src/HOL/SPARK/Tools/spark_vcs.ML

modernized structure Proof_Context;

(*  Title:      HOL/SPARK/Tools/spark_vcs.ML
    Author:     Stefan Berghofer
    Copyright:  secunet Security Networks AG

Store for verification conditions generated by SPARK/Ada.
*)

signature SPARK_VCS =
sig
  val set_vcs: Fdl_Parser.decls -> Fdl_Parser.rules ->
    (string * string) * Fdl_Parser.vcs -> Path.T -> theory -> theory
  val add_proof_fun: (typ option -> 'a -> term) ->
    string * ((string list * string) option * 'a) ->
    theory -> theory
  val add_type: string * typ -> theory -> theory
  val lookup_vc: theory -> string -> (Element.context_i list *
    (string * thm list option * Element.context_i * Element.statement_i)) option
  val get_vcs: theory ->
    Element.context_i list * (binding * thm) list * (string *
    (string * thm list option * Element.context_i * Element.statement_i)) list
  val mark_proved: string -> thm list -> theory -> theory
  val close: theory -> theory
  val is_closed: theory -> bool
end;

structure SPARK_VCs: SPARK_VCS =
struct

open Fdl_Parser;


(** theory data **)

fun err_unfinished () = error "An unfinished SPARK environment is still open."

val strip_number = pairself implode o take_suffix Fdl_Lexer.is_digit o raw_explode;

val name_ord = prod_ord string_ord (option_ord int_ord) o
  pairself (strip_number ##> Int.fromString);

structure VCtab = Table(type key = string val ord = name_ord);

structure VCs = Theory_Data
(
  type T =
    {pfuns: ((string list * string) option * term) Symtab.table,
     type_map: typ Symtab.table,
     env:
       {ctxt: Element.context_i list,
        defs: (binding * thm) list,
        types: fdl_type tab,
        funs: (string list * string) tab,
        ids: (term * string) Symtab.table * Name.context,
        proving: bool,
        vcs: (string * thm list option *
          (string * expr) list * (string * expr) list) VCtab.table,
        path: Path.T} option}
  val empty : T = {pfuns = Symtab.empty, type_map = Symtab.empty, env = NONE}
  val extend = I
  fun merge ({pfuns = pfuns1, type_map = type_map1, env = NONE},
        {pfuns = pfuns2, type_map = type_map2, env = NONE}) =
        {pfuns = Symtab.merge (eq_pair (op =) (op aconv)) (pfuns1, pfuns2),
         type_map = Symtab.merge (op =) (type_map1, type_map2),
         env = NONE}
    | merge _ = err_unfinished ()
)


(** utilities **)

val to_lower = raw_explode #> map Symbol.to_ascii_lower #> implode;

val lcase_eq = (op =) o pairself (to_lower o Long_Name.base_name);

fun mk_unop s t =
  let val T = fastype_of t
  in Const (s, T --> T) $ t end;

fun mk_times (t, u) =
  let
    val setT = fastype_of t;
    val T = HOLogic.dest_setT setT;
    val U = HOLogic.dest_setT (fastype_of u)
  in
    Const (@{const_name Sigma}, setT --> (T --> HOLogic.mk_setT U) -->
      HOLogic.mk_setT (HOLogic.mk_prodT (T, U))) $ t $ Abs ("", T, u)
  end;

fun get_type thy ty =
  let val {type_map, ...} = VCs.get thy
  in Symtab.lookup type_map ty end;

fun mk_type _ "integer" = HOLogic.intT
  | mk_type _ "boolean" = HOLogic.boolT
  | mk_type thy ty =
      (case get_type thy ty of
         NONE =>
           Syntax.check_typ (Proof_Context.init_global thy)
             (Type (Sign.full_name thy (Binding.name ty), []))
       | SOME T => T);

val booleanN = "boolean";
val integerN = "integer";

fun define_overloaded (def_name, eq) lthy =
  let
    val ((c, _), rhs) = eq |> Syntax.check_term lthy |>
      Logic.dest_equals |>> dest_Free;
    val ((_, (_, thm)), lthy') = Local_Theory.define
      ((Binding.name c, NoSyn), ((Binding.name def_name, []), rhs)) lthy
    val ctxt_thy = Proof_Context.init_global (Proof_Context.theory_of lthy');
    val thm' = singleton (Proof_Context.export lthy' ctxt_thy) thm
  in (thm', lthy') end;

fun strip_underscores s =
  strip_underscores (unsuffix "_" s) handle Fail _ => s;

fun strip_tilde s =
  unsuffix "~" s ^ "_init" handle Fail _ => s;

val mangle_name = strip_underscores #> strip_tilde;

fun mk_variables thy xs ty (tab, ctxt) =
  let
    val T = mk_type thy ty;
    val (ys, ctxt') = Name.variants (map mangle_name xs) ctxt;
    val zs = map (Free o rpair T) ys;
  in (zs, (fold (Symtab.update o apsnd (rpair ty)) (xs ~~ zs) tab, ctxt')) end;

fun get_record_info thy T = (case Record.dest_recTs T of
    [(tyname, [@{typ unit}])] =>
      Record.get_info thy (Long_Name.qualifier tyname)
  | _ => NONE);

fun find_field fname = find_first (curry lcase_eq fname o fst);

fun find_field' fname = get_first (fn (flds, fldty) =>
  if member (op =) flds fname then SOME fldty else NONE);

fun assoc_ty_err thy T s msg =
  error ("Type " ^ Syntax.string_of_typ_global thy T ^
    " associated with SPARK type " ^ s ^ "\n" ^ msg);


