src/Tools/Code/code_thingol.ML
author haftmann
Fri Jul 16 13:57:46 2010 +0200 (2010-07-16)
changeset 37841 ff1c9cb6dc5d
parent 37744 3daaf23b9ab4
child 37871 c7ce7685e087
permissions -rw-r--r--
don't fail gracefully
     1 (*  Title:      Tools/Code/code_thingol.ML
     2     Author:     Florian Haftmann, TU Muenchen
     3 
     4 Intermediate language ("Thin-gol") representing executable code.
     5 Representation and translation.
     6 *)
     7 
     8 infix 8 `%%;
     9 infix 4 `$;
    10 infix 4 `$$;
    11 infixr 3 `|=>;
    12 infixr 3 `|==>;
    13 
    14 signature BASIC_CODE_THINGOL =
    15 sig
    16   type vname = string;
    17   datatype dict =
    18       DictConst of string * dict list list
    19     | DictVar of string list * (vname * (int * int));
    20   datatype itype =
    21       `%% of string * itype list
    22     | ITyVar of vname;
    23   type const = string * ((itype list * dict list list) * itype list (*types of arguments*))
    24   datatype iterm =
    25       IConst of const
    26     | IVar of vname option
    27     | `$ of iterm * iterm
    28     | `|=> of (vname option * itype) * iterm
    29     | ICase of ((iterm * itype) * (iterm * iterm) list) * iterm;
    30         (*((term, type), [(selector pattern, body term )]), primitive term)*)
    31   val `$$ : iterm * iterm list -> iterm;
    32   val `|==> : (vname option * itype) list * iterm -> iterm;
    33   type typscheme = (vname * sort) list * itype;
    34 end;
    35 
    36 signature CODE_THINGOL =
    37 sig
    38   include BASIC_CODE_THINGOL
    39   val fun_tyco: string
    40   val unfoldl: ('a -> ('a * 'b) option) -> 'a -> 'a * 'b list
    41   val unfoldr: ('a -> ('b * 'a) option) -> 'a -> 'b list * 'a
    42   val unfold_fun: itype -> itype list * itype
    43   val unfold_fun_n: int -> itype -> itype list * itype
    44   val unfold_app: iterm -> iterm * iterm list
    45   val unfold_abs: iterm -> (vname option * itype) list * iterm
    46   val split_let: iterm -> (((iterm * itype) * iterm) * iterm) option
    47   val unfold_let: iterm -> ((iterm * itype) * iterm) list * iterm
    48   val split_pat_abs: iterm -> ((iterm * itype) * iterm) option
    49   val unfold_pat_abs: iterm -> (iterm * itype) list * iterm
    50   val unfold_const_app: iterm -> (const * iterm list) option
    51   val is_IVar: iterm -> bool
    52   val eta_expand: int -> const * iterm list -> iterm
    53   val contains_dictvar: iterm -> bool
    54   val locally_monomorphic: iterm -> bool
    55   val add_constnames: iterm -> string list -> string list
    56   val add_tyconames: iterm -> string list -> string list
    57   val fold_varnames: (string -> 'a -> 'a) -> iterm -> 'a -> 'a
    58 
    59   type naming
    60   val empty_naming: naming
    61   val lookup_class: naming -> class -> string option
    62   val lookup_classrel: naming -> class * class -> string option
    63   val lookup_tyco: naming -> string -> string option
    64   val lookup_instance: naming -> class * string -> string option
    65   val lookup_const: naming -> string -> string option
    66   val ensure_declared_const: theory -> string -> naming -> string * naming
    67 
    68   datatype stmt =
    69       NoStmt
    70     | Fun of string * ((typscheme * ((iterm list * iterm) * (thm option * bool)) list) * thm option)
    71     | Datatype of string * ((vname * sort) list *
    72         ((string * vname list (*type argument wrt. canonical order*)) * itype list) list)
    73     | Datatypecons of string * string
    74     | Class of class * (vname * ((class * string) list * (string * itype) list))
    75     | Classrel of class * class
    76     | Classparam of string * class
    77     | Classinst of (class * (string * (vname * sort) list) (*class and arity*))
    78           * ((class * (string * (string * dict list list))) list (*super instances*)
    79         * (((string * const) * (thm * bool)) list (*class parameter instances*)
    80           * ((string * const) * (thm * bool)) list (*super class parameter instances*)))
    81   type program = stmt Graph.T
    82   val empty_funs: program -> string list
    83   val map_terms_bottom_up: (iterm -> iterm) -> iterm -> iterm
    84   val map_terms_stmt: (iterm -> iterm) -> stmt -> stmt
    85   val is_cons: program -> string -> bool
    86   val is_case: stmt -> bool
    87   val contr_classparam_typs: program -> string -> itype option list
    88   val labelled_name: theory -> program -> string -> string
    89   val group_stmts: theory -> program
    90     -> ((string * stmt) list * (string * stmt) list
    91       * ((string * stmt) list * (string * stmt) list)) list
    92 
    93   val read_const_exprs: theory -> string list -> string list * string list
    94   val consts_program: theory -> bool -> string list -> string list * (naming * program)
    95   val eval_conv: theory
    96     -> (naming -> program -> ((string * sort) list * typscheme) * iterm -> string list -> cterm -> thm)
    97     -> cterm -> thm
    98   val eval: theory -> ((term -> term) -> 'a -> 'a)
    99     -> (naming -> program -> ((string * sort) list * typscheme) * iterm -> string list -> 'a)
   100     -> term -> 'a
   101 end;
   102 
   103 structure Code_Thingol: CODE_THINGOL =
   104 struct
   105 
   106 (** auxiliary **)
   107 
   108 fun unfoldl dest x =
   109   case dest x
   110    of NONE => (x, [])
   111     | SOME (x1, x2) =>
   112         let val (x', xs') = unfoldl dest x1 in (x', xs' @ [x2]) end;
   113 
   114 fun unfoldr dest x =
   115   case dest x
   116    of NONE => ([], x)
   117     | SOME (x1, x2) =>
   118         let val (xs', x') = unfoldr dest x2 in (x1::xs', x') end;
   119 
   120 
   121 (** language core - types, terms **)
   122 
   123 type vname = string;
   124 
   125 datatype dict =
