src/HOL/Tools/inductive_set_package.ML

add_inductive_i now takes typ instead of typ option as argument.

(*  Title:      HOL/Tools/inductive_set_package.ML
    ID:         $Id$
    Author:     Stefan Berghofer, TU Muenchen

Wrapper for defining inductive sets using package for inductive predicates,
including infrastructure for converting between predicates and sets.
*)

signature INDUCTIVE_SET_PACKAGE =
sig
  val to_set_att: thm list -> attribute
  val to_pred_att: thm list -> attribute
  val pred_set_conv_att: attribute
  val add_inductive_i: bool -> bstring -> bool -> bool -> bool ->
    ((string * typ) * mixfix) list ->
    (string * typ) list -> ((bstring * Attrib.src list) * term) list -> thm list ->
      local_theory -> InductivePackage.inductive_result * local_theory
  val add_inductive: bool -> bool -> (string * string option * mixfix) list ->
    (string * string option * mixfix) list ->
    ((bstring * Attrib.src list) * string) list -> (thmref * Attrib.src list) list ->
    local_theory -> InductivePackage.inductive_result * local_theory
  val setup: theory -> theory
end;

structure InductiveSetPackage: INDUCTIVE_SET_PACKAGE =
struct

val note_theorem = LocalTheory.note Thm.theoremK;


(**** simplify {(x1, ..., xn). (x1, ..., xn) : S} to S ****)

val subset_antisym = thm "subset_antisym";

val collect_mem_simproc =
  Simplifier.simproc (theory "Set") "Collect_mem" ["Collect t"] (fn thy => fn ss =>
    fn S as Const ("Collect", Type ("fun", [_, T])) $ t =>
         let val (u, Ts, ps) = HOLogic.strip_split t
         in case u of
           (c as Const ("op :", _)) $ q $ S' =>
             (case try (HOLogic.dest_tuple' ps) q of
                NONE => NONE
              | SOME ts =>
                  if not (loose_bvar (S', 0)) andalso
                    ts = map Bound (length ps downto 0)
                  then
                    let val simp = full_simp_tac (Simplifier.inherit_context ss
                      (HOL_basic_ss addsimps [split_paired_all, split_conv])) 1
                    in
                      SOME (Goal.prove (Simplifier.the_context ss) [] []
                        (Const ("==", T --> T --> propT) $ S $ S')
                        (K (EVERY
                          [rtac eq_reflection 1, rtac subset_antisym 1,
                           rtac subsetI 1, dtac CollectD 1, simp,
                           rtac subsetI 1, rtac CollectI 1, simp])))
                    end
                  else NONE)
         | _ => NONE
         end
     | _ => NONE);

(***********************************************************************************)
(* simplifies (%x y. (x, y) : S & P x y) to (%x y. (x, y) : S Int {(x, y). P x y}) *)
(* and        (%x y. (x, y) : S | P x y) to (%x y. (x, y) : S Un {(x, y). P x y})  *)
(* used for converting "strong" (co)induction rules                                *)
(***********************************************************************************)

val anyt = Free ("t", TFree ("'t", []));