(** generate properties of enumeration types **)

fun add_enum_type tyname tyname' thy =
  let
    val {case_name, ...} = the (Datatype_Data.get_info thy tyname');
    val cs = map Const (the (Datatype_Data.get_constrs thy tyname'));
    val k = length cs;
    val T = Type (tyname', []);
    val p = Const (@{const_name pos}, T --> HOLogic.intT);
    val v = Const (@{const_name val}, HOLogic.intT --> T);
    val card = Const (@{const_name card},
      HOLogic.mk_setT T --> HOLogic.natT) $ HOLogic.mk_UNIV T;

    fun mk_binrel_def s f = Logic.mk_equals
      (Const (s, T --> T --> HOLogic.boolT),
       Abs ("x", T, Abs ("y", T,
         Const (s, HOLogic.intT --> HOLogic.intT --> HOLogic.boolT) $
           (f $ Bound 1) $ (f $ Bound 0))));

    val (((def1, def2), def3), lthy) = thy |>

      Class.instantiation ([tyname'], [], @{sort enum}) |>

      define_overloaded ("pos_" ^ tyname ^ "_def", Logic.mk_equals
        (p,
         list_comb (Const (case_name, replicate k HOLogic.intT @
             [T] ---> HOLogic.intT),
           map (HOLogic.mk_number HOLogic.intT) (0 upto k - 1)))) ||>>

      define_overloaded ("less_eq_" ^ tyname ^ "_def",
        mk_binrel_def @{const_name less_eq} p) ||>>
      define_overloaded ("less_" ^ tyname ^ "_def",
        mk_binrel_def @{const_name less} p);

    val UNIV_eq = Goal.prove lthy [] []
      (HOLogic.mk_Trueprop (HOLogic.mk_eq
         (HOLogic.mk_UNIV T, HOLogic.mk_set T cs)))
      (fn _ =>
         rtac @{thm subset_antisym} 1 THEN
         rtac @{thm subsetI} 1 THEN
         Datatype_Aux.exh_tac (K (#exhaust (Datatype_Data.the_info
           (Proof_Context.theory_of lthy) tyname'))) 1 THEN
         ALLGOALS (asm_full_simp_tac (simpset_of lthy)));

    val finite_UNIV = Goal.prove lthy [] []
      (HOLogic.mk_Trueprop (Const (@{const_name finite},
         HOLogic.mk_setT T --> HOLogic.boolT) $ HOLogic.mk_UNIV T))
      (fn _ => simp_tac (simpset_of lthy addsimps [UNIV_eq]) 1);

    val card_UNIV = Goal.prove lthy [] []
      (HOLogic.mk_Trueprop (HOLogic.mk_eq
         (card, HOLogic.mk_number HOLogic.natT k)))
      (fn _ => simp_tac (simpset_of lthy addsimps [UNIV_eq]) 1);

    val range_pos = Goal.prove lthy [] []
      (HOLogic.mk_Trueprop (HOLogic.mk_eq
         (Const (@{const_name image}, (T --> HOLogic.intT) -->
            HOLogic.mk_setT T --> HOLogic.mk_setT HOLogic.intT) $
              p $ HOLogic.mk_UNIV T,
          Const (@{const_name atLeastLessThan}, HOLogic.intT -->
            HOLogic.intT --> HOLogic.mk_setT HOLogic.intT) $
              HOLogic.mk_number HOLogic.intT 0 $
              (@{term int} $ card))))
      (fn _ =>
         simp_tac (simpset_of lthy addsimps [card_UNIV]) 1 THEN
         simp_tac (simpset_of lthy addsimps [UNIV_eq, def1]) 1 THEN
         rtac @{thm subset_antisym} 1 THEN
         simp_tac (simpset_of lthy) 1 THEN
         rtac @{thm subsetI} 1 THEN
         asm_full_simp_tac (simpset_of lthy addsimps @{thms interval_expand}
           delsimps @{thms atLeastLessThan_iff}) 1);

    val lthy' =
      Class.prove_instantiation_instance (fn _ =>
        Class.intro_classes_tac [] THEN
        rtac finite_UNIV 1 THEN
        rtac range_pos 1 THEN
        simp_tac (HOL_basic_ss addsimps [def3]) 1 THEN
        simp_tac (HOL_basic_ss addsimps [def2]) 1) lthy;

    val (pos_eqs, val_eqs) = split_list (map_index (fn (i, c) =>
      let
        val n = HOLogic.mk_number HOLogic.intT i;
        val th = Goal.prove lthy' [] []
          (HOLogic.mk_Trueprop (HOLogic.mk_eq (p $ c, n)))
          (fn _ => simp_tac (simpset_of lthy' addsimps [def1]) 1);
        val th' = Goal.prove lthy' [] []
          (HOLogic.mk_Trueprop (HOLogic.mk_eq (v $ n, c)))
          (fn _ =>
             rtac (@{thm inj_pos} RS @{thm injD}) 1 THEN
             simp_tac (simpset_of lthy' addsimps
               [@{thm pos_val}, range_pos, card_UNIV, th]) 1)
      in (th, th') end) cs);

    val first_el = Goal.prove lthy' [] []
      (HOLogic.mk_Trueprop (HOLogic.mk_eq
         (Const (@{const_name first_el}, T), hd cs)))
      (fn _ => simp_tac (simpset_of lthy' addsimps
         [@{thm first_el_def}, hd val_eqs]) 1);

