src/HOL/Codatatype/Tools/bnf_sugar.ML
author blanchet
Thu Aug 30 15:57:14 2012 +0200 (2012-08-30)
changeset 49031 632ee0da3c5b
parent 49030 d0f4f113e43d
child 49032 c2a7bedd57d8
permissions -rw-r--r--
generate "case_disc" property
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(*  Title:      HOL/Codatatype/Tools/bnf_sugar.ML
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    Author:     Jasmin Blanchette, TU Muenchen
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    Copyright   2012
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Sugar on top of a BNF.
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*)
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signature BNF_SUGAR =
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sig
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end;
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structure BNF_Sugar : BNF_SUGAR =
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struct
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open BNF_Util
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open BNF_FP_Util
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open BNF_Sugar_Tactics
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val case_congN = "case_cong"
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val case_discsN = "case_discs"
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val casesN = "cases"
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val ctr_selsN = "ctr_sels"
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val disc_disjointN = "disc_disjoint"
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val disc_exhaustN = "disc_exhaust"
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val discsN = "discs"
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val distinctN = "distinct"
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val selsN = "sels"
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val splitN = "split"
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val split_asmN = "split_asm"
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val weak_case_cong_thmsN = "weak_case_cong"
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fun mk_half_pairs [] = []
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  | mk_half_pairs (x :: xs) = fold_rev (cons o pair x) xs (mk_half_pairs xs);
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fun index_of_half_row _ 0 = 0
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  | index_of_half_row n j = index_of_half_row n (j - 1) + n - j;
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fun index_of_half_cell n j k = index_of_half_row n j + k - (j + 1);
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fun prepare_sugar prep_term (((raw_ctrs, raw_caseof), disc_names), sel_namess) no_defs_lthy =
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  let
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    (* TODO: sanity checks on arguments *)
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    (* TODO: normalize types of constructors w.r.t. each other *)
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    val ctrs0 = map (prep_term no_defs_lthy) raw_ctrs;
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    val caseof0 = prep_term no_defs_lthy raw_caseof;
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    val n = length ctrs0;
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    val ks = 1 upto n;
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    val (T_name, As0) = dest_Type (body_type (fastype_of (hd ctrs0)));
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    val b = Binding.qualified_name T_name;
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    val (As, B) =
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      no_defs_lthy
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      |> mk_TFrees (length As0)
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      ||> the_single o fst o mk_TFrees 1;
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    fun mk_undef T Ts = Const (@{const_name undefined}, Ts ---> T);
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    fun mk_ctr Ts ctr =
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      let val Ts0 = snd (dest_Type (body_type (fastype_of ctr))) in
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        Term.subst_atomic_types (Ts0 ~~ Ts) ctr
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      end;
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    fun mk_caseof Ts T =
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      let val (binders, body) = strip_type (fastype_of caseof0) in
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        Term.subst_atomic_types ((body, T) :: (snd (dest_Type (List.last binders)) ~~ Ts)) caseof0
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      end;
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    val T = Type (T_name, As);
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    val ctrs = map (mk_ctr As) ctrs0;
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    val ctr_Tss = map (binder_types o fastype_of) ctrs;
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    val ms = map length ctr_Tss;
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    val caseofB = mk_caseof As B;
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    val caseofB_Ts = map (fn Ts => Ts ---> B) ctr_Tss;
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    val (((((xss, yss), fs), (v, v')), p), names_lthy) = no_defs_lthy |>
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      mk_Freess "x" ctr_Tss
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      ||>> mk_Freess "y" ctr_Tss
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      ||>> mk_Frees "f" caseofB_Ts
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      ||>> yield_singleton (apfst (op ~~) oo mk_Frees' "v") T
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      ||>> yield_singleton (mk_Frees "P") HOLogic.boolT;
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    val xctrs = map2 (curry Term.list_comb) ctrs xss;
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    val yctrs = map2 (curry Term.list_comb) ctrs yss;
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    val eta_fs = map2 (fn f => fn xs => fold_rev Term.lambda xs (Term.list_comb (f, xs))) fs xss;
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    val exist_xs_v_eq_ctrs =
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      map2 (fn xctr => fn xs => list_exists_free xs (HOLogic.mk_eq (v, xctr))) xctrs xss;
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    fun mk_caseof_args k xs x T =