   126     DictConst of string * dict list list
   127   | DictVar of string list * (vname * (int * int));
   128 
   129 datatype itype =
   130     `%% of string * itype list
   131   | ITyVar of vname;
   132 
   133 type const = string * ((itype list * dict list list) * itype list (*types of arguments*))
   134 
   135 datatype iterm =
   136     IConst of const
   137   | IVar of vname option
   138   | `$ of iterm * iterm
   139   | `|=> of (vname option * itype) * iterm
   140   | ICase of ((iterm * itype) * (iterm * iterm) list) * iterm;
   141     (*see also signature*)
   142 
   143 fun is_IVar (IVar _) = true
   144   | is_IVar _ = false;
   145 
   146 val op `$$ = Library.foldl (op `$);
   147 val op `|==> = Library.foldr (op `|=>);
   148 
   149 val unfold_app = unfoldl
   150   (fn op `$ t => SOME t
   151     | _ => NONE);
   152 
   153 val unfold_abs = unfoldr
   154   (fn op `|=> t => SOME t
   155     | _ => NONE);
   156 
   157 val split_let = 
   158   (fn ICase (((td, ty), [(p, t)]), _) => SOME (((p, ty), td), t)
   159     | _ => NONE);
   160 
   161 val unfold_let = unfoldr split_let;
   162 
   163 fun unfold_const_app t =
   164  case unfold_app t
   165   of (IConst c, ts) => SOME (c, ts)
   166    | _ => NONE;
   167 
   168 fun fold_constexprs f =
   169   let
   170     fun fold' (IConst c) = f c
   171       | fold' (IVar _) = I
   172       | fold' (t1 `$ t2) = fold' t1 #> fold' t2
   173       | fold' (_ `|=> t) = fold' t
   174       | fold' (ICase (((t, _), ds), _)) = fold' t
   175           #> fold (fn (pat, body) => fold' pat #> fold' body) ds
   176   in fold' end;
   177 
   178 val add_constnames = fold_constexprs (fn (c, _) => insert (op =) c);
   179 
   180 fun add_tycos (tyco `%% tys) = insert (op =) tyco #> fold add_tycos tys
   181   | add_tycos (ITyVar _) = I;
   182 
   183 val add_tyconames = fold_constexprs (fn (_, ((tys, _), _)) => fold add_tycos tys);
   184 
   185 fun fold_varnames f =
   186   let
   187     fun fold_aux add f =
   188       let
   189         fun fold_term _ (IConst _) = I
   190           | fold_term vs (IVar (SOME v)) = if member (op =) vs v then I else f v
   191           | fold_term _ (IVar NONE) = I
   192           | fold_term vs (t1 `$ t2) = fold_term vs t1 #> fold_term vs t2
   193           | fold_term vs ((SOME v, _) `|=> t) = fold_term (insert (op =) v vs) t
   194           | fold_term vs ((NONE, _) `|=> t) = fold_term vs t
   195           | fold_term vs (ICase (((t, _), ds), _)) = fold_term vs t #> fold (fold_case vs) ds
   196         and fold_case vs (p, t) = fold_term (add p vs) t;
   197       in fold_term [] end;
   198     fun add t = fold_aux add (insert (op =)) t;
   199   in fold_aux add f end;
   200 
   201 fun exists_var t v = fold_varnames (fn w => fn b => v = w orelse b) t false;
   202 
   203 fun split_pat_abs ((NONE, ty) `|=> t) = SOME ((IVar NONE, ty), t)
   204   | split_pat_abs ((SOME v, ty) `|=> t) = SOME (case t
   205      of ICase (((IVar (SOME w), _), [(p, t')]), _) =>
   206           if v = w andalso (exists_var p v orelse not (exists_var t' v))
   207           then ((p, ty), t')
   208           else ((IVar (SOME v), ty), t)
   209       | _ => ((IVar (SOME v), ty), t))
   210   | split_pat_abs _ = NONE;
   211 
   212 val unfold_pat_abs = unfoldr split_pat_abs;
   213 
   214 fun unfold_abs_eta [] t = ([], t)
   215   | unfold_abs_eta (_ :: tys) (v_ty `|=> t) =
   216       let
   217         val (vs_tys, t') = unfold_abs_eta tys t;
   218       in (v_ty :: vs_tys, t') end
   219   | unfold_abs_eta tys t =
   220       let
   221         val ctxt = fold_varnames Name.declare t Name.context;
   222         val vs_tys = (map o apfst) SOME (Name.names ctxt "a" tys);
   223       in (vs_tys, t `$$ map (IVar o fst) vs_tys) end;
   224 
   225 fun eta_expand k (c as (name, (_, tys)), ts) =
   226   let
   227     val j = length ts;
   228     val l = k - j;
   229     val _ = if l > length tys
   230       then error ("Impossible eta-expansion for constant " ^ quote name) else ();
   231     val ctxt = (fold o fold_varnames) Name.declare ts Name.context;
   232     val vs_tys = (map o apfst) SOME
   233       (Name.names ctxt "a" ((take l o drop j) tys));
   234   in vs_tys `|==> IConst c `$$ ts @ map (IVar o fst) vs_tys end;
   235 
   236 fun contains_dictvar t =
   237   let
   238     fun cont_dict (DictConst (_, dss)) = (exists o exists) cont_dict dss
   239       | cont_dict (DictVar _) = true;
   240     fun cont_term (IConst (_, ((_, dss), _))) = (exists o exists) cont_dict dss
   241       | cont_term (IVar _) = false
   242       | cont_term (t1 `$ t2) = cont_term t1 orelse cont_term t2
   243       | cont_term (_ `|=> t) = cont_term t
   244       | cont_term (ICase (_, t)) = cont_term t;
   245   in cont_term t end;
   246   
   247 fun locally_monomorphic (IConst _) = false
   248   | locally_monomorphic (IVar _) = true
   249   | locally_monomorphic (t `$ _) = locally_monomorphic t
   250   | locally_monomorphic (_ `|=> t) = locally_monomorphic t
   251   | locally_monomorphic (ICase ((_, ds), _)) = exists (locally_monomorphic o snd) ds;
   252 
   253 
   254 (** namings **)
   255 
   256 (* policies *)
   257 
   258 local
   259   fun thyname_of_class thy = #theory_name o Name_Space.the_entry (Sign.class_space thy);
   260   fun thyname_of_instance thy inst = case AxClass.thynames_of_arity thy inst
   261    of [] => error ("No such instance: " ^ quote (snd inst ^ " :: " ^ fst inst))
   262     | thyname :: _ => thyname;
   263   fun thyname_of_const thy c = case AxClass.class_of_param thy c
   264    of SOME class => thyname_of_class thy class
   265     | NONE => (case Code.get_type_of_constr_or_abstr thy c
   266        of SOME (tyco, _) => Codegen.thyname_of_type thy tyco
   267         | NONE => Codegen.thyname_of_const thy c);
