naming (Name_Space.restricted strict scope)

   | restricted_context NONE = I;

 fun local_theory' restricted target f = present_transaction (fn int =>

   (fn Theory (gthy, _) =>

         let

           val (finish, lthy) = Named_Target.switch target gthy;

           val lthy' = lthy

             |> restricted_context restricted

             |> Local_Theory.new_group

             |> f int

             |> Local_Theory.reset_group;

         in Theory (finish lthy', SOME lthy') end

     | _ => raise UNDEF))

   (K ());

 fun local_theory restricted target f = local_theory' restricted target (K f);

 fun present_local_theory target = present_transaction (fn _ =>

   (fn Theory (gthy, _) =>

         let val (finish, lthy) = Named_Target.switch target gthy;

         in Theory (finish lthy, SOME lthy) end

     | _ => raise UNDEF));

 (* proof transitions *)

 fun end_proof f = transaction (fn int =>

   (fn Proof (prf, (finish, _)) =>

         let val state = Proof_Node.current prf in

           if can (Proof.assert_bottom true) state then

             let

               val ctxt' = f int state;

               val gthy' = finish ctxt';

             in Theory (gthy', SOME ctxt') end

           else raise UNDEF

         end

     | Skipped_Proof (0, (gthy, _)) => Theory (gthy, NONE)

     | _ => raise UNDEF));

 local

 fun begin_proof init = transaction (fn int =>

   (fn Theory (gthy, _) =>

     let

       val (finish, prf) = init int gthy;

       val document = Options.default_string "document";

       val skip = (document = "" orelse document = "false") andalso Goal.skip_proofs_enabled ();

       val schematic_goal = try Proof.schematic_goal prf;

       val _ =

         if skip andalso schematic_goal = SOME true then

           warning "Cannot skip proof of schematic goal statement"

         else ();

     in

       if skip andalso schematic_goal = SOME false then

         Skipped_Proof (0, (finish (Proof.global_skip_proof true prf), gthy))

       else Proof (Proof_Node.init prf, (finish, gthy))

     end

   | _ => raise UNDEF));

 in

 fun local_theory_to_proof' restricted target f = begin_proof

   (fn int => fn gthy =>

     let

       val (finish, lthy) = Named_Target.switch target gthy;

       val prf = lthy

         |> restricted_context restricted

         |> Local_Theory.new_group

         |> f int;

     in (finish o Local_Theory.reset_group, prf) end);

 fun local_theory_to_proof restricted target f =

   local_theory_to_proof' restricted target (K f);

 fun theory_to_proof f = begin_proof

   (fn _ => fn gthy =>

     (Context.Theory o Sign.reset_group o Sign.change_check o Proof_Context.theory_of,

       (case gthy of

         Context.Theory thy => f (Sign.new_group thy)

       | _ => raise UNDEF)));

 end;

 fun forget_proof strict = transaction (fn _ =>

   (fn Proof (prf, (_, orig_gthy)) =>

         if strict andalso not (Proof.has_bottom_goal (Proof_Node.current prf))

         then raise UNDEF else Theory (orig_gthy, NONE)

     | Skipped_Proof (_, (_, orig_gthy)) => Theory (orig_gthy, NONE)

     | _ => raise UNDEF));

 fun proofs' f = transaction (fn int =>

   (fn Proof (prf, x) => Proof (Proof_Node.applys (f int) prf, x)

     | skip as Skipped_Proof _ => skip

     | _ => raise UNDEF));

 fun proof' f = proofs' ((Seq.single o Seq.Result) oo f);

 val proofs = proofs' o K;

 val proof = proof' o K;

 (* skipped proofs *)

 fun actual_proof f = transaction (fn _ =>

   (fn Proof (prf, x) => Proof (f prf, x)

     | _ => raise UNDEF));

 fun skip_proof f = transaction (fn _ =>

   (fn skip as Skipped_Proof _ => (f (); skip)

     | _ => raise UNDEF));

 val skip_proof_open = transaction (fn _ =>

   (fn Skipped_Proof (d, x) => Skipped_Proof (d + 1, x)

     | _ => raise UNDEF));

 val skip_proof_close = transaction (fn _ =>

   (fn Skipped_Proof (0, (gthy, _)) => Theory (gthy, NONE)

     | Skipped_Proof (d, x) => Skipped_Proof (d - 1, x)

     | _ => raise UNDEF));

 (** toplevel transactions **)

 (* runtime position *)

 fun exec_id id (tr as Transition {pos, ...}) =

   position (Position.put_id (Document_ID.print id) pos) tr;

 fun setmp_thread_position (Transition {pos, ...}) f x =

   Position.setmp_thread_data pos f x;

 (* post-transition hooks *)

 local

   val hooks =

     Synchronized.var "Toplevel.hooks" ([]: (transition -> state -> state -> unit) list);

 in

 fun add_hook hook = Synchronized.change hooks (cons hook);

 fun get_hooks () = Synchronized.value hooks;

 end;

