(*  Title:      Pure/Isar/toplevel.ML

    ID:         $Id$

    Author:     Markus Wenzel, TU Muenchen

Isabelle/Isar toplevel transactions.

*)

signature TOPLEVEL =

sig

  exception UNDEF

  type generic_theory

  type node

  val theory_node: node -> generic_theory option

  val proof_node: node -> ProofHistory.T option

  val cases_node: (generic_theory -> 'a) -> (Proof.state -> 'a) -> node -> 'a

  val presentation_context: node option -> xstring option -> Proof.context

  type state

  val toplevel: state

  val is_toplevel: state -> bool

  val is_theory: state -> bool

  val is_proof: state -> bool

  val level: state -> int

  val node_history_of: state -> node History.T

  val node_of: state -> node

  val node_case: (generic_theory -> 'a) -> (Proof.state -> 'a) -> state -> 'a

  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 enter_proof_body: state -> Proof.state

  val print_state_context: state -> unit

  val print_state: bool -> state -> unit

  val quiet: bool ref

  val debug: bool ref

  val interact: bool ref

  val timing: bool ref

  val profiling: int ref

  val skip_proofs: bool ref

  exception TERMINATE

  exception RESTART

  exception CONTEXT of Proof.context * exn

  exception TOPLEVEL_ERROR

  val exn_message: exn -> string

  val program: (unit -> 'a) -> 'a

  type transition

  val undo_limit: bool -> int option

  val empty: transition

  val name: string -> transition -> transition

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

  val interactive: bool -> transition -> transition

  val print: transition -> transition

  val no_timing: transition -> transition

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

    transition -> transition

  val init_empty: (state -> bool) -> (unit -> unit) -> transition -> transition

  val exit: transition -> transition

  val undo_exit: transition -> transition

  val kill: transition -> transition

  val history: (node History.T -> node History.T) -> transition -> transition

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

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

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

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

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

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

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

  val end_local_theory: transition -> transition

  val local_theory: xstring option -> (local_theory -> local_theory) -> transition -> transition

  val present_local_theory: xstring option -> (bool -> node -> unit) -> transition -> transition

  val local_theory_to_proof': xstring option -> (bool -> local_theory -> Proof.state) ->

    transition -> transition

  val local_theory_to_proof: xstring 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: transition -> transition

  val present_proof: (bool -> node -> unit) -> transition -> transition

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

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

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

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

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

  val skip_proof: (int History.T -> int History.T) -> transition -> transition

  val skip_proof_to_theory: (int -> bool) -> transition -> transition

  val unknown_theory: transition -> transition

  val unknown_proof: transition -> transition

  val unknown_context: transition -> transition

  val error_msg: transition -> exn * string -> unit

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

  val present_excursion: (transition * (state -> state -> 'a -> 'a)) list -> 'a -> 'a

  val excursion: transition list -> unit

end;

structure Toplevel: TOPLEVEL =

struct

(** toplevel state **)

exception UNDEF;

(* local theory wrappers *)

type generic_theory = Context.generic;    (*theory or local_theory*)

val loc_init = TheoryTarget.context;

val loc_exit = ProofContext.theory_of o LocalTheory.exit;

fun loc_begin loc (Context.Theory thy) = loc_init (the_default "-" loc) thy

  | loc_begin NONE (Context.Proof lthy) = lthy

  | loc_begin (SOME loc) (Context.Proof lthy) = loc_init loc (loc_exit lthy);

fun loc_finish _ (Context.Theory _) = Context.Theory o loc_exit

  | loc_finish NONE (Context.Proof _) = Context.Proof o LocalTheory.restore

  | loc_finish (SOME _) (Context.Proof lthy) = fn lthy' =>

      Context.Proof (LocalTheory.reinit (LocalTheory.raw_theory (K (loc_exit lthy')) lthy));

(* datatype node *)

datatype node =

  Theory of generic_theory * Proof.context option | (*theory with presentation context*)

  Proof of ProofHistory.T * ((Proof.context -> generic_theory) * generic_theory) |

    (*history of proof states, finish, original theory*)

  SkipProof of int History.T * (generic_theory * generic_theory);

    (*history of proof depths, resulting theory, original theory*)

val the_global_theory = fn Theory (Context.Theory thy, _) => thy | _ => raise UNDEF;

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

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

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

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

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

fun presentation_context (SOME (Theory (_, SOME ctxt))) NONE = ctxt

  | presentation_context (SOME node) NONE = cases_node Context.proof_of Proof.context_of node

  | presentation_context (SOME node) (SOME loc) =

      loc_init loc (cases_node Context.theory_of Proof.theory_of node)

  | presentation_context NONE _ = raise UNDEF;