   268   fun purify_base "==>" = "follows"
   269     | purify_base "op &" = "and"
   270     | purify_base "op |" = "or"
   271     | purify_base "op -->" = "implies"
   272     | purify_base "op =" = "eq"
   273     | purify_base s = Name.desymbolize false s;
   274   fun namify thy get_basename get_thyname name =
   275     let
   276       val prefix = get_thyname thy name;
   277       val base = (purify_base o get_basename) name;
   278     in Long_Name.append prefix base end;
   279 in
   280 
   281 fun namify_class thy = namify thy Long_Name.base_name thyname_of_class;
   282 fun namify_classrel thy = namify thy (fn (sub_class, super_class) => 
   283     Long_Name.base_name super_class ^ "_" ^ Long_Name.base_name sub_class)
   284   (fn thy => thyname_of_class thy o fst);
   285   (*order fits nicely with composed projections*)
   286 fun namify_tyco thy "fun" = "Pure.fun"
   287   | namify_tyco thy tyco = namify thy Long_Name.base_name Codegen.thyname_of_type tyco;
   288 fun namify_instance thy = namify thy (fn (class, tyco) => 
   289   Long_Name.base_name class ^ "_" ^ Long_Name.base_name tyco) thyname_of_instance;
   290 fun namify_const thy = namify thy Long_Name.base_name thyname_of_const;
   291 
   292 end; (* local *)
   293 
   294 
   295 (* data *)
   296 
   297 datatype naming = Naming of {
   298   class: class Symtab.table * Name.context,
   299   classrel: string Symreltab.table * Name.context,
   300   tyco: string Symtab.table * Name.context,
   301   instance: string Symreltab.table * Name.context,
   302   const: string Symtab.table * Name.context
   303 }
   304 
   305 fun dest_Naming (Naming naming) = naming;
   306 
   307 val empty_naming = Naming {
   308   class = (Symtab.empty, Name.context),
   309   classrel = (Symreltab.empty, Name.context),
   310   tyco = (Symtab.empty, Name.context),
   311   instance = (Symreltab.empty, Name.context),
   312   const = (Symtab.empty, Name.context)
   313 };
   314 
   315 local
   316   fun mk_naming (class, classrel, tyco, instance, const) =
   317     Naming { class = class, classrel = classrel,
   318       tyco = tyco, instance = instance, const = const };
   319   fun map_naming f (Naming { class, classrel, tyco, instance, const }) =
   320     mk_naming (f (class, classrel, tyco, instance, const));
   321 in
   322   fun map_class f = map_naming
   323     (fn (class, classrel, tyco, inst, const) =>
   324       (f class, classrel, tyco, inst, const));
   325   fun map_classrel f = map_naming
   326     (fn (class, classrel, tyco, inst, const) =>
   327       (class, f classrel, tyco, inst, const));
   328   fun map_tyco f = map_naming
   329     (fn (class, classrel, tyco, inst, const) =>
   330       (class, classrel, f tyco, inst, const));
   331   fun map_instance f = map_naming
   332     (fn (class, classrel, tyco, inst, const) =>
   333       (class, classrel, tyco, f inst, const));
   334   fun map_const f = map_naming
   335     (fn (class, classrel, tyco, inst, const) =>
   336       (class, classrel, tyco, inst, f const));
   337 end; (*local*)
   338 
   339 fun add_variant update (thing, name) (tab, used) =
   340   let
   341     val (name', used') = yield_singleton Name.variants name used;
   342     val tab' = update (thing, name') tab;
   343   in (tab', used') end;
   344 
   345 fun declare thy mapp lookup update namify thing =
   346   mapp (add_variant update (thing, namify thy thing))
   347   #> `(fn naming => the (lookup naming thing));
   348 
   349 
   350 (* lookup and declare *)
   351 
   352 local
   353 
   354 val suffix_class = "class";
   355 val suffix_classrel = "classrel"
   356 val suffix_tyco = "tyco";
   357 val suffix_instance = "inst";
   358 val suffix_const = "const";
   359 
   360 fun add_suffix nsp NONE = NONE
   361   | add_suffix nsp (SOME name) = SOME (Long_Name.append name nsp);
   362 
   363 in
   364 
   365 val lookup_class = add_suffix suffix_class
   366   oo Symtab.lookup o fst o #class o dest_Naming;
   367 val lookup_classrel = add_suffix suffix_classrel
   368   oo Symreltab.lookup o fst o #classrel o dest_Naming;
   369 val lookup_tyco = add_suffix suffix_tyco
   370   oo Symtab.lookup o fst o #tyco o dest_Naming;
   371 val lookup_instance = add_suffix suffix_instance
   372   oo Symreltab.lookup o fst o #instance o dest_Naming;
   373 val lookup_const = add_suffix suffix_const
   374   oo Symtab.lookup o fst o #const o dest_Naming;
   375 
   376 fun declare_class thy = declare thy map_class
   377   lookup_class Symtab.update_new namify_class;
   378 fun declare_classrel thy = declare thy map_classrel
   379   lookup_classrel Symreltab.update_new namify_classrel;
   380 fun declare_tyco thy = declare thy map_tyco
   381   lookup_tyco Symtab.update_new namify_tyco;
   382 fun declare_instance thy = declare thy map_instance
   383   lookup_instance Symreltab.update_new namify_instance;
   384 fun declare_const thy = declare thy map_const
   385   lookup_const Symtab.update_new namify_const;
   386 
   387 fun ensure_declared_const thy const naming =
   388   case lookup_const naming const
   389    of SOME const' => (const', naming)
   390     | NONE => declare_const thy const naming;
   391 
   392 val fun_tyco = Long_Name.append (namify_tyco Pure.thy "fun") suffix_tyco
   393   (*depends on add_suffix*);
   394 
   395 val unfold_fun = unfoldr
   396   (fn tyco `%% [ty1, ty2] => if tyco = fun_tyco then SOME (ty1, ty2) else NONE
   397     | _ => NONE);
   398 
   399 fun unfold_fun_n n ty =
   400   let
   401     val (tys1, ty1) = unfold_fun ty;
   402     val (tys3, tys2) = chop n tys1;
   403     val ty3 = Library.foldr (fn (ty1, ty2) => fun_tyco `%% [ty1, ty2]) (tys2, ty1);
   404   in (tys3, ty3) end;
   405 
   406 end; (* local *)
   407 
   408 
   409 (** statements, abstract programs **)