    val last_el = Goal.prove lthy' [] []
      (HOLogic.mk_Trueprop (HOLogic.mk_eq
         (Const (@{const_name last_el}, T), List.last cs)))
      (fn _ => simp_tac (simpset_of lthy' addsimps
         [@{thm last_el_def}, List.last val_eqs, card_UNIV]) 1);

    val simp_att = [Attrib.internal (K Simplifier.simp_add)]

  in
    lthy' |>
    Local_Theory.note
      ((Binding.name (tyname ^ "_card_UNIV"), simp_att), [card_UNIV]) ||>>
    Local_Theory.note
      ((Binding.name (tyname ^ "_pos"), simp_att), pos_eqs) ||>>
    Local_Theory.note
      ((Binding.name (tyname ^ "_val"), simp_att), val_eqs) ||>>
    Local_Theory.note
      ((Binding.name (tyname ^ "_first_el"), simp_att), [first_el]) ||>>
    Local_Theory.note
      ((Binding.name (tyname ^ "_last_el"), simp_att), [last_el]) |> snd |>
    Local_Theory.exit_global
  end;


fun check_no_assoc thy s = case get_type thy s of
    NONE => ()
  | SOME _ => error ("Cannot associate a type with " ^ s ^
      "\nsince it is no record or enumeration type");

fun check_enum [] [] = NONE 
  | check_enum els [] = SOME ("has no element(s) " ^ commas els)
  | check_enum [] cs = SOME ("has extra element(s) " ^
      commas (map (Long_Name.base_name o fst) cs))
  | check_enum (el :: els) ((cname, _) :: cs) =
      if lcase_eq (el, cname) then check_enum els cs
      else SOME ("either has no element " ^ el ^
        " or it is at the wrong position");

fun add_type_def (s, Basic_Type ty) (ids, thy) =
      (check_no_assoc thy s;
       (ids,
        Typedecl.abbrev_global (Binding.name s, [], NoSyn)
          (mk_type thy ty) thy |> snd))

  | add_type_def (s, Enum_Type els) ((tab, ctxt), thy) =
      let
        val (thy', tyname) = (case get_type thy s of
            NONE =>
              let
                val tyb = Binding.name s;
                val tyname = Sign.full_name thy tyb
              in
                (thy |>
                 Datatype.add_datatype {strict = true, quiet = true} [s]
                   [([], tyb, NoSyn,
                     map (fn s => (Binding.name s, [], NoSyn)) els)] |> snd |>
                 add_enum_type s tyname,
                 tyname)
              end
          | SOME (T as Type (tyname, [])) =>
              (case Datatype_Data.get_constrs thy tyname of
                 NONE => assoc_ty_err thy T s "is not a datatype"
               | SOME cs => (case check_enum els cs of
                   NONE => (thy, tyname)
                 | SOME msg => assoc_ty_err thy T s msg)));
        val cs = map Const (the (Datatype_Data.get_constrs thy' tyname))
      in
        ((fold (Symtab.update_new o apsnd (rpair s)) (els ~~ cs) tab,
          fold Name.declare els ctxt),
         thy')
      end

  | add_type_def (s, Array_Type (argtys, resty)) (ids, thy) =
      (check_no_assoc thy s;
       (ids,
        Typedecl.abbrev_global (Binding.name s, [], NoSyn)
          (foldr1 HOLogic.mk_prodT (map (mk_type thy) argtys) -->
             mk_type thy resty) thy |> snd))

  | add_type_def (s, Record_Type fldtys) (ids, thy) =
      (ids,
       let val fldTs = maps (fn (flds, ty) =>
         map (rpair (mk_type thy ty)) flds) fldtys
       in case get_type thy s of
           NONE =>
             Record.add_record true ([], Binding.name s) NONE
               (map (fn (fld, T) => (Binding.name fld, T, NoSyn)) fldTs) thy
         | SOME rT =>
             (case get_record_info thy rT of
                NONE => assoc_ty_err thy rT s "is not a record type"
              | SOME {fields, ...} =>
                  (case subtract (lcase_eq o pairself fst) fldTs fields of
                     [] => ()
                   | flds => assoc_ty_err thy rT s ("has extra field(s) " ^
                       commas (map (Long_Name.base_name o fst) flds));
                   map (fn (fld, T) =>
                     case AList.lookup lcase_eq fields fld of
                       NONE => assoc_ty_err thy rT s ("has no field " ^ fld)
                     | SOME U => T = U orelse assoc_ty_err thy rT s
                         ("has field " ^
                          fld ^ " whose type\n" ^
                          Syntax.string_of_typ_global thy U ^
                          "\ndoes not match declared type\n" ^
                          Syntax.string_of_typ_global thy T)) fldTs;
                   thy))
       end)

  | add_type_def (s, Pending_Type) (ids, thy) =
      (check_no_assoc thy s;
       (ids, Typedecl.typedecl_global (Binding.name s, [], NoSyn) thy |> snd));


fun term_of_expr thy types funs pfuns =
  let
    fun tm_of vs (Funct ("->", [e, e'])) =
          (HOLogic.mk_imp (fst (tm_of vs e), fst (tm_of vs e')), booleanN)

      | tm_of vs (Funct ("<->", [e, e'])) =
          (HOLogic.mk_eq (fst (tm_of vs e), fst (tm_of vs e')), booleanN)

      | tm_of vs (Funct ("or", [e, e'])) =
          (HOLogic.mk_disj (fst (tm_of vs e), fst (tm_of vs e')), booleanN)