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      map2 (fn Ts => fn i => if i = k then fold_rev Term.lambda xs x else mk_undef T Ts) ctr_Tss ks;
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    fun disc_spec b exist_xs_v_eq_ctr =
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      HOLogic.mk_Trueprop (HOLogic.mk_eq (Free (Binding.name_of b, T --> HOLogic.boolT) $ v,
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        exist_xs_v_eq_ctr));
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    fun sel_spec b x xs k =
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      let val T' = fastype_of x in
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        HOLogic.mk_Trueprop (HOLogic.mk_eq (Free (Binding.name_of b, T --> T') $ v,
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            Term.list_comb (mk_caseof As T', mk_caseof_args k xs x T') $ v))
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      end;
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    val (((raw_discs, (_, raw_disc_defs)), (raw_selss, (_, raw_sel_defss))), (lthy', lthy)) =
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      no_defs_lthy
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      |> apfst (apsnd split_list o split_list) o fold_map2 (fn b => fn exist_xs_v_eq_ctr =>
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        Specification.definition (SOME (b, NONE, NoSyn),
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          ((Thm.def_binding b, []), disc_spec b exist_xs_v_eq_ctr))) disc_names exist_xs_v_eq_ctrs
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      ||>> apfst (apsnd split_list o split_list) o fold_map3 (fn bs => fn xs => fn k =>
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        apfst (apsnd split_list o split_list) o fold_map2 (fn b => fn x =>
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          Specification.definition (SOME (b, NONE, NoSyn),
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            ((Thm.def_binding b, []), sel_spec b x xs k))) bs xs) sel_namess xss ks
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      ||> `Local_Theory.restore;
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    (*transforms defined frees into consts (and more)*)
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    val phi = Proof_Context.export_morphism lthy lthy';
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    val disc_defs = map (Morphism.thm phi) raw_disc_defs;
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    val sel_defss = map (map (Morphism.thm phi)) raw_sel_defss;
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    val discs0 = map (Morphism.term phi) raw_discs;
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    val selss0 = map (map (Morphism.term phi)) raw_selss;
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    fun mk_disc_or_sel Ts t =
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      Term.subst_atomic_types (snd (dest_Type (domain_type (fastype_of t))) ~~ Ts) t;
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    val discs = map (mk_disc_or_sel As) discs0;
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    val selss = map (map (mk_disc_or_sel As)) selss0;
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    fun mk_imp_p Q = Logic.list_implies (Q, HOLogic.mk_Trueprop p);
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    val goal_exhaust =
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      let
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        fun mk_prem xctr xs =
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          fold_rev Logic.all xs (mk_imp_p [HOLogic.mk_Trueprop (HOLogic.mk_eq (v, xctr))]);
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      in
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        mk_imp_p (map2 mk_prem xctrs xss)
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      end;
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    val goal_injects =
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      let
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        fun mk_goal _ _ [] [] = NONE
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          | mk_goal xctr yctr xs ys =
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            SOME (HOLogic.mk_Trueprop (HOLogic.mk_eq
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              (HOLogic.mk_eq (xctr, yctr),
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               Library.foldr1 HOLogic.mk_conj (map2 (curry HOLogic.mk_eq) xs ys))));
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      in
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        map_filter I (map4 mk_goal xctrs yctrs xss yss)
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      end;
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    val goal_half_distincts =
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      map (HOLogic.mk_Trueprop o HOLogic.mk_not o HOLogic.mk_eq) (mk_half_pairs xctrs);
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    val goal_cases =
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      let
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        val lhs0 = Term.list_comb (caseofB, eta_fs);
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        fun mk_goal xctr xs f =
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          HOLogic.mk_Trueprop (HOLogic.mk_eq (lhs0 $ xctr, Term.list_comb (f, xs)));
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      in
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        map3 mk_goal xctrs xss fs
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      end;
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    val goals = [[goal_exhaust], goal_injects, goal_half_distincts, goal_cases];
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    fun after_qed thmss lthy =
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      let
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        val [[exhaust_thm], inject_thms, half_distinct_thms, case_thms] = thmss;
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        val other_half_distinct_thms = map (fn thm => thm RS not_sym) half_distinct_thms;
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        val nchotomy_thm =
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          let
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            val goal =
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              HOLogic.mk_Trueprop (HOLogic.mk_all (fst v', snd v',
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                Library.foldr1 HOLogic.mk_disj exist_xs_v_eq_ctrs));