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

  | reset_presentation node = node;

(* datatype state *)

type state_info = node History.T * ((theory -> unit) * (theory -> unit));

datatype state =

  Toplevel of state_info option |  (*outer toplevel, leftover end state*)

  State of state_info;

val toplevel = Toplevel NONE;

fun is_toplevel (Toplevel _) = true

  | is_toplevel _ = false;

fun level (Toplevel _) = 0

  | level (State (node, _)) =

      (case History.current node of

        Theory _ => 0

      | Proof (prf, _) => Proof.level (ProofHistory.current prf)

      | SkipProof (h, _) => History.current h + 1);   (*different notion of proof depth!*)

fun str_of_state (Toplevel _) = "at top level"

  | str_of_state (State (node, _)) =

      (case History.current node of

        Theory (Context.Theory _, _) => "in theory mode"

      | Theory (Context.Proof _, _) => "in local theory mode"

      | Proof _ => "in proof mode"

      | SkipProof _ => "in skipped proof mode");

(* top node *)

fun node_history_of (Toplevel _) = raise UNDEF

  | node_history_of (State (node, _)) = node;

val node_of = History.current o node_history_of;

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

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 _ => raise UNDEF) I;

fun proof_position_of state =

  (case node_of state of

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

  | _ => raise UNDEF);

val enter_proof_body = node_case (Proof.init o Context.proof_of) Proof.enter_forward;

(* print state *)

val pretty_context = LocalTheory.pretty o Context.cases (TheoryTarget.init NONE) I;

fun print_state_context state =

  (case try node_of state of

    NONE => []

  | SOME (Theory (gthy, _)) => pretty_context gthy

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

  | SOME (SkipProof (_, (gthy, _))) => pretty_context gthy)

  |> Pretty.chunks |> Pretty.writeln;

fun print_state prf_only state =

  (case try node_of state of

    NONE => []

  | SOME (Theory (gthy, _)) => if prf_only then [] else pretty_context gthy

  | SOME (Proof (prf, _)) =>

      Proof.pretty_state (ProofHistory.position prf) (ProofHistory.current prf)

  | SOME (SkipProof (h, _)) =>

      [Pretty.str ("skipped proof: depth " ^ string_of_int (History.current h))])

  |> Pretty.markup_chunks Markup.state |> Pretty.writeln;

(** toplevel transitions **)

val quiet = ref false;

val debug = Output.debugging;

val interact = ref false;

val timing = Output.timing;

val profiling = ref 0;

val skip_proofs = ref false;

exception TERMINATE;

exception RESTART;

exception EXCURSION_FAIL of exn * string;

exception FAILURE of state * exn;

exception TOPLEVEL_ERROR;

(* print exceptions *)

exception CONTEXT of Proof.context * exn;

fun exn_context NONE exn = exn

  | exn_context (SOME ctxt) exn = CONTEXT (ctxt, exn);

local

fun if_context NONE _ _ = []

  | if_context (SOME ctxt) f xs = map (f ctxt) xs;

fun raised name [] = "exception " ^ name ^ " raised"

  | raised name [msg] = "exception " ^ name ^ " raised: " ^ msg

  | raised name msgs = cat_lines (("exception " ^ name ^ " raised:") :: msgs);

in

fun exn_message e =

  let

    val detailed = ! debug;

    fun exn_msg _ (CONTEXT (ctxt, exn)) = exn_msg (SOME ctxt) exn

      | exn_msg ctxt (Exn.EXCEPTIONS (exns, "")) = cat_lines (map (exn_msg ctxt) exns)

      | exn_msg ctxt (Exn.EXCEPTIONS (exns, msg)) = cat_lines (map (exn_msg ctxt) exns @ [msg])

      | exn_msg ctxt (EXCURSION_FAIL (exn, loc)) =

          exn_msg ctxt exn ^ Markup.markup Markup.location ("\n" ^ loc)

      | exn_msg _ TERMINATE = "Exit."

      | exn_msg _ RESTART = "Restart."

      | exn_msg _ Interrupt = "Interrupt."

      | exn_msg _ TimeLimit.TimeOut = "Timeout."

      | exn_msg _ TOPLEVEL_ERROR = "Error."

      | exn_msg _ (SYS_ERROR msg) = "## SYSTEM ERROR ##\n" ^ msg

      | exn_msg _ (ERROR msg) = msg

      | exn_msg _ (Fail msg) = raised "Fail" [msg]

      | exn_msg _ (THEORY (msg, thys)) =

          raised "THEORY" (msg :: (if detailed then map Context.str_of_thy thys else []))

      | exn_msg _ (Syntax.AST (msg, asts)) = raised "AST" (msg ::