 (* apply transitions *)

 fun get_timing (Transition {timing, ...}) = timing;

 fun put_timing timing = map_transition (fn (name, pos, _, trans) => (name, pos, timing, trans));

 local

 fun app int (tr as Transition {trans, ...}) =

   setmp_thread_position tr (fn state =>

     let

       val timing_start = Timing.start ();

       val (result, opt_err) = apply_trans int trans state;

       val timing_result = Timing.result timing_start;

       val timing_props =

         Markup.command_timing :: (Markup.nameN, name_of tr) :: Position.properties_of (pos_of tr);

       val _ = Timing.protocol_message timing_props timing_result;

     in (result, Option.map (fn UNDEF => ERROR (type_error tr) | exn => exn) opt_err) end);

 in

 fun transition int tr st =

   let

     val (st', opt_err) =

       Context.setmp_generic_context (try (Context.Proof o presentation_context_of) st)

         (fn () => app int tr st) ();

     val opt_err' = opt_err |> Option.map

       (fn Runtime.EXCURSION_FAIL exn_info => exn_info

         | exn => (Runtime.exn_context (try context_of st) exn, at_command tr));

     val _ = get_hooks () |> List.app (fn f => (try (fn () => f tr st st') (); ()));

   in (st', opt_err') end;

 end;

 (* managed commands *)

 fun command_errors int tr st =

   (case transition int tr st of

     (st', NONE) => ([], SOME st')

   | (_, SOME (exn, _)) => (Runtime.exn_messages exn, NONE));

 fun command_exception int tr st =

   (case transition int tr st of

     (st', NONE) => st'

   | (_, SOME (exn, info)) =>

       if Exn.is_interrupt exn then Exn.reraise exn

       else raise Runtime.EXCURSION_FAIL (exn, info));

 val command = command_exception false;

 (* reset state *)

 local

 fun reset_state check trans st =

   if check st then NONE

   else #2 (command_errors false (trans empty) st);

 in

 val reset_theory = reset_state is_theory (forget_proof false);

 val reset_proof =

   reset_state is_proof

     (transaction (fn _ =>

       (fn Theory (gthy, _) => Skipped_Proof (0, (gthy, gthy))

         | _ => raise UNDEF)));

 end;

 (* scheduled proof result *)

 datatype result =

   Result of transition * state |

   Result_List of result list |

   Result_Future of result future;

 fun join_results (Result x) = [x]

   | join_results (Result_List xs) = maps join_results xs

   | join_results (Result_Future x) = join_results (Future.join x);

 local

 structure Result = Proof_Data

 (

   type T = result;

   fun init _ = Result_List [];

 );

 val get_result = Result.get o Proof.context_of;

 val put_result = Proof.map_context o Result.put;

 fun timing_estimate elem =

   let val trs = tl (Thy_Syntax.flat_element elem)

   in fold (fn tr => fn t => get_timing tr + t) trs Time.zeroTime end;

 fun proof_future_enabled estimate st =

   (case try proof_of st of

     NONE => false

   | SOME state =>

       not (Proof.is_relevant state) andalso

        (if can (Proof.assert_bottom true) state

         then Goal.future_enabled 1

         else Goal.future_enabled 2 orelse Goal.future_enabled_timing estimate));

 fun atom_result keywords tr st =

   let

     val st' =

       if Goal.future_enabled 1 andalso Keyword.is_diag keywords (name_of tr) then

         (Execution.fork

           {name = "Toplevel.diag", pos = pos_of tr, pri = ~1}

           (fn () => command tr st); st)

       else command tr st;

   in (Result (tr, st'), st') end;

 in

 fun element_result keywords (Thy_Syntax.Element (tr, NONE)) st = atom_result keywords tr st

   | element_result keywords (elem as Thy_Syntax.Element (head_tr, SOME element_rest)) st =

       let

         val (head_result, st') = atom_result keywords head_tr st;

         val (body_elems, end_tr) = element_rest;

         val estimate = timing_estimate elem;

       in

         if not (proof_future_enabled estimate st')

         then

           let

             val proof_trs = maps Thy_Syntax.flat_element body_elems @ [end_tr];

             val (proof_results, st'') = fold_map (atom_result keywords) proof_trs st';

           in (Result_List (head_result :: proof_results), st'') end

         else

           let

             val finish = Context.Theory o Proof_Context.theory_of;

             val future_proof =

               Proof.future_proof (fn state =>

                 Execution.fork

                   {name = "Toplevel.future_proof", pos = pos_of head_tr, pri = ~1}

                   (fn () =>

                     let

                       val State (SOME (Proof (prf, (_, orig_gthy))), prev) = st';

                       val prf' = Proof_Node.apply (K state) prf;

                       val (result, result_state) =

                         State (SOME (Proof (prf', (finish, orig_gthy))), prev)

                         |> fold_map (element_result keywords) body_elems ||> command end_tr;

                     in (Result_List result, presentation_context_of result_state) end))

               #> (fn (res, state') => state' |> put_result (Result_Future res));

             val forked_proof =

               proof (future_proof #>

                 (fn state => state |> Proof.local_done_proof |> put_result (get_result state))) o

               end_proof (fn _ => future_proof #>

                 (fn state => state |> Proof.global_done_proof |> Result.put (get_result state)));

             val st'' = st'

               |> command (head_tr |> reset_trans |> forked_proof);

             val end_result = Result (end_tr, st'');

             val result =

               Result_List [head_result, Result.get (presentation_context_of st''), end_result];

           in (result, st'') end

       end;

 end;

 end;