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          in
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            Skip_Proof.prove lthy [] [] goal (fn _ => mk_nchotomy_tac n exhaust_thm)
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          end;
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        val sel_thmss =
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          let
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            fun mk_thm k xs goal_case case_thm x sel_def =
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              let
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                val T = fastype_of x;
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                val cTs =
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                  map ((fn T' => certifyT lthy (if T' = B then T else T')) o TFree)
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                    (rev (Term.add_tfrees goal_case []));
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                val cxs = map (certify lthy) (mk_caseof_args k xs x T);
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              in
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                Local_Defs.fold lthy [sel_def]
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                  (Drule.instantiate' (map SOME cTs) (map SOME cxs) case_thm)
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              end;
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            fun mk_thms k xs goal_case case_thm sel_defs =
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              map2 (mk_thm k xs goal_case case_thm) xs sel_defs;
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          in
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            map5 mk_thms ks xss goal_cases case_thms sel_defss
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          end;
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        val discD_thms = map (fn def => def RS iffD1) disc_defs;
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        val discI_thms =
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          map2 (fn m => fn def => funpow m (fn thm => exI RS thm) (def RS iffD2)) ms disc_defs;
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        val not_disc_thms =
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          map2 (fn m => fn def => funpow m (fn thm => allI RS thm)
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                  (Local_Defs.unfold lthy @{thms not_ex} (def RS @{thm ssubst[of _ _ Not]})))
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            ms disc_defs;
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        val disc_thms =
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          let
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            fun get_distinct_thm k k' =
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              if k > k' then nth half_distinct_thms (index_of_half_cell n (k' - 1) (k - 1))
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              else nth other_half_distinct_thms (index_of_half_cell n (k' - 1) (k' - 1))
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            fun mk_thm ((k, discI), not_disc) k' =
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              if k = k' then refl RS discI else get_distinct_thm k k' RS not_disc;
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          in
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            map_product mk_thm (ks ~~ discI_thms ~~ not_disc_thms) ks
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          end;
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        val disc_disjoint_thms =
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          let
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            fun get_disc_thm k k' = nth disc_thms ((k' - 1) * n + (k - 1));
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            fun mk_goal ((_, disc), (_, disc')) =
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              Logic.all v (Logic.mk_implies (HOLogic.mk_Trueprop (disc $ v),
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                HOLogic.mk_Trueprop (HOLogic.mk_not (disc' $ v))));
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            fun prove tac goal = Skip_Proof.prove lthy [] [] goal (K tac);
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            val bundles = ks ~~ ms ~~ discD_thms ~~ discs;
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            val half_pairs = mk_half_pairs bundles;
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            val goal_halves = map mk_goal half_pairs;
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            val half_thms =
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              map2 (fn ((((k, m), discD), _), (((k', _), _), _)) =>
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                prove (mk_half_disc_disjoint_tac m discD (get_disc_thm k k')))
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              half_pairs goal_halves;
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            val goal_other_halves = map (mk_goal o swap) half_pairs;
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            val other_half_thms =
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              map2 (prove o mk_other_half_disc_disjoint_tac) half_thms goal_other_halves;
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          in
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            half_thms @ other_half_thms
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          end;
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        val disc_exhaust_thm =
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          let
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            fun mk_prem disc = mk_imp_p [HOLogic.mk_Trueprop (disc $ v)];
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            val goal = fold Logic.all [p, v] (mk_imp_p (map mk_prem discs));
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          in
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            Skip_Proof.prove lthy [] [] goal (fn _ => mk_disc_exhaust_tac n exhaust_thm discI_thms)
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          end;
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        val ctr_sel_thms =
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          let
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            fun mk_goal ctr disc sels =
