File datatype_abs_proofs.ML (Isabelle2005: October 2005)

# File datatype_abs_proofs.ML

    (*  Title:      HOL/Tools/datatype_abs_proofs.ML
        ID:         $Id: datatype_abs_proofs.ML,v 1.41 2005/09/15 15:16:57 wenzelm Exp $
        Author:     Stefan Berghofer, TU Muenchen

    Proofs and defintions independent of concrete representation
    of datatypes  (i.e. requiring only abstract properties such as
    injectivity / distinctness of constructors and induction)

     - case distinction (exhaustion) theorems
     - characteristic equations for primrec combinators
     - characteristic equations for case combinators
     - equations for splitting "P (case ...)" expressions
     - datatype size function
     - "nchotomy" and "case_cong" theorems for TFL

    *)

    signature DATATYPE_ABS_PROOFS =
    sig
      val prove_casedist_thms : string list ->
        DatatypeAux.descr list -> (string * sort) list -> thm ->
        theory attribute list -> theory -> theory * thm list
      val prove_primrec_thms : bool -> string list ->
        DatatypeAux.descr list -> (string * sort) list ->
          DatatypeAux.datatype_info Symtab.table -> thm list list -> thm list list ->
            simpset -> thm -> theory -> theory * (string list * thm list)
      val prove_case_thms : bool -> string list ->
        DatatypeAux.descr list -> (string * sort) list ->
          string list -> thm list -> theory -> theory * (thm list list * string list)
      val prove_split_thms : string list ->
        DatatypeAux.descr list -> (string * sort) list ->
          thm list list -> thm list list -> thm list -> thm list list -> theory ->
            theory * (thm * thm) list
      val prove_size_thms : bool -> string list ->
        DatatypeAux.descr list -> (string * sort) list ->
          string list -> thm list -> theory -> theory * thm list
      val prove_nchotomys : string list -> DatatypeAux.descr list ->
        (string * sort) list -> thm list -> theory -> theory * thm list
      val prove_weak_case_congs : string list -> DatatypeAux.descr list ->
        (string * sort) list -> theory -> theory * thm list
      val prove_case_congs : string list ->
        DatatypeAux.descr list -> (string * sort) list ->
          thm list -> thm list list -> theory -> theory * thm list
    end;

    structure DatatypeAbsProofs: DATATYPE_ABS_PROOFS =
    struct

    open DatatypeAux;

    (************************ case distinction theorems ***************************)

    fun prove_casedist_thms new_type_names descr sorts induct case_names_exhausts thy =
      let
        val _ = message "Proving case distinction theorems ...";

        val descr' = List.concat descr;
        val recTs = get_rec_types descr' sorts;
        val newTs = Library.take (length (hd descr), recTs);

        val {maxidx, ...} = rep_thm induct;
        val induct_Ps = map head_of (HOLogic.dest_conj (HOLogic.dest_Trueprop (concl_of induct)));

        fun prove_casedist_thm ((i, t), T) =
          let
            val dummyPs = map (fn (Var (_, Type (_, [T', T'']))) =>
              Abs ("z", T', Const ("True", T''))) induct_Ps;
            val P = Abs ("z", T, HOLogic.imp $ HOLogic.mk_eq (Var (("a", maxidx+1), T), Bound 0) $
              Var (("P", 0), HOLogic.boolT))
            val insts = Library.take (i, dummyPs) @ (P::(Library.drop (i + 1, dummyPs)));
            val cert = cterm_of (Theory.sign_of thy);
            val insts' = (map cert induct_Ps) ~~ (map cert insts);
            val induct' = refl RS ((List.nth
              (split_conj_thm (cterm_instantiate insts' induct), i)) RSN (2, rev_mp))

          in prove_goalw_cterm [] (cert t) (fn prems =>
            [rtac induct' 1,
             REPEAT (rtac TrueI 1),
             REPEAT ((rtac impI 1) THEN (eresolve_tac prems 1)),
             REPEAT (rtac TrueI 1)])
          end;

        val casedist_thms = map prove_casedist_thm ((0 upto (length newTs - 1)) ~~
          (DatatypeProp.make_casedists descr sorts) ~~ newTs)
      in thy |> store_thms_atts "exhaust" new_type_names (map single case_names_exhausts) casedist_thms end;