            (if detailed then map (Pretty.string_of o Syntax.pretty_ast) asts else []))

      | exn_msg ctxt (TYPE (msg, Ts, ts)) = raised "TYPE" (msg ::

            (if detailed then

              if_context ctxt Syntax.string_of_typ Ts @ if_context ctxt Syntax.string_of_term ts

             else []))

      | exn_msg ctxt (TERM (msg, ts)) = raised "TERM" (msg ::

            (if detailed then if_context ctxt Syntax.string_of_term ts else []))

      | exn_msg ctxt (THM (msg, i, thms)) = raised ("THM " ^ string_of_int i) (msg ::

            (if detailed then if_context ctxt ProofContext.string_of_thm thms else []))

      | exn_msg _ exn = raised (General.exnMessage exn) []

  in exn_msg NONE e end;

end;

(* controlled execution *)

local

fun debugging f x =

  if ! debug then exception_trace (fn () => f x)

  else f x;

fun toplevel_error f x =

  let val ctxt = try ML_Context.the_local_context () in

    f x handle exn =>

      (Output.error_msg (exn_message (exn_context ctxt exn)); raise TOPLEVEL_ERROR)

  end;

in

fun controlled_execution f =

  f

  |> debugging

  |> interruptible;

fun program f =

 (f

  |> debugging

  |> toplevel_error) ();

end;

(* node transactions and recovery from stale theories *)

(*NB: proof commands should be non-destructive!*)

local

fun is_stale state = Context.is_stale (theory_of state) handle UNDEF => false;

fun is_draft_theory (Theory (gthy, _)) = Context.is_draft (Context.theory_of gthy)

  | is_draft_theory _ = false;

fun stale_error NONE = SOME (ERROR "Stale theory encountered after successful execution!")

  | stale_error some = some;

fun map_theory f = History.map_current

  (fn Theory (gthy, ctxt) => Theory (Context.mapping f (LocalTheory.raw_theory f) gthy, ctxt)

    | node => node);

in

fun transaction hist pos f (node, term) =

  let

    val _ = is_draft_theory (History.current node) andalso

      error "Illegal draft theory in toplevel state";

    val cont_node = node |> History.map_current reset_presentation;

    val back_node = cont_node |> map_theory Theory.copy |> map_theory Theory.checkpoint;

    fun state_error e nd = (State (nd, term), e);

    val (result, err) =

      cont_node

      |> (f

          |> (if hist then History.apply' (History.current back_node) else History.map_current)

          |> controlled_execution)

      |> map_theory Theory.checkpoint

      |> state_error NONE

      handle exn => state_error (SOME exn) cont_node;

    val (result', err') =

      if is_stale result then state_error (stale_error err) back_node

      else (result, err);

  in

    (case err' of

      NONE => result'

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

  end;

end;

(* primitive transitions *)

(*Note: Recovery from stale theories is provided only for theory-level

  operations via Transaction.  Other node or state operations should

  not touch theories at all.  Interrupts are enabled only for Keep and

  Transaction.*)

datatype trans =

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

                                                    (*init node; with exit/kill operation*)

  InitEmpty of (state -> bool) * (unit -> unit) |   (*init empty toplevel*)

  Exit |                                            (*conclude node -- deferred until init*)

  UndoExit |                                        (*continue after conclusion*)

  Kill |                                            (*abort node*)

  History of node History.T -> node History.T |     (*history operation (undo etc.)*)

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

  Transaction of bool * (bool -> node -> node);     (*node transaction*)

fun undo_limit int = if int then NONE else SOME 0;

fun safe_exit (Toplevel (SOME (node, (exit, _)))) =

    (case try the_global_theory (History.current node) of

      SOME thy => controlled_execution exit thy

    | NONE => ())

  | safe_exit _ = ();

local

fun keep_state int f = controlled_execution (fn x => tap (f int) x);

fun apply_tr int _ (Init (f, term)) (state as Toplevel _) =

      let val node = Theory (Context.Theory (Theory.checkpoint (f int)), NONE)

      in safe_exit state; State (History.init (undo_limit int) node, term) end

  | apply_tr int _ (InitEmpty (check, f)) (state as Toplevel _) =

      if check state then (safe_exit state; keep_state int (fn _ => fn _ => f ()) toplevel)

      else raise UNDEF

  | apply_tr _ _ Exit (State (node, term)) =

      (the_global_theory (History.current node); Toplevel (SOME (node, term)))

  | apply_tr _ _ UndoExit (Toplevel (SOME state_info)) = State state_info

  | apply_tr _ _ Kill (State (node, (_, kill))) =

      (kill (the_global_theory (History.current node)); toplevel)

  | apply_tr _ _ (History f) (State (node, term)) = State (f node, term)

  | apply_tr int _ (Keep f) state = keep_state int f state

  | apply_tr int pos (Transaction (hist, f)) (State state) =

      transaction hist pos (fn x => f int x) state

  | apply_tr _ _ _ _ = raise UNDEF;

