src/HOL/Tools/inductive_package.ML
author berghofe
Fri May 31 18:49:31 2002 +0200 (2002-05-31 ago)
changeset 13197 0567f4fd1415
parent 12922 ed70a600f0ea
child 13626 282fbabec862
permissions -rw-r--r--
Changed interface of MetaSimplifier.rewrite_term.
     1 (*  Title:      HOL/Tools/inductive_package.ML
     2     ID:         $Id$
     3     Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
     4     Author:     Stefan Berghofer, TU Muenchen
     5     Author:     Markus Wenzel, TU Muenchen
     6     License:    GPL (GNU GENERAL PUBLIC LICENSE)
     7 
     8 (Co)Inductive Definition module for HOL.
     9 
    10 Features:
    11   * least or greatest fixedpoints
    12   * user-specified product and sum constructions
    13   * mutually recursive definitions
    14   * definitions involving arbitrary monotone operators
    15   * automatically proves introduction and elimination rules
    16 
    17 The recursive sets must *already* be declared as constants in the
    18 current theory!
    19 
    20   Introduction rules have the form
    21   [| ti:M(Sj), ..., P(x), ... |] ==> t: Sk
    22   where M is some monotone operator (usually the identity)
    23   P(x) is any side condition on the free variables
    24   ti, t are any terms
    25   Sj, Sk are two of the sets being defined in mutual recursion
    26 
    27 Sums are used only for mutual recursion.  Products are used only to
    28 derive "streamlined" induction rules for relations.
    29 *)
    30 
    31 signature INDUCTIVE_PACKAGE =
    32 sig
    33   val quiet_mode: bool ref
    34   val unify_consts: Sign.sg -> term list -> term list -> term list * term list
    35   val split_rule_vars: term list -> thm -> thm
    36   val get_inductive: theory -> string -> ({names: string list, coind: bool} *
    37     {defs: thm list, elims: thm list, raw_induct: thm, induct: thm,
    38      intrs: thm list, mk_cases: string -> thm, mono: thm, unfold: thm}) option
    39   val the_mk_cases: theory -> string -> string -> thm
    40   val print_inductives: theory -> unit
    41   val mono_add_global: theory attribute
    42   val mono_del_global: theory attribute
    43   val get_monos: theory -> thm list
    44   val inductive_forall_name: string
    45   val inductive_forall_def: thm
    46   val rulify: thm -> thm
    47   val inductive_cases: ((bstring * Args.src list) * string list) list -> theory -> theory
    48   val inductive_cases_i: ((bstring * theory attribute list) * term list) list -> theory -> theory
    49   val add_inductive_i: bool -> bool -> bstring -> bool -> bool -> bool -> term list ->
    50     ((bstring * term) * theory attribute list) list -> thm list -> theory -> theory *
    51       {defs: thm list, elims: thm list, raw_induct: thm, induct: thm,
    52        intrs: thm list, mk_cases: string -> thm, mono: thm, unfold: thm}
    53   val add_inductive: bool -> bool -> string list ->
    54     ((bstring * string) * Args.src list) list -> (xstring * Args.src list) list ->
    55     theory -> theory *
    56       {defs: thm list, elims: thm list, raw_induct: thm, induct: thm,
    57        intrs: thm list, mk_cases: string -> thm, mono: thm, unfold: thm}
    58   val setup: (theory -> theory) list
    59 end;
    60 
    61 structure InductivePackage: INDUCTIVE_PACKAGE =
    62 struct
    63 
    64 
    65 (** theory context references **)
    66 
    67 val mono_name = "HOL.mono";
    68 val gfp_name = "Gfp.gfp";
    69 val lfp_name = "Lfp.lfp";
    70 val vimage_name = "Set.vimage";
    71 val Const _ $ (vimage_f $ _) $ _ = HOLogic.dest_Trueprop (Thm.concl_of vimageD);
    72 
    73 val inductive_forall_name = "HOL.induct_forall";
    74 val inductive_forall_def = thm "induct_forall_def";
    75 val inductive_conj_name = "HOL.induct_conj";
    76 val inductive_conj_def = thm "induct_conj_def";
    77 val inductive_conj = thms "induct_conj";
    78 val inductive_atomize = thms "induct_atomize";
    79 val inductive_rulify1 = thms "induct_rulify1";
    80 val inductive_rulify2 = thms "induct_rulify2";
    81 
    82 
    83 
    84 (** theory data **)
    85 
    86 (* data kind 'HOL/inductive' *)
    87 
    88 type inductive_info =
    89   {names: string list, coind: bool} * {defs: thm list, elims: thm list, raw_induct: thm,
    90     induct: thm, intrs: thm list, mk_cases: string -> thm, mono: thm, unfold: thm};
    91 
    92 structure InductiveArgs =
    93 struct
    94   val name = "HOL/inductive";
    95   type T = inductive_info Symtab.table * thm list;
    96 
    97   val empty = (Symtab.empty, []);
    98   val copy = I;
    99   val prep_ext = I;
   100   fun merge ((tab1, monos1), (tab2, monos2)) =
   101     (Symtab.merge (K true) (tab1, tab2), Drule.merge_rules (monos1, monos2));
   102 
   103   fun print sg (tab, monos) =
   104     [Pretty.strs ("(co)inductives:" :: map #1 (Sign.cond_extern_table sg Sign.constK tab)),