    (*************************** primrec combinators ******************************)

    fun prove_primrec_thms flat_names new_type_names descr sorts
        (dt_info : datatype_info Symtab.table) constr_inject dist_rewrites dist_ss induct thy =
      let
        val _ = message "Constructing primrec combinators ...";

        val big_name = space_implode "_" new_type_names;
        val thy0 = add_path flat_names big_name thy;

        val descr' = List.concat descr;
        val recTs = get_rec_types descr' sorts;
        val used = foldr add_typ_tfree_names [] recTs;
        val newTs = Library.take (length (hd descr), recTs);

        val induct_Ps = map head_of (HOLogic.dest_conj (HOLogic.dest_Trueprop (concl_of induct)));

        val big_rec_name' = big_name ^ "_rec_set";
        val rec_set_names = map (Sign.full_name (Theory.sign_of thy0))
          (if length descr' = 1 then [big_rec_name'] else
            (map ((curry (op ^) (big_rec_name' ^ "_")) o string_of_int)
              (1 upto (length descr'))));

        val (rec_result_Ts, reccomb_fn_Ts) = DatatypeProp.make_primrec_Ts descr sorts used;

        val rec_set_Ts = map (fn (T1, T2) => reccomb_fn_Ts ---> HOLogic.mk_setT
          (HOLogic.mk_prodT (T1, T2))) (recTs ~~ rec_result_Ts);

        val rec_fns = map (uncurry (mk_Free "f"))
          (reccomb_fn_Ts ~~ (1 upto (length reccomb_fn_Ts)));
        val rec_sets = map (fn c => list_comb (Const c, rec_fns))
          (rec_set_names ~~ rec_set_Ts);

        (* introduction rules for graph of primrec function *)

        fun make_rec_intr T set_name ((rec_intr_ts, l), (cname, cargs)) =
          let
            fun mk_prem ((dt, U), (j, k, prems, t1s, t2s)) =
              let val free1 = mk_Free "x" U j
              in (case (strip_dtyp dt, strip_type U) of
                 ((_, DtRec m), (Us, _)) =>
                   let
                     val free2 = mk_Free "y" (Us ---> List.nth (rec_result_Ts, m)) k;
                     val i = length Us
                   in (j + 1, k + 1, HOLogic.mk_Trueprop (HOLogic.list_all
                         (map (pair "x") Us, HOLogic.mk_mem (HOLogic.mk_prod
                           (app_bnds free1 i, app_bnds free2 i),
                             List.nth (rec_sets, m)))) :: prems,
                       free1::t1s, free2::t2s)
                   end
               | _ => (j + 1, k, prems, free1::t1s, t2s))
              end;

            val Ts = map (typ_of_dtyp descr' sorts) cargs;
            val (_, _, prems, t1s, t2s) = foldr mk_prem (1, 1, [], [], []) (cargs ~~ Ts)

          in (rec_intr_ts @ [Logic.list_implies (prems, HOLogic.mk_Trueprop (HOLogic.mk_mem
            (HOLogic.mk_prod (list_comb (Const (cname, Ts ---> T), t1s),
              list_comb (List.nth (rec_fns, l), t1s @ t2s)), set_name)))], l + 1)
          end;

        val (rec_intr_ts, _) = Library.foldl (fn (x, ((d, T), set_name)) =>
          Library.foldl (make_rec_intr T set_name) (x, #3 (snd d)))
            (([], 0), descr' ~~ recTs ~~ rec_sets);

        val (thy1, {intrs = rec_intrs, elims = rec_elims, ...}) =
          setmp InductivePackage.quiet_mode (!quiet_mode)
            (InductivePackage.add_inductive_i false true big_rec_name' false false true
               rec_sets (map (fn x => (("", x), [])) rec_intr_ts) []) thy0;