fun strong_ind_simproc tab =
  Simplifier.simproc_i HOL.thy "strong_ind" [anyt] (fn thy => fn ss => fn t =>
    let
      fun close p t f =
        let val vs = Term.add_vars t []
        in Drule.instantiate' [] (rev (map (SOME o cterm_of thy o Var) vs))
          (p (fold (fn x as (_, T) => fn u => all T $ lambda (Var x) u) vs t) f)
        end;
      fun mkop "op &" T x = SOME (Const ("op Int", T --> T --> T), x)
        | mkop "op |" T x = SOME (Const ("op Un", T --> T --> T), x)
        | mkop _ _ _ = NONE;
      fun mk_collect p T t =
        let val U = HOLogic.dest_setT T
        in HOLogic.Collect_const U $
          HOLogic.ap_split' (HOLogic.prod_factors p) U HOLogic.boolT t
        end;
      fun decomp (Const (s, _) $ ((m as Const ("op :",
            Type (_, [_, Type (_, [T, _])]))) $ p $ S) $ u) =
              mkop s T (m, p, S, mk_collect p T (head_of u))
        | decomp (Const (s, _) $ u $ ((m as Const ("op :",
            Type (_, [_, Type (_, [T, _])]))) $ p $ S)) =
              mkop s T (m, p, mk_collect p T (head_of u), S)
        | decomp _ = NONE;
      val simp = full_simp_tac (Simplifier.inherit_context ss
        (HOL_basic_ss addsimps [mem_Collect_eq, split_conv])) 1;
      fun mk_rew t = (case strip_abs_vars t of
          [] => NONE
        | xs => (case decomp (strip_abs_body t) of
            NONE => NONE
          | SOME (bop, (m, p, S, S')) =>
              SOME (close (Goal.prove (Simplifier.the_context ss) [] [])
                (Logic.mk_equals (t, list_abs (xs, m $ p $ (bop $ S $ S'))))
                (K (EVERY
                  [rtac eq_reflection 1, REPEAT (rtac ext 1), rtac iffI 1,
                   EVERY [etac conjE 1, rtac IntI 1, simp, simp,
                     etac IntE 1, rtac conjI 1, simp, simp] ORELSE
                   EVERY [etac disjE 1, rtac UnI1 1, simp, rtac UnI2 1, simp,
                     etac UnE 1, rtac disjI1 1, simp, rtac disjI2 1, simp]])))
                handle ERROR _ => NONE))
    in
      case strip_comb t of
        (h as Const (name, _), ts) => (case Symtab.lookup tab name of
          SOME _ =>
            let val rews = map mk_rew ts
            in
              if forall is_none rews then NONE
              else SOME (fold (fn th1 => fn th2 => combination th2 th1)
                (map2 (fn SOME r => K r | NONE => reflexive o cterm_of thy)
                   rews ts) (reflexive (cterm_of thy h)))
            end
        | NONE => NONE)
      | _ => NONE
    end);

(* only eta contract terms occurring as arguments of functions satisfying p *)
fun eta_contract p =
  let
    fun eta b (Abs (a, T, body)) =
          (case eta b body of
             body' as (f $ Bound 0) =>
               if loose_bvar1 (f, 0) orelse not b then Abs (a, T, body')
               else incr_boundvars ~1 f
           | body' => Abs (a, T, body'))
      | eta b (t $ u) = eta b t $ eta (p (head_of t)) u
      | eta b t = t
  in eta false end;

fun eta_contract_thm p =
  Conv.fconv_rule (Conv.then_conv (Thm.beta_conversion true, fn ct =>
    Thm.transitive (Thm.eta_conversion ct)
      (Thm.symmetric (Thm.eta_conversion
        (cterm_of (theory_of_cterm ct) (eta_contract p (term_of ct)))))));


(***********************************************************)
(* rules for converting between predicate and set notation *)
(*                                                         *)
(* rules for converting predicates to sets have the form   *)
(* P (%x y. (x, y) : s) = (%x y. (x, y) : S s)             *)
(*                                                         *)
(* rules for converting sets to predicates have the form   *)
(* S {(x, y). p x y} = {(x, y). P p x y}                   *)
(*                                                         *)
(* where s and p are parameters                            *)
(***********************************************************)

structure PredSetConvData = GenericDataFun
(
  type T =
    {(* rules for converting predicates to sets *)
     to_set_simps: thm list,
     (* rules for converting sets to predicates *)
     to_pred_simps: thm list,
     (* arities of functions of type t set => ... => u set *)
     set_arities: (typ * (int list list option list * int list list option)) list Symtab.table,
     (* arities of functions of type (t => ... => bool) => u => ... => bool *)
     pred_arities: (typ * (int list list option list * int list list option)) list Symtab.table};
  val empty = {to_set_simps = [], to_pred_simps = [],
    set_arities = Symtab.empty, pred_arities = Symtab.empty};
  val extend = I;
  fun merge _
    ({to_set_simps = to_set_simps1, to_pred_simps = to_pred_simps1,
      set_arities = set_arities1, pred_arities = pred_arities1},
     {to_set_simps = to_set_simps2, to_pred_simps = to_pred_simps2,
      set_arities = set_arities2, pred_arities = pred_arities2}) =
    {to_set_simps = Thm.merge_thms (to_set_simps1, to_set_simps2),
     to_pred_simps = Thm.merge_thms (to_pred_simps1, to_pred_simps2),
     set_arities = Symtab.merge_list op = (set_arities1, set_arities2),
     pred_arities = Symtab.merge_list op = (pred_arities1, pred_arities2)};
);

fun name_type_of (Free p) = SOME p
  | name_type_of (Const p) = SOME p
  | name_type_of _ = NONE;

fun map_type f (Free (s, T)) = Free (s, f T)
  | map_type f (Var (ixn, T)) = Var (ixn, f T)
  | map_type f _ = error "map_type";

fun find_most_specific is_inst f eq xs T =
  find_first (fn U => is_inst (T, f U)
    andalso forall (fn U' => eq (f U, f U') orelse not
      (is_inst (T, f U') andalso is_inst (f U', f U)))
        xs) xs;

fun lookup_arity thy arities (s, T) = case Symtab.lookup arities s of
    NONE => NONE
  | SOME xs => find_most_specific (Sign.typ_instance thy) fst (op =) xs T;

fun lookup_rule thy f rules = find_most_specific
  (swap #> Pattern.matches thy) (f #> fst) (op aconv) rules;

fun infer_arities thy arities (optf, t) fs = case strip_comb t of
    (Abs (s, T, u), []) => infer_arities thy arities (NONE, u) fs
  | (Abs _, _) => infer_arities thy arities (NONE, Envir.beta_norm t) fs
  | (u, ts) => (case Option.map (lookup_arity thy arities) (name_type_of u) of
      SOME (SOME (_, (arity, _))) =>
        (fold (infer_arities thy arities) (arity ~~ List.take (ts, length arity)) fs
           handle Subscript => error "infer_arities: bad term")
    | _ => fold (infer_arities thy arities) (map (pair NONE) ts)
      (case optf of
         NONE => fs
       | SOME f => AList.update op = (u, the_default f
           (Option.map (curry op inter f) (AList.lookup op = fs u))) fs));


(**************************************************************)
(*    derive the to_pred equation from the to_set equation    *)
(*                                                            *)
(* 1. instantiate each set parameter with {(x, y). p x y}     *)
(* 2. apply %P. {(x, y). P x y} to both sides of the equation *)
(* 3. simplify                                                *)
(**************************************************************)

fun mk_to_pred_inst thy fs =
  map (fn (x, ps) =>
    let
      val U = HOLogic.dest_setT (fastype_of x);
      val x' = map_type (K (HOLogic.prodT_factors' ps U ---> HOLogic.boolT)) x
    in
      (cterm_of thy x,
       cterm_of thy (HOLogic.Collect_const U $
         HOLogic.ap_split' ps U HOLogic.boolT x'))
    end) fs;

fun mk_to_pred_eq p fs optfs' T thm =
  let
    val thy = theory_of_thm thm;
    val insts = mk_to_pred_inst thy fs;
    val thm' = Thm.instantiate ([], insts) thm;
    val thm'' = (case optfs' of
        NONE => thm' RS sym
      | SOME fs' =>
          let
            val U = HOLogic.dest_setT (body_type T);
            val Ts = HOLogic.prodT_factors' fs' U;
            (* FIXME: should cterm_instantiate increment indexes? *)
            val arg_cong' = Thm.incr_indexes (Thm.maxidx_of thm + 1) arg_cong;
            val (arg_cong_f, _) = arg_cong' |> cprop_of |> Drule.strip_imp_concl |>
              Thm.dest_comb |> snd |> Drule.strip_comb |> snd |> hd |> Thm.dest_comb
          in
            thm' RS (Drule.cterm_instantiate [(arg_cong_f,
              cterm_of thy (Abs ("P", Ts ---> HOLogic.boolT,
                HOLogic.Collect_const U $ HOLogic.ap_split' fs' U
                  HOLogic.boolT (Bound 0))))] arg_cong' RS sym)
          end)
  in
    Simplifier.simplify (HOL_basic_ss addsimps [mem_Collect_eq, split_conv]
      addsimprocs [collect_mem_simproc]) thm'' |>
        zero_var_indexes |> eta_contract_thm (equal p)
  end;


(**** declare rules for converting predicates to sets ****)

fun add ctxt thm {to_set_simps, to_pred_simps, set_arities, pred_arities} =
  case prop_of thm of
    Const ("Trueprop", _) $ (Const ("op =", Type (_, [T, _])) $ lhs $ rhs) =>
      (case body_type T of
         Type ("bool", []) =>
           let
             val thy = Context.theory_of ctxt;
             fun factors_of t fs = case strip_abs_body t of
                 Const ("op :", _) $ u $ S =>
                   if is_Free S orelse is_Var S then
                     let val ps = HOLogic.prod_factors u
                     in (SOME ps, (S, ps) :: fs) end
                   else (NONE, fs)
               | _ => (NONE, fs);
             val (h, ts) = strip_comb lhs
             val (pfs, fs) = fold_map factors_of ts [];
             val ((h', ts'), fs') = (case rhs of
                 Abs _ => (case strip_abs_body rhs of
                     Const ("op :", _) $ u $ S =>
                       (strip_comb S, SOME (HOLogic.prod_factors u))
                   | _ => error "member symbol on right-hand side expected")
               | _ => (strip_comb rhs, NONE))
           in
             case (name_type_of h, name_type_of h') of
               (SOME (s, T), SOME (s', T')) =>
                 (case Symtab.lookup set_arities s' of
                    NONE => ()
                  | SOME xs => if exists (fn (U, _) =>
                        Sign.typ_instance thy (T', U) andalso
                        Sign.typ_instance thy (U, T')) xs
                      then
                        error ("Clash of conversion rules for operator " ^ s')
                      else ();
                  {to_set_simps = thm :: to_set_simps,
                   to_pred_simps =
                     mk_to_pred_eq h fs fs' T' thm :: to_pred_simps,
                   set_arities = Symtab.insert_list op = (s',
                     (T', (map (AList.lookup op = fs) ts', fs'))) set_arities,
                   pred_arities = Symtab.insert_list op = (s,
                     (T, (pfs, fs'))) pred_arities})
             | _ => error "set / predicate constant expected"
           end
       | _ => error "equation between predicates expected")
  | _ => error "equation expected";

val pred_set_conv_att = Thm.declaration_attribute
  (fn thm => fn ctxt => PredSetConvData.map (add ctxt thm) ctxt);


(**** convert theorem in set notation to predicate notation ****)

fun is_pred tab t =
  case Option.map (Symtab.lookup tab o fst) (name_type_of t) of
    SOME (SOME _) => true | _ => false;

fun to_pred_simproc rules =
  let val rules' = map mk_meta_eq rules
  in
    Simplifier.simproc_i HOL.thy "to_pred" [anyt]
      (fn thy => K (lookup_rule thy (prop_of #> Logic.dest_equals) rules'))
  end;

fun to_pred_proc thy rules t = case lookup_rule thy I rules t of
    NONE => NONE
  | SOME (lhs, rhs) =>
      SOME (Envir.subst_vars
        (Pattern.match thy (lhs, t) (Vartab.empty, Vartab.empty)) rhs);

fun to_pred thms ctxt thm =
  let
    val thy = Context.theory_of ctxt;
    val {to_pred_simps, set_arities, pred_arities, ...} =
      fold (add ctxt) thms (PredSetConvData.get ctxt);
    val fs = filter (is_Var o fst)
      (infer_arities thy set_arities (NONE, prop_of thm) []);
    (* instantiate each set parameter with {(x, y). p x y} *)
    val insts = mk_to_pred_inst thy fs
  in
    thm |>
    Thm.instantiate ([], insts) |>
    Simplifier.full_simplify (HOL_basic_ss addsimprocs
      [to_pred_simproc (mem_Collect_eq :: split_conv :: to_pred_simps)]) |>
    eta_contract_thm (is_pred pred_arities)
  end;

val to_pred_att = Thm.rule_attribute o to_pred;
    

(**** convert theorem in predicate notation to set notation ****)

fun to_set thms ctxt thm =
  let
    val thy = Context.theory_of ctxt;
    val {to_set_simps, pred_arities, ...} =
      fold (add ctxt) thms (PredSetConvData.get ctxt);
    val fs = filter (is_Var o fst)
      (infer_arities thy pred_arities (NONE, prop_of thm) []);
    (* instantiate each predicate parameter with %x y. (x, y) : s *)
    val insts = map (fn (x, ps) =>
      let
        val Ts = binder_types (fastype_of x);
        val T = HOLogic.mk_tupleT ps Ts;
        val x' = map_type (K (HOLogic.mk_setT T)) x
      in
        (cterm_of thy x,
         cterm_of thy (list_abs (map (pair "x") Ts, HOLogic.mk_mem
           (HOLogic.mk_tuple' ps T (map Bound (length ps downto 0)), x'))))
      end) fs
  in
    Simplifier.full_simplify (HOL_basic_ss addsimps to_set_simps
        addsimprocs [strong_ind_simproc pred_arities])
      (Thm.instantiate ([], insts) thm)
  end;

val to_set_att = Thm.rule_attribute o to_set;


(**** preprocessor for code generator ****)

fun codegen_preproc thy =
  let
    val {to_pred_simps, set_arities, pred_arities, ...} =
      PredSetConvData.get (Context.Theory thy);
    fun preproc thm =
      if exists_Const (fn (s, _) => case Symtab.lookup set_arities s of
          NONE => false
        | SOME arities => exists (fn (_, (xs, _)) =>
            forall is_none xs) arities) (prop_of thm)
      then
        thm |>
        Simplifier.full_simplify (HOL_basic_ss addsimprocs
          [to_pred_simproc (mem_Collect_eq :: split_conv :: to_pred_simps)]) |>
        eta_contract_thm (is_pred pred_arities)
      else thm
  in map preproc end;

fun code_ind_att optmod = to_pred_att [] #> InductiveCodegen.add optmod NONE;


(**** definition of inductive sets ****)

fun add_ind_set_def verbose alt_name coind no_elim no_ind cs
    intros monos params cnames_syn ctxt =
  let
    val thy = ProofContext.theory_of ctxt;
    val {set_arities, pred_arities, to_pred_simps, ...} =
      PredSetConvData.get (Context.Proof ctxt);
    fun infer (Abs (_, _, t)) = infer t
      | infer (Const ("op :", _) $ t $ u) =
          infer_arities thy set_arities (SOME (HOLogic.prod_factors t), u)
      | infer (t $ u) = infer t #> infer u
      | infer _ = I;
    val new_arities = filter_out
      (fn (x as Free (_, Type ("fun", _)), _) => x mem params
        | _ => false) (fold (snd #> infer) intros []);
    val params' = map (fn x => (case AList.lookup op = new_arities x of
        SOME fs =>
          let
            val T = HOLogic.dest_setT (fastype_of x);
            val Ts = HOLogic.prodT_factors' fs T;
            val x' = map_type (K (Ts ---> HOLogic.boolT)) x
          in
            (x, (x',
              (HOLogic.Collect_const T $
                 HOLogic.ap_split' fs T HOLogic.boolT x',
               list_abs (map (pair "x") Ts, HOLogic.mk_mem
                 (HOLogic.mk_tuple' fs T (map Bound (length fs downto 0)),
                  x)))))
          end
       | NONE => (x, (x, (x, x))))) params;
    val (params1, (params2, params3)) =
      params' |> map snd |> split_list ||> split_list;

    (* equations for converting sets to predicates *)
    val ((cs', cs_info), eqns) = cs |> map (fn c as Free (s, T) =>
      let
        val fs = the_default [] (AList.lookup op = new_arities c);
        val U = HOLogic.dest_setT (body_type T);
        val Ts = HOLogic.prodT_factors' fs U;
        val c' = Free (s ^ "p",
          map fastype_of params1 @ Ts ---> HOLogic.boolT)
      in
        ((c', (fs, U, Ts)),
         (list_comb (c, params2),
          HOLogic.Collect_const U $ HOLogic.ap_split' fs U HOLogic.boolT
            (list_comb (c', params1))))
      end) |> split_list |>> split_list;
    val eqns' = eqns @
      map (prop_of #> HOLogic.dest_Trueprop #> HOLogic.dest_eq)
        (mem_Collect_eq :: split_conv :: to_pred_simps);

    (* predicate version of the introduction rules *)
    val intros' =
      map (fn (name_atts, t) => (name_atts,
        t |>
        map_aterms (fn u =>
          (case AList.lookup op = params' u of
             SOME (_, (u', _)) => u'
           | NONE => u)) |>
        Pattern.rewrite_term thy [] [to_pred_proc thy eqns'] |>
        eta_contract (member op = cs' orf is_pred pred_arities))) intros;
    val cnames_syn' = map (fn (s, _) => (s ^ "p", NoSyn)) cnames_syn;
    val monos' = map (to_pred [] (Context.Proof ctxt)) monos;
    val ({preds, intrs, elims, raw_induct, ...}, ctxt1) =
      InductivePackage.add_ind_def verbose "" coind
        no_elim no_ind cs' intros' monos' params1 cnames_syn' ctxt;

    (* define inductive sets using previously defined predicates *)
    val (defs, ctxt2) = LocalTheory.defs Thm.internalK
      (map (fn ((c_syn, (fs, U, _)), p) => (c_syn, (("", []),
         fold_rev lambda params (HOLogic.Collect_const U $
           HOLogic.ap_split' fs U HOLogic.boolT (list_comb (p, params3))))))
         (cnames_syn ~~ cs_info ~~ preds)) ctxt1;

    (* prove theorems for converting predicate to set notation *)
    val ctxt3 = fold
      (fn (((p, c as Free (s, _)), (fs, U, Ts)), (_, (_, def))) => fn ctxt =>
        let val conv_thm =
          Goal.prove ctxt (map (fst o dest_Free) params) []
            (HOLogic.mk_Trueprop (HOLogic.mk_eq
              (list_comb (p, params3),
               list_abs (map (pair "x") Ts, HOLogic.mk_mem
                 (HOLogic.mk_tuple' fs U (map Bound (length fs downto 0)),
                  list_comb (c, params))))))
            (K (REPEAT (rtac ext 1) THEN simp_tac (HOL_basic_ss addsimps
              [def, mem_Collect_eq, split_conv]) 1))
        in
          ctxt |> note_theorem ((s ^ "p_" ^ s ^ "_eq",
            [Attrib.internal (K pred_set_conv_att)]),
              [conv_thm]) |> snd
        end) (preds ~~ cs ~~ cs_info ~~ defs) ctxt2;

    (* convert theorems to set notation *)
    val rec_name = if alt_name = "" then
      space_implode "_" (map fst cnames_syn) else alt_name;
    val cnames = map (Sign.full_name (ProofContext.theory_of ctxt3) o #1) cnames_syn;  (* FIXME *)
    val (intr_names, intr_atts) = split_list (map fst intros);
    val raw_induct' = to_set [] (Context.Proof ctxt3) raw_induct;
    val (intrs', elims', induct, ctxt4) =
      InductivePackage.declare_rules rec_name coind no_ind cnames
      (map (to_set [] (Context.Proof ctxt3)) intrs) intr_names intr_atts
      (map (fn th => (to_set [] (Context.Proof ctxt3) th,
         map fst (fst (RuleCases.get th)))) elims)
      raw_induct' ctxt3
  in
    ({intrs = intrs', elims = elims', induct = induct,
      raw_induct = raw_induct', preds = map fst defs},
     ctxt4)
  end;

val add_inductive_i = InductivePackage.gen_add_inductive_i add_ind_set_def;
val add_inductive = InductivePackage.gen_add_inductive add_ind_set_def;

val mono_add_att = to_pred_att [] #> InductivePackage.mono_add;
val mono_del_att = to_pred_att [] #> InductivePackage.mono_del;


(** package setup **)

(* setup theory *)

val setup =
  Attrib.add_attributes
    [("pred_set_conv", Attrib.no_args pred_set_conv_att,
      "declare rules for converting between predicate and set notation"),
     ("to_set", Attrib.syntax (Attrib.thms >> to_set_att),
      "convert rule to set notation"),
     ("to_pred", Attrib.syntax (Attrib.thms >> to_pred_att),
      "convert rule to predicate notation")] #>
  Code.add_attribute ("ind_set",
    Scan.option (Args.$$$ "target" |-- Args.colon |-- Args.name) >> code_ind_att) #>
  Codegen.add_preprocessor codegen_preproc #>
  Attrib.add_attributes [("mono_set", Attrib.add_del_args mono_add_att mono_del_att,
    "declaration of monotonicity rule for set operators")] #>
  Context.theory_map (Simplifier.map_ss (fn ss =>
    ss addsimprocs [collect_mem_simproc]));

(* outer syntax *)

local structure P = OuterParse and K = OuterKeyword in

val ind_set_decl = InductivePackage.gen_ind_decl add_ind_set_def;

val inductive_setP =
  OuterSyntax.command "inductive_set" "define inductive sets" K.thy_decl (ind_set_decl false);

val coinductive_setP =
  OuterSyntax.command "coinductive_set" "define coinductive sets" K.thy_decl (ind_set_decl true);

val _ = OuterSyntax.add_parsers [inductive_setP, coinductive_setP];

end;

end;