src/Pure/variable.ML
author wenzelm
Sun Nov 27 21:53:38 2011 +0100 (2011-11-27)
changeset 45650 d314a4e8038f
parent 45472 2046f8e2ecd7
child 45666 d83797ef0d2d
permissions -rw-r--r--
tuned;
     1 (*  Title:      Pure/variable.ML
     2     Author:     Makarius
     3 
     4 Fixed type/term variables and polymorphic term abbreviations.
     5 *)
     6 
     7 signature VARIABLE =
     8 sig
     9   val is_body: Proof.context -> bool
    10   val set_body: bool -> Proof.context -> Proof.context
    11   val restore_body: Proof.context -> Proof.context -> Proof.context
    12   val names_of: Proof.context -> Name.context
    13   val binds_of: Proof.context -> (typ * term) Vartab.table
    14   val maxidx_of: Proof.context -> int
    15   val sorts_of: Proof.context -> sort list
    16   val constraints_of: Proof.context -> typ Vartab.table * sort Vartab.table
    17   val is_declared: Proof.context -> string -> bool
    18   val check_name: binding -> string
    19   val default_type: Proof.context -> string -> typ option
    20   val def_type: Proof.context -> bool -> indexname -> typ option
    21   val def_sort: Proof.context -> indexname -> sort option
    22   val declare_names: term -> Proof.context -> Proof.context
    23   val declare_constraints: term -> Proof.context -> Proof.context
    24   val declare_term: term -> Proof.context -> Proof.context
    25   val declare_typ: typ -> Proof.context -> Proof.context
    26   val declare_prf: Proofterm.proof -> Proof.context -> Proof.context
    27   val declare_thm: thm -> Proof.context -> Proof.context
    28   val global_thm_context: thm -> Proof.context
    29   val variant_frees: Proof.context -> term list -> (string * 'a) list -> (string * 'a) list
    30   val bind_term: indexname * term option -> Proof.context -> Proof.context
    31   val expand_binds: Proof.context -> term -> term
    32   val lookup_const: Proof.context -> string -> string option
    33   val is_const: Proof.context -> string -> bool
    34   val declare_const: string * string -> Proof.context -> Proof.context
    35   val is_fixed: Proof.context -> string -> bool
    36   val newly_fixed: Proof.context -> Proof.context -> string -> bool
    37   val fixed_ord: Proof.context -> string * string -> order
    38   val intern_fixed: Proof.context -> string -> string
    39   val markup_fixed: Proof.context -> string -> Markup.T
    40   val lookup_fixed: Proof.context -> string -> string option
    41   val revert_fixed: Proof.context -> string -> string
    42   val add_fixed_names: Proof.context -> term -> string list -> string list
    43   val add_fixed: Proof.context -> term -> (string * typ) list -> (string * typ) list
    44   val add_free_names: Proof.context -> term -> string list -> string list
    45   val add_frees: Proof.context -> term -> (string * typ) list -> (string * typ) list
    46   val add_fixes_binding: binding list -> Proof.context -> string list * Proof.context
    47   val add_fixes: string list -> Proof.context -> string list * Proof.context
    48   val add_fixes_direct: string list -> Proof.context -> Proof.context
    49   val auto_fixes: term -> Proof.context -> Proof.context
    50   val variant_fixes: string list -> Proof.context -> string list * Proof.context
    51   val dest_fixes: Proof.context -> (string * string) list
    52   val invent_types: sort list -> Proof.context -> (string * sort) list * Proof.context
    53   val export_terms: Proof.context -> Proof.context -> term list -> term list
    54   val exportT_terms: Proof.context -> Proof.context -> term list -> term list
    55   val exportT: Proof.context -> Proof.context -> thm list -> thm list
    56   val export_prf: Proof.context -> Proof.context -> Proofterm.proof -> Proofterm.proof