      | tm_of vs (Funct ("and", [e, e'])) =
          (HOLogic.mk_conj (fst (tm_of vs e), fst (tm_of vs e')), booleanN)

      | tm_of vs (Funct ("not", [e])) =
          (HOLogic.mk_not (fst (tm_of vs e)), booleanN)

      | tm_of vs (Funct ("=", [e, e'])) =
          (HOLogic.mk_eq (fst (tm_of vs e), fst (tm_of vs e')), booleanN)

      | tm_of vs (Funct ("<>", [e, e'])) = (HOLogic.mk_not
          (HOLogic.mk_eq (fst (tm_of vs e), fst (tm_of vs e'))), booleanN)

      | tm_of vs (Funct ("<", [e, e'])) = (HOLogic.mk_binrel @{const_name less}
          (fst (tm_of vs e), fst (tm_of vs e')), booleanN)

      | tm_of vs (Funct (">", [e, e'])) = (HOLogic.mk_binrel @{const_name less}
          (fst (tm_of vs e'), fst (tm_of vs e)), booleanN)

      | tm_of vs (Funct ("<=", [e, e'])) = (HOLogic.mk_binrel @{const_name less_eq}
          (fst (tm_of vs e), fst (tm_of vs e')), booleanN)

      | tm_of vs (Funct (">=", [e, e'])) = (HOLogic.mk_binrel @{const_name less_eq}
          (fst (tm_of vs e'), fst (tm_of vs e)), booleanN)

      | tm_of vs (Funct ("+", [e, e'])) = (HOLogic.mk_binop @{const_name plus}
          (fst (tm_of vs e), fst (tm_of vs e')), integerN)

      | tm_of vs (Funct ("-", [e, e'])) = (HOLogic.mk_binop @{const_name minus}
          (fst (tm_of vs e), fst (tm_of vs e')), integerN)

      | tm_of vs (Funct ("*", [e, e'])) = (HOLogic.mk_binop @{const_name times}
          (fst (tm_of vs e), fst (tm_of vs e')), integerN)

      | tm_of vs (Funct ("/", [e, e'])) = (HOLogic.mk_binop @{const_name divide}
          (fst (tm_of vs e), fst (tm_of vs e')), integerN)

      | tm_of vs (Funct ("div", [e, e'])) = (HOLogic.mk_binop @{const_name sdiv}
          (fst (tm_of vs e), fst (tm_of vs e')), integerN)

      | tm_of vs (Funct ("mod", [e, e'])) = (HOLogic.mk_binop @{const_name mod}
          (fst (tm_of vs e), fst (tm_of vs e')), integerN)

      | tm_of vs (Funct ("-", [e])) =
          (mk_unop @{const_name uminus} (fst (tm_of vs e)), integerN)

      | tm_of vs (Funct ("**", [e, e'])) =
          (Const (@{const_name power}, HOLogic.intT --> HOLogic.natT -->
             HOLogic.intT) $ fst (tm_of vs e) $
               (@{const nat} $ fst (tm_of vs e')), integerN)

      | tm_of (tab, _) (Ident s) =
          (case Symtab.lookup tab s of
             SOME t_ty => t_ty
           | NONE => error ("Undeclared identifier " ^ s))

      | tm_of _ (Number i) = (HOLogic.mk_number HOLogic.intT i, integerN)

      | tm_of vs (Quantifier (s, xs, ty, e)) =
          let
            val (ys, vs') = mk_variables thy xs ty vs;
            val q = (case s of
                "for_all" => HOLogic.mk_all
              | "for_some" => HOLogic.mk_exists)
          in
            (fold_rev (fn Free (x, T) => fn t => q (x, T, t))
               ys (fst (tm_of vs' e)),
             booleanN)
          end

      | tm_of vs (Funct (s, es)) =

          (* record field selection *)
          (case try (unprefix "fld_") s of
             SOME fname => (case es of
               [e] =>
                 let
                   val (t, rcdty) = tm_of vs e;
                   val rT = mk_type thy rcdty
                 in case (get_record_info thy rT, lookup types rcdty) of
                     (SOME {fields, ...}, SOME (Record_Type fldtys)) =>
                       (case (find_field fname fields,
                            find_field' fname fldtys) of
                          (SOME (fname', fT), SOME fldty) =>
                            (Const (fname', rT --> fT) $ t, fldty)
                        | _ => error ("Record " ^ rcdty ^
                            " has no field named " ^ fname))
                   | _ => error (rcdty ^ " is not a record type")
                 end
             | _ => error ("Function " ^ s ^ " expects one argument"))
           | NONE =>

          (* record field update *)
          (case try (unprefix "upf_") s of
             SOME fname => (case es of
               [e, e'] =>
                 let
                   val (t, rcdty) = tm_of vs e;
                   val rT = mk_type thy rcdty;
                   val (u, fldty) = tm_of vs e';
                   val fT = mk_type thy fldty
                 in case get_record_info thy rT of
                     SOME {fields, ...} =>
                       (case find_field fname fields of
                          SOME (fname', fU) =>
                            if fT = fU then
                              (Const (fname' ^ "_update",
                                 (fT --> fT) --> rT --> rT) $
                                   Abs ("x", fT, u) $ t,
                               rcdty)
                            else error ("Type\n" ^
                              Syntax.string_of_typ_global thy fT ^
                              "\ndoes not match type\n" ^
                              Syntax.string_of_typ_global thy fU ^
                              "\nof field " ^ fname)
                        | NONE => error ("Record " ^ rcdty ^
                            " has no field named " ^ fname))
                   | _ => error (rcdty ^ " is not a record type")
                 end
             | _ => error ("Function " ^ s ^ " expects two arguments"))
           | NONE =>

          (* enumeration type to integer *)
          (case try (unsuffix "__pos") s of
             SOME tyname => (case es of
               [e] => (Const (@{const_name pos},
                 mk_type thy tyname --> HOLogic.intT) $ fst (tm_of vs e), integerN)
             | _ => error ("Function " ^ s ^ " expects one argument"))
           | NONE =>

          (* integer to enumeration type *)
          (case try (unsuffix "__val") s of
             SOME tyname => (case es of
               [e] => (Const (@{const_name val},
                 HOLogic.intT --> mk_type thy tyname) $ fst (tm_of vs e), tyname)
             | _ => error ("Function " ^ s ^ " expects one argument"))
           | NONE =>

          (* successor / predecessor of enumeration type element *)
          if s = "succ" orelse s = "pred" then (case es of
              [e] =>
                let
                  val (t, tyname) = tm_of vs e;
                  val T = mk_type thy tyname
                in (Const
                  (if s = "succ" then @{const_name succ}
                   else @{const_name pred}, T --> T) $ t, tyname)
                end
            | _ => error ("Function " ^ s ^ " expects one argument"))

          (* user-defined proof function *)
          else
            (case Symtab.lookup pfuns s of
               SOME (SOME (_, resty), t) =>
                 (list_comb (t, map (fst o tm_of vs) es), resty)
             | _ => error ("Undeclared proof function " ^ s))))))

      | tm_of vs (Element (e, es)) =
          let val (t, ty) = tm_of vs e
          in case lookup types ty of
              SOME (Array_Type (_, elty)) =>
                (t $ foldr1 HOLogic.mk_prod (map (fst o tm_of vs) es), elty)
            | _ => error (ty ^ " is not an array type")
          end

      | tm_of vs (Update (e, es, e')) =
          let val (t, ty) = tm_of vs e
          in case lookup types ty of
              SOME (Array_Type (idxtys, elty)) =>
                let
                  val T = foldr1 HOLogic.mk_prodT (map (mk_type thy) idxtys);
                  val U = mk_type thy elty;
                  val fT = T --> U
                in
                  (Const (@{const_name fun_upd}, fT --> T --> U --> fT) $
                     t $ foldr1 HOLogic.mk_prod (map (fst o tm_of vs) es) $
                       fst (tm_of vs e'),
                   ty)
                end
            | _ => error (ty ^ " is not an array type")
          end

      | tm_of vs (Record (s, flds)) =
          let
            val T = mk_type thy s;
            val {extension = (ext_name, _), fields, ...} =
              (case get_record_info thy T of
                 NONE => error (s ^ " is not a record type")
               | SOME info => info);
            val flds' = map (apsnd (tm_of vs)) flds;
            val fnames = map (Long_Name.base_name o fst) fields;
            val fnames' = map fst flds;
            val (fvals, ftys) = split_list (map (fn s' =>
              case AList.lookup lcase_eq flds' s' of
                SOME fval_ty => fval_ty
              | NONE => error ("Field " ^ s' ^ " missing in record " ^ s))
                  fnames);
            val _ = (case subtract lcase_eq fnames fnames' of
                [] => ()
              | xs => error ("Extra field(s) " ^ commas xs ^
                  " in record " ^ s));
            val _ = (case duplicates (op =) fnames' of
                [] => ()
              | xs => error ("Duplicate field(s) " ^ commas xs ^
                  " in record " ^ s))
          in
            (list_comb
               (Const (ext_name,
                  map (mk_type thy) ftys @ [HOLogic.unitT] ---> T),
                fvals @ [HOLogic.unit]),
             s)
          end

      | tm_of vs (Array (s, default, assocs)) =
          (case lookup types s of
             SOME (Array_Type (idxtys, elty)) =>
               let
                 val Ts = map (mk_type thy) idxtys;
                 val T = foldr1 HOLogic.mk_prodT Ts;
                 val U = mk_type thy elty;
                 fun mk_idx' T (e, NONE) = HOLogic.mk_set T [fst (tm_of vs e)]
                   | mk_idx' T (e, SOME e') = Const (@{const_name atLeastAtMost},
                       T --> T --> HOLogic.mk_setT T) $
                         fst (tm_of vs e) $ fst (tm_of vs e');
                 fun mk_idx idx =
                   if length Ts <> length idx then
                     error ("Arity mismatch in construction of array " ^ s)
                   else foldr1 mk_times (map2 mk_idx' Ts idx);
                 fun mk_upd (idxs, e) t =
                   if length idxs = 1 andalso forall (is_none o snd) (hd idxs)
                   then
                     Const (@{const_name fun_upd}, (T --> U) -->
                         T --> U --> T --> U) $ t $
                       foldl1 HOLogic.mk_prod
                         (map (fst o tm_of vs o fst) (hd idxs)) $
                       fst (tm_of vs e)
                   else
                     Const (@{const_name fun_upds}, (T --> U) -->
                         HOLogic.mk_setT T --> U --> T --> U) $ t $
                       foldl1 (HOLogic.mk_binop @{const_name sup})
                         (map mk_idx idxs) $
                       fst (tm_of vs e)
               in
                 (fold mk_upd assocs
                    (case default of
                       SOME e => Abs ("x", T, fst (tm_of vs e))
                     | NONE => Const (@{const_name undefined}, T --> U)),
                  s)
               end
           | _ => error (s ^ " is not an array type"))

  in tm_of end;


fun term_of_rule thy types funs pfuns ids rule =
  let val tm_of = fst o term_of_expr thy types funs pfuns ids
  in case rule of
      Inference_Rule (es, e) => Logic.list_implies
        (map (HOLogic.mk_Trueprop o tm_of) es, HOLogic.mk_Trueprop (tm_of e))
    | Substitution_Rule (es, e, e') => Logic.list_implies
        (map (HOLogic.mk_Trueprop o tm_of) es,
         HOLogic.mk_Trueprop (HOLogic.mk_eq (tm_of e, tm_of e')))
  end;


val builtin = Symtab.make (map (rpair ())
  ["->", "<->", "or", "and", "not", "=", "<>", "<", ">", "<=", ">=",
   "+", "-", "*", "/", "div", "mod", "**"]);

fun complex_expr (Number _) = false
  | complex_expr (Ident _) = false 
  | complex_expr (Funct (s, es)) =
      not (Symtab.defined builtin s) orelse exists complex_expr es
  | complex_expr (Quantifier (_, _, _, e)) = complex_expr e
  | complex_expr _ = true;

fun complex_rule (Inference_Rule (es, e)) =
      complex_expr e orelse exists complex_expr es
  | complex_rule (Substitution_Rule (es, e, e')) =
      complex_expr e orelse complex_expr e' orelse
      exists complex_expr es;

val is_pfun =
  Symtab.defined builtin orf
  can (unprefix "fld_") orf can (unprefix "upf_") orf
  can (unsuffix "__pos") orf can (unsuffix "__val") orf
  equal "succ" orf equal "pred";

fun fold_opt f = the_default I o Option.map f;
fun fold_pair f g (x, y) = f x #> g y;

fun fold_expr f g (Funct (s, es)) = f s #> fold (fold_expr f g) es
  | fold_expr f g (Ident s) = g s
  | fold_expr f g (Number _) = I
  | fold_expr f g (Quantifier (_, _, _, e)) = fold_expr f g e
  | fold_expr f g (Element (e, es)) =
      fold_expr f g e #> fold (fold_expr f g) es
  | fold_expr f g (Update (e, es, e')) =
      fold_expr f g e #> fold (fold_expr f g) es #> fold_expr f g e'
  | fold_expr f g (Record (_, flds)) = fold (fold_expr f g o snd) flds
  | fold_expr f g (Array (_, default, assocs)) =
      fold_opt (fold_expr f g) default #>
      fold (fold_pair
        (fold (fold (fold_pair
          (fold_expr f g) (fold_opt (fold_expr f g)))))
        (fold_expr f g)) assocs;

val add_expr_pfuns = fold_expr
  (fn s => if is_pfun s then I else insert (op =) s) (K I);

val add_expr_idents = fold_expr (K I) (insert (op =));

fun pfun_type thy (argtys, resty) =
  map (mk_type thy) argtys ---> mk_type thy resty;

fun check_pfun_type thy s t optty1 optty2 =
  let
    val T = fastype_of t;
    fun check ty =
      let val U = pfun_type thy ty
      in
        T = U orelse
        error ("Type\n" ^
          Syntax.string_of_typ_global thy T ^
          "\nof function " ^
          Syntax.string_of_term_global thy t ^
          " associated with proof function " ^ s ^
          "\ndoes not match declared type\n" ^
          Syntax.string_of_typ_global thy U)
      end
  in (Option.map check optty1; Option.map check optty2; ()) end;

fun upd_option x y = if is_some x then x else y;

fun check_pfuns_types thy funs =
  Symtab.map (fn s => fn (optty, t) =>
   let val optty' = lookup funs s
   in
     (check_pfun_type thy s t optty optty';
      (NONE |> upd_option optty |> upd_option optty', t))
   end);


(** the VC store **)

fun err_vcs names = error (Pretty.string_of
  (Pretty.big_list "The following verification conditions have not been proved:"
    (map Pretty.str names)))

fun set_env (env as {funs, ...}) thy = VCs.map (fn
    {pfuns, type_map, env = NONE} =>
      {pfuns = check_pfuns_types thy funs pfuns,
       type_map = type_map,
       env = SOME env}
  | _ => err_unfinished ()) thy;

fun mk_pat s = (case Int.fromString s of
    SOME i => [HOLogic.mk_Trueprop (Var (("C", i), HOLogic.boolT))]
  | NONE => error ("Bad conclusion identifier: C" ^ s));

fun mk_vc thy types funs pfuns ids (tr, proved, ps, cs) =
  let val prop_of =
    HOLogic.mk_Trueprop o fst o term_of_expr thy types funs pfuns ids
  in
    (tr, proved,
     Element.Assumes (map (fn (s', e) =>
       ((Binding.name ("H" ^ s'), []), [(prop_of e, [])])) ps),
     Element.Shows (map (fn (s', e) =>
       (Attrib.empty_binding, [(prop_of e, mk_pat s')])) cs))
  end;

fun fold_vcs f vcs =
  VCtab.fold (fn (_, (_, _, ps, cs)) => fold f ps #> fold f cs) vcs;

fun pfuns_of_vcs pfuns vcs =
  fold_vcs (add_expr_pfuns o snd) vcs [] |>
  filter_out (Symtab.defined pfuns);

fun declare_missing_pfuns thy funs pfuns vcs (tab, ctxt) =
  let
    val (fs, (tys, Ts)) =
      pfuns_of_vcs pfuns vcs |>
      map_filter (fn s => lookup funs s |>
        Option.map (fn ty => (s, (SOME ty, pfun_type thy ty)))) |>
      split_list ||> split_list;
    val (fs', ctxt') = Name.variants fs ctxt
  in
    (fold Symtab.update_new (fs ~~ (tys ~~ map Free (fs' ~~ Ts))) pfuns,
     Element.Fixes (map2 (fn s => fn T =>
       (Binding.name s, SOME T, NoSyn)) fs' Ts),
     (tab, ctxt'))
  end;

fun add_proof_fun prep (s, (optty, raw_t)) thy =
  VCs.map (fn
      {env = SOME {proving = true, ...}, ...} => err_unfinished ()
    | {pfuns, type_map, env} =>
        let
          val optty' = (case env of
              SOME {funs, ...} => lookup funs s
            | NONE => NONE);
          val optty'' = NONE |> upd_option optty |> upd_option optty';
          val t = prep (Option.map (pfun_type thy) optty'') raw_t;
          val _ = (case fold_aterms (fn u =>
              if is_Var u orelse is_Free u then insert (op =) u else I) t [] of
              [] => ()
            | ts => error ("Term\n" ^ Syntax.string_of_term_global thy t ^
                "\nto be associated with proof function " ^ s ^
                " contains free variable(s) " ^
                commas (map (Syntax.string_of_term_global thy) ts)));
        in
          (check_pfun_type thy s t optty optty';
           if is_some optty'' orelse is_none env then
             {pfuns = Symtab.update_new (s, (optty'', t)) pfuns,
              type_map = type_map,
              env = env}
               handle Symtab.DUP _ => error ("Proof function " ^ s ^
                 " already associated with function")
           else error ("Undeclared proof function " ^ s))
        end) thy;

fun add_type (s, T as Type (tyname, Ts)) thy =
      thy |>
      VCs.map (fn
          {env = SOME _, ...} => err_unfinished ()
        | {pfuns, type_map, env} =>
            {pfuns = pfuns,
             type_map = Symtab.update_new (s, T) type_map,
             env = env}
              handle Symtab.DUP _ => error ("SPARK type " ^ s ^
                " already associated with type")) |>
      (fn thy' =>
         case Datatype_Data.get_constrs thy' tyname of
           NONE => thy'
         | SOME cs =>
             if null Ts then
               (map
                  (fn (_, Type (_, [])) => ()
                    | (cname, _) => assoc_ty_err thy T s
                        ("has illegal constructor " ^
                         Long_Name.base_name cname)) cs;
                add_enum_type s tyname thy')
             else assoc_ty_err thy T s "is illegal")
  | add_type (s, T) thy = assoc_ty_err thy T s "is illegal";

val is_closed = is_none o #env o VCs.get;

fun lookup_vc thy name =
  (case VCs.get thy of
    {env = SOME {vcs, types, funs, ids, ctxt, ...}, pfuns, ...} =>
      (case VCtab.lookup vcs name of
         SOME vc =>           
           let val (pfuns', ctxt', ids') =
             declare_missing_pfuns thy funs pfuns vcs ids
           in SOME (ctxt @ [ctxt'], mk_vc thy types funs pfuns' ids' vc) end
       | NONE => NONE)
  | _ => NONE);

fun get_vcs thy = (case VCs.get thy of
    {env = SOME {vcs, types, funs, ids, ctxt, defs, ...}, pfuns, ...} =>
      let val (pfuns', ctxt', ids') =
        declare_missing_pfuns thy funs pfuns vcs ids
      in
        (ctxt @ [ctxt'], defs,
         VCtab.dest vcs |>
         map (apsnd (mk_vc thy types funs pfuns' ids')))
      end
  | _ => ([], [], []));

fun mark_proved name thms = VCs.map (fn
    {pfuns, type_map,
     env = SOME {ctxt, defs, types, funs, ids, vcs, path, ...}} =>
      {pfuns = pfuns,
       type_map = type_map,
       env = SOME {ctxt = ctxt, defs = defs,
         types = types, funs = funs, ids = ids,
         proving = true,
         vcs = VCtab.map_entry name (fn (trace, _, ps, cs) =>
           (trace, SOME thms, ps, cs)) vcs,
         path = path}}
  | x => x);

fun close thy =
  thy |>
  VCs.map (fn
      {pfuns, type_map, env = SOME {vcs, path, ...}} =>
        (case VCtab.fold_rev (fn vc as (_, (_, p, _, _)) =>
             (if is_some p then apfst else apsnd) (cons vc)) vcs ([], []) of
           (proved, []) =>
             (Thm.join_proofs (maps (the o #2 o snd) proved);
              File.write (Path.ext "prv" path)
                (concat (map (fn (s, _) => snd (strip_number s) ^
                   " -- proved by " ^ Distribution.version ^ "\n") proved));
              {pfuns = pfuns, type_map = type_map, env = NONE})
         | (_, unproved) => err_vcs (map fst unproved))
    | _ => error "No SPARK environment is currently open") |>
  Sign.parent_path;