   410 
   411 type typscheme = (vname * sort) list * itype;
   412 datatype stmt =
   413     NoStmt
   414   | Fun of string * ((typscheme * ((iterm list * iterm) * (thm option * bool)) list) * thm option)
   415   | Datatype of string * ((vname * sort) list * ((string * vname list) * itype list) list)
   416   | Datatypecons of string * string
   417   | Class of class * (vname * ((class * string) list * (string * itype) list))
   418   | Classrel of class * class
   419   | Classparam of string * class
   420   | Classinst of (class * (string * (vname * sort) list))
   421         * ((class * (string * (string * dict list list))) list
   422       * (((string * const) * (thm * bool)) list
   423         * ((string * const) * (thm * bool)) list))
   424       (*see also signature*);
   425 
   426 type program = stmt Graph.T;
   427 
   428 fun empty_funs program =
   429   Graph.fold (fn (name, (Fun (c, ((_, []), _)), _)) => cons c
   430                | _ => I) program [];
   431 
   432 fun map_terms_bottom_up f (t as IConst _) = f t
   433   | map_terms_bottom_up f (t as IVar _) = f t
   434   | map_terms_bottom_up f (t1 `$ t2) = f
   435       (map_terms_bottom_up f t1 `$ map_terms_bottom_up f t2)
   436   | map_terms_bottom_up f ((v, ty) `|=> t) = f
   437       ((v, ty) `|=> map_terms_bottom_up f t)
   438   | map_terms_bottom_up f (ICase (((t, ty), ps), t0)) = f
   439       (ICase (((map_terms_bottom_up f t, ty), (map o pairself)
   440         (map_terms_bottom_up f) ps), map_terms_bottom_up f t0));
   441 
   442 fun map_classparam_instances_as_term f =
   443   (map o apfst o apsnd) (fn const => case f (IConst const) of IConst const' => const')
   444 
   445 fun map_terms_stmt f NoStmt = NoStmt
   446   | map_terms_stmt f (Fun (c, ((tysm, eqs), case_cong))) = Fun (c, ((tysm, (map o apfst)
   447       (fn (ts, t) => (map f ts, f t)) eqs), case_cong))
   448   | map_terms_stmt f (stmt as Datatype _) = stmt
   449   | map_terms_stmt f (stmt as Datatypecons _) = stmt
   450   | map_terms_stmt f (stmt as Class _) = stmt
   451   | map_terms_stmt f (stmt as Classrel _) = stmt
   452   | map_terms_stmt f (stmt as Classparam _) = stmt
   453   | map_terms_stmt f (Classinst (arity, (super_instances, classparam_instances))) =
   454       Classinst (arity, (super_instances, (pairself o map_classparam_instances_as_term) f classparam_instances));
   455 
   456 fun is_cons program name = case Graph.get_node program name
   457  of Datatypecons _ => true
   458   | _ => false;
   459 
   460 fun is_case (Fun (_, (_, SOME _))) = true
   461   | is_case _ = false;
   462 
   463 fun contr_classparam_typs program name = case Graph.get_node program name
   464  of Classparam (_, class) => let
   465         val Class (_, (_, (_, params))) = Graph.get_node program class;
   466         val SOME ty = AList.lookup (op =) params name;
   467         val (tys, res_ty) = unfold_fun ty;
   468         fun no_tyvar (_ `%% tys) = forall no_tyvar tys
   469           | no_tyvar (ITyVar _) = false;
   470       in if no_tyvar res_ty
   471         then map (fn ty => if no_tyvar ty then NONE else SOME ty) tys
   472         else []
   473       end
   474   | _ => [];
   475 
   476 fun labelled_name thy program name = case Graph.get_node program name
   477  of Fun (c, _) => quote (Code.string_of_const thy c)
   478   | Datatype (tyco, _) => "type " ^ quote (Sign.extern_type thy tyco)
   479   | Datatypecons (c, _) => quote (Code.string_of_const thy c)
   480   | Class (class, _) => "class " ^ quote (Sign.extern_class thy class)
   481   | Classrel (sub, super) => let
   482         val Class (sub, _) = Graph.get_node program sub
   483         val Class (super, _) = Graph.get_node program super
   484       in quote (Sign.extern_class thy sub ^ " < " ^ Sign.extern_class thy super) end
   485   | Classparam (c, _) => quote (Code.string_of_const thy c)
   486   | Classinst ((class, (tyco, _)), _) => let
   487         val Class (class, _) = Graph.get_node program class
   488         val Datatype (tyco, _) = Graph.get_node program tyco
   489       in quote (Sign.extern_type thy tyco ^ " :: " ^ Sign.extern_class thy class) end
   490 
   491 fun linear_stmts program =
   492   rev (Graph.strong_conn program)
   493   |> map (AList.make (Graph.get_node program));
   494 
   495 fun group_stmts thy program =
   496   let
   497     fun is_fun (_, Fun _) = true | is_fun _ = false;
   498     fun is_datatypecons (_, Datatypecons _) = true | is_datatypecons _ = false;
   499     fun is_datatype (_, Datatype _) = true | is_datatype _ = false;
   500     fun is_class (_, Class _) = true | is_class _ = false;
   501     fun is_classrel (_, Classrel _) = true | is_classrel _ = false;
   502     fun is_classparam (_, Classparam _) = true | is_classparam _ = false;
   503     fun is_classinst (_, Classinst _) = true | is_classinst _ = false;
   504     fun group stmts =
   505       if forall (is_datatypecons orf is_datatype) stmts
   506       then (filter is_datatype stmts, [], ([], []))
   507       else if forall (is_class orf is_classrel orf is_classparam) stmts
   508       then ([], filter is_class stmts, ([], []))
   509       else if forall (is_fun orf is_classinst) stmts
   510       then ([], [], List.partition is_fun stmts)
   511       else error ("Illegal mutual dependencies: " ^
   512         (commas o map (labelled_name thy program o fst)) stmts)
   513   in
   514     linear_stmts program
   515     |> map group
   516   end;
   517 
   518 
   519 (** translation kernel **)
   520 
   521 (* generic mechanisms *)
   522 
   523 fun ensure_stmt lookup declare generate thing (dep, (naming, program)) =
   524   let
   525     fun add_dep name = case dep of NONE => I
   526       | SOME dep => Graph.add_edge (dep, name);