    57   val export: Proof.context -> Proof.context -> thm list -> thm list
    58   val export_morphism: Proof.context -> Proof.context -> morphism
    59   val importT_inst: term list -> Proof.context -> ((indexname * sort) * typ) list * Proof.context
    60   val import_inst: bool -> term list -> Proof.context ->
    61     (((indexname * sort) * typ) list * ((indexname * typ) * term) list) * Proof.context
    62   val importT_terms: term list -> Proof.context -> term list * Proof.context
    63   val import_terms: bool -> term list -> Proof.context -> term list * Proof.context
    64   val importT: thm list -> Proof.context -> ((ctyp * ctyp) list * thm list) * Proof.context
    65   val import_prf: bool -> Proofterm.proof -> Proof.context -> Proofterm.proof * Proof.context
    66   val import: bool -> thm list -> Proof.context ->
    67     (((ctyp * ctyp) list * (cterm * cterm) list) * thm list) * Proof.context
    68   val tradeT: (Proof.context -> thm list -> thm list) -> Proof.context -> thm list -> thm list
    69   val trade: (Proof.context -> thm list -> thm list) -> Proof.context -> thm list -> thm list
    70   val focus: term -> Proof.context -> ((string * (string * typ)) list * term) * Proof.context
    71   val focus_cterm: cterm -> Proof.context -> ((string * cterm) list * cterm) * Proof.context
    72   val focus_subgoal: int -> thm -> Proof.context -> ((string * cterm) list * cterm) * Proof.context
    73   val warn_extra_tfrees: Proof.context -> Proof.context -> unit
    74   val polymorphic_types: Proof.context -> term list -> (indexname * sort) list * term list
    75   val polymorphic: Proof.context -> term list -> term list
    76 end;
    77 
    78 structure Variable: VARIABLE =
    79 struct
    80 
    81 (** local context data **)
    82 
    83 type fixes = string Name_Space.table;
    84 val empty_fixes: fixes = Name_Space.empty_table Markup.fixedN;
    85 
    86 datatype data = Data of
    87  {is_body: bool,                        (*inner body mode*)
    88   names: Name.context,                  (*type/term variable names*)
    89   consts: string Symtab.table,          (*consts within the local scope*)
    90   fixes: fixes,                         (*term fixes -- global name space, intern ~> extern*)
    91   binds: (typ * term) Vartab.table,     (*term bindings*)
    92   type_occs: string list Symtab.table,  (*type variables -- possibly within term variables*)
    93   maxidx: int,                          (*maximum var index*)
    94   sorts: sort Ord_List.T,               (*declared sort occurrences*)
    95   constraints:
    96     typ Vartab.table *                  (*type constraints*)
    97     sort Vartab.table};                 (*default sorts*)
    98 
    99 fun make_data (is_body, names, consts, fixes, binds, type_occs, maxidx, sorts, constraints) =
   100   Data {is_body = is_body, names = names, consts = consts, fixes = fixes, binds = binds,
   101     type_occs = type_occs, maxidx = maxidx, sorts = sorts, constraints = constraints};
   102 
   103 structure Data = Proof_Data
   104 (
   105   type T = data;
   106   fun init _ =
   107     make_data (false, Name.context, Symtab.empty, empty_fixes, Vartab.empty,
   108       Symtab.empty, ~1, [], (Vartab.empty, Vartab.empty));
   109 );
   110 
   111 fun map_data f =
   112   Data.map (fn Data {is_body, names, consts, fixes, binds, type_occs, maxidx, sorts, constraints} =>
   113     make_data (f (is_body, names, consts, fixes, binds, type_occs, maxidx, sorts, constraints)));
   114 
   115 fun map_names f =
   116   map_data (fn (is_body, names, consts, fixes, binds, type_occs, maxidx, sorts, constraints) =>
   117     (is_body, f names, consts, fixes, binds, type_occs, maxidx, sorts, constraints));
   118 
   119 fun map_consts f =
