src/Pure/context.ML

improved treatment of intermediate checkpoints: actual copy
instead of extend, purge after end;
tuned;

(*  Title:      Pure/context.ML
    ID:         $Id$
    Author:     Markus Wenzel, TU Muenchen

Generic theory contexts with unique identity, arbitrarily typed data,
graph-based development.  Implicit theory context in ML.
*)

signature BASIC_CONTEXT =
sig
  type theory
  type theory_ref
  exception THEORY of string * theory list
  val context: theory -> unit
  val the_context: unit -> theory
end;

signature CONTEXT =
sig
  include BASIC_CONTEXT
  exception DATA_FAIL of exn * string
  (*theory context*)
  val theory_name: theory -> string
  val parents_of: theory -> theory list
  val ancestors_of: theory -> theory list
  val is_stale: theory -> bool
  val ProtoPureN: string
  val PureN: string
  val CPureN: string
  val draftN: string
  val exists_name: string -> theory -> bool
  val names_of: theory -> string list
  val pretty_thy: theory -> Pretty.T
  val string_of_thy: theory -> string
  val pprint_thy: theory -> pprint_args -> unit
  val pretty_abbrev_thy: theory -> Pretty.T
  val str_of_thy: theory -> string
  val check_thy: string -> theory -> theory
  val eq_thy: theory * theory -> bool
  val subthy: theory * theory -> bool
  val merge: theory * theory -> theory                     (*exception TERM*)
  val merge_refs: theory_ref * theory_ref -> theory_ref    (*exception TERM*)
  val self_ref: theory -> theory_ref
  val deref: theory_ref -> theory
  val copy_thy: theory -> theory
  val checkpoint_thy: theory -> theory
  val finish_thy: theory -> theory
  val theory_data: theory -> string list
  val pre_pure_thy: theory
  val begin_thy: (theory -> Pretty.pp) -> string -> theory list -> theory
  (*ML theory context*)
  val get_context: unit -> theory option
  val set_context: theory option -> unit
  val reset_context: unit -> unit
  val setmp: theory option -> ('a -> 'b) -> 'a -> 'b
  val pass: theory option -> ('a -> 'b) -> 'a -> 'b * theory option
  val pass_theory: theory -> ('a -> 'b) -> 'a -> 'b * theory
  val save: ('a -> 'b) -> 'a -> 'b
  val >> : (theory -> theory) -> unit
  val ml_output: (string -> unit) * (string -> unit)
  val use_mltext: string -> bool -> theory option -> unit
  val use_mltext_theory: string -> bool -> theory -> theory
  val use_let: string -> string -> string -> theory -> theory
  val add_setup: (theory -> theory) list -> unit
  val setup: unit -> (theory -> theory) list
end;

signature PRIVATE_CONTEXT =
sig
  include CONTEXT
  structure TheoryData:
  sig
    val declare: string -> Object.T -> (Object.T -> Object.T) -> (Object.T -> Object.T) ->
      (Pretty.pp -> Object.T * Object.T -> Object.T) -> serial
    val init: serial -> theory -> theory
    val get: serial -> (Object.T -> 'a) -> theory -> 'a
    val put: serial -> ('a -> Object.T) -> 'a -> theory -> theory
  end
end;

structure Context: PRIVATE_CONTEXT =
struct

(*** theory context ***)

(** theory data **)

(* data kinds and access methods *)

exception DATA_FAIL of exn * string;

local

type kind =
 {name: string,
  empty: Object.T,
  copy: Object.T -> Object.T,
  extend: Object.T -> Object.T,
  merge: Pretty.pp -> Object.T * Object.T -> Object.T};

val kinds = ref (Inttab.empty: kind Inttab.table);

fun invoke meth_name meth_fn k =
  (case Inttab.lookup (! kinds, k) of
    SOME kind => meth_fn kind |> transform_failure (fn exn =>
      DATA_FAIL (exn, "Theory data method " ^ #name kind ^ "." ^ meth_name ^ " failed"))
  | NONE => sys_error ("Invalid theory data identifier " ^ string_of_int k));

in

fun invoke_name k    = invoke "name" (K o #name) k ();
fun invoke_empty k   = invoke "empty" (K o #empty) k ();
val invoke_copy      = invoke "copy" #copy;
val invoke_extend    = invoke "extend" #extend;
fun invoke_merge pp  = invoke "merge" (fn kind => #merge kind pp);

fun declare_theory_data name e cp ext mrg =
  let
    val k = serial ();
    val kind = {name = name, empty = e, copy = cp, extend = ext, merge = mrg};
    val _ = conditional (Inttab.exists (equal name o #name o #2) (! kinds)) (fn () =>
      warning ("Duplicate declaration of theory data " ^ quote name));
    val _ = kinds := Inttab.update ((k, kind), ! kinds);
  in k end;

val copy_data = Inttab.map' invoke_copy;
val extend_data = Inttab.map' invoke_extend;
fun merge_data pp = Inttab.join (SOME oo invoke_merge pp) o pairself extend_data;

end;