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

  | apply_union int pos (tr :: trs) state =

      apply_tr int pos tr state

        handle UNDEF => apply_union int pos trs state

          | FAILURE (alt_state, UNDEF) => apply_union int pos trs alt_state

          | exn as FAILURE _ => raise exn

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

in

fun apply_trans int pos trs state = (apply_union int pos 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*)

  int_only: bool,            (*interactive-only*)

  print: bool,               (*print result state*)

  no_timing: bool,           (*suppress timing*)

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

fun make_transition (name, pos, int_only, print, no_timing, trans) =

  Transition {name = name, pos = pos, int_only = int_only, print = print, no_timing = no_timing,

    trans = trans};

fun map_transition f (Transition {name, pos, int_only, print, no_timing, trans}) =

  make_transition (f (name, pos, int_only, print, no_timing, trans));

val empty = make_transition ("<unknown>", Position.none, false, false, false, []);

(* diagnostics *)

fun str_of_transition (Transition {name, pos, ...}) = quote name ^ Position.str_of pos;

fun command_msg msg tr = msg ^ "command " ^ str_of_transition tr;

fun at_command tr = command_msg "At " tr ^ ".";

fun type_error tr state =

  ERROR (command_msg "Illegal application of " tr ^ " " ^ str_of_state state);

(* modify transitions *)

fun name nm = map_transition (fn (_, pos, int_only, print, no_timing, trans) =>

  (nm, pos, int_only, print, no_timing, trans));

fun position pos = map_transition (fn (name, _, int_only, print, no_timing, trans) =>

  (name, pos, int_only, print, no_timing, trans));

fun interactive int_only = map_transition (fn (name, pos, _, print, no_timing, trans) =>

  (name, pos, int_only, print, no_timing, trans));

val no_timing = map_transition (fn (name, pos, int_only, print, _, trans) =>

  (name, pos, int_only, print, true, trans));

fun add_trans tr = map_transition (fn (name, pos, int_only, print, no_timing, trans) =>

  (name, pos, int_only, print, no_timing, trans @ [tr]));

val print = map_transition (fn (name, pos, int_only, _, no_timing, trans) =>

  (name, pos, int_only, true, no_timing, trans));

(* basic transitions *)

fun init_theory f exit kill = add_trans (Init (f, (exit, kill)));

fun init_empty check f = add_trans (InitEmpty (check, f));

val exit = add_trans Exit;

val undo_exit = add_trans UndoExit;

val kill = add_trans Kill;

val history = add_trans o History;

val keep' = add_trans o Keep;

fun map_current f = add_trans (Transaction (false, f));

fun app_current f = add_trans (Transaction (true, f));

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

fun imperative f = keep (fn _ => f ());

val unknown_theory = imperative (fn () => warning "Unknown theory context");

val unknown_proof = imperative (fn () => warning "Unknown proof context");

val unknown_context = imperative (fn () => warning "Unknown context");

(* theory transitions *)

fun generic_theory f = app_current (fn _ =>

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

    | _ => raise UNDEF));

fun theory' f = app_current (fn int =>

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

    | _ => raise UNDEF));

fun theory f = theory' (K f);

fun begin_local_theory begin f = app_current (fn _ =>

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

        let

          val lthy = f thy;

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

        in Theory (gthy, SOME lthy) end

    | _ => raise UNDEF));

val end_local_theory = app_current (fn _ =>

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

    | _ => raise UNDEF));

local

fun local_theory_presentation loc f g = app_current (fn int =>

  (fn Theory (gthy, _) =>

        let

          val finish = loc_finish loc gthy;

          val lthy' = f (loc_begin loc gthy);

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

    | _ => raise UNDEF) #> tap (g int));

in

fun local_theory loc f = local_theory_presentation loc f (K I);

fun present_local_theory loc g = local_theory_presentation loc I g;

end;