   120   map_data (fn (is_body, names, consts, fixes, binds, type_occs, maxidx, sorts, constraints) =>
   121     (is_body, names, f consts, fixes, binds, type_occs, maxidx, sorts, constraints));
   122 
   123 fun map_fixes f =
   124   map_data (fn (is_body, names, consts, fixes, binds, type_occs, maxidx, sorts, constraints) =>
   125     (is_body, names, consts, f fixes, binds, type_occs, maxidx, sorts, constraints));
   126 
   127 fun map_binds f =
   128   map_data (fn (is_body, names, consts, fixes, binds, type_occs, maxidx, sorts, constraints) =>
   129     (is_body, names, consts, fixes, f binds, type_occs, maxidx, sorts, constraints));
   130 
   131 fun map_type_occs f =
   132   map_data (fn (is_body, names, consts, fixes, binds, type_occs, maxidx, sorts, constraints) =>
   133     (is_body, names, consts, fixes, binds, f type_occs, maxidx, sorts, constraints));
   134 
   135 fun map_maxidx f =
   136   map_data (fn (is_body, names, consts, fixes, binds, type_occs, maxidx, sorts, constraints) =>
   137     (is_body, names, consts, fixes, binds, type_occs, f maxidx, sorts, constraints));
   138 
   139 fun map_sorts f =
   140   map_data (fn (is_body, names, consts, fixes, binds, type_occs, maxidx, sorts, constraints) =>
   141     (is_body, names, consts, fixes, binds, type_occs, maxidx, f sorts, constraints));
   142 
   143 fun map_constraints f =
   144   map_data (fn (is_body, names, consts, fixes, binds, type_occs, maxidx, sorts, constraints) =>
   145     (is_body, names, consts, fixes, binds, type_occs, maxidx, sorts, f constraints));
   146 
   147 fun rep_data ctxt = Data.get ctxt |> (fn Data rep => rep);
   148 
   149 val is_body = #is_body o rep_data;
   150 
   151 fun set_body b =
   152   map_data (fn (_, names, consts, fixes, binds, type_occs, maxidx, sorts, constraints) =>
   153     (b, names, consts, fixes, binds, type_occs, maxidx, sorts, constraints));
   154 
   155 fun restore_body ctxt = set_body (is_body ctxt);
   156 
   157 val names_of = #names o rep_data;
   158 val fixes_of = #fixes o rep_data;
   159 val fixes_space = #1 o fixes_of;
   160 val binds_of = #binds o rep_data;
   161 val type_occs_of = #type_occs o rep_data;
   162 val maxidx_of = #maxidx o rep_data;
   163 val sorts_of = #sorts o rep_data;
   164 val constraints_of = #constraints o rep_data;
   165 
   166 val is_declared = Name.is_declared o names_of;
   167 
   168 val check_name =
   169   Long_Name.base_name o Name_Space.full_name Name_Space.default_naming o tap Binding.check;
   170 
   171 
   172 
   173 (** declarations **)
   174 
   175 (* default sorts and types *)
   176 
   177 fun default_type ctxt x = Vartab.lookup (#1 (constraints_of ctxt)) (x, ~1);
   178 
   179 fun def_type ctxt pattern xi =
   180   let val {binds, constraints = (types, _), ...} = rep_data ctxt in
   181     (case Vartab.lookup types xi of
   182       NONE =>
   183         if pattern then NONE
   184         else Vartab.lookup binds xi |> Option.map (Type.mark_polymorphic o #1)
   185     | some => some)
   186   end;
   187 
   188 val def_sort = Vartab.lookup o #2 o constraints_of;
   189 
   190 
   191 (* names *)
   192 
   193 fun declare_type_names t =
   194   map_names (fold_types (fold_atyps Term.declare_typ_names) t) #>
   195   map_maxidx (fold_types Term.maxidx_typ t);
   196 
   197 fun declare_names t =
   198   declare_type_names t #>
   199   map_names (fold_aterms Term.declare_term_frees t) #>
   200   map_maxidx (Term.maxidx_term t);
   201 
   202 
   203 (* type occurrences *)
   204 
   205 fun decl_type_occsT T = fold_atyps (fn TFree (a, _) => Symtab.default (a, []) | _ => I) T;
   206 
   207 val decl_type_occs = fold_term_types
   208   (fn Free (x, _) => fold_atyps (fn TFree (a, _) => Symtab.insert_list (op =) (a, x) | _ => I)