(** datatype theory **)

datatype theory =
  Theory of
  (*identity*)
   {self: theory ref option,            (*dynamic self reference -- follows theory changes*)
    id: serial * string,                (*identifier of this theory*)
    ids: string Inttab.table,           (*identifiers of ancestors*)
    iids: string Inttab.table} *        (*identifiers of intermediate checkpoints*)
  (*data*)
  Object.T Inttab.table *               (*record of arbitrarily typed data*)
  (*ancestry of graph development*)
   {parents: theory list,               (*immediate predecessors*)
    ancestors: theory list} *           (*all predecessors*)
  (*history of linear development*)
   {name: string,                       (*prospective name of finished theory*)
    version: int,                       (*checkpoint counter*)
    intermediates: theory list};        (*intermediate checkpoints*)

exception THEORY of string * theory list;

fun rep_theory (Theory args) = args;

val identity_of = #1 o rep_theory;
val data_of     = #2 o rep_theory;
val ancestry_of = #3 o rep_theory;
val history_of  = #4 o rep_theory;

fun make_identity self id ids iids = {self = self, id = id, ids = ids, iids = iids};
fun make_ancestry parents ancestors = {parents = parents, ancestors = ancestors};
fun make_history name vers ints = {name = name, version = vers, intermediates = ints};

val parents_of = #parents o ancestry_of;
val ancestors_of = #ancestors o ancestry_of;
val theory_name = #name o history_of;


(* staleness *)

fun eq_id ((i: int, _), (j, _)) = i = j;

fun is_stale
    (Theory ({self = SOME (ref (Theory ({id = id', ...}, _, _, _))), id, ...}, _, _, _)) =
      not (eq_id (id, id'))
  | is_stale (Theory ({self = NONE, ...}, _, _, _)) = true;

fun vitalize (thy as Theory ({self = SOME r, ...}, _, _, _)) = (r := thy; thy)
  | vitalize (thy as Theory ({self = NONE, id, ids, iids}, data, ancestry, history)) =
      let
        val r = ref thy;
        val thy' = Theory (make_identity (SOME r) id ids iids, data, ancestry, history);
      in r := thy'; thy' end;


(* names *)

val ProtoPureN = "ProtoPure";
val PureN = "Pure";
val CPureN = "CPure";

val draftN = "#";
fun draft_id (_, name) = (name = draftN);
val is_draft = draft_id o #id o identity_of;

fun exists_name name (Theory ({id, ids, iids, ...}, _, _, _)) =
  name = #2 id orelse
  Inttab.exists (equal name o #2) ids orelse
  Inttab.exists (equal name o #2) iids;

fun names_of (Theory ({id, ids, iids, ...}, _, _, _)) =
  rev (#2 id :: Inttab.fold (cons o #2) iids (Inttab.fold (cons o #2) ids []));

fun pretty_thy thy =
  Pretty.str_list "{" "}" (names_of thy @ (if is_stale thy then ["!"] else []));

val string_of_thy = Pretty.string_of o pretty_thy;
val pprint_thy = Pretty.pprint o pretty_thy;

fun pretty_abbrev_thy thy =
  let
    val names = names_of thy;
    val n = length names;
    val abbrev = if n > 5 then "..." :: List.drop (names, n - 5) else names;
  in Pretty.str_list "{" "}" abbrev end;

val str_of_thy = Pretty.str_of o pretty_abbrev_thy;


(* consistency *)

fun check_thy pos thy =
  if is_stale thy then
    raise TERM ("Stale theory encountered (in " ^ pos ^ "):\n" ^ string_of_thy thy, [])
  else thy;

fun check_ins id ids =
  if draft_id id orelse is_some (Inttab.lookup (ids, #1 id)) then ids
  else if Inttab.exists (equal (#2 id) o #2) ids then
    raise TERM ("Different versions of theory component " ^ quote (#2 id), [])
  else Inttab.update (id, ids);

fun check_insert intermediate id (ids, iids) =
  let val ids' = check_ins id ids and iids' = check_ins id iids
  in if intermediate then (ids, iids') else (ids', iids) end;

fun check_merge
    (Theory ({id = id1, ids = ids1, iids = iids1, ...}, _, _, history1))
    (Theory ({id = id2, ids = ids2, iids = iids2, ...}, _, _, history2)) =
  (Inttab.fold check_ins ids2 ids1, Inttab.fold check_ins iids2 iids1)
  |> check_insert (#version history1 > 0) id1
  |> check_insert (#version history2 > 0) id2;