   105      Pretty.big_list "monotonicity rules:" (map (Display.pretty_thm_sg sg) monos)]
   106     |> Pretty.chunks |> Pretty.writeln;
   107 end;
   108 
   109 structure InductiveData = TheoryDataFun(InductiveArgs);
   110 val print_inductives = InductiveData.print;
   111 
   112 
   113 (* get and put data *)
   114 
   115 fun get_inductive thy name = Symtab.lookup (fst (InductiveData.get thy), name);
   116 
   117 fun the_inductive thy name =
   118   (case get_inductive thy name of
   119     None => error ("Unknown (co)inductive set " ^ quote name)
   120   | Some info => info);
   121 
   122 val the_mk_cases = (#mk_cases o #2) oo the_inductive;
   123 
   124 fun put_inductives names info thy =
   125   let
   126     fun upd ((tab, monos), name) = (Symtab.update_new ((name, info), tab), monos);
   127     val tab_monos = foldl upd (InductiveData.get thy, names)
   128       handle Symtab.DUP name => error ("Duplicate definition of (co)inductive set " ^ quote name);
   129   in InductiveData.put tab_monos thy end;
   130 
   131 
   132 
   133 (** monotonicity rules **)
   134 
   135 val get_monos = #2 o InductiveData.get;
   136 fun map_monos f = InductiveData.map (Library.apsnd f);
   137 
   138 fun mk_mono thm =
   139   let
   140     fun eq2mono thm' = [standard (thm' RS (thm' RS eq_to_mono))] @
   141       (case concl_of thm of
   142           (_ $ (_ $ (Const ("Not", _) $ _) $ _)) => []
   143         | _ => [standard (thm' RS (thm' RS eq_to_mono2))]);
   144     val concl = concl_of thm
   145   in
   146     if Logic.is_equals concl then
   147       eq2mono (thm RS meta_eq_to_obj_eq)
   148     else if can (HOLogic.dest_eq o HOLogic.dest_Trueprop) concl then
   149       eq2mono thm
   150     else [thm]
   151   end;
   152 
   153 
   154 (* attributes *)
   155 
   156 fun mono_add_global (thy, thm) = (map_monos (Drule.add_rules (mk_mono thm)) thy, thm);
   157 fun mono_del_global (thy, thm) = (map_monos (Drule.del_rules (mk_mono thm)) thy, thm);
   158 
   159 val mono_attr =
   160  (Attrib.add_del_args mono_add_global mono_del_global,
   161   Attrib.add_del_args Attrib.undef_local_attribute Attrib.undef_local_attribute);
   162 
   163 
   164 
   165 (** misc utilities **)
   166 
   167 val quiet_mode = ref false;
   168 fun message s = if ! quiet_mode then () else writeln s;
   169 fun clean_message s = if ! quick_and_dirty then () else message s;
   170 
   171 fun coind_prefix true = "co"
   172   | coind_prefix false = "";
   173 
   174 
   175 (*the following code ensures that each recursive set always has the
   176   same type in all introduction rules*)
   177 fun unify_consts sign cs intr_ts =
   178   (let
   179     val {tsig, ...} = Sign.rep_sg sign;
   180     val add_term_consts_2 =
   181       foldl_aterms (fn (cs, Const c) => c ins cs | (cs, _) => cs);
   182     fun varify (t, (i, ts)) =
   183       let val t' = map_term_types (incr_tvar (i + 1)) (#1 (Type.varify (t, [])))
   184       in (maxidx_of_term t', t'::ts) end;
   185     val (i, cs') = foldr varify (cs, (~1, []));
   186     val (i', intr_ts') = foldr varify (intr_ts, (i, []));
   187     val rec_consts = foldl add_term_consts_2 ([], cs');
   188     val intr_consts = foldl add_term_consts_2 ([], intr_ts');
   189     fun unify (env, (cname, cT)) =
   190       let val consts = map snd (filter (fn c => fst c = cname) intr_consts)
   191       in foldl (fn ((env', j'), Tp) => (Type.unify tsig (env', j') Tp))
   192           (env, (replicate (length consts) cT) ~~ consts)
   193       end;
   194     val (env, _) = foldl unify ((Vartab.empty, i'), rec_consts);
   195     fun typ_subst_TVars_2 env T = let val T' = typ_subst_TVars_Vartab env T
   196       in if T = T' then T else typ_subst_TVars_2 env T' end;
   197     val subst = fst o Type.freeze_thaw o
   198       (map_term_types (typ_subst_TVars_2 env))
   199 
   200   in (map subst cs', map subst intr_ts')
   201   end) handle Type.TUNIFY =>
   202     (warning "Occurrences of recursive constant have non-unifiable types"; (cs, intr_ts));
   203 
   204 
   205 (*make injections used in mutually recursive definitions*)
   206 fun mk_inj cs sumT c x =
   207   let
   208     fun mk_inj' T n i =
   209       if n = 1 then x else
   210       let val n2 = n div 2;
   211           val Type (_, [T1, T2]) = T
   212       in
   213         if i <= n2 then
   214           Const ("Inl", T1 --> T) $ (mk_inj' T1 n2 i)
   215         else
   216           Const ("Inr", T2 --> T) $ (mk_inj' T2 (n - n2) (i - n2))
   217       end
   218   in mk_inj' sumT (length cs) (1 + find_index_eq c cs)
   219   end;
   220 
   221 (*make "vimage" terms for selecting out components of mutually rec.def*)
   222 fun mk_vimage cs sumT t c = if length cs < 2 then t else
   223   let
   224     val cT = HOLogic.dest_setT (fastype_of c);
   225     val vimageT = [cT --> sumT, HOLogic.mk_setT sumT] ---> HOLogic.mk_setT cT
   226   in