   527     val (name, naming') = case lookup naming thing
   528      of SOME name => (name, naming)
   529       | NONE => declare thing naming;
   530   in case try (Graph.get_node program) name
   531    of SOME stmt => program
   532         |> add_dep name
   533         |> pair naming'
   534         |> pair dep
   535         |> pair name
   536     | NONE => program
   537         |> Graph.default_node (name, NoStmt)
   538         |> add_dep name
   539         |> pair naming'
   540         |> curry generate (SOME name)
   541         ||> snd
   542         |-> (fn stmt => (apsnd o Graph.map_node name) (K stmt))
   543         |> pair dep
   544         |> pair name
   545   end;
   546 
   547 exception PERMISSIVE of unit;
   548 
   549 fun translation_error thy permissive some_thm msg sub_msg =
   550   if permissive
   551   then raise PERMISSIVE ()
   552   else let
   553     val err_thm = case some_thm
   554      of SOME thm => "\n(in code equation " ^ Display.string_of_thm_global thy thm ^ ")"
   555       | NONE => "";
   556   in error (msg ^ err_thm ^ ":\n" ^ sub_msg) end;
   557 
   558 fun not_wellsorted thy permissive some_thm ty sort e =
   559   let
   560     val err_class = Sorts.class_error (Syntax.pp_global thy) e;
   561     val err_typ = "Type " ^ Syntax.string_of_typ_global thy ty ^ " not of sort "
   562       ^ Syntax.string_of_sort_global thy sort;
   563   in translation_error thy permissive some_thm "Wellsortedness error" (err_typ ^ "\n" ^ err_class) end;
   564 
   565 
   566 (* translation *)
   567 
   568 fun ensure_tyco thy algbr eqngr permissive tyco =
   569   let
   570     val (vs, cos) = Code.get_type thy tyco;
   571     val stmt_datatype =
   572       fold_map (translate_tyvar_sort thy algbr eqngr permissive) vs
   573       ##>> fold_map (fn ((c, vs), tys) =>
   574         ensure_const thy algbr eqngr permissive c
   575         ##>> pair (map (unprefix "'") vs)
   576         ##>> fold_map (translate_typ thy algbr eqngr permissive) tys) cos
   577       #>> (fn info => Datatype (tyco, info));
   578   in ensure_stmt lookup_tyco (declare_tyco thy) stmt_datatype tyco end
   579 and ensure_const thy algbr eqngr permissive c =
   580   let
   581     fun stmt_datatypecons tyco =
   582       ensure_tyco thy algbr eqngr permissive tyco
   583       #>> (fn tyco => Datatypecons (c, tyco));
   584     fun stmt_classparam class =
   585       ensure_class thy algbr eqngr permissive class
   586       #>> (fn class => Classparam (c, class));
   587     fun stmt_fun cert =
   588       let
   589         val ((vs, ty), eqns) = Code.equations_of_cert thy cert;
   590         val some_case_cong = Code.get_case_cong thy c;
   591       in
   592         fold_map (translate_tyvar_sort thy algbr eqngr permissive) vs
   593         ##>> translate_typ thy algbr eqngr permissive ty
   594         ##>> translate_eqns thy algbr eqngr permissive eqns
   595         #>> (fn info => Fun (c, (info, some_case_cong)))
   596       end;
   597     val stmt_const = case Code.get_type_of_constr_or_abstr thy c
   598      of SOME (tyco, _) => stmt_datatypecons tyco
   599       | NONE => (case AxClass.class_of_param thy c
   600          of SOME class => stmt_classparam class
   601           | NONE => stmt_fun (Code_Preproc.cert eqngr c))
   602   in ensure_stmt lookup_const (declare_const thy) stmt_const c end
   603 and ensure_class thy (algbr as (_, algebra)) eqngr permissive class =
   604   let
   605     val super_classes = (Sorts.minimize_sort algebra o Sorts.super_classes algebra) class;
   606     val cs = #params (AxClass.get_info thy class);
   607     val stmt_class =
   608       fold_map (fn super_class => ensure_class thy algbr eqngr permissive super_class
   609         ##>> ensure_classrel thy algbr eqngr permissive (class, super_class)) super_classes
   610       ##>> fold_map (fn (c, ty) => ensure_const thy algbr eqngr permissive c
   611         ##>> translate_typ thy algbr eqngr permissive ty) cs
   612       #>> (fn info => Class (class, (unprefix "'" Name.aT, info)))
   613   in ensure_stmt lookup_class (declare_class thy) stmt_class class end
   614 and ensure_classrel thy algbr eqngr permissive (sub_class, super_class) =
   615   let
   616     val stmt_classrel =
   617       ensure_class thy algbr eqngr permissive sub_class
   618       ##>> ensure_class thy algbr eqngr permissive super_class
   619       #>> Classrel;
   620   in ensure_stmt lookup_classrel (declare_classrel thy) stmt_classrel (sub_class, super_class) end
   621 and ensure_inst thy (algbr as (_, algebra)) eqngr permissive (class, tyco) =
   622   let
   623     val super_classes = (Sorts.minimize_sort algebra o Sorts.super_classes algebra) class;
   624     val these_classparams = these o try (#params o AxClass.get_info thy);
   625     val classparams = these_classparams class;
   626     val further_classparams = maps these_classparams
   627       ((Sorts.complete_sort algebra o Sorts.super_classes algebra) class);
   628     val vs = Name.names Name.context "'a" (Sorts.mg_domain algebra tyco [class]);
   629     val sorts' = Sorts.mg_domain (Sign.classes_of thy) tyco [class];
   630     val vs' = map2 (fn (v, sort1) => fn sort2 => (v,
   631       Sorts.inter_sort (Sign.classes_of thy) (sort1, sort2))) vs sorts';
   632     val arity_typ = Type (tyco, map TFree vs);
   633     val arity_typ' = Type (tyco, map (fn (v, sort) => TVar ((v, 0), sort)) vs');
   634     fun translate_super_instance super_class =
   635       ensure_class thy algbr eqngr permissive super_class
   636       ##>> ensure_classrel thy algbr eqngr permissive (class, super_class)
   637       ##>> translate_dicts thy algbr eqngr permissive NONE (arity_typ, [super_class])
   638       #>> (fn ((super_class, classrel), [DictConst (inst, dss)]) =>
   639             (super_class, (classrel, (inst, dss))));