        (* prove uniqueness and termination of primrec combinators *)

        val _ = message "Proving termination and uniqueness of primrec functions ...";

        fun mk_unique_tac ((tac, intrs), ((((i, (tname, _, constrs)), elim), T), T')) =
          let
            val distinct_tac = (etac Pair_inject 1) THEN
              (if i < length newTs then
                 full_simp_tac (HOL_ss addsimps (List.nth (dist_rewrites, i))) 1
               else full_simp_tac dist_ss 1);

            val inject = map (fn r => r RS iffD1)
              (if i < length newTs then List.nth (constr_inject, i)
                else #inject (the (Symtab.lookup dt_info tname)));

            fun mk_unique_constr_tac n ((tac, intr::intrs, j), (cname, cargs)) =
              let
                val k = length (List.filter is_rec_type cargs)

              in (EVERY [DETERM tac,
                    REPEAT (etac ex1E 1), rtac ex1I 1,
                    DEPTH_SOLVE_1 (ares_tac [intr] 1),
                    REPEAT_DETERM_N k (etac thin_rl 1 THEN rotate_tac 1 1),
                    etac elim 1,
                    REPEAT_DETERM_N j distinct_tac,
                    etac Pair_inject 1, TRY (dresolve_tac inject 1),
                    REPEAT (etac conjE 1), hyp_subst_tac 1,
                    REPEAT (EVERY [etac allE 1, dtac mp 1, atac 1]),
                    TRY (hyp_subst_tac 1),
                    rtac refl 1,
                    REPEAT_DETERM_N (n - j - 1) distinct_tac],
                  intrs, j + 1)
              end;

            val (tac', intrs', _) = Library.foldl (mk_unique_constr_tac (length constrs))
              ((tac, intrs, 0), constrs);

          in (tac', intrs') end;

        val rec_unique_thms =
          let
            val rec_unique_ts = map (fn (((set_t, T1), T2), i) =>
              Const ("Ex1", (T2 --> HOLogic.boolT) --> HOLogic.boolT) $
                absfree ("y", T2, HOLogic.mk_mem (HOLogic.mk_prod
                  (mk_Free "x" T1 i, Free ("y", T2)), set_t)))
                    (rec_sets ~~ recTs ~~ rec_result_Ts ~~ (1 upto length recTs));
            val cert = cterm_of (Theory.sign_of thy1)
            val insts = map (fn ((i, T), t) => absfree ("x" ^ (string_of_int i), T, t))
              ((1 upto length recTs) ~~ recTs ~~ rec_unique_ts);
            val induct' = cterm_instantiate ((map cert induct_Ps) ~~
              (map cert insts)) induct;
            val (tac, _) = Library.foldl mk_unique_tac
              (((rtac induct' THEN_ALL_NEW ObjectLogic.atomize_tac) 1
                  THEN rewtac (mk_meta_eq choice_eq), rec_intrs),
                descr' ~~ rec_elims ~~ recTs ~~ rec_result_Ts);

          in split_conj_thm (prove_goalw_cterm []
            (cert (HOLogic.mk_Trueprop (mk_conj rec_unique_ts))) (K [tac]))
          end;

        val rec_total_thms = map (fn r => r RS theI') rec_unique_thms;

        (* define primrec combinators *)

        val big_reccomb_name = (space_implode "_" new_type_names) ^ "_rec";
        val reccomb_names = map (Sign.full_name (Theory.sign_of thy1))
          (if length descr' = 1 then [big_reccomb_name] else
            (map ((curry (op ^) (big_reccomb_name ^ "_")) o string_of_int)
              (1 upto (length descr'))));
        val reccombs = map (fn ((name, T), T') => list_comb
          (Const (name, reccomb_fn_Ts @ [T] ---> T'), rec_fns))
            (reccomb_names ~~ recTs ~~ rec_result_Ts);

        val (thy2, reccomb_defs) = thy1 |>
          Theory.add_consts_i (map (fn ((name, T), T') =>
            (Sign.base_name name, reccomb_fn_Ts @ [T] ---> T', NoSyn))
              (reccomb_names ~~ recTs ~~ rec_result_Ts)) |>
          (PureThy.add_defs_i false o map Thm.no_attributes) (map (fn ((((name, comb), set), T), T') =>
            ((Sign.base_name name) ^ "_def", Logic.mk_equals (comb, absfree ("x", T,
               Const ("The", (T' --> HOLogic.boolT) --> T') $ absfree ("y", T',
                 HOLogic.mk_mem (HOLogic.mk_prod (Free ("x", T), Free ("y", T')), set))))))
                   (reccomb_names ~~ reccombs ~~ rec_sets ~~ recTs ~~ rec_result_Ts)) |>>
          parent_path flat_names;