(* theory references *)

(*theory_ref provides a safe way to store dynamic references to a
  theory -- a plain theory value would become stale as the self
  reference moves on*)

datatype theory_ref = TheoryRef of theory ref;

val self_ref = TheoryRef o the o #self o identity_of o check_thy "Context.self_ref";
fun deref (TheoryRef (ref thy)) = thy;


(* equality and inclusion *)  (* FIXME proper_subthy; no subthy_internal *)

local

fun exists_ids (Theory ({id, ids, iids, ...}, _, _, _)) (i, _) =
  i = #1 id orelse
  is_some (Inttab.lookup (ids, i)) orelse
  is_some (Inttab.lookup (iids, i));

fun member_ids (Theory ({id, ...}, _, _, _), thy) = exists_ids thy id;

fun subset_ids (Theory ({id, ids, iids, ...}, _, _, _), thy) =
  exists_ids thy id andalso
  Inttab.forall (exists_ids thy) ids andalso
  Inttab.forall (exists_ids thy) iids;

in

val eq_thy = eq_id o pairself (#id o identity_of o check_thy "Context.eq_thy");
fun subthy thys = eq_thy thys orelse member_ids thys;
fun subthy_internal thys = eq_thy thys orelse subset_ids thys;

end;


(* trivial merge *)

fun merge (thy1, thy2) =
  if subthy (thy2, thy1) then thy1
  else if subthy (thy1, thy2) then thy2
  else (check_merge thy1 thy2;
    raise TERM (cat_lines ["Attempt to perform non-trivial merge of theories:",
      str_of_thy thy1, str_of_thy thy2], []));

fun merge_refs (ref1, ref2) = self_ref (merge (deref ref1, deref ref2));



(** build theories **)

(* primitives *)

fun create_thy name self id ids iids data ancestry history =
  let
    val intermediate = #version history > 0;
    val (ids', iids') = check_insert intermediate id (ids, iids);
    val id' = (serial (), name);
    val _ = check_insert intermediate id' (ids', iids');
    val identity' = make_identity self id' ids' iids';
  in vitalize (Theory (identity', data, ancestry, history)) end;

fun change_thy name f (thy as Theory ({self, id, ids, iids}, data, ancestry, history)) =
  let
    val _ = check_thy "Context.change_thy" thy;
    val (self', data', ancestry') =
      if is_draft thy then (self, data, ancestry)    (*destructive change!*)
      else if #version history > 0
      then (NONE, copy_data data, ancestry)
      else (NONE, extend_data data, make_ancestry [thy] (thy :: #ancestors ancestry));
    val data'' = f data';
  in create_thy name self' id ids iids data'' ancestry' history end;

fun name_thy name = change_thy name I;
val modify_thy = change_thy draftN;
val extend_thy = modify_thy I;

fun copy_thy (thy as Theory ({id, ids, iids, ...}, data, ancestry, history)) =
  (check_thy "Context.copy_thy" thy;
    create_thy draftN NONE id ids iids (copy_data data) ancestry history);

val pre_pure_thy = create_thy draftN NONE (serial (), draftN) Inttab.empty Inttab.empty
  Inttab.empty (make_ancestry [] []) (make_history ProtoPureN 0 []);


(* named theory nodes *)

fun merge_thys pp (thy1, thy2) =
  if subthy_internal (thy2, thy1) then thy1
  else if subthy_internal (thy1, thy2) then thy2
  else if exists_name CPureN thy1 <> exists_name CPureN thy2 then
    error "Cannot merge Pure and CPure developments"
  else
    let
      val (ids, iids) = check_merge thy1 thy2;
      val data = merge_data (pp thy1) (data_of thy1, data_of thy2);
      val ancestry = make_ancestry [] [];
      val history = make_history "" 0 [];
    in create_thy draftN NONE (serial (), draftN) ids iids data ancestry history end;

fun begin_thy pp name imports =
  if name = draftN then error ("Illegal theory name: " ^ quote draftN)
  else
    let
      val parents = gen_distinct eq_thy imports;  (* FIXME maximals *)
      val ancestors = gen_distinct eq_thy (parents @ List.concat (map ancestors_of parents));
      val Theory ({id, ids, iids, ...}, data, _, _) =
        (case parents of
          [] => error "No parent theories"
        | thy :: thys => extend_thy (Library.foldl (merge_thys pp) (thy, thys)));
      val ancestry = make_ancestry parents ancestors;
      val history = make_history name 0 [];
    in create_thy draftN NONE id ids iids data ancestry history end;