   209     | _ => decl_type_occsT);
   210 
   211 val declare_type_occsT = map_type_occs o fold_types decl_type_occsT;
   212 val declare_type_occs = map_type_occs o decl_type_occs;
   213 
   214 
   215 (* constraints *)
   216 
   217 fun constrain_tvar (xi, S) =
   218   if S = dummyS then Vartab.delete_safe xi else Vartab.update (xi, S);
   219 
   220 fun declare_constraints t = map_constraints (fn (types, sorts) =>
   221   let
   222     val types' = fold_aterms
   223       (fn Free (x, T) => Vartab.update ((x, ~1), T)
   224         | Var v => Vartab.update v
   225         | _ => I) t types;
   226     val sorts' = (fold_types o fold_atyps)
   227       (fn TFree (x, S) => constrain_tvar ((x, ~1), S)
   228         | TVar v => constrain_tvar v
   229         | _ => I) t sorts;
   230   in (types', sorts') end)
   231   #> declare_type_occsT t
   232   #> declare_type_names t;
   233 
   234 
   235 (* common declarations *)
   236 
   237 fun declare_internal t =
   238   declare_names t #>
   239   declare_type_occs t #>
   240   map_sorts (Sorts.insert_term t);
   241 
   242 fun declare_term t =
   243   declare_internal t #>
   244   declare_constraints t;
   245 
   246 val declare_typ = declare_term o Logic.mk_type;
   247 
   248 val declare_prf = Proofterm.fold_proof_terms declare_internal (declare_internal o Logic.mk_type);
   249 
   250 val declare_thm = Thm.fold_terms declare_internal;
   251 fun global_thm_context th = declare_thm th (Proof_Context.init_global (Thm.theory_of_thm th));
   252 
   253 
   254 (* renaming term/type frees *)
   255 
   256 fun variant_frees ctxt ts frees =
   257   let
   258     val names = names_of (fold declare_names ts ctxt);
   259     val xs = fst (fold_map Name.variant (map #1 frees) names);
   260   in xs ~~ map snd frees end;
   261 
   262 
   263 
   264 (** term bindings **)
   265 
   266 fun bind_term (xi, NONE) = map_binds (Vartab.delete_safe xi)
   267   | bind_term ((x, i), SOME t) =
   268       let
   269         val u = Term.close_schematic_term t;
   270         val U = Term.fastype_of u;
   271       in declare_term u #> map_binds (Vartab.update ((x, i), (U, u))) end;
   272 
   273 fun expand_binds ctxt =
   274   let
   275     val binds = binds_of ctxt;
   276     val get = fn Var (xi, _) => Vartab.lookup binds xi | _ => NONE;
   277   in Envir.beta_norm o Envir.expand_term get end;
   278 
   279 
   280 
   281 (** consts **)
   282 
   283 val lookup_const = Symtab.lookup o #consts o rep_data;
   284 val is_const = is_some oo lookup_const;
   285 
   286 val declare_fixed = map_consts o Symtab.delete_safe;
   287 val declare_const = map_consts o Symtab.update;
   288 
   289 
   290 
   291 (** fixes **)
   292 
   293 (* specialized name space *)
   294 
   295 fun is_fixed ctxt x = can (Name_Space.the_entry (fixes_space ctxt)) x;
   296 fun newly_fixed inner outer x = is_fixed inner x andalso not (is_fixed outer x);
   297 
   298 val fixed_ord = Name_Space.entry_ord o fixes_space;
   299 val intern_fixed = Name_Space.intern o fixes_space;
   300 
   301 fun lookup_fixed ctxt x =
   302   let val x' = intern_fixed ctxt x
   303   in if is_fixed ctxt x' then SOME x' else NONE end;
   304 
   305 fun revert_fixed ctxt x =
   306   (case Symtab.lookup (#2 (fixes_of ctxt)) x of
   307     SOME x' => if intern_fixed ctxt x' = x then x' else x
   308   | NONE => x);
   309 
   310 fun markup_fixed ctxt x =
   311   Name_Space.markup (fixes_space ctxt) x
   312   |> Markup.name (revert_fixed ctxt x);
   313 
   314 fun dest_fixes ctxt =
   315   let val (space, tab) = fixes_of ctxt
   316   in sort (Name_Space.entry_ord space o pairself #2) (map swap (Symtab.dest tab)) end;
   317 
   318 
   319 (* collect variables *)
   320 