        (* prove characteristic equations for primrec combinators *)

        val _ = message "Proving characteristic theorems for primrec combinators ..."

        val rec_thms = map (fn t => prove_goalw_cterm reccomb_defs
          (cterm_of (Theory.sign_of thy2) t) (fn _ =>
            [rtac the1_equality 1,
             resolve_tac rec_unique_thms 1,
             resolve_tac rec_intrs 1,
             REPEAT (rtac allI 1 ORELSE resolve_tac rec_total_thms 1)]))
               (DatatypeProp.make_primrecs new_type_names descr sorts thy2)

      in
        thy2 |> Theory.add_path (space_implode "_" new_type_names) |>
        PureThy.add_thmss [(("recs", rec_thms), [])] |>>
        Theory.parent_path |> apsnd (pair reccomb_names o List.concat)
      end;

    (***************************** case combinators *******************************)

    fun prove_case_thms flat_names new_type_names descr sorts reccomb_names primrec_thms thy =
      let
        val _ = message "Proving characteristic theorems for case combinators ...";

        val thy1 = add_path flat_names (space_implode "_" new_type_names) thy;

        val descr' = List.concat descr;
        val recTs = get_rec_types descr' sorts;
        val used = foldr add_typ_tfree_names [] recTs;
        val newTs = Library.take (length (hd descr), recTs);
        val T' = TFree (variant used "'t", HOLogic.typeS);

        fun mk_dummyT dt = binder_types (typ_of_dtyp descr' sorts dt) ---> T';

        val case_dummy_fns = map (fn (_, (_, _, constrs)) => map (fn (_, cargs) =>
          let
            val Ts = map (typ_of_dtyp descr' sorts) cargs;
            val Ts' = map mk_dummyT (List.filter is_rec_type cargs)
          in Const ("arbitrary", Ts @ Ts' ---> T')
          end) constrs) descr';

        val case_names = map (fn s =>
          Sign.full_name (Theory.sign_of thy1) (s ^ "_case")) new_type_names;

        (* define case combinators via primrec combinators *)

        val (case_defs, thy2) = Library.foldl (fn ((defs, thy),
          ((((i, (_, _, constrs)), T), name), recname)) =>
            let
              val (fns1, fns2) = ListPair.unzip (map (fn ((_, cargs), j) =>
                let
                  val Ts = map (typ_of_dtyp descr' sorts) cargs;
                  val Ts' = Ts @ map mk_dummyT (List.filter is_rec_type cargs);
                  val frees' = map (uncurry (mk_Free "x")) (Ts' ~~ (1 upto length Ts'));
                  val frees = Library.take (length cargs, frees');
                  val free = mk_Free "f" (Ts ---> T') j
                in
                 (free, list_abs_free (map dest_Free frees',
                   list_comb (free, frees)))
                end) (constrs ~~ (1 upto length constrs)));

              val caseT = (map (snd o dest_Free) fns1) @ [T] ---> T';
              val fns = (List.concat (Library.take (i, case_dummy_fns))) @
                fns2 @ (List.concat (Library.drop (i + 1, case_dummy_fns)));
              val reccomb = Const (recname, (map fastype_of fns) @ [T] ---> T');
              val decl = (Sign.base_name name, caseT, NoSyn);
              val def = ((Sign.base_name name) ^ "_def",
                Logic.mk_equals (list_comb (Const (name, caseT), fns1),
                  list_comb (reccomb, (List.concat (Library.take (i, case_dummy_fns))) @
                    fns2 @ (List.concat (Library.drop (i + 1, case_dummy_fns))) )));
              val (thy', [def_thm]) = thy |>
                Theory.add_consts_i [decl] |> (PureThy.add_defs_i false o map Thm.no_attributes) [def];

            in (defs @ [def_thm], thy')
            end) (([], thy1), (hd descr) ~~ newTs ~~ case_names ~~
              (Library.take (length newTs, reccomb_names)));

        val case_thms = map (map (fn t => prove_goalw_cterm (case_defs @
          (map mk_meta_eq primrec_thms)) (cterm_of (Theory.sign_of thy2) t)
            (fn _ => [rtac refl 1])))
              (DatatypeProp.make_cases new_type_names descr sorts thy2)

      in
        thy2 |>
        parent_path flat_names |>
        store_thmss "cases" new_type_names case_thms |>
        apsnd (rpair case_names)
      end;

    (******************************* case splitting *******************************)

    fun prove_split_thms new_type_names descr sorts constr_inject dist_rewrites
        casedist_thms case_thms thy =
      let
        val _ = message "Proving equations for case splitting ...";

        val descr' = List.concat descr;
        val recTs = get_rec_types descr' sorts;
        val newTs = Library.take (length (hd descr), recTs);

        fun prove_split_thms ((((((t1, t2), inject), dist_rewrites'),
            exhaustion), case_thms'), T) =
          let
            val cert = cterm_of (Theory.sign_of thy);
            val _ $ (_ $ lhs $ _) = hd (Logic.strip_assums_hyp (hd (prems_of exhaustion)));
            val exhaustion' = cterm_instantiate
              [(cert lhs, cert (Free ("x", T)))] exhaustion;
            val tacsf = K [rtac exhaustion' 1, ALLGOALS (asm_simp_tac
              (HOL_ss addsimps (dist_rewrites' @ inject @ case_thms')))]
          in
            (prove_goalw_cterm [] (cert t1) tacsf,
             prove_goalw_cterm [] (cert t2) tacsf)
          end;

        val split_thm_pairs = map prove_split_thms
          ((DatatypeProp.make_splits new_type_names descr sorts thy) ~~ constr_inject ~~
            dist_rewrites ~~ casedist_thms ~~ case_thms ~~ newTs);

        val (split_thms, split_asm_thms) = ListPair.unzip split_thm_pairs

      in
        thy |> store_thms "split" new_type_names split_thms |>>>
          store_thms "split_asm" new_type_names split_asm_thms |> apsnd ListPair.zip
      end;

    (******************************* size functions *******************************)

    fun prove_size_thms flat_names new_type_names descr sorts reccomb_names primrec_thms thy =
      if exists (fn (_, (_, _, constrs)) => exists (fn (_, cargs) => exists (fn dt =>
        is_rec_type dt andalso not (null (fst (strip_dtyp dt)))) cargs) constrs)
          (List.concat descr)
      then
        (thy, [])
      else
      let
        val _ = message "Proving equations for size function ...";

        val big_name = space_implode "_" new_type_names;
        val thy1 = add_path flat_names big_name thy;

        val descr' = List.concat descr;
        val recTs = get_rec_types descr' sorts;

        val size_name = "Nat.size";
        val size_names = replicate (length (hd descr)) size_name @
          map (Sign.full_name (Theory.sign_of thy1)) (DatatypeProp.indexify_names
            (map (fn T => name_of_typ T ^ "_size") (Library.drop (length (hd descr), recTs))));
        val def_names = map (fn s => s ^ "_def") (DatatypeProp.indexify_names
          (map (fn T => name_of_typ T ^ "_size") recTs));

        fun plus (t1, t2) = Const ("op +", [HOLogic.natT, HOLogic.natT] ---> HOLogic.natT) $ t1 $ t2;

        fun make_sizefun (_, cargs) =
          let
            val Ts = map (typ_of_dtyp descr' sorts) cargs;
            val k = length (List.filter is_rec_type cargs);
            val t = if k = 0 then HOLogic.zero else
              foldl1 plus (map Bound (k - 1 downto 0) @ [HOLogic.mk_nat 1])
          in
            foldr (fn (T, t') => Abs ("x", T, t')) t (Ts @ replicate k HOLogic.natT)
          end;

        val fs = List.concat (map (fn (_, (_, _, constrs)) => map make_sizefun constrs) descr');
        val fTs = map fastype_of fs;