   640     fun translate_classparam_instance (c, ty) =
   641       let
   642         val raw_const = Const (c, map_type_tfree (K arity_typ') ty);
   643         val thm = AxClass.unoverload_conv thy (Thm.cterm_of thy raw_const);
   644         val const = (apsnd Logic.unvarifyT_global o dest_Const o snd
   645           o Logic.dest_equals o Thm.prop_of) thm;
   646       in
   647         ensure_const thy algbr eqngr permissive c
   648         ##>> translate_const thy algbr eqngr permissive (SOME thm) (const, NONE)
   649         #>> (fn (c, IConst const') => ((c, const'), (thm, true)))
   650       end;
   651     val stmt_inst =
   652       ensure_class thy algbr eqngr permissive class
   653       ##>> ensure_tyco thy algbr eqngr permissive tyco
   654       ##>> fold_map (translate_tyvar_sort thy algbr eqngr permissive) vs
   655       ##>> fold_map translate_super_instance super_classes
   656       ##>> fold_map translate_classparam_instance classparams
   657       ##>> fold_map translate_classparam_instance further_classparams
   658       #>> (fn (((((class, tyco), arity_args), super_instances),
   659         classparam_instances), further_classparam_instances) =>
   660           Classinst ((class, (tyco, arity_args)), (super_instances,
   661             (classparam_instances, further_classparam_instances))));
   662   in ensure_stmt lookup_instance (declare_instance thy) stmt_inst (class, tyco) end
   663 and translate_typ thy algbr eqngr permissive (TFree (v, _)) =
   664       pair (ITyVar (unprefix "'" v))
   665   | translate_typ thy algbr eqngr permissive (Type (tyco, tys)) =
   666       ensure_tyco thy algbr eqngr permissive tyco
   667       ##>> fold_map (translate_typ thy algbr eqngr permissive) tys
   668       #>> (fn (tyco, tys) => tyco `%% tys)
   669 and translate_term thy algbr eqngr permissive some_thm (Const (c, ty), some_abs) =
   670       translate_app thy algbr eqngr permissive some_thm (((c, ty), []), some_abs)
   671   | translate_term thy algbr eqngr permissive some_thm (Free (v, _), some_abs) =
   672       pair (IVar (SOME v))
   673   | translate_term thy algbr eqngr permissive some_thm (Abs (v, ty, t), some_abs) =
   674       let
   675         val (v', t') = Syntax.variant_abs (Name.desymbolize false v, ty, t);
   676         val v'' = if member (op =) (Term.add_free_names t' []) v'
   677           then SOME v' else NONE
   678       in
   679         translate_typ thy algbr eqngr permissive ty
   680         ##>> translate_term thy algbr eqngr permissive some_thm (t', some_abs)
   681         #>> (fn (ty, t) => (v'', ty) `|=> t)
   682       end
   683   | translate_term thy algbr eqngr permissive some_thm (t as _ $ _, some_abs) =
   684       case strip_comb t
   685        of (Const (c, ty), ts) =>
   686             translate_app thy algbr eqngr permissive some_thm (((c, ty), ts), some_abs)
   687         | (t', ts) =>
   688             translate_term thy algbr eqngr permissive some_thm (t', some_abs)
   689             ##>> fold_map (translate_term thy algbr eqngr permissive some_thm o rpair NONE) ts
   690             #>> (fn (t, ts) => t `$$ ts)
   691 and translate_eqn thy algbr eqngr permissive ((args, (rhs, some_abs)), (some_thm, proper)) =
   692   fold_map (translate_term thy algbr eqngr permissive some_thm) args
   693   ##>> translate_term thy algbr eqngr permissive some_thm (rhs, some_abs)
   694   #>> rpair (some_thm, proper)
   695 and translate_eqns thy algbr eqngr permissive eqns prgrm =
   696   prgrm |> fold_map (translate_eqn thy algbr eqngr permissive) eqns
   697     handle PERMISSIVE () => ([], prgrm)
   698 and translate_const thy algbr eqngr permissive some_thm ((c, ty), some_abs) =
   699   let
   700     val _ = if (case some_abs of NONE => true | SOME abs => not (c = abs))
   701         andalso Code.is_abstr thy c
   702         then translation_error thy permissive some_thm
   703           "Abstraction violation" ("constant " ^ Code.string_of_const thy c)
   704       else ()
   705     val arg_typs = Sign.const_typargs thy (c, ty);
   706     val sorts = Code_Preproc.sortargs eqngr c;
   707     val function_typs = (fst o Term.strip_type) ty;
   708   in
   709     ensure_const thy algbr eqngr permissive c
   710     ##>> fold_map (translate_typ thy algbr eqngr permissive) arg_typs
   711     ##>> fold_map (translate_dicts thy algbr eqngr permissive some_thm) (arg_typs ~~ sorts)
   712     ##>> fold_map (translate_typ thy algbr eqngr permissive) function_typs
   713     #>> (fn (((c, arg_typs), dss), function_typs) => IConst (c, ((arg_typs, dss), function_typs)))
   714   end
   715 and translate_app_const thy algbr eqngr permissive some_thm ((c_ty, ts), some_abs) =
   716   translate_const thy algbr eqngr permissive some_thm (c_ty, some_abs)
   717   ##>> fold_map (translate_term thy algbr eqngr permissive some_thm o rpair NONE) ts
   718   #>> (fn (t, ts) => t `$$ ts)
   719 and translate_case thy algbr eqngr permissive some_thm (num_args, (t_pos, case_pats)) (c_ty, ts) =
   720   let
   721     fun arg_types num_args ty = (fst o chop num_args o fst o strip_type) ty;
   722     val tys = arg_types num_args (snd c_ty);
   723     val ty = nth tys t_pos;
   724     fun mk_constr c t = let val n = Code.args_number thy c
   725       in ((c, arg_types n (fastype_of t) ---> ty), n) end;
   726     val constrs = if null case_pats then []
   727       else map2 mk_constr case_pats (nth_drop t_pos ts);
   728     fun casify naming constrs ty ts =
   729       let
   730         val undefineds = map_filter (lookup_const naming) (Code.undefineds thy);
   731         fun collapse_clause vs_map ts body =
   732           let
   733           in case body
   734            of IConst (c, _) => if member (op =) undefineds c
   735                 then []