   321 fun add_free_names ctxt =
   322   fold_aterms (fn Free (x, _) => not (is_fixed ctxt x) ? insert (op =) x | _ => I);
   323 
   324 fun add_frees ctxt =
   325   fold_aterms (fn Free (x, T) => not (is_fixed ctxt x) ? insert (op =) (x, T) | _ => I);
   326 
   327 fun add_fixed_names ctxt =
   328   fold_aterms (fn Free (x, _) => is_fixed ctxt x ? insert (op =) x | _ => I);
   329 
   330 fun add_fixed ctxt =
   331   fold_aterms (fn Free (x, T) => is_fixed ctxt x ? insert (op =) (x, T) | _ => I);
   332 
   333 
   334 (* declarations *)
   335 
   336 local
   337 
   338 fun err_dups dups =
   339   error ("Duplicate fixed variable(s): " ^ commas (map Binding.print dups));
   340 
   341 fun new_fixed ((x, x'), pos) ctxt =
   342   if is_some (lookup_fixed ctxt x') then err_dups [Binding.make (x, pos)]
   343   else
   344     ctxt
   345     |> map_fixes
   346       (Name_Space.define ctxt true Name_Space.default_naming (Binding.make (x', pos), x) #> snd #>>
   347         Name_Space.alias Name_Space.default_naming (Binding.make (x, pos)) x')
   348     |> declare_fixed x
   349     |> declare_constraints (Syntax.free x');
   350 
   351 fun new_fixes names' xs xs' ps =
   352   map_names (K names') #>
   353   fold new_fixed ((xs ~~ xs') ~~ ps) #>
   354   pair xs';
   355 
   356 in
   357 
   358 fun add_fixes_binding bs ctxt =
   359   let
   360     val _ =
   361       (case filter (can Name.dest_skolem o Binding.name_of) bs of
   362         [] => ()
   363       | bads => error ("Illegal internal Skolem constant(s): " ^ commas (map Binding.print bads)));
   364     val _ =
   365       (case duplicates (op = o pairself Binding.name_of) bs of
   366         [] => ()
   367       | dups => err_dups dups);
   368 
   369     val xs = map check_name bs;
   370     val names = names_of ctxt;
   371     val (xs', names') =
   372       if is_body ctxt then fold_map Name.variant xs names |>> map Name.skolem
   373       else (xs, fold Name.declare xs names);
   374   in ctxt |> new_fixes names' xs xs' (map Binding.pos_of bs) end;
   375 
   376 fun variant_fixes raw_xs ctxt =
   377   let
   378     val names = names_of ctxt;
   379     val xs = map (fn x => Name.clean x |> can Name.dest_internal x ? Name.internal) raw_xs;
   380     val (xs', names') = fold_map Name.variant xs names |>> (is_body ctxt ? map Name.skolem);
   381   in ctxt |> new_fixes names' xs xs' (replicate (length xs) Position.none) end;
   382 
   383 end;
   384 
   385 val add_fixes = add_fixes_binding o map Binding.name;
   386 
   387 fun add_fixes_direct xs ctxt = ctxt
   388   |> set_body false
   389   |> (snd o add_fixes xs)
   390   |> restore_body ctxt;
   391 
   392 fun auto_fixes t ctxt = ctxt
   393   |> not (is_body ctxt) ? add_fixes_direct (rev (add_free_names ctxt t []))
   394   |> declare_term t;
   395 
   396 fun invent_types Ss ctxt =
   397   let
   398     val tfrees = Name.invent (names_of ctxt) Name.aT (length Ss) ~~ Ss;
   399     val ctxt' = fold (declare_constraints o Logic.mk_type o TFree) tfrees ctxt;
   400   in (tfrees, ctxt') end;
   401 
   402 
   403 
   404 (** export -- generalize type/term variables (beware of closure sizes) **)
   405 
   406 fun export_inst inner outer =
   407   let
   408     val declared_outer = is_declared outer;
   409     fun still_fixed x = is_fixed outer x orelse not (is_fixed inner x);
   410 
   411     val gen_fixes =
   412       Symtab.fold (fn (y, _) => not (is_fixed outer y) ? cons y)
   413         (#2 (fixes_of inner)) [];
   414 
   415     val type_occs_inner = type_occs_of inner;
   416     fun gen_fixesT ts =
   417       Symtab.fold (fn (a, xs) =>
   418         if declared_outer a orelse exists still_fixed xs
   419         then I else cons a) (fold decl_type_occs ts type_occs_inner) [];