   227     Const (vimage_name, vimageT) $
   228       Abs ("y", cT, mk_inj cs sumT c (Bound 0)) $ t
   229   end;
   230 
   231 (** proper splitting **)
   232 
   233 fun prod_factors p (Const ("Pair", _) $ t $ u) =
   234       p :: prod_factors (1::p) t @ prod_factors (2::p) u
   235   | prod_factors p _ = [];
   236 
   237 fun mg_prod_factors ts (fs, t $ u) = if t mem ts then
   238         let val f = prod_factors [] u
   239         in overwrite (fs, (t, f inter if_none (assoc (fs, t)) f)) end
   240       else mg_prod_factors ts (mg_prod_factors ts (fs, t), u)
   241   | mg_prod_factors ts (fs, Abs (_, _, t)) = mg_prod_factors ts (fs, t)
   242   | mg_prod_factors ts (fs, _) = fs;
   243 
   244 fun prodT_factors p ps (T as Type ("*", [T1, T2])) =
   245       if p mem ps then prodT_factors (1::p) ps T1 @ prodT_factors (2::p) ps T2
   246       else [T]
   247   | prodT_factors _ _ T = [T];
   248 
   249 fun ap_split p ps (Type ("*", [T1, T2])) T3 u =
   250       if p mem ps then HOLogic.split_const (T1, T2, T3) $
   251         Abs ("v", T1, ap_split (2::p) ps T2 T3 (ap_split (1::p) ps T1
   252           (prodT_factors (2::p) ps T2 ---> T3) (incr_boundvars 1 u) $ Bound 0))
   253       else u
   254   | ap_split _ _ _ _ u =  u;
   255 
   256 fun mk_tuple p ps (Type ("*", [T1, T2])) (tms as t::_) =
   257       if p mem ps then HOLogic.mk_prod (mk_tuple (1::p) ps T1 tms, 
   258         mk_tuple (2::p) ps T2 (drop (length (prodT_factors (1::p) ps T1), tms)))
   259       else t
   260   | mk_tuple _ _ _ (t::_) = t;
   261 
   262 fun split_rule_var' ((t as Var (v, Type ("fun", [T1, T2])), ps), rl) =
   263       let val T' = prodT_factors [] ps T1 ---> T2
   264           val newt = ap_split [] ps T1 T2 (Var (v, T'))
   265           val cterm = Thm.cterm_of (#sign (rep_thm rl))
   266       in
   267           instantiate ([], [(cterm t, cterm newt)]) rl
   268       end
   269   | split_rule_var' (_, rl) = rl;
   270 
   271 val remove_split = rewrite_rule [split_conv RS eq_reflection];
   272 
   273 fun split_rule_vars vs rl = standard (remove_split (foldr split_rule_var'
   274   (mg_prod_factors vs ([], #prop (rep_thm rl)), rl)));
   275 
   276 fun split_rule vs rl = standard (remove_split (foldr split_rule_var'
   277   (mapfilter (fn (t as Var ((a, _), _)) =>
   278     apsome (pair t) (assoc (vs, a))) (term_vars (#prop (rep_thm rl))), rl)));
   279 
   280 
   281 (** process rules **)
   282 
   283 local
   284 
   285 fun err_in_rule sg name t msg =
   286   error (cat_lines ["Ill-formed introduction rule " ^ quote name, Sign.string_of_term sg t, msg]);
   287 
   288 fun err_in_prem sg name t p msg =
   289   error (cat_lines ["Ill-formed premise", Sign.string_of_term sg p,
   290     "in introduction rule " ^ quote name, Sign.string_of_term sg t, msg]);
   291 
   292 val bad_concl = "Conclusion of introduction rule must have form \"t : S_i\"";
   293 
   294 val all_not_allowed = 
   295     "Introduction rule must not have a leading \"!!\" quantifier";
   296 
   297 fun atomize_term sg = MetaSimplifier.rewrite_term sg inductive_atomize [];
   298 
   299 in
   300 
   301 fun check_rule sg cs ((name, rule), att) =
   302   let
   303     val concl = Logic.strip_imp_concl rule;
   304     val prems = Logic.strip_imp_prems rule;
   305     val aprems = map (atomize_term sg) prems;
   306     val arule = Logic.list_implies (aprems, concl);
   307 
   308     fun check_prem (prem, aprem) =
   309       if can HOLogic.dest_Trueprop aprem then ()
   310       else err_in_prem sg name rule prem "Non-atomic premise";
   311   in
   312     (case concl of
   313       Const ("Trueprop", _) $ (Const ("op :", _) $ t $ u) =>
   314         if u mem cs then
   315           if exists (Logic.occs o rpair t) cs then
   316             err_in_rule sg name rule "Recursion term on left of member symbol"
   317           else seq check_prem (prems ~~ aprems)
   318         else err_in_rule sg name rule bad_concl
   319       | Const ("all", _) $ _ => err_in_rule sg name rule all_not_allowed
   320       | _ => err_in_rule sg name rule bad_concl);
   321     ((name, arule), att)
   322   end;
   323 
   324 val rulify =
   325   standard o Tactic.norm_hhf_rule o
   326   hol_simplify inductive_rulify2 o hol_simplify inductive_rulify1 o
   327   hol_simplify inductive_conj;
   328 
   329 end;
   330 
   331 
   332 
   333 (** properties of (co)inductive sets **)
   334 
   335 (* elimination rules *)
   336 
   337 fun mk_elims cs cTs params intr_ts intr_names =
   338   let
   339     val used = foldr add_term_names (intr_ts, []);
   340     val [aname, pname] = variantlist (["a", "P"], used);
   341     val P = HOLogic.mk_Trueprop (Free (pname, HOLogic.boolT));
   342 
   343     fun dest_intr r =
   344       let val Const ("op :", _) $ t $ u =
   345         HOLogic.dest_Trueprop (Logic.strip_imp_concl r)
   346       in (u, t, Logic.strip_imp_prems r) end;
   347 
