src/HOL/Tools/typedef_package.ML

generic Syntax.pretty/string_of operations;

(*  Title:      HOL/Tools/typedef_package.ML
    ID:         $Id$
    Author:     Markus Wenzel and Stefan Berghofer, TU Muenchen

Gordon/HOL-style type definitions: create a new syntactic type
represented by a non-empty subset.
*)

signature TYPEDEF_PACKAGE =
sig
  val quiet_mode: bool ref
  val add_typedecls: (bstring * string list * mixfix) list -> theory -> theory
  type info =
   {rep_type: typ, abs_type: typ, Rep_name: string, Abs_name: string,
    type_definition: thm, set_def: thm option, Rep: thm, Rep_inverse: thm,
    Abs_inverse: thm, Rep_inject: thm, Abs_inject: thm, Rep_cases: thm,
    Abs_cases: thm, Rep_induct: thm, Abs_induct: thm};
  val get_info: theory -> string -> info option
  val add_typedef: bool -> string option -> bstring * string list * mixfix ->
    string -> (bstring * bstring) option -> tactic -> theory -> (string * info) * theory
  val add_typedef_i: bool -> string option -> bstring * string list * mixfix ->
    term -> (bstring * bstring) option -> tactic -> theory -> (string * info) * theory
  val typedef: (bool * string) * (bstring * string list * mixfix) * string
    * (string * string) option -> theory -> Proof.state
  val typedef_i: (bool * string) * (bstring * string list * mixfix) * term
    * (string * string) option -> theory -> Proof.state
end;

structure TypedefPackage: TYPEDEF_PACKAGE =
struct

(** theory context references **)

val type_definitionN = "Typedef.type_definition";

val Rep = thm "type_definition.Rep";
val Rep_inverse = thm "type_definition.Rep_inverse";
val Abs_inverse = thm "type_definition.Abs_inverse";
val Rep_inject = thm "type_definition.Rep_inject";
val Abs_inject = thm "type_definition.Abs_inject";
val Rep_cases = thm "type_definition.Rep_cases";
val Abs_cases = thm "type_definition.Abs_cases";
val Rep_induct = thm "type_definition.Rep_induct";
val Abs_induct = thm "type_definition.Abs_induct";



(** type declarations **)

fun HOL_arity (raw_name, args, mx) thy =
  thy |> AxClass.axiomatize_arity_i
    (Sign.full_name thy (Syntax.type_name raw_name mx),
      replicate (length args) HOLogic.typeS, HOLogic.typeS);

fun add_typedecls decls thy =
  if can (Theory.assert_super HOL.thy) thy then
    thy |> Sign.add_typedecls decls |> fold HOL_arity decls
  else thy |> Sign.add_typedecls decls;



(** type definitions **)

(* messages *)

val quiet_mode = ref false;
fun message s = if ! quiet_mode then () else writeln s;


(* theory data *)

type info =
 {rep_type: typ, abs_type: typ, Rep_name: string, Abs_name: string,
  type_definition: thm, set_def: thm option, Rep: thm, Rