(*  Title:      Pure/Isar/code.ML

    Author:     Florian Haftmann, TU Muenchen

Abstract executable ingredients of theory.  Management of data

dependent on executable ingredients as synchronized cache; purged

on any change of underlying executable ingredients.

*)

signature CODE =

sig

  (*constants*)

  val check_const: theory -> term -> string

  val read_bare_const: theory -> string -> string * typ

  val read_const: theory -> string -> string

  val string_of_const: theory -> string -> string

  val cert_signature: theory -> typ -> typ

  val read_signature: theory -> string -> typ

  val const_typ: theory -> string -> typ

  val subst_signatures: theory -> term -> term

  val args_number: theory -> string -> int

  (*constructor sets*)

  val constrset_of_consts: theory -> (string * typ) list

    -> string * ((string * sort) list * (string * typ list) list)

  (*code equations*)

  val mk_eqn: theory -> thm * bool -> thm * bool

  val mk_eqn_warning: theory -> thm -> (thm * bool) option

  val mk_eqn_liberal: theory -> thm -> (thm * bool) option

  val assert_eqn: theory -> thm * bool -> thm * bool

  val assert_eqns_const: theory -> string

    -> (thm * bool) list -> (thm * bool) list

  val const_typ_eqn: theory -> thm -> string * typ

  val typscheme_eqn: theory -> thm -> (string * sort) list * typ

  val typscheme_eqns: theory -> string -> thm list -> (string * sort) list * typ

  val standard_typscheme: theory -> thm list -> thm list

  (*executable code*)

  val add_type: string -> theory -> theory

  val add_type_cmd: string -> theory -> theory

  val add_signature: string * typ -> theory -> theory

  val add_signature_cmd: string * string -> theory -> theory

  val add_datatype: (string * typ) list -> theory -> theory

  val add_datatype_cmd: string list -> theory -> theory

  val type_interpretation:

    (string * ((string * sort) list * (string * typ list) list)

      -> theory -> theory) -> theory -> theory

  val add_eqn: thm -> theory -> theory

  val add_nbe_eqn: thm -> theory -> theory

  val add_default_eqn: thm -> theory -> theory

  val add_default_eqn_attribute: attribute

  val add_default_eqn_attrib: Attrib.src

  val del_eqn: thm -> theory -> theory

  val del_eqns: string -> theory -> theory

  val add_case: thm -> theory -> theory

  val add_undefined: string -> theory -> theory

  val get_datatype: theory -> string -> ((string * sort) list * (string * typ list) list)

  val get_datatype_of_constr: theory -> string -> string option

  val these_eqns: theory -> string -> (thm * bool) list

  val all_eqns: theory -> (thm * bool) list

  val get_case_scheme: theory -> string -> (int * (int * string list)) option

  val undefineds: theory -> string list

  val print_codesetup: theory -> unit

  (*infrastructure*)

  val set_code_target_attr: (string -> thm -> theory -> theory) -> theory -> theory

  val purge_data: theory -> theory

end;

signature CODE_DATA_ARGS =

sig

  type T

  val empty: T

end;

signature CODE_DATA =

sig

  type T

  val change: theory -> (T -> T) -> T

  val change_yield: theory -> (T -> 'a * T) -> 'a * T

end;

signature PRIVATE_CODE =

sig

  include CODE

  val declare_data: Object.T -> serial

  val change_data: serial * ('a -> Object.T) * (Object.T -> 'a)

    -> theory -> ('a -> 'a) -> 'a

  val change_yield_data: serial * ('a -> Object.T) * (Object.T -> 'a)

    -> theory -> ('a -> 'b * 'a) -> 'b * 'a

end;

structure Code : PRIVATE_CODE =

struct

(** auxiliary **)

(* printing *)

fun string_of_typ thy = setmp_CRITICAL show_sorts true (Syntax.string_of_typ_global thy);

fun string_of_const thy c = case AxClass.inst_of_param thy c

 of SOME (c, tyco) => Sign.extern_const thy c ^ " " ^ enclose "[" "]" (Sign.extern_type thy tyco)

  | NONE => Sign.extern_const thy c;

(* constants *)

fun typ_equiv tys = Type.raw_instance tys andalso Type.raw_instance (swap tys);

fun check_bare_const thy t = case try dest_Const t

 of SOME c_ty => c_ty

  | NONE => error ("Not a constant: " ^ Syntax.string_of_term_global thy t);

fun check_const thy = AxClass.unoverload_const thy o check_bare_const thy;

fun read_bare_const thy = check_bare_const thy o Syntax.read_term_global thy;

fun read_const thy = AxClass.unoverload_const thy o read_bare_const thy;

(** data store **)

(* code equations *)

type eqns = bool * (thm * bool) list;

  (*default flag, theorems with proper flag *)

fun add_drop_redundant thy (thm, proper) thms =

  let

    val args_of = snd o strip_comb o map_types Type.strip_sorts

      o fst o Logic.dest_equals o Thm.plain_prop_of;

    val args = args_of thm;

    val incr_idx = Logic.incr_indexes ([], Thm.maxidx_of thm + 1);

    fun matches_args args' = length args <= length args' andalso

      Pattern.matchess thy (args, (map incr_idx o take (length args)) args');

    fun drop (thm', proper') = if (proper orelse not proper')

      andalso matches_args (args_of thm') then 

        (warning ("Code generator: dropping redundant code equation\n" ^

            Display.string_of_thm_global thy thm'); true)

      else false;

  in (thm, proper) :: filter_out drop thms end;

fun add_thm thy _ thm (false, thms) = (false, add_drop_redundant thy thm thms)

  | add_thm thy true thm (true, thms) = (true, thms @ [thm])

  | add_thm thy false thm (true, thms) = (false, [thm]);

fun del_thm thm = apsnd (remove (eq_fst Thm.eq_thm_prop) (thm, true));

(* executable code data *)

datatype spec = Spec of {

  history_concluded: bool,

  signatures: int Symtab.table * typ Symtab.table,

  eqns: ((bool * eqns) * (serial * eqns) list) Symtab.table

    (*with explicit history*),

  dtyps: ((serial * ((string * sort) list * (string * typ list) list)) list) Symtab.table

    (*with explicit history*),

  cases: (int * (int * string list)) Symtab.table * unit Symtab.table

};

fun make_spec (history_concluded, ((signatures, eqns), (dtyps, cases))) =

  Spec { history_concluded = history_concluded,

    signatures = signatures, eqns = eqns, dtyps = dtyps, cases = cases };

fun map_spec f (Spec { history_concluded = history_concluded, signatures = signatures,

  eqns = eqns, dtyps = dtyps, cases = cases }) =

  make_spec (f (history_concluded, ((signatures, eqns), (dtyps, cases))));

fun merge_spec (Spec { history_concluded = _, signatures = (tycos1, sigs1), eqns = eqns1,

    dtyps = dtyps1, cases = (cases1, undefs1) },

  Spec { history_concluded = _, signatures = (tycos2, sigs2), eqns = eqns2,

    dtyps = dtyps2, cases = (cases2, undefs2) }) =

  let

    val signatures = (Symtab.merge (op =) (tycos1, tycos2),

      Symtab.merge typ_equiv (sigs1, sigs2));

    fun merge_eqns ((_, history1), (_, history2)) =

      let

        val raw_history = AList.merge (op = : serial * serial -> bool)

          (K true) (history1, history2)

        val filtered_history = filter_out (fst o snd) raw_history

        val history = if null filtered_history

          then raw_history else filtered_history;

      in ((false, (snd o hd) history), history) end;

    val eqns = Symtab.join (K merge_eqns) (eqns1, eqns2);

    val dtyps = Symtab.join (K (AList.merge (op =) (K true))) (dtyps1, dtyps2);

    val cases = (Symtab.merge (K true) (cases1, cases2),

      Symtab.merge (K true) (undefs1, undefs2));

  in make_spec (false, ((signatures, eqns), (dtyps, cases))) end;

fun history_concluded (Spec { history_concluded, ... }) = history_concluded;

fun the_signatures (Spec { signatures, ... }) = signatures;

fun the_eqns (Spec { eqns, ... }) = eqns;

fun the_dtyps (Spec { dtyps, ... }) = dtyps;

fun the_cases (Spec { cases, ... }) = cases;

val map_history_concluded = map_spec o apfst;

val map_signatures = map_spec o apsnd o apfst o apfst;

val map_eqns = map_spec o apsnd o apfst o apsnd;

val map_dtyps = map_spec o apsnd o apsnd o apfst;

val map_cases = map_spec o apsnd o apsnd o apsnd;

(* data slots dependent on executable code *)

(*private copy avoids potential conflict of table exceptions*)

structure Datatab = Table(type key = int val ord = int_ord);

local

type kind = { empty: Object.T };

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

fun invoke f k = case Datatab.lookup (! kinds) k

 of SOME kind => f kind

  | NONE => sys_error "Invalid code data identifier";

in

fun declare_data empty =

  let

    val k = serial ();

    val kind = { empty = empty };

    val _ = CRITICAL (fn () => Unsynchronized.change kinds (Datatab.update (k, kind)));

  in k end;

fun invoke_init k = invoke (fn kind => #empty kind) k;

end; (*local*)

(* theory store *)

local

type data = Object.T Datatab.table;

fun create_data data = Synchronized.var "code data" data;

fun empty_data () = create_data Datatab.empty;

structure Code_Data = TheoryDataFun

(

  type T = spec * data Synchronized.var;

  val empty = (make_spec (false, (((Symtab.empty, Symtab.empty), Symtab.empty),

    (Symtab.empty, (Symtab.empty, Symtab.empty)))), empty_data ());

  fun copy (spec, data) = (spec, create_data (Synchronized.value data));

  val extend = copy;

  fun merge _ ((spec1, _), (spec2, _)) =

    (merge_spec (spec1, spec2), empty_data ());

);

fun thy_data f thy = f ((snd o Code_Data.get) thy);

fun get_ensure_init kind data =

  case Datatab.lookup (Synchronized.value data) kind

   of SOME x => x

    | NONE => let val y = invoke_init kind

        in (Synchronized.change data (Datatab.update (kind, y)); y) end;

in

(* access to executable code *)

val the_exec = fst o Code_Data.get;

fun map_exec_purge f =

  Code_Data.map (fn (exec, data) => (f exec, empty_data ()));

val purge_data = (Code_Data.map o apsnd) (fn _ => empty_data ());

fun change_eqns delete c f = (map_exec_purge o map_eqns

  o (if delete then Symtab.map_entry c else Symtab.map_default (c, ((false, (true, [])), [])))

    o apfst) (fn (_, eqns) => (true, f eqns));

fun del_eqns c = change_eqns true c (K (false, []));

(* tackling equation history *)

fun get_eqns thy c =

  Symtab.lookup ((the_eqns o the_exec) thy) c

  |> Option.map (snd o snd o fst)

  |> these;

fun continue_history thy = if (history_concluded o the_exec) thy

  then thy

    |> (Code_Data.map o apfst o map_history_concluded) (K false)

    |> SOME

  else NONE;

fun conclude_history thy = if (history_concluded o the_exec) thy

  then NONE

  else thy

    |> (Code_Data.map o apfst)

        ((map_eqns o Symtab.map) (fn ((changed, current), history) =>

          ((false, current),

            if changed then (serial (), current) :: history else history))

        #> map_history_concluded (K true))

    |> SOME;

val _ = Context.>> (Context.map_theory (Code_Data.init

  #> Theory.at_begin continue_history

  #> Theory.at_end conclude_history));

(* access to data dependent on abstract executable code *)

fun change_data (kind, mk, dest) =

  let

    fun chnge data_ref f =

      let

        val data = get_ensure_init kind data_ref;

        val data' = f (dest data);

      in (Synchronized.change data_ref (Datatab.update (kind, mk data')); data') end;

  in thy_data chnge end;

fun change_yield_data (kind, mk, dest) =

  let

    fun chnge data_ref f =

      let

        val data = get_ensure_init kind data_ref;

        val (x, data') = f (dest data);

      in (x, (Synchronized.change data_ref (Datatab.update (kind, mk data')); data')) end;

  in thy_data chnge end;

end; (*local*)

(** foundation **)

(* constants *)

fun arity_number thy tyco = case Symtab.lookup ((fst o the_signatures o the_exec) thy) tyco

 of SOME n => n

  | NONE => Sign.arity_number thy tyco;

fun build_tsig thy =

  let

    val (tycos, _) = (the_signatures o the_exec) thy;

    val decls = (#types o Type.rep_tsig o Sign.tsig_of) thy

      |> apsnd (Symtab.fold (fn (tyco, n) =>

          Symtab.update (tyco, Type.LogicalType n)) tycos);

  in Type.build_tsig ((Name_Space.empty "", Sorts.empty_algebra), [], decls) end;

fun cert_signature thy = Logic.varifyT o Type.cert_typ (build_tsig thy) o Type.no_tvars;

fun read_signature thy = cert_signature thy o Type.strip_sorts

  o Syntax.parse_typ (ProofContext.init thy);

fun expand_signature thy = Type.cert_typ_mode Type.mode_syntax (Sign.tsig_of thy);

fun lookup_typ thy = Symtab.lookup ((snd o the_signatures o the_exec) thy);

fun const_typ thy c = case lookup_typ thy c

 of SOME ty => ty

  | NONE => (Type.strip_sorts o Sign.the_const_type thy) c;

fun subst_signature thy c ty =

  let

    fun mk_subst (Type (tyco, tys1)) (ty2 as Type (tyco2, tys2)) =

          fold2 mk_subst tys1 tys2

      | mk_subst ty (TVar (v, sort)) = Vartab.update (v, ([], ty))

  in case lookup_typ thy c

   of SOME ty' => Envir.subst_type (mk_subst ty (expand_signature thy ty') Vartab.empty) ty'

    | NONE => ty

  end;

fun subst_signatures thy = map_aterms (fn Const (c, ty) => Const (c, subst_signature thy c ty) | t => t);

fun args_number thy = length o fst o strip_type o const_typ thy;

(* datatypes *)

fun constrset_of_consts thy cs =

  let

    val _ = map (fn (c, _) => if (is_some o AxClass.class_of_param thy) c

      then error ("Is a class parameter: " ^ string_of_const thy c) else ()) cs;

    fun no_constr s (c, ty) = error ("Not a datatype constructor:\n" ^ string_of_const thy c

      ^ " :: " ^ string_of_typ thy ty ^ "\n" ^ enclose "(" ")" s);

    fun last_typ c_ty ty =

      let

        val tfrees = Term.add_tfreesT ty [];

        val (tyco, vs) = ((apsnd o map) (dest_TFree) o dest_Type o snd o strip_type) ty

          handle TYPE _ => no_constr "bad type" c_ty

        val _ = if has_duplicates (eq_fst (op =)) vs

          then no_constr "duplicate type variables in datatype" c_ty else ();

        val _ = if length tfrees <> length vs

          then no_constr "type variables missing in datatype" c_ty else ();

      in (tyco, vs) end;

    fun ty_sorts (c, raw_ty) =

      let

        val ty = subst_signature thy c raw_ty;

        val ty_decl = (Logic.unvarifyT o const_typ thy) c;

        val (tyco, _) = last_typ (c, ty) ty_decl;

        val (_, vs) = last_typ (c, ty) ty;

      in ((tyco, map snd vs), (c, (map fst vs, ty))) end;

    fun add ((tyco', sorts'), c) ((tyco, sorts), cs) =

      let

        val _ = if (tyco' : string) <> tyco

          then error "Different type constructors in constructor set"

          else ();

        val sorts'' = map2 (curry (Sorts.inter_sort (Sign.classes_of thy))) sorts' sorts

      in ((tyco, sorts), c :: cs) end;

    fun inst vs' (c, (vs, ty)) =

      let

        val the_v = the o AList.lookup (op =) (vs ~~ vs');

        val ty' = map_atyps (fn TFree (v, _) => TFree (the_v v)) ty;

      in (c, (fst o strip_type) ty') end;

    val c' :: cs' = map ty_sorts cs;

    val ((tyco, sorts), cs'') = fold add cs' (apsnd single c');

    val vs = Name.names Name.context Name.aT sorts;

    val cs''' = map (inst vs) cs'';

  in (tyco, (vs, rev cs''')) end;

fun get_datatype thy tyco =

  case these (Symtab.lookup ((the_dtyps o the_exec) thy) tyco)

   of (_, spec) :: _ => spec

    | [] => arity_number thy tyco

        |> Name.invents Name.context Name.aT

        |> map (rpair [])

        |> rpair [];

fun get_datatype_of_constr thy c =

  case (snd o strip_type o const_typ thy) c

   of Type (tyco, _) => if member (op =) ((map fst o snd o get_datatype thy) tyco) c

       then SOME tyco else NONE

    | _ => NONE;

fun is_constr thy = is_some o get_datatype_of_constr thy;

(* code equations *)

exception BAD_THM of string;

fun bad_thm msg = raise BAD_THM msg;

fun error_thm f thm = f thm handle BAD_THM msg => error msg;

fun warning_thm f thm = SOME (f thm) handle BAD_THM msg => (warning msg; NONE)

fun try_thm f thm = SOME (f thm) handle BAD_THM _ => NONE;

fun is_linear thm =

  let val (_, args) = (strip_comb o fst o Logic.dest_equals o Thm.plain_prop_of) thm

  in not (has_duplicates (op =) ((fold o fold_aterms)

    (fn Var (v, _) => cons v | _ => I) args [])) end;

fun gen_assert_eqn thy is_constr_pat (thm, proper) =

  let

    val (lhs, rhs) = (Logic.dest_equals o Thm.plain_prop_of) thm

      handle TERM _ => bad_thm ("Not an equation: " ^ Display.string_of_thm_global thy thm)

           | THM _ => bad_thm ("Not an equation: " ^ Display.string_of_thm_global thy thm);

    fun vars_of t = fold_aterms (fn Var (v, _) => insert (op =) v

      | Free _ => bad_thm ("Illegal free variable in equation\n"

          ^ Display.string_of_thm_global thy thm)

      | _ => I) t [];

    fun tvars_of t = fold_term_types (fn _ =>

      fold_atyps (fn TVar (v, _) => insert (op =) v

        | TFree _ => bad_thm 

      ("Illegal free type variable in equation\n" ^ Display.string_of_thm_global thy thm))) t [];

    val lhs_vs = vars_of lhs;

    val rhs_vs = vars_of rhs;

    val lhs_tvs = tvars_of lhs;

    val rhs_tvs = tvars_of rhs;

    val _ = if null (subtract (op =) lhs_vs rhs_vs)

      then ()

      else bad_thm ("Free variables on right hand side of equation\n"

        ^ Display.string_of_thm_global thy thm);

    val _ = if null (subtract (op =) lhs_tvs rhs_tvs)

      then ()

      else bad_thm ("Free type variables on right hand side of equation\n"

        ^ Display.string_of_thm_global thy thm)

    val (head, args) = (strip_comb o fst o Logic.dest_equals o Thm.plain_prop_of) thm;

    val (c, ty) = case head

     of Const (c_ty as (_, ty)) => (AxClass.unoverload_const thy c_ty, ty)

      | _ => bad_thm ("Equation not headed by constant\n" ^ Display.string_of_thm_global thy thm);

    fun check _ (Abs _) = bad_thm

          ("Abstraction on left hand side of equation\n"

            ^ Display.string_of_thm_global thy thm)

      | check 0 (Var _) = ()

      | check _ (Var _) = bad_thm

          ("Variable with application on left hand side of equation\n"

            ^ Display.string_of_thm_global thy thm)

      | check n (t1 $ t2) = (check (n+1) t1; check 0 t2)

      | check n (Const (c_ty as (_, ty))) =

          let

            val c' = AxClass.unoverload_const thy c_ty

          in if n = (length o fst o strip_type o subst_signature thy c') ty

            then if not proper orelse is_constr_pat c'

              then ()

              else bad_thm (quote c ^ " is not a constructor, on left hand side of equation\n"

                ^ Display.string_of_thm_global thy thm)

            else bad_thm

              ("Partially applied constant " ^ quote c ^ " on left hand side of equation\n"

                 ^ Display.string_of_thm_global thy thm)

          end;

    val _ = map (check 0) args;

    val _ = if not proper orelse is_linear thm then ()

      else bad_thm ("Duplicate variables on left hand side of equation\n"

        ^ Display.string_of_thm_global thy thm);

    val _ = if (is_none o AxClass.class_of_param thy) c

      then ()

      else bad_thm ("Overloaded constant as head in equation\n"

        ^ Display.string_of_thm_global thy thm)

    val _ = if not (is_constr thy c)

      then ()

      else bad_thm ("Constructor as head in equation\n"

        ^ Display.string_of_thm_global thy thm)

    val ty_decl = Sign.the_const_type thy c;

    val _ = if Sign.typ_equiv thy (Type.strip_sorts ty_decl, Type.strip_sorts ty)

      then () else bad_thm ("Type\n" ^ string_of_typ thy ty

           ^ "\nof equation\n"

           ^ Display.string_of_thm_global thy thm

           ^ "\nis incompatible with declared function type\n"

           ^ string_of_typ thy ty_decl)

  in (thm, proper) end;

fun assert_eqn thy = error_thm (gen_assert_eqn thy (is_constr thy));

fun meta_rewrite thy = LocalDefs.meta_rewrite_rule (ProofContext.init thy);

fun mk_eqn thy = error_thm (gen_assert_eqn thy (K true)) o

  apfst (meta_rewrite thy);

fun mk_eqn_warning thy = Option.map (fn (thm, _) => (thm, is_linear thm))

  o warning_thm (gen_assert_eqn thy (K true)) o rpair false o meta_rewrite thy;

fun mk_eqn_liberal thy = Option.map (fn (thm, _) => (thm, is_linear thm))

  o try_thm (gen_assert_eqn thy (K true)) o rpair false o meta_rewrite thy;

val head_eqn = dest_Const o fst o strip_comb o fst o Logic.dest_equals o Thm.plain_prop_of;

fun const_typ_eqn thy thm =

  let

    val (c, ty) = head_eqn thm;

    val c' = AxClass.unoverload_const thy (c, ty);

      (*permissive wrt. to overloaded constants!*)

  in (c', ty) end;

fun const_eqn thy = fst o const_typ_eqn thy;

fun raw_typscheme thy (c, ty) =

  (map dest_TFree (Sign.const_typargs thy (c, ty)), Type.strip_sorts ty);

fun typscheme thy (c, ty) = raw_typscheme thy (c, subst_signature thy c ty);

fun typscheme_eqn thy = typscheme thy o apsnd Logic.unvarifyT o const_typ_eqn thy;

fun typscheme_eqns thy c [] = 

      let

        val raw_ty = const_typ thy c;

        val tvars = Term.add_tvar_namesT raw_ty [];

        val tvars' = case AxClass.class_of_param thy c

         of SOME class => [TFree (Name.aT, [class])]

          | NONE => Name.invent_list [] Name.aT (length tvars)

              |> map (fn v => TFree (v, []));

        val ty = typ_subst_TVars (tvars ~~ tvars') raw_ty;

      in raw_typscheme thy (c, ty) end

  | typscheme_eqns thy c (thm :: _) = typscheme_eqn thy thm;

fun assert_eqns_const thy c eqns =

  let

    fun cert (eqn as (thm, _)) = if c = const_eqn thy thm

      then eqn else error ("Wrong head of code equation,\nexpected constant "

        ^ string_of_const thy c ^ "\n" ^ Display.string_of_thm_global thy thm)

  in map (cert o assert_eqn thy) eqns end;

fun standard_typscheme thy thms =

  let

    fun tvars_of T = rev (Term.add_tvarsT T []);

    val vss = map (tvars_of o snd o head_eqn) thms;

    fun inter_sorts vs =

      fold (curry (Sorts.inter_sort (Sign.classes_of thy)) o snd) vs [];

    val sorts = map_transpose inter_sorts vss;

    val vts = Name.names Name.context Name.aT sorts

      |> map (fn (v, sort) => TVar ((v, 0), sort));

  in map2 (fn vs => Thm.certify_instantiate (vs ~~ vts, [])) vss thms end;

fun these_eqns thy c =

  get_eqns thy c

  |> (map o apfst) (Thm.transfer thy)

  |> burrow_fst (standard_typscheme thy);

fun all_eqns thy =

  Symtab.dest ((the_eqns o the_exec) thy)

  |> maps (snd o snd o fst o snd);

(* cases *)

fun case_certificate thm =

  let

    val ((head, raw_case_expr), cases) = (apfst Logic.dest_equals

      o apsnd Logic.dest_conjunctions o Logic.dest_implies o Thm.plain_prop_of) thm;

    val _ = case head of Free _ => true

      | Var _ => true

      | _ => raise TERM ("case_cert", []);

    val ([(case_var, _)], case_expr) = Term.strip_abs_eta 1 raw_case_expr;

    val (Const (case_const, _), raw_params) = strip_comb case_expr;

    val n = find_index (fn Free (v, _) => v = case_var | _ => false) raw_params;

    val _ = if n = ~1 then raise TERM ("case_cert", []) else ();

    val params = map (fst o dest_Var) (nth_drop n raw_params);

    fun dest_case t =

      let

        val (head' $ t_co, rhs) = Logic.dest_equals t;

        val _ = if head' = head then () else raise TERM ("case_cert", []);

        val (Const (co, _), args) = strip_comb t_co;

        val (Var (param, _), args') = strip_comb rhs;

        val _ = if args' = args then () else raise TERM ("case_cert", []);

      in (param, co) end;

    fun analyze_cases cases =

      let

        val co_list = fold (AList.update (op =) o dest_case) cases [];

      in map (the o AList.lookup (op =) co_list) params end;

    fun analyze_let t =

      let

        val (head' $ arg, Var (param', _) $ arg') = Logic.dest_equals t;

        val _ = if head' = head then () else raise TERM ("case_cert", []);

        val _ = if arg' = arg then () else raise TERM ("case_cert", []);

        val _ = if [param'] = params then () else raise TERM ("case_cert", []);

      in [] end;

    fun analyze (cases as [let_case]) =

          (analyze_cases cases handle Bind => analyze_let let_case)

      | analyze cases = analyze_cases cases;

  in (case_const, (n, analyze cases)) end;

fun case_cert thm = case_certificate thm

  handle Bind => error "bad case certificate"

       | TERM _ => error "bad case certificate";

fun get_case_scheme thy = Symtab.lookup ((fst o the_cases o the_exec) thy);

val undefineds = Symtab.keys o snd o the_cases o the_exec;

(* diagnostic *)

fun print_codesetup thy =

  let

    val ctxt = ProofContext.init thy;

    val exec = the_exec thy;

    fun pretty_eqns (s, (_, eqns)) =

      (Pretty.block o Pretty.fbreaks) (

        Pretty.str s :: map (Display.pretty_thm ctxt o fst) eqns

      );

    fun pretty_dtyp (s, []) =

          Pretty.str s

      | pretty_dtyp (s, cos) =

          (Pretty.block o Pretty.breaks) (

            Pretty.str s

            :: Pretty.str "="

            :: separate (Pretty.str "|") (map (fn (c, []) => Pretty.str (string_of_const thy c)

                 | (c, tys) =>

                     (Pretty.block o Pretty.breaks)

                        (Pretty.str (string_of_const thy c)

                          :: Pretty.str "of"

                          :: map (Pretty.quote o Syntax.pretty_typ_global thy) tys)) cos)

          );

    val eqns = the_eqns exec

      |> Symtab.dest

      |> (map o apfst) (string_of_const thy)

      |> (map o apsnd) (snd o fst)

      |> sort (string_ord o pairself fst);

    val dtyps = the_dtyps exec

      |> Symtab.dest

      |> map (fn (dtco, (_, (vs, cos)) :: _) =>

          (string_of_typ thy (Type (dtco, map TFree vs)), cos))

      |> sort (string_ord o pairself fst)

  in

    (Pretty.writeln o Pretty.chunks) [

      Pretty.block (

        Pretty.str "code equations:"

        :: Pretty.fbrk

        :: (Pretty.fbreaks o map pretty_eqns) eqns

      ),

      Pretty.block (

        Pretty.str "datatypes:"

        :: Pretty.fbrk

        :: (Pretty.fbreaks o map pretty_dtyp) dtyps

      )

    ]

  end;

(** declaring executable ingredients **)

(* constant signatures *)

fun add_type tyco thy =

  case Symtab.lookup ((snd o #types o Type.rep_tsig o Sign.tsig_of) thy) tyco

   of SOME (Type.Abbreviation (vs, _, _)) =>

          (map_exec_purge o map_signatures o apfst)

            (Symtab.update (tyco, length vs)) thy

    | _ => error ("No such type abbreviation: " ^ quote tyco);

fun add_type_cmd s thy = add_type (Sign.intern_type thy s) thy;

fun gen_add_signature prep_const prep_signature (raw_c, raw_ty) thy =

  let

    val c = prep_const thy raw_c;

    val ty = prep_signature thy raw_ty;

    val ty' = expand_signature thy ty;

    val ty'' = Sign.the_const_type thy c;

    val _ = if typ_equiv (ty', ty'') then () else

      error ("Illegal constant signature: " ^ Syntax.string_of_typ_global thy ty);

  in

    thy

    |> (map_exec_purge o map_signatures o apsnd) (Symtab.update (c, ty))

  end;

val add_signature = gen_add_signature (K I) cert_signature;

val add_signature_cmd = gen_add_signature read_const read_signature;

(* datatypes *)

structure Type_Interpretation =

  Interpretation(type T = string * serial val eq = eq_snd (op =) : T * T -> bool);

fun add_datatype raw_cs thy =

  let

    val cs = map (fn c_ty as (_, ty) => (AxClass.unoverload_const thy c_ty, ty)) raw_cs;

    val (tyco, vs_cos) = constrset_of_consts thy cs;

    val old_cs = (map fst o snd o get_datatype thy) tyco;

    fun drop_outdated_cases cases = fold Symtab.delete_safe

      (Symtab.fold (fn (c, (_, (_, cos))) =>

        if exists (member (op =) old_cs) cos

          then insert (op =) c else I) cases []) cases;

  in

    thy

    |> fold (del_eqns o fst) cs

    |> map_exec_purge

        ((map_dtyps o Symtab.map_default (tyco, [])) (cons (serial (), vs_cos))