   736                 else [(ts, body)]
   737             | ICase (((IVar (SOME v), _), subclauses), _) =>
   738                 if forall (fn (pat', body') => exists_var pat' v
   739                   orelse not (exists_var body' v)) subclauses
   740                 then case AList.lookup (op =) vs_map v
   741                  of SOME i => maps (fn (pat', body') =>
   742                       collapse_clause (AList.delete (op =) v vs_map)
   743                         (nth_map i (K pat') ts) body') subclauses
   744                   | NONE => [(ts, body)]
   745                 else [(ts, body)]
   746             | _ => [(ts, body)]
   747           end;
   748         fun mk_clause mk tys t =
   749           let
   750             val (vs, body) = unfold_abs_eta tys t;
   751             val vs_map = fold_index (fn (i, (SOME v, _)) => cons (v, i) | _ => I) vs [];
   752             val ts = map (IVar o fst) vs;
   753           in map mk (collapse_clause vs_map ts body) end;
   754         val t = nth ts t_pos;
   755         val ts_clause = nth_drop t_pos ts;
   756         val clauses = if null case_pats
   757           then mk_clause (fn ([t], body) => (t, body)) [ty] (the_single ts_clause)
   758           else maps (fn ((constr as IConst (_, (_, tys)), n), t) =>
   759             mk_clause (fn (ts, body) => (constr `$$ ts, body)) (take n tys) t)
   760               (constrs ~~ ts_clause);
   761       in ((t, ty), clauses) end;
   762   in
   763     translate_const thy algbr eqngr permissive some_thm (c_ty, NONE)
   764     ##>> fold_map (fn (constr, n) => translate_const thy algbr eqngr permissive some_thm (constr, NONE)
   765       #>> rpair n) constrs
   766     ##>> translate_typ thy algbr eqngr permissive ty
   767     ##>> fold_map (translate_term thy algbr eqngr permissive some_thm o rpair NONE) ts
   768     #-> (fn (((t, constrs), ty), ts) =>
   769       `(fn (_, (naming, _)) => ICase (casify naming constrs ty ts, t `$$ ts)))
   770   end
   771 and translate_app_case thy algbr eqngr permissive some_thm (case_scheme as (num_args, _)) ((c, ty), ts) =
   772   if length ts < num_args then
   773     let
   774       val k = length ts;
   775       val tys = (take (num_args - k) o drop k o fst o strip_type) ty;
   776       val ctxt = (fold o fold_aterms) Term.declare_term_frees ts Name.context;
   777       val vs = Name.names ctxt "a" tys;
   778     in
   779       fold_map (translate_typ thy algbr eqngr permissive) tys
   780       ##>> translate_case thy algbr eqngr permissive some_thm case_scheme ((c, ty), ts @ map Free vs)
   781       #>> (fn (tys, t) => map2 (fn (v, _) => pair (SOME v)) vs tys `|==> t)
   782     end
   783   else if length ts > num_args then
   784     translate_case thy algbr eqngr permissive some_thm case_scheme ((c, ty), take num_args ts)
   785     ##>> fold_map (translate_term thy algbr eqngr permissive some_thm o rpair NONE) (drop num_args ts)
   786     #>> (fn (t, ts) => t `$$ ts)
   787   else
   788     translate_case thy algbr eqngr permissive some_thm case_scheme ((c, ty), ts)
   789 and translate_app thy algbr eqngr permissive some_thm (c_ty_ts as ((c, _), _), some_abs) =
   790   case Code.get_case_scheme thy c
   791    of SOME case_scheme => translate_app_case thy algbr eqngr permissive some_thm case_scheme c_ty_ts
   792     | NONE => translate_app_const thy algbr eqngr permissive some_thm (c_ty_ts, some_abs)
   793 and translate_tyvar_sort thy (algbr as (proj_sort, _)) eqngr permissive (v, sort) =
   794   fold_map (ensure_class thy algbr eqngr permissive) (proj_sort sort)
   795   #>> (fn sort => (unprefix "'" v, sort))
   796 and translate_dicts thy (algbr as (proj_sort, algebra)) eqngr permissive some_thm (ty, sort) =
   797   let
   798     datatype typarg =
   799         Global of (class * string) * typarg list list
   800       | Local of (class * class) list * (string * (int * sort));
   801     fun class_relation (Global ((_, tyco), yss), _) class =
   802           Global ((class, tyco), yss)
   803       | class_relation (Local (classrels, v), sub_class) super_class =
   804           Local ((sub_class, super_class) :: classrels, v);
   805     fun type_constructor (tyco, _) yss class =
   806       Global ((class, tyco), (map o map) fst yss);
   807     fun type_variable (TFree (v, sort)) =
   808       let
   809         val sort' = proj_sort sort;
   810       in map_index (fn (n, class) => (Local ([], (v, (n, sort'))), class)) sort' end;
   811     val typargs = Sorts.of_sort_derivation algebra
   812       {class_relation = K (Sorts.classrel_derivation algebra class_relation),
   813        type_constructor = type_constructor,
   814        type_variable = type_variable} (ty, proj_sort sort)
   815       handle Sorts.CLASS_ERROR e => not_wellsorted thy permissive some_thm ty sort e;
   816     fun mk_dict (Global (inst, yss)) =
   817           ensure_inst thy algbr eqngr permissive inst
   818           ##>> (fold_map o fold_map) mk_dict yss
   819           #>> (fn (inst, dss) => DictConst (inst, dss))
   820       | mk_dict (Local (classrels, (v, (n, sort)))) =
   821           fold_map (ensure_classrel thy algbr eqngr permissive) classrels
   822           #>> (fn classrels => DictVar (classrels, (unprefix "'" v, (n, length sort))))
   823   in fold_map mk_dict typargs end;
   824 
   825 
   826 (* store *)
   827 
   828 structure Program = Code_Data
   829 (
   830   type T = naming * program;
   831   val empty = (empty_naming, Graph.empty);
   832 );
   833 
   834 fun cache_generation thy (algebra, eqngr) f name =
   835   Program.change_yield thy (fn naming_program => (NONE, naming_program)
   836     |> f thy algebra eqngr name
   837     |-> (fn name => fn (_, naming_program) => (name, naming_program)));
   838 
   839 fun transient_generation thy (algebra, eqngr) f name =