   420   in (gen_fixesT, gen_fixes) end;
   421 
   422 fun exportT_inst inner outer = #1 (export_inst inner outer);
   423 
   424 fun exportT_terms inner outer =
   425   let val mk_tfrees = exportT_inst inner outer in
   426     fn ts => ts |> map
   427       (Term_Subst.generalize (mk_tfrees ts, [])
   428         (fold (Term.fold_types Term.maxidx_typ) ts ~1 + 1))
   429   end;
   430 
   431 fun export_terms inner outer =
   432   let val (mk_tfrees, tfrees) = export_inst inner outer in
   433     fn ts => ts |> map
   434       (Term_Subst.generalize (mk_tfrees ts, tfrees)
   435         (fold Term.maxidx_term ts ~1 + 1))
   436   end;
   437 
   438 fun export_prf inner outer prf =
   439   let
   440     val (mk_tfrees, frees) = export_inst (declare_prf prf inner) outer;
   441     val tfrees = mk_tfrees [];
   442     val idx = Proofterm.maxidx_proof prf ~1 + 1;
   443     val gen_term = Term_Subst.generalize_same (tfrees, frees) idx;
   444     val gen_typ = Term_Subst.generalizeT_same tfrees idx;
   445   in Same.commit (Proofterm.map_proof_terms_same gen_term gen_typ) prf end;
   446 
   447 
   448 fun gen_export (mk_tfrees, frees) ths =
   449   let
   450     val tfrees = mk_tfrees (map Thm.full_prop_of ths);
   451     val maxidx = fold Thm.maxidx_thm ths ~1;
   452   in map (Thm.generalize (tfrees, frees) (maxidx + 1)) ths end;
   453 
   454 fun exportT inner outer = gen_export (exportT_inst inner outer, []);
   455 fun export inner outer = gen_export (export_inst inner outer);
   456 
   457 fun export_morphism inner outer =
   458   let
   459     val fact = export inner outer;
   460     val term = singleton (export_terms inner outer);
   461     val typ = Logic.type_map term;
   462   in Morphism.morphism {binding = [], typ = [typ], term = [term], fact = [fact]} end;
   463 
   464 
   465 
   466 (** import -- fix schematic type/term variables **)
   467 
   468 fun importT_inst ts ctxt =
   469   let
   470     val tvars = rev (fold Term.add_tvars ts []);
   471     val (tfrees, ctxt') = invent_types (map #2 tvars) ctxt;
   472   in (tvars ~~ map TFree tfrees, ctxt') end;
   473 
   474 fun import_inst is_open ts ctxt =
   475   let
   476     val ren = Name.clean #> (if is_open then I else Name.internal);
   477     val (instT, ctxt') = importT_inst ts ctxt;
   478     val vars = map (apsnd (Term_Subst.instantiateT instT)) (rev (fold Term.add_vars ts []));
   479     val (xs, ctxt'') = variant_fixes (map (ren o #1 o #1) vars) ctxt';
   480     val inst = vars ~~ map Free (xs ~~ map #2 vars);
   481   in ((instT, inst), ctxt'') end;
   482 
   483 fun importT_terms ts ctxt =
   484   let val (instT, ctxt') = importT_inst ts ctxt
   485   in (map (Term_Subst.instantiate (instT, [])) ts, ctxt') end;
   486 
   487 fun import_terms is_open ts ctxt =
   488   let val (inst, ctxt') = import_inst is_open ts ctxt
   489   in (map (Term_Subst.instantiate inst) ts, ctxt') end;
   490 
   491 fun importT ths ctxt =
   492   let
   493     val thy = Proof_Context.theory_of ctxt;
   494     val (instT, ctxt') = importT_inst (map Thm.full_prop_of ths) ctxt;
   495     val insts' as (instT', _) = Thm.certify_inst thy (instT, []);
   496     val ths' = map (Thm.instantiate insts') ths;
   497   in ((instT', ths'), ctxt') end;
   498 
   499 fun import_prf is_open prf ctxt =
   500   let
   501     val ts = rev (Proofterm.fold_proof_terms cons (cons o Logic.mk_type) prf []);
   502     val (insts, ctxt') = import_inst is_open ts ctxt;
   503   in (Proofterm.instantiate insts prf, ctxt') end;
   504 
   505 fun import is_open ths ctxt =
   506   let
   507     val thy = Proof_Context.theory_of ctxt;
   508     val (insts, ctxt') = import_inst is_open (map Thm.full_prop_of ths) ctxt;