   348     val intrs = map dest_intr intr_ts ~~ intr_names;
   349 
   350     fun mk_elim (c, T) =
   351       let
   352         val a = Free (aname, T);
   353 
   354         fun mk_elim_prem (_, t, ts) =
   355           list_all_free (map dest_Free ((foldr add_term_frees (t::ts, [])) \\ params),
   356             Logic.list_implies (HOLogic.mk_Trueprop (HOLogic.mk_eq (a, t)) :: ts, P));
   357         val c_intrs = (filter (equal c o #1 o #1) intrs);
   358       in
   359         (Logic.list_implies (HOLogic.mk_Trueprop (HOLogic.mk_mem (a, c)) ::
   360           map mk_elim_prem (map #1 c_intrs), P), map #2 c_intrs)
   361       end
   362   in
   363     map mk_elim (cs ~~ cTs)
   364   end;
   365 
   366 
   367 (* premises and conclusions of induction rules *)
   368 
   369 fun mk_indrule cs cTs params intr_ts =
   370   let
   371     val used = foldr add_term_names (intr_ts, []);
   372 
   373     (* predicates for induction rule *)
   374 
   375     val preds = map Free (variantlist (if length cs < 2 then ["P"] else
   376       map (fn i => "P" ^ string_of_int i) (1 upto length cs), used) ~~
   377         map (fn T => T --> HOLogic.boolT) cTs);
   378 
   379     (* transform an introduction rule into a premise for induction rule *)
   380 
   381     fun mk_ind_prem r =
   382       let
   383         val frees = map dest_Free ((add_term_frees (r, [])) \\ params);
   384 
   385         val pred_of = curry (Library.gen_assoc (op aconv)) (cs ~~ preds);
   386 
   387         fun subst (s as ((m as Const ("op :", T)) $ t $ u)) =
   388               (case pred_of u of
   389                   None => (m $ fst (subst t) $ fst (subst u), None)
   390                 | Some P => (HOLogic.mk_binop inductive_conj_name (s, P $ t), Some (s, P $ t)))
   391           | subst s =
   392               (case pred_of s of
   393                   Some P => (HOLogic.mk_binop "op Int"
   394                     (s, HOLogic.Collect_const (HOLogic.dest_setT
   395                       (fastype_of s)) $ P), None)
   396                 | None => (case s of
   397                      (t $ u) => (fst (subst t) $ fst (subst u), None)
   398                    | (Abs (a, T, t)) => (Abs (a, T, fst (subst t)), None)
   399                    | _ => (s, None)));
   400 
   401         fun mk_prem (s, prems) = (case subst s of
   402               (_, Some (t, u)) => t :: u :: prems
   403             | (t, _) => t :: prems);
   404 
   405         val Const ("op :", _) $ t $ u =
   406           HOLogic.dest_Trueprop (Logic.strip_imp_concl r)
   407 
   408       in list_all_free (frees,
   409            Logic.list_implies (map HOLogic.mk_Trueprop (foldr mk_prem
   410              (map HOLogic.dest_Trueprop (Logic.strip_imp_prems r), [])),
   411                HOLogic.mk_Trueprop (the (pred_of u) $ t)))
   412       end;
   413 
   414     val ind_prems = map mk_ind_prem intr_ts;
   415     val factors = foldl (mg_prod_factors preds) ([], ind_prems);
   416 
   417     (* make conclusions for induction rules *)
   418 
   419     fun mk_ind_concl ((c, P), (ts, x)) =
   420       let val T = HOLogic.dest_setT (fastype_of c);
   421           val ps = if_none (assoc (factors, P)) [];
   422           val Ts = prodT_factors [] ps T;
   423           val (frees, x') = foldr (fn (T', (fs, s)) =>
   424             ((Free (s, T'))::fs, Symbol.bump_string s)) (Ts, ([], x));
   425           val tuple = mk_tuple [] ps T frees;
   426       in ((HOLogic.mk_binop "op -->"
   427         (HOLogic.mk_mem (tuple, c), P $ tuple))::ts, x')
   428       end;
   429 
   430     val mutual_ind_concl = HOLogic.mk_Trueprop (foldr1 HOLogic.mk_conj
   431         (fst (foldr mk_ind_concl (cs ~~ preds, ([], "xa")))))
   432 
   433   in (preds, ind_prems, mutual_ind_concl,
   434     map (apfst (fst o dest_Free)) factors)
   435   end;
   436 
   437 
   438 (* prepare cases and induct rules *)
   439 
   440 (*
   441   transform mutual rule:
   442     HH ==> (x1:A1 --> P1 x1) & ... & (xn:An --> Pn xn)
   443   into i-th projection:
   444     xi:Ai ==> HH ==> Pi xi
   445 *)
   446 
   447 fun project_rules [name] rule = [(name, rule)]
   448   | project_rules names mutual_rule =
   449       let
   450         val n = length names;
   451         fun proj i =
   452           (if i < n then (fn th => th RS conjunct1) else I)
   453             (Library.funpow (i - 1) (fn th => th RS conjunct2) mutual_rule)
   454             RS mp |> Thm.permute_prems 0 ~1 |> Drule.standard;
   455       in names ~~ map proj (1 upto n) end;
   456 
   457 fun add_cases_induct no_elim no_induct names elims induct =
   458   let
   459     fun cases_spec (name, elim) thy =
   460       thy
   461       |> Theory.add_path (Sign.base_name name)
   462       |> (#1 o PureThy.add_thms [(("cases", elim), [InductAttrib.cases_set_global name])])
   463       |> Theory.parent_path;