(* undoable checkpoints *)

fun checkpoint_thy thy =
  if not (is_draft thy) then thy
  else
    let
      val {name, version, intermediates} = history_of thy;
      val thy' as Theory (identity', data', ancestry', _) =
        name_thy (name ^ ":" ^ string_of_int version) thy;
      val history' = make_history name (version + 1) (thy' :: intermediates);
    in vitalize (Theory (identity', data', ancestry', history')) end;

fun finish_thy thy =
  let
    val {name, version, intermediates} = history_of thy;
    val rs = map (the o #self o identity_of o check_thy "Context.finish_thy") intermediates;
    val thy' as Theory ({self, id, ids, ...}, data', ancestry', _) = name_thy name thy;
    val identity' = make_identity self id ids Inttab.empty;
    val history' = make_history name 0 [];
    val thy'' = vitalize (Theory (identity', data', ancestry', history'));
  in List.app (fn r => r := thy'') rs; thy'' end;


(* theory data *)

fun theory_data thy =
  map invoke_name (Inttab.keys (data_of thy))
  |> map (rpair ()) |> Symtab.make_multi |> Symtab.dest
  |> map (apsnd length)
  |> map (fn (name, 1) => name | (name, n) => name ^ enclose "[" "]" (string_of_int n));

structure TheoryData =
struct

val declare = declare_theory_data;

fun get k dest thy =
  (case Inttab.lookup (data_of thy, k) of
    SOME x => (dest x handle Match =>
      error ("Failed to access theory data " ^ quote (invoke_name k)))
  | NONE => error ("Uninitialized theory data " ^ quote (invoke_name k)));

fun put k mk x = modify_thy (curry Inttab.update (k, mk x));
fun init k = put k I (invoke_empty k);

end;



(** ML theory context **)

local
  val current_theory = ref (NONE: theory option);
in
  fun get_context () = ! current_theory;
  fun set_context opt_thy = current_theory := opt_thy;
  fun setmp opt_thy f x = Library.setmp current_theory opt_thy f x;
end;

fun the_context () =
  (case get_context () of
    SOME thy => thy
  | _ => error "Unknown theory context");

fun context thy = set_context (SOME thy);
fun reset_context () = set_context NONE;

fun pass opt_thy f x =
  setmp opt_thy (fn x => let val y = f x in (y, get_context ()) end) x;

fun pass_theory thy f x =
  (case pass (SOME thy) f x of
    (y, SOME thy') => (y, thy')
  | (_, NONE) => error "Lost theory context in ML");

fun save f x = setmp (get_context ()) f x;


(* map context *)

nonfix >>;
fun >> f = set_context (SOME (f (the_context ())));


(* use ML text *)

val ml_output = (writeln, error_msg);

fun use_output verb txt = use_text ml_output verb (Symbol.escape txt);

fun use_mltext txt verb opt_thy = setmp opt_thy (fn () => use_output verb txt) ();
fun use_mltext_theory txt verb thy = #2 (pass_theory thy (use_output verb) txt);

fun use_context txt = use_mltext_theory ("Context.>> (" ^ txt ^ ");") false;

fun use_let bind body txt =
  use_context ("let " ^ bind ^ " = " ^ txt ^ " in\n" ^ body ^ " end");


(* delayed theory setup *)

local
  val setup_fns = ref ([]: (theory -> theory) list);
in
  fun add_setup fns = setup_fns := ! setup_fns @ fns;
  fun setup () = let val fns = ! setup_fns in setup_fns := []; fns end;
end;

end;

structure BasicContext: BASIC_CONTEXT = Context;
open BasicContext;



(*** type-safe interface for theory data ***)

signature THEORY_DATA_ARGS =
sig
  val name: string
  type T
  val empty: T
  val copy: T -> T
  val extend: T -> T
  val merge: Pretty.pp -> T * T -> T
  val print: theory -> T -> unit
end;

signature THEORY_DATA =
sig
  type T
  val init: theory -> theory
  val print: theory -> unit
  val get: theory -> T
  val get_sg: theory -> T    (*obsolete*)
  val put: T -> theory -> theory
  val map: (T -> T) -> theory -> theory
end;

functor TheoryDataFun(Data: THEORY_DATA_ARGS): THEORY_DATA =
struct

structure TheoryData = Context.TheoryData;

type T = Data.T;
exception Data of T;

val kind = TheoryData.declare Data.name
  (Data Data.empty)
  (fn Data x => Data (Data.copy x))
  (fn Data x => Data (Data.extend x))
  (fn pp => fn (Data x1, Data x2) => Data (Data.merge pp (x1, x2)));

val init = TheoryData.init kind;
val get = TheoryData.get kind (fn Data x => x);
val get_sg = get;
fun print thy = Data.print thy (get thy);
val put = TheoryData.put kind Data;
fun map f thy = put (f (get thy)) thy;

end;

(*hide private interface!*)
structure Context: CONTEXT = Context;