   509     val insts' = Thm.certify_inst thy insts;
   510     val ths' = map (Thm.instantiate insts') ths;
   511   in ((insts', ths'), ctxt') end;
   512 
   513 
   514 (* import/export *)
   515 
   516 fun gen_trade imp exp f ctxt ths =
   517   let val ((_, ths'), ctxt') = imp ths ctxt
   518   in exp ctxt' ctxt (f ctxt' ths') end;
   519 
   520 val tradeT = gen_trade importT exportT;
   521 val trade = gen_trade (import true) export;
   522 
   523 
   524 (* focus on outermost parameters: !!x y z. B *)
   525 
   526 fun focus_params t ctxt =
   527   let
   528     val (xs, Ts) =
   529       split_list (Term.variant_frees t (Term.strip_all_vars t));  (*as they are printed :-*)
   530     val (xs', ctxt') = variant_fixes xs ctxt;
   531     val ps = xs' ~~ Ts;
   532     val ctxt'' = ctxt' |> fold (declare_constraints o Free) ps;
   533   in ((xs, ps), ctxt'') end;
   534 
   535 fun focus t ctxt =
   536   let
   537     val ((xs, ps), ctxt') = focus_params t ctxt;
   538     val t' = Term.subst_bounds (rev (map Free ps), Term.strip_all_body t);
   539   in (((xs ~~ ps), t'), ctxt') end;
   540 
   541 fun forall_elim_prop t prop =
   542   Thm.beta_conversion false (Thm.capply (Thm.dest_arg prop) t)
   543   |> Thm.cprop_of |> Thm.dest_arg;
   544 
   545 fun focus_cterm goal ctxt =
   546   let
   547     val cert = Thm.cterm_of (Thm.theory_of_cterm goal);
   548     val ((xs, ps), ctxt') = focus_params (Thm.term_of goal) ctxt;
   549     val ps' = map (cert o Free) ps;
   550     val goal' = fold forall_elim_prop ps' goal;
   551   in ((xs ~~ ps', goal'), ctxt') end;
   552 
   553 fun focus_subgoal i st =
   554   let
   555     val all_vars = Thm.fold_terms Term.add_vars st [];
   556     val no_binds = map (fn (xi, _) => (xi, NONE)) all_vars;
   557   in
   558     fold bind_term no_binds #>
   559     fold (declare_constraints o Var) all_vars #>
   560     focus_cterm (Thm.cprem_of st i)
   561   end;
   562 
   563 
   564 
   565 (** implicit polymorphism **)
   566 
   567 (* warn_extra_tfrees *)
   568 
   569 fun warn_extra_tfrees ctxt1 ctxt2 =
   570   let
   571     fun occs_typ a = Term.exists_subtype (fn TFree (b, _) => a = b | _ => false);
   572     fun occs_free a x =
   573       (case def_type ctxt1 false (x, ~1) of
   574         SOME T => if occs_typ a T then I else cons (a, x)
   575       | NONE => cons (a, x));
   576 
   577     val occs1 = type_occs_of ctxt1;
   578     val occs2 = type_occs_of ctxt2;
   579     val extras = Symtab.fold (fn (a, xs) =>
   580       if Symtab.defined occs1 a then I else fold (occs_free a) xs) occs2 [];
   581     val tfrees = map #1 extras |> sort_distinct string_ord;
   582     val frees = map #2 extras |> sort_distinct string_ord;
   583   in
   584     if null extras orelse not (Context_Position.is_visible ctxt2) then ()
   585     else warning ("Introduced fixed type variable(s): " ^ commas tfrees ^ " in " ^
   586       space_implode " or " (map quote frees))
   587   end;
   588 
   589 
   590 (* polymorphic terms *)
   591 
   592 fun polymorphic_types ctxt ts =
   593   let
   594     val ctxt' = fold declare_term ts ctxt;
   595     val occs = type_occs_of ctxt;
   596     val occs' = type_occs_of ctxt';
   597     val types = Symtab.fold (fn (a, _) => if Symtab.defined occs a then I else cons a) occs' [];
   598     val idx = maxidx_of ctxt' + 1;
   599     val Ts' = (fold o fold_types o fold_atyps)
   600       (fn T as TFree _ =>
   601           (case Term_Subst.generalizeT types idx T of TVar v => insert (op =) v | _ => I)
   602         | _ => I) ts [];
   603     val ts' = map (Term_Subst.generalize (types, []) idx) ts;
   604   in (rev Ts', ts') end;
   605 
   606 fun polymorphic ctxt ts = snd (polymorphic_types ctxt ts);
   607 
   608 end;