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              Logic.all v (Logic.mk_implies (HOLogic.mk_Trueprop (disc $ v),
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                HOLogic.mk_Trueprop (HOLogic.mk_eq ((null sels ? swap)
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                  (Term.list_comb (ctr, map (fn sel => sel $ v) sels), v)))));
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            val goals = map3 mk_goal ctrs discs selss;
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          in
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            map4 (fn goal => fn m => fn discD => fn sel_thms =>
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              Skip_Proof.prove lthy [] [] goal (fn {context = ctxt, ...} =>
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                mk_ctr_sel_tac ctxt m discD sel_thms))
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              goals ms discD_thms sel_thmss
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          end;
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        val case_disc_thm =
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          let
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            fun mk_core f sels = Term.list_comb (f, map (fn sel => sel $ v) sels);
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            fun mk_rhs _ [f] [sels] = mk_core f sels
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              | mk_rhs (disc :: discs) (f :: fs) (sels :: selss) =
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                Const (@{const_name If}, HOLogic.boolT --> B --> B --> B) $
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                  (disc $ v) $ mk_core f sels $ mk_rhs discs fs selss;
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            val lhs = Term.list_comb (caseofB, eta_fs) $ v;
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            val rhs = mk_rhs discs fs selss;
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            val goal = HOLogic.mk_Trueprop (HOLogic.mk_eq (lhs, rhs));
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            val Tinst = map (pairself (certifyT lthy)) (map Logic.varifyT_global As ~~ As);
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            val exhaust_thm' =
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              Drule.instantiate' [] [SOME (certify lthy v)]
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                (Thm.instantiate (Tinst, []) (Drule.zero_var_indexes exhaust_thm));
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          in
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            Skip_Proof.prove lthy [] [] goal (fn {context = ctxt, ...} =>
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              mk_case_disc_tac ctxt exhaust_thm' case_thms disc_thms sel_thmss)
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            |> singleton (Proof_Context.export names_lthy lthy)
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          end;
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        val case_cong_thm = TrueI;
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        val weak_case_cong_thms = TrueI;
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        val split_thms = [];
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        val split_asm_thms = [];
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        (* case syntax *)
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        fun note thmN thms =
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          snd o Local_Theory.note
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            ((Binding.qualify true (Binding.name_of b) (Binding.name thmN), []), thms);
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      in
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        lthy
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        |> note case_congN [case_cong_thm]
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        |> note case_discsN [case_disc_thm]
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        |> note casesN case_thms
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        |> note ctr_selsN ctr_sel_thms
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        |> note discsN disc_thms
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        |> note disc_disjointN disc_disjoint_thms
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        |> note disc_exhaustN [disc_exhaust_thm]
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        |> note distinctN (half_distinct_thms @ other_half_distinct_thms)
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        |> note exhaustN [exhaust_thm]
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        |> note injectN inject_thms
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        |> note nchotomyN [nchotomy_thm]
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        |> note selsN (flat sel_thmss)
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        |> note splitN split_thms
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        |> note split_asmN split_asm_thms
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        |> note weak_case_cong_thmsN [weak_case_cong_thms]
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      end;
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  in
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    (goals, after_qed, lthy')
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  end;
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val parse_binding_list = Parse.$$$ "[" |--  Parse.list Parse.binding --| Parse.$$$ "]";
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val bnf_sugar_cmd = (fn (goalss, after_qed, lthy) =>
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  Proof.theorem NONE after_qed (map (map (rpair [])) goalss) lthy) oo
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  prepare_sugar Syntax.read_term;
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val _ =
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  Outer_Syntax.local_theory_to_proof @{command_spec "bnf_sugar"} "adds sugar on top of a BNF"
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    (((Parse.$$$ "[" |-- Parse.list Parse.term --| Parse.$$$ "]") -- Parse.term --
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      parse_binding_list -- (Parse.$$$ "[" |-- Parse.list parse_binding_list --| Parse.$$$ "]"))
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      >> bnf_sugar_cmd);
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end;