(** set up verification conditions **)

fun partition_opt f =
  let
    fun part ys zs [] = (rev ys, rev zs)
      | part ys zs (x :: xs) = (case f x of
            SOME y => part (y :: ys) zs xs
          | NONE => part ys (x :: zs) xs)
  in part [] [] end;

fun dest_def (id, (Substitution_Rule ([], Ident s, rhs))) = SOME (id, (s, rhs))
  | dest_def _ = NONE;

fun mk_rulename (s, i) = Binding.name (s ^ string_of_int i);

fun add_const (s, ty) ((tab, ctxt), thy) =
  let
    val T = mk_type thy ty;
    val b = Binding.name s;
    val c = Const (Sign.full_name thy b, T)
  in
    (c,
     ((Symtab.update (s, (c, ty)) tab, Name.declare s ctxt),
      Sign.add_consts_i [(b, T, NoSyn)] thy))
  end;

fun add_def types funs pfuns consts (id, (s, e)) (ids as (tab, ctxt), thy) =
  (case lookup consts s of
     SOME ty =>
       let
         val (t, ty') = term_of_expr thy types funs pfuns ids e;
         val T = mk_type thy ty;
         val T' = mk_type thy ty';
         val _ = T = T' orelse
           error ("Declared type " ^ ty ^ " of " ^ s ^
             "\ndoes not match type " ^ ty' ^ " in definition");
         val id' = mk_rulename id;
         val lthy = Named_Target.theory_init thy;
         val ((t', (_, th)), lthy') = Specification.definition
           (NONE, ((id', []), HOLogic.mk_Trueprop (HOLogic.mk_eq
             (Free (s, T), t)))) lthy;
         val phi = Proof_Context.export_morphism lthy' lthy
       in
         ((id', Morphism.thm phi th),
          ((Symtab.update (s, (Morphism.term phi t', ty)) tab,
            Name.declare s ctxt),
           Local_Theory.exit_global lthy'))
       end
   | NONE => error ("Undeclared constant " ^ s));

fun add_var (s, ty) (ids, thy) =
  let val ([Free p], ids') = mk_variables thy [s] ty ids
  in (p, (ids', thy)) end;

fun add_init_vars vcs (ids_thy as ((tab, _), _)) =
  fold_map add_var
    (map_filter
       (fn s => case try (unsuffix "~") s of
          SOME s' => (case Symtab.lookup tab s' of
            SOME (_, ty) => SOME (s, ty)
          | NONE => error ("Undeclared identifier " ^ s'))
        | NONE => NONE)
       (fold_vcs (add_expr_idents o snd) vcs []))
    ids_thy;

fun is_trivial_vc ([], [(_, Ident "true")]) = true
  | is_trivial_vc _ = false;

fun rulenames rules = commas
  (map (fn ((s, i), _) => s ^ "(" ^ string_of_int i ^ ")") rules);

(* sort definitions according to their dependency *)
fun sort_defs _ _ [] sdefs = rev sdefs
  | sort_defs pfuns consts defs sdefs =
      (case find_first (fn (_, (_, e)) =>
         forall (Symtab.defined pfuns) (add_expr_pfuns e []) andalso
         forall (fn id =>
           member (fn (s, (_, (s', _))) => s = s') sdefs id orelse
           consts id)
             (add_expr_idents e [])) defs of
         SOME d => sort_defs pfuns consts
           (remove (op =) d defs) (d :: sdefs)
       | NONE => error ("Bad definitions: " ^ rulenames defs));

fun set_vcs ({types, vars, consts, funs} : decls)
      (rules, _) ((_, ident), vcs) path thy =
  let
    val {pfuns, ...} = VCs.get thy;
    val (defs, rules') = partition_opt dest_def rules;
    val consts' =
      subtract (fn ((_, (s, _)), (s', _)) => s = s') defs (items consts);
    (* ignore all complex rules in rls files *)
    val (rules'', other_rules) =
      List.partition (complex_rule o snd) rules';
    val _ = if null rules'' then ()
      else warning ("Ignoring rules: " ^ rulenames rules'');

    val vcs' = VCtab.make (maps (fn (tr, vcs) =>
      map (fn (s, (ps, cs)) => (s, (tr, NONE, ps, cs)))
        (filter_out (is_trivial_vc o snd) vcs)) vcs);

    val _ = (case filter_out (is_some o lookup funs)
        (pfuns_of_vcs pfuns vcs') of
        [] => ()
      | fs => error ("Undeclared proof function(s) " ^ commas fs));

    val (((defs', vars''), ivars), (ids, thy')) =
      ((Symtab.empty |>
        Symtab.update ("false", (HOLogic.false_const, booleanN)) |>
        Symtab.update ("true", (HOLogic.true_const, booleanN)),
        Name.context),
       thy |> Sign.add_path (Long_Name.base_name ident)) |>
      fold add_type_def (items types) |>
      fold (snd oo add_const) consts' |> (fn ids_thy as ((tab, _), _) =>
        ids_thy |>
        fold_map (add_def types funs pfuns consts)
          (sort_defs pfuns (Symtab.defined tab) defs []) ||>>
        fold_map add_var (items vars) ||>>
        add_init_vars vcs');

    val ctxt =
      [Element.Fixes (map (fn (s, T) =>
         (Binding.name s, SOME T, NoSyn)) (vars'' @ ivars)),
       Element.Assumes (map (fn (id, rl) =>
         ((mk_rulename id, []),
          [(term_of_rule thy' types funs pfuns ids rl, [])]))
           other_rules),
       Element.Notes (Thm.definitionK,
         [((Binding.name "defns", []), map (rpair [] o single o snd) defs')])]
          
  in
    set_env {ctxt = ctxt, defs = defs', types = types, funs = funs,
      ids = ids, proving = false, vcs = vcs', path = path} thy'
  end;

end;