   464     val cases_specs = if no_elim then [] else map2 cases_spec (names, elims);
   465 
   466     fun induct_spec (name, th) = #1 o PureThy.add_thms
   467       [(("", RuleCases.save induct th), [InductAttrib.induct_set_global name])];
   468     val induct_specs = if no_induct then [] else map induct_spec (project_rules names induct);
   469   in Library.apply (cases_specs @ induct_specs) end;
   470 
   471 
   472 
   473 (** proofs for (co)inductive sets **)
   474 
   475 (* prove monotonicity -- NOT subject to quick_and_dirty! *)
   476 
   477 fun prove_mono setT fp_fun monos thy =
   478  (message "  Proving monotonicity ...";
   479   Goals.prove_goalw_cterm []      (*NO quick_and_dirty_prove_goalw_cterm here!*)
   480     (Thm.cterm_of (Theory.sign_of thy) (HOLogic.mk_Trueprop
   481       (Const (mono_name, (setT --> setT) --> HOLogic.boolT) $ fp_fun)))
   482     (fn _ => [rtac monoI 1, REPEAT (ares_tac (flat (map mk_mono monos) @ get_monos thy) 1)]));
   483 
   484 
   485 (* prove introduction rules *)
   486 
   487 fun prove_intrs coind mono fp_def intr_ts rec_sets_defs thy =
   488   let
   489     val _ = clean_message "  Proving the introduction rules ...";
   490 
   491     val unfold = standard (mono RS (fp_def RS
   492       (if coind then def_gfp_unfold else def_lfp_unfold)));
   493 
   494     fun select_disj 1 1 = []
   495       | select_disj _ 1 = [rtac disjI1]
   496       | select_disj n i = (rtac disjI2)::(select_disj (n - 1) (i - 1));
   497 
   498     val intrs = map (fn (i, intr) => quick_and_dirty_prove_goalw_cterm thy rec_sets_defs
   499       (Thm.cterm_of (Theory.sign_of thy) intr) (fn prems =>
   500        [(*insert prems and underlying sets*)
   501        cut_facts_tac prems 1,
   502        stac unfold 1,
   503        REPEAT (resolve_tac [vimageI2, CollectI] 1),
   504        (*Now 1-2 subgoals: the disjunction, perhaps equality.*)
   505        EVERY1 (select_disj (length intr_ts) i),
   506        (*Not ares_tac, since refl must be tried before any equality assumptions;
   507          backtracking may occur if the premises have extra variables!*)
   508        DEPTH_SOLVE_1 (resolve_tac [refl, exI, conjI] 1 APPEND assume_tac 1),
   509        (*Now solve the equations like Inl 0 = Inl ?b2*)
   510        REPEAT (rtac refl 1)])
   511       |> rulify) (1 upto (length intr_ts) ~~ intr_ts)
   512 
   513   in (intrs, unfold) end;
   514 
   515 
   516 (* prove elimination rules *)
   517 
   518 fun prove_elims cs cTs params intr_ts intr_names unfold rec_sets_defs thy =
   519   let
   520     val _ = clean_message "  Proving the elimination rules ...";
   521 
   522     val rules1 = [CollectE, disjE, make_elim vimageD, exE];
   523     val rules2 = [conjE, Inl_neq_Inr, Inr_neq_Inl] @ map make_elim [Inl_inject, Inr_inject];
   524   in
   525     mk_elims cs cTs params intr_ts intr_names |> map (fn (t, cases) =>
   526       quick_and_dirty_prove_goalw_cterm thy rec_sets_defs
   527         (Thm.cterm_of (Theory.sign_of thy) t) (fn prems =>
   528           [cut_facts_tac [hd prems] 1,
   529            dtac (unfold RS subst) 1,
   530            REPEAT (FIRSTGOAL (eresolve_tac rules1)),
   531            REPEAT (FIRSTGOAL (eresolve_tac rules2)),
   532            EVERY (map (fn prem => DEPTH_SOLVE_1 (ares_tac [prem, conjI] 1)) (tl prems))])
   533         |> rulify
   534         |> RuleCases.name cases)
   535   end;
   536 
   537 
   538 (* derivation of simplified elimination rules *)
   539 
   540 local
   541 
   542 (*cprop should have the form t:Si where Si is an inductive set*)
   543 val mk_cases_err = "mk_cases: proposition not of form \"t : S_i\"";
   544 
   545 (*delete needless equality assumptions*)
   546 val refl_thin = prove_goal HOL.thy "!!P. a = a ==> P ==> P" (fn _ => [assume_tac 1]);
   547 val elim_rls = [asm_rl, FalseE, refl_thin, conjE, exE, Pair_inject];
   548 val elim_tac = REPEAT o Tactic.eresolve_tac elim_rls;
   549 
   550 fun simp_case_tac solved ss i =
   551   EVERY' [elim_tac, asm_full_simp_tac ss, elim_tac, REPEAT o bound_hyp_subst_tac] i
   552   THEN_MAYBE (if solved then no_tac else all_tac);
   553 
   554 in
   555 
   556 fun mk_cases_i elims ss cprop =
   557   let
   558     val prem = Thm.assume cprop;
   559     val tac = ALLGOALS (simp_case_tac false ss) THEN prune_params_tac;
   560     fun mk_elim rl = Drule.standard (Tactic.rule_by_tactic tac (prem RS rl));
   561   in
   562     (case get_first (try mk_elim) elims of
   563       Some r => r
   564     | None => error (Pretty.string_of (Pretty.block
   565         [Pretty.str mk_cases_err, Pretty.fbrk, Display.pretty_cterm cprop])))
   566   end;
   567 
   568 fun mk_cases elims s =
   569   mk_cases_i elims (simpset()) (Thm.read_cterm (Thm.sign_of_thm (hd elims)) (s, propT));
   570 
   571 fun smart_mk_cases thy ss cprop =
   572   let
   573     val c = #1 (Term.dest_Const (Term.head_of (#2 (HOLogic.dest_mem (HOLogic.dest_Trueprop