        #> (map_cases o apfst) drop_outdated_cases)

    |> Type_Interpretation.data (tyco, serial ())

  end;

fun type_interpretation f =  Type_Interpretation.interpretation

  (fn (tyco, _) => fn thy => f (tyco, get_datatype thy tyco) thy);

fun add_datatype_cmd raw_cs thy =

  let

    val cs = map (read_bare_const thy) raw_cs;

  in add_datatype cs thy end;

(* code equations *)

fun gen_add_eqn default (thm, proper) thy =

  let

    val thm' = Thm.close_derivation thm;

    val c = const_eqn thy thm';

  in change_eqns false c (add_thm thy default (thm', proper)) thy end;

fun add_eqn thm thy =

  gen_add_eqn false (mk_eqn thy (thm, true)) thy;

fun add_warning_eqn thm thy =

  case mk_eqn_warning thy thm

   of SOME eqn => gen_add_eqn false eqn thy

    | NONE => thy;

fun add_default_eqn thm thy =

  case mk_eqn_liberal thy thm

   of SOME eqn => gen_add_eqn true eqn thy

    | NONE => thy;

fun add_nbe_eqn thm thy =

  gen_add_eqn false (mk_eqn thy (thm, false)) thy;

val add_default_eqn_attribute = Thm.declaration_attribute

  (fn thm => Context.mapping (add_default_eqn thm) I);

val add_default_eqn_attrib = Attrib.internal (K add_default_eqn_attribute);

fun del_eqn thm thy = case mk_eqn_liberal thy thm

 of SOME (thm, _) => change_eqns true (const_eqn thy thm) (del_thm thm) thy

  | NONE => thy;

(* c.f. src/HOL/Tools/recfun_codegen.ML *)

structure Code_Target_Attr = Theory_Data

(

  type T = (string -> thm -> theory -> theory) option;

  val empty = NONE;

  val extend = I;

  fun merge (f1, f2) = if is_some f1 then f1 else f2;

);

fun set_code_target_attr f = Code_Target_Attr.map (K (SOME f));

fun code_target_attr prefix thm thy =

  let

    val attr = the_default ((K o K) I) (Code_Target_Attr.get thy);

  in thy |> add_warning_eqn thm |> attr prefix thm end;

(* setup *)

val _ = Context.>> (Context.map_theory

  (let

    fun mk_attribute f = Thm.declaration_attribute (fn thm => Context.mapping (f thm) I);

    val code_attribute_parser =

      Args.del |-- Scan.succeed (mk_attribute del_eqn)

      || Args.$$$ "nbe" |-- Scan.succeed (mk_attribute add_nbe_eqn)

      || (Args.$$$ "target" |-- Args.colon |-- Args.name >>

           (mk_attribute o code_target_attr))

      || Scan.succeed (mk_attribute add_warning_eqn);

  in

    Type_Interpretation.init

    #> Attrib.setup (Binding.name "code") (Scan.lift code_attribute_parser)

        "declare theorems for code generation"

  end));

(* cases *)

fun add_case thm thy =

  let

    val (c, (k, case_pats)) = case_cert thm;

    val _ = case filter_out (is_constr thy) case_pats

     of [] => ()

      | cs => error ("Non-constructor(s) in case certificate: " ^ commas (map quote cs));

    val entry = (1 + Int.max (1, length case_pats), (k, case_pats))

  in (map_exec_purge o map_cases o apfst) (Symtab.update (c, entry)) thy end;

fun add_undefined c thy =

  (map_exec_purge o map_cases o apsnd) (Symtab.update (c, ())) thy;

end; (*struct*)

(** type-safe interfaces for data dependent on executable code **)

functor Code_Data(Data: CODE_DATA_ARGS): CODE_DATA =

struct

type T = Data.T;

exception Data of T;

fun dest (Data x) = x

val kind = Code.declare_data (Data Data.empty);

val data_op = (kind, Data, dest);

val change = Code.change_data data_op;

fun change_yield thy = Code.change_yield_data data_op thy;

end;

structure Code : CODE = struct open Code; end;