   840   (NONE, (empty_naming, Graph.empty))
   841   |> f thy algebra eqngr name
   842   |-> (fn name => fn (_, naming_program) => (name, naming_program));
   843 
   844 
   845 (* program generation *)
   846 
   847 fun consts_program thy permissive cs =
   848   let
   849     fun project_consts cs (naming, program) =
   850       let
   851         val cs_all = Graph.all_succs program cs;
   852       in (cs, (naming, Graph.subgraph (member (op =) cs_all) program)) end;
   853     fun generate_consts thy algebra eqngr =
   854       fold_map (ensure_const thy algebra eqngr permissive);
   855     val invoke_generation = if permissive
   856       then transient_generation else cache_generation
   857   in
   858     invoke_generation thy (Code_Preproc.obtain thy cs []) generate_consts cs
   859     |-> project_consts
   860   end;
   861 
   862 
   863 (* value evaluation *)
   864 
   865 fun ensure_value thy algbr eqngr t =
   866   let
   867     val ty = fastype_of t;
   868     val vs = fold_term_types (K (fold_atyps (insert (eq_fst op =)
   869       o dest_TFree))) t [];
   870     val stmt_value =
   871       fold_map (translate_tyvar_sort thy algbr eqngr false) vs
   872       ##>> translate_typ thy algbr eqngr false ty
   873       ##>> translate_term thy algbr eqngr false NONE (Code.subst_signatures thy t, NONE)
   874       #>> (fn ((vs, ty), t) => Fun
   875         (Term.dummy_patternN, (((vs, ty), [(([], t), (NONE, true))]), NONE)));
   876     fun term_value (dep, (naming, program1)) =
   877       let
   878         val Fun (_, ((vs_ty, [(([], t), _)]), _)) =
   879           Graph.get_node program1 Term.dummy_patternN;
   880         val deps = Graph.imm_succs program1 Term.dummy_patternN;
   881         val program2 = Graph.del_nodes [Term.dummy_patternN] program1;
   882         val deps_all = Graph.all_succs program2 deps;
   883         val program3 = Graph.subgraph (member (op =) deps_all) program2;
   884       in (((naming, program3), ((vs_ty, t), deps)), (dep, (naming, program2))) end;
   885   in
   886     ensure_stmt ((K o K) NONE) pair stmt_value Term.dummy_patternN
   887     #> snd
   888     #> term_value
   889   end;
   890 
   891 fun base_evaluator thy evaluator algebra eqngr vs t =
   892   let
   893     val (((naming, program), (((vs', ty'), t'), deps)), _) =
   894       cache_generation thy (algebra, eqngr) ensure_value t;
   895     val vs'' = map (fn (v, _) => (v, (the o AList.lookup (op =) vs o prefix "'") v)) vs';
   896   in evaluator naming program ((vs'', (vs', ty')), t') deps end;
   897 
   898 fun eval_conv thy = Code_Preproc.eval_conv thy o base_evaluator thy;
   899 fun eval thy postproc = Code_Preproc.eval thy postproc o base_evaluator thy;
   900 
   901 
   902 (** diagnostic commands **)
   903 
   904 fun read_const_exprs thy =
   905   let
   906     fun consts_of thy' = Symtab.fold (fn (c, (_, NONE)) => cons c | _ => I)
   907       ((snd o #constants o Consts.dest o #consts o Sign.rep_sg) thy') [];
   908     fun belongs_here thy' c = forall
   909       (fn thy'' => not (Sign.declared_const thy'' c)) (Theory.parents_of thy');
   910     fun consts_of_select thy' = filter (belongs_here thy') (consts_of thy');
   911     fun read_const_expr "*" = ([], consts_of thy)
   912       | read_const_expr s = if String.isSuffix ".*" s
   913           then ([], consts_of_select (Thy_Info.the_theory (unsuffix ".*" s) thy))
   914           else ([Code.read_const thy s], []);
   915   in pairself flat o split_list o map read_const_expr end;
   916 
   917 fun code_depgr thy consts =
   918   let
   919     val (_, eqngr) = Code_Preproc.obtain thy consts [];
   920     val all_consts = Graph.all_succs eqngr consts;
   921   in Graph.subgraph (member (op =) all_consts) eqngr end;
   922 
   923 fun code_thms thy = Pretty.writeln o Code_Preproc.pretty thy o code_depgr thy;
   924 
   925 fun code_deps thy consts =
   926   let
   927     val eqngr = code_depgr thy consts;
   928     val constss = Graph.strong_conn eqngr;
   929     val mapping = Symtab.empty |> fold (fn consts => fold (fn const =>
   930       Symtab.update (const, consts)) consts) constss;
   931     fun succs consts = consts
   932       |> maps (Graph.imm_succs eqngr)
   933       |> subtract (op =) consts
   934       |> map (the o Symtab.lookup mapping)
   935       |> distinct (op =);
   936     val conn = [] |> fold (fn consts => cons (consts, succs consts)) constss;
   937     fun namify consts = map (Code.string_of_const thy) consts
   938       |> commas;
   939     val prgr = map (fn (consts, constss) =>
   940       { name = namify consts, ID = namify consts, dir = "", unfold = true,
   941         path = "", parents = map namify constss }) conn;
   942   in Present.display_graph prgr end;
   943 
   944 local
   945 
   946 fun code_thms_cmd thy = code_thms thy o op @ o read_const_exprs thy;
   947 fun code_deps_cmd thy = code_deps thy o op @ o read_const_exprs thy;
   948 
   949 in
   950 
   951 val _ =
   952   Outer_Syntax.improper_command "code_thms" "print system of code equations for code" Keyword.diag
   953     (Scan.repeat1 Parse.term_group
   954       >> (fn cs => Toplevel.no_timing o Toplevel.unknown_theory
   955         o Toplevel.keep ((fn thy => code_thms_cmd thy cs) o Toplevel.theory_of)));
   956 
   957 val _ =
   958   Outer_Syntax.improper_command "code_deps" "visualize dependencies of code equations for code"
   959     Keyword.diag
   960     (Scan.repeat1 Parse.term_group
   961       >> (fn cs => Toplevel.no_timing o Toplevel.unknown_theory
   962         o Toplevel.keep ((fn thy => code_deps_cmd thy cs) o Toplevel.theory_of)));
   963 
   964 end;
   965 
   966 end; (*struct*)
   967 
   968 
   969 structure Basic_Code_Thingol: BASIC_CODE_THINGOL = Code_Thingol;