   574       (Logic.strip_imp_concl (Thm.term_of cprop))))))) handle TERM _ => error mk_cases_err;
   575     val (_, {elims, ...}) = the_inductive thy c;
   576   in mk_cases_i elims ss cprop end;
   577 
   578 end;
   579 
   580 
   581 (* inductive_cases(_i) *)
   582 
   583 fun gen_inductive_cases prep_att prep_prop args thy =
   584   let
   585     val cert_prop = Thm.cterm_of (Theory.sign_of thy) o prep_prop (ProofContext.init thy);
   586     val mk_cases = smart_mk_cases thy (Simplifier.simpset_of thy) o cert_prop;
   587 
   588     val facts = args |> map (fn ((a, atts), props) =>
   589      ((a, map (prep_att thy) atts), map (Thm.no_attributes o single o mk_cases) props));
   590   in thy |> IsarThy.theorems_i Drule.lemmaK facts |> #1 end;
   591 
   592 val inductive_cases = gen_inductive_cases Attrib.global_attribute ProofContext.read_prop;
   593 val inductive_cases_i = gen_inductive_cases (K I) ProofContext.cert_prop;
   594 
   595 
   596 (* mk_cases_meth *)
   597 
   598 fun mk_cases_meth (ctxt, raw_props) =
   599   let
   600     val thy = ProofContext.theory_of ctxt;
   601     val ss = Simplifier.get_local_simpset ctxt;
   602     val cprops = map (Thm.cterm_of (Theory.sign_of thy) o ProofContext.read_prop ctxt) raw_props;
   603   in Method.erule 0 (map (smart_mk_cases thy ss) cprops) end;
   604 
   605 val mk_cases_args = Method.syntax (Scan.lift (Scan.repeat1 Args.name));
   606 
   607 
   608 (* prove induction rule *)
   609 
   610 fun prove_indrule cs cTs sumT rec_const params intr_ts mono
   611     fp_def rec_sets_defs thy =
   612   let
   613     val _ = clean_message "  Proving the induction rule ...";
   614 
   615     val sign = Theory.sign_of thy;
   616 
   617     val sum_case_rewrites =
   618       (if PureThy.get_name thy = "Datatype" then PureThy.get_thms thy "sum.cases"
   619         else
   620           (case ThyInfo.lookup_theory "Datatype" of
   621             None => []
   622           | Some thy' => PureThy.get_thms thy' "sum.cases")) |> map mk_meta_eq;
   623 
   624     val (preds, ind_prems, mutual_ind_concl, factors) =
   625       mk_indrule cs cTs params intr_ts;
   626 
   627     (* make predicate for instantiation of abstract induction rule *)
   628 
   629     fun mk_ind_pred _ [P] = P
   630       | mk_ind_pred T Ps =
   631          let val n = (length Ps) div 2;
   632              val Type (_, [T1, T2]) = T
   633          in Const ("Datatype.sum.sum_case",
   634            [T1 --> HOLogic.boolT, T2 --> HOLogic.boolT, T] ---> HOLogic.boolT) $
   635              mk_ind_pred T1 (take (n, Ps)) $ mk_ind_pred T2 (drop (n, Ps))
   636          end;
   637 
   638     val ind_pred = mk_ind_pred sumT preds;
   639 
   640     val ind_concl = HOLogic.mk_Trueprop
   641       (HOLogic.all_const sumT $ Abs ("x", sumT, HOLogic.mk_binop "op -->"
   642         (HOLogic.mk_mem (Bound 0, rec_const), ind_pred $ Bound 0)));
   643 
   644     (* simplification rules for vimage and Collect *)
   645 
   646     val vimage_simps = if length cs < 2 then [] else
   647       map (fn c => quick_and_dirty_prove_goalw_cterm thy [] (Thm.cterm_of sign
   648         (HOLogic.mk_Trueprop (HOLogic.mk_eq
   649           (mk_vimage cs sumT (HOLogic.Collect_const sumT $ ind_pred) c,
   650            HOLogic.Collect_const (HOLogic.dest_setT (fastype_of c)) $
   651              nth_elem (find_index_eq c cs, preds)))))
   652         (fn _ => [rtac vimage_Collect 1, rewrite_goals_tac sum_case_rewrites, rtac refl 1])) cs;
   653 
   654     val induct = quick_and_dirty_prove_goalw_cterm thy [inductive_conj_def] (Thm.cterm_of sign
   655       (Logic.list_implies (ind_prems, ind_concl))) (fn prems =>
   656         [rtac (impI RS allI) 1,
   657          DETERM (etac (mono RS (fp_def RS def_lfp_induct)) 1),
   658          rewrite_goals_tac (map mk_meta_eq (vimage_Int::Int_Collect::vimage_simps)),
   659          fold_goals_tac rec_sets_defs,
   660          (*This CollectE and disjE separates out the introduction rules*)
   661          REPEAT (FIRSTGOAL (eresolve_tac [CollectE, disjE, exE])),
   662          (*Now break down the individual cases.  No disjE here in case
   663            some premise involves disjunction.*)
   664          REPEAT (FIRSTGOAL (etac conjE ORELSE' hyp_subst_tac)),
   665          rewrite_goals_tac sum_case_rewrites,
   666          EVERY (map (fn prem =>
   667            DEPTH_SOLVE_1 (ares_tac [prem, conjI, refl] 1)) prems)]);
   668 
   669     val lemma = quick_and_dirty_prove_goalw_cterm thy rec_sets_defs (Thm.cterm_of sign
   670       (Logic.mk_implies (ind_concl, mutual_ind_concl))) (fn prems =>
   671         [cut_facts_tac prems 1,
   672          REPEAT (EVERY
   673            [REPEAT (resolve_tac [conjI, impI] 1),
   674             TRY (dtac vimageD 1), etac allE 1, dtac mp 1, atac 1,
   675             rewrite_goals_tac sum_case_rewrites,
   676             atac 1])])