        val (thy', size_def_thms) = thy1 |>
          Theory.add_consts_i (map (fn (s, T) =>
            (Sign.base_name s, T --> HOLogic.natT, NoSyn))
              (Library.drop (length (hd descr), size_names ~~ recTs))) |>
          (PureThy.add_defs_i true o map Thm.no_attributes) (map (fn (((s, T), def_name), rec_name) =>
            (def_name, Logic.mk_equals (Const (s, T --> HOLogic.natT),
              list_comb (Const (rec_name, fTs @ [T] ---> HOLogic.natT), fs))))
                (size_names ~~ recTs ~~ def_names ~~ reccomb_names)) |>>
          parent_path flat_names;

        val rewrites = size_def_thms @ map mk_meta_eq primrec_thms;

        val size_thms = map (fn t => prove_goalw_cterm rewrites
          (cterm_of (Theory.sign_of thy') t) (fn _ => [rtac refl 1]))
            (DatatypeProp.make_size descr sorts thy')

      in
        thy' |> Theory.add_path big_name |>
        PureThy.add_thmss [(("size", size_thms), [])] |>>
        Theory.parent_path |> apsnd List.concat
      end;

    fun prove_weak_case_congs new_type_names descr sorts thy =
      let
        fun prove_weak_case_cong t =
           prove_goalw_cterm [] (cterm_of (Theory.sign_of thy) t)
             (fn prems => [rtac ((hd prems) RS arg_cong) 1])

        val weak_case_congs = map prove_weak_case_cong (DatatypeProp.make_weak_case_congs
          new_type_names descr sorts thy)

      in thy |> store_thms "weak_case_cong" new_type_names weak_case_congs end;

    (************************* additional theorems for TFL ************************)

    fun prove_nchotomys new_type_names descr sorts casedist_thms thy =
      let
        val _ = message "Proving additional theorems for TFL ...";

        fun prove_nchotomy (t, exhaustion) =
          let
            (* For goal i, select the correct disjunct to attack, then prove it *)
            fun tac i 0 = EVERY [TRY (rtac disjI1 i),
                  hyp_subst_tac i, REPEAT (rtac exI i), rtac refl i]
              | tac i n = rtac disjI2 i THEN tac i (n - 1)
          in
            prove_goalw_cterm [] (cterm_of (Theory.sign_of thy) t) (fn _ =>
              [rtac allI 1,
               exh_tac (K exhaustion) 1,
               ALLGOALS (fn i => tac i (i-1))])
          end;

        val nchotomys =
          map prove_nchotomy (DatatypeProp.make_nchotomys descr sorts ~~ casedist_thms)

      in thy |> store_thms "nchotomy" new_type_names nchotomys end;

    fun prove_case_congs new_type_names descr sorts nchotomys case_thms thy =
      let
        fun prove_case_cong ((t, nchotomy), case_rewrites) =
          let
            val (Const ("==>", _) $ tm $ _) = t;
            val (Const ("Trueprop", _) $ (Const ("op =", _) $ _ $ Ma)) = tm;
            val cert = cterm_of (Theory.sign_of thy);
            val nchotomy' = nchotomy RS spec;
            val nchotomy'' = cterm_instantiate
              [(cert (hd (add_term_vars (concl_of nchotomy', []))), cert Ma)] nchotomy'
          in
            prove_goalw_cterm [] (cert t) (fn prems =>
              let val simplify = asm_simp_tac (HOL_ss addsimps (prems @ case_rewrites))
              in [simp_tac (HOL_ss addsimps [hd prems]) 1,
                  cut_facts_tac [nchotomy''] 1,
                  REPEAT (etac disjE 1 THEN REPEAT (etac exE 1) THEN simplify 1),
                  REPEAT (etac exE 1) THEN simplify 1 (* Get last disjunct *)]
              end)
          end;

        val case_congs = map prove_case_cong (DatatypeProp.make_case_congs
          new_type_names descr sorts thy ~~ nchotomys ~~ case_thms)

      in thy |> store_thms "case_cong" new_type_names case_congs end;

    end;