(* proof transitions *)

fun end_proof f = map_current (fn int =>

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

        let val state = ProofHistory.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

    | SkipProof (h, (gthy, _)) =>

        if History.current h = 0 then Theory (gthy, NONE) else raise UNDEF

    | _ => raise UNDEF));

local

fun begin_proof init finish = app_current (fn int =>

  (fn Theory (gthy, _) =>

    let

      val prf = init int gthy;

      val schematic = Proof.schematic_goal prf;

    in

      if ! skip_proofs andalso schematic then

        warning "Cannot skip proof of schematic goal statement"

      else ();

      if ! skip_proofs andalso not schematic then

        SkipProof

          (History.init (undo_limit int) 0, (finish gthy (Proof.global_skip_proof int prf), gthy))

      else Proof (ProofHistory.init (undo_limit int) prf, (finish gthy, gthy))

    end

  | _ => raise UNDEF));

in

fun local_theory_to_proof' loc f = begin_proof

  (fn int => fn gthy => f int (loc_begin loc gthy))

  (loc_finish loc);

fun local_theory_to_proof loc f = local_theory_to_proof' loc (K f);

fun theory_to_proof f = begin_proof

  (K (fn Context.Theory thy => f thy | _ => raise UNDEF))

  (K (Context.Theory o ProofContext.theory_of));

end;

val forget_proof = map_current (fn _ =>

  (fn Proof (_, (_, orig_gthy)) => Theory (orig_gthy, NONE)

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

    | _ => raise UNDEF));

fun present_proof f = map_current (fn int =>

  (fn Proof (prf, x) => Proof (ProofHistory.apply I prf, x)

    | SkipProof (h, x) => SkipProof (History.apply I h, x)

    | _ => raise UNDEF) #> tap (f int));

fun proofs' f = map_current (fn int =>

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

    | SkipProof (h, x) => SkipProof (History.apply I h, x)

    | _ => raise UNDEF));

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

val proofs = proofs' o K;

val proof = proof' o K;

fun actual_proof f = map_current (fn _ =>

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

    | _ => raise UNDEF));

fun skip_proof f = map_current (fn _ =>

  (fn SkipProof (h, x) => SkipProof (f h, x)

    | _ => raise UNDEF));

fun skip_proof_to_theory p = map_current (fn _ =>

  (fn SkipProof (h, (gthy, _)) =>

    if p (History.current h) then Theory (gthy, NONE)

    else raise UNDEF

  | _ => raise UNDEF));

(** toplevel transactions **)

(* thread position *)

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

  Position.setmp_thread_data pos f x;

fun error_msg tr exn_info =

  setmp_thread_position tr (fn () => Output.error_msg (exn_message (EXCURSION_FAIL exn_info))) ();

(* apply transitions *)

local

fun app int (tr as Transition {trans, pos, int_only, print, no_timing, ...}) =

  setmp_thread_position tr (fn state =>

    let

      val _ = if not int andalso int_only then warning (command_msg "Interactive-only " tr) else ();

      fun do_timing f x = (warning (command_msg "" tr); timeap f x);

      fun do_profiling f x = profile (! profiling) f x;

      val (result, status) =

         state |> (apply_trans int pos trans

          |> (if ! profiling > 0 andalso not no_timing then do_profiling else I)

          |> (if ! profiling > 0 orelse ! timing andalso not no_timing then do_timing else I));

      val _ = if int andalso not (! quiet) andalso print then print_state false result else ();

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

in

fun transition int tr st =

  let val ctxt = try context_of st in

    (case app int tr st of

      (_, SOME TERMINATE) => NONE

    | (_, SOME RESTART) => SOME (toplevel, NONE)

    | (state', SOME (EXCURSION_FAIL exn_info)) => SOME (state', SOME exn_info)

    | (state', SOME exn) => SOME (state', SOME (exn_context ctxt exn, at_command tr))

    | (state', NONE) => SOME (state', NONE))

  end;

end;

(* excursion: toplevel -- apply transformers/presentation -- toplevel *)

local

fun excur [] x = x

  | excur ((tr, pr) :: trs) (st, res) =

      (case transition (! interact) tr st of

        SOME (st', NONE) =>

          excur trs (st', pr st st' res handle exn =>

            raise EXCURSION_FAIL (exn, "Presentation failed\n" ^ at_command tr))

      | SOME (st', SOME exn_info) => raise EXCURSION_FAIL exn_info

      | NONE => raise EXCURSION_FAIL (TERMINATE, at_command tr));

fun no_pr _ _ _ = ();

in

fun present_excursion trs res =

  (case excur trs (toplevel, res) of

    (state as Toplevel _, res') => (safe_exit state; res')

  | _ => error "Unfinished development at end of input")

  handle exn => error (exn_message exn);

fun excursion trs = present_excursion (map (rpair no_pr) trs) ();

end;

end;