   677 
   678   in standard (split_rule factors (induct RS lemma)) end;
   679 
   680 
   681 
   682 (** specification of (co)inductive sets **)
   683 
   684 fun cond_declare_consts declare_consts cs paramTs cnames =
   685   if declare_consts then
   686     Theory.add_consts_i (map (fn (c, n) => (n, paramTs ---> fastype_of c, NoSyn)) (cs ~~ cnames))
   687   else I;
   688 
   689 fun mk_ind_def declare_consts alt_name coind cs intr_ts monos thy
   690       params paramTs cTs cnames =
   691   let
   692     val sumT = fold_bal (fn (T, U) => Type ("+", [T, U])) cTs;
   693     val setT = HOLogic.mk_setT sumT;
   694 
   695     val fp_name = if coind then gfp_name else lfp_name;
   696 
   697     val used = foldr add_term_names (intr_ts, []);
   698     val [sname, xname] = variantlist (["S", "x"], used);
   699 
   700     (* transform an introduction rule into a conjunction  *)
   701     (*   [| t : ... S_i ... ; ... |] ==> u : S_j          *)
   702     (* is transformed into                                *)
   703     (*   x = Inj_j u & t : ... Inj_i -`` S ... & ...      *)
   704 
   705     fun transform_rule r =
   706       let
   707         val frees = map dest_Free ((add_term_frees (r, [])) \\ params);
   708         val subst = subst_free
   709           (cs ~~ (map (mk_vimage cs sumT (Free (sname, setT))) cs));
   710         val Const ("op :", _) $ t $ u =
   711           HOLogic.dest_Trueprop (Logic.strip_imp_concl r)
   712 
   713       in foldr (fn ((x, T), P) => HOLogic.mk_exists (x, T, P))
   714         (frees, foldr1 HOLogic.mk_conj
   715           (((HOLogic.eq_const sumT) $ Free (xname, sumT) $ (mk_inj cs sumT u t))::
   716             (map (subst o HOLogic.dest_Trueprop)
   717               (Logic.strip_imp_prems r))))
   718       end
   719 
   720     (* make a disjunction of all introduction rules *)
   721 
   722     val fp_fun = absfree (sname, setT, (HOLogic.Collect_const sumT) $
   723       absfree (xname, sumT, foldr1 HOLogic.mk_disj (map transform_rule intr_ts)));
   724 
   725     (* add definiton of recursive sets to theory *)
   726 
   727     val rec_name = if alt_name = "" then space_implode "_" cnames else alt_name;
   728     val full_rec_name = Sign.full_name (Theory.sign_of thy) rec_name;
   729 
   730     val rec_const = list_comb
   731       (Const (full_rec_name, paramTs ---> setT), params);
   732 
   733     val fp_def_term = Logic.mk_equals (rec_const,
   734       Const (fp_name, (setT --> setT) --> setT) $ fp_fun);
   735 
   736     val def_terms = fp_def_term :: (if length cs < 2 then [] else
   737       map (fn c => Logic.mk_equals (c, mk_vimage cs sumT rec_const c)) cs);
   738 
   739     val (thy', [fp_def :: rec_sets_defs]) =
   740       thy
   741       |> cond_declare_consts declare_consts cs paramTs cnames
   742       |> (if length cs < 2 then I
   743           else Theory.add_consts_i [(rec_name, paramTs ---> setT, NoSyn)])
   744       |> Theory.add_path rec_name
   745       |> PureThy.add_defss_i false [(("defs", def_terms), [])];
   746 
   747     val mono = prove_mono setT fp_fun monos thy'
   748 
   749   in (thy', mono, fp_def, rec_sets_defs, rec_const, sumT) end;
   750 
   751 fun add_ind_def verbose declare_consts alt_name coind no_elim no_ind cs
   752     intros monos thy params paramTs cTs cnames induct_cases =
   753   let
   754     val _ =
   755       if verbose then message ("Proofs for " ^ coind_prefix coind ^ "inductive set(s) " ^
   756         commas_quote cnames) else ();
   757 
   758     val ((intr_names, intr_ts), intr_atts) = apfst split_list (split_list intros);
   759 
   760     val (thy1, mono, fp_def, rec_sets_defs, rec_const, sumT) =
   761       mk_ind_def declare_consts alt_name coind cs intr_ts monos thy
   762         params paramTs cTs cnames;
   763 
   764     val (intrs, unfold) = prove_intrs coind mono fp_def intr_ts rec_sets_defs thy1;
   765     val elims = if no_elim then [] else
   766       prove_elims cs cTs params intr_ts intr_names unfold rec_sets_defs thy1;
   767     val raw_induct = if no_ind then Drule.asm_rl else
   768       if coind then standard (rule_by_tactic
   769         (rewrite_tac [mk_meta_eq vimage_Un] THEN
   770           fold_tac rec_sets_defs) (mono RS (fp_def RS def_Collect_coinduct)))
   771       else
   772         prove_indrule cs cTs sumT rec_const params intr_ts mono fp_def
   773           rec_sets_defs thy1;
   774     val induct =
   775       if coind orelse no_ind orelse length cs > 1 then (raw_induct, [RuleCases.consumes 0])
   776       else (raw_induct RSN (2, rev_mp), [RuleCases.consumes 1]);
   777 
   778     val (thy2, intrs') =
   779       thy1 |> PureThy.add_thms ((intr_names ~~ intrs) ~~ intr_atts);
   780     val (thy3, ([intrs'', elims'], [induct'])) =
   781       thy2
   782       |> PureThy.add_thmss
   783         [(("intros", intrs'), []),
   784           (("elims", elims), [RuleCases.consumes 1])]
   785       |>>> PureThy.add_thms
   786         [((coind_prefix coind ^ "induct", rulify (#1 induct)),
   787          (RuleCases.case_names induct_cases :: #2 induct))]
   788       |>> Theory.parent_path;
   789   in (thy3,
   790     {defs = fp_def :: rec_sets_defs,
   791      mono = mono,
   792      unfold = unfold,
   793      intrs = intrs'',
   794      elims = elims',
   795      mk_cases = mk_cases elims',
   796      raw_induct = rulify raw_induct,
   797      induct = induct'})
   798   end;
   799 
   800 
   801 (* external interfaces *)
   802 
   803 fun try_term f msg sign t =
   804   (case Library.try f t of
   805     Some x => x
   806   | None => error (msg ^ Sign.string_of_term sign t));
   807 
   808 fun add_inductive_i verbose declare_consts alt_name coind no_elim no_ind cs pre_intros monos thy =
   809   let
   810     val _ = Theory.requires thy "Inductive" (coind_prefix coind ^ "inductive definitions");
   811     val sign = Theory.sign_of thy;
   812 
   813     (*parameters should agree for all mutually recursive components*)
   814     val (_, params) = strip_comb (hd cs);
   815     val paramTs = map (try_term (snd o dest_Free) "Parameter in recursive\
   816       \ component is not a free variable: " sign) params;
   817 
   818     val cTs = map (try_term (HOLogic.dest_setT o fastype_of)
   819       "Recursive component not of type set: " sign) cs;
   820 
   821     val full_cnames = map (try_term (fst o dest_Const o head_of)
   822       "Recursive set not previously declared as constant: " sign) cs;
   823     val cnames = map Sign.base_name full_cnames;
   824 
   825     val save_sign =
   826       thy |> Theory.copy |> cond_declare_consts declare_consts cs paramTs cnames |> Theory.sign_of;
   827     val intros = map (check_rule save_sign cs) pre_intros;
   828     val induct_cases = map (#1 o #1) intros;
   829 
   830     val (thy1, result as {elims, induct, ...}) =
   831       add_ind_def verbose declare_consts alt_name coind no_elim no_ind cs intros monos
   832         thy params paramTs cTs cnames induct_cases;
   833     val thy2 = thy1
   834       |> put_inductives full_cnames ({names = full_cnames, coind = coind}, result)
   835       |> add_cases_induct no_elim (no_ind orelse coind orelse length cs > 1)
   836           full_cnames elims induct;
   837   in (thy2, result) end;
   838 
   839 fun add_inductive verbose coind c_strings intro_srcs raw_monos thy =
   840   let
   841     val sign = Theory.sign_of thy;
   842     val cs = map (term_of o HOLogic.read_cterm sign) c_strings;
   843 
   844     val intr_names = map (fst o fst) intro_srcs;
   845     fun read_rule s = Thm.read_cterm sign (s, propT)
   846       handle ERROR => error ("The error(s) above occurred for " ^ s);
   847     val intr_ts = map (Thm.term_of o read_rule o snd o fst) intro_srcs;
   848     val intr_atts = map (map (Attrib.global_attribute thy) o snd) intro_srcs;
   849     val (cs', intr_ts') = unify_consts sign cs intr_ts;
   850 
   851     val (thy', monos) = thy |> IsarThy.apply_theorems raw_monos;
   852   in
   853     add_inductive_i verbose false "" coind false false cs'
   854       ((intr_names ~~ intr_ts') ~~ intr_atts) monos thy'
   855   end;
   856 
   857 
   858 
   859 (** package setup **)
   860 
   861 (* setup theory *)
   862 
   863 val setup =
   864  [InductiveData.init,
   865   Method.add_methods [("ind_cases", mk_cases_meth oo mk_cases_args,
   866     "dynamic case analysis on sets")],
   867   Attrib.add_attributes [("mono", mono_attr, "declaration of monotonicity rule")]];
   868 
   869 
   870 (* outer syntax *)
   871 
   872 local structure P = OuterParse and K = OuterSyntax.Keyword in
   873 
   874 fun mk_ind coind ((sets, intrs), monos) =
   875   #1 o add_inductive true coind sets (map P.triple_swap intrs) monos;
   876 
   877 fun ind_decl coind =
   878   Scan.repeat1 P.term --
   879   (P.$$$ "intros" |--
   880     P.!!! (Scan.repeat1 (P.opt_thm_name ":" -- P.prop))) --
   881   Scan.optional (P.$$$ "monos" |-- P.!!! P.xthms1) []
   882   >> (Toplevel.theory o mk_ind coind);
   883 
   884 val inductiveP =
   885   OuterSyntax.command "inductive" "define inductive sets" K.thy_decl (ind_decl false);
   886 
   887 val coinductiveP =
   888   OuterSyntax.command "coinductive" "define coinductive sets" K.thy_decl (ind_decl true);
   889 
   890 
   891 val ind_cases =
   892   P.and_list1 (P.opt_thm_name ":" -- Scan.repeat1 P.prop)
   893   >> (Toplevel.theory o inductive_cases);
   894 
   895 val inductive_casesP =
   896   OuterSyntax.command "inductive_cases"
   897     "create simplified instances of elimination rules (improper)" K.thy_script ind_cases;
   898 
   899 val _ = OuterSyntax.add_keywords ["intros", "monos"];
   900 val _ = OuterSyntax.add_parsers [inductiveP, coinductiveP, inductive_casesP];
   901 
   902 end;
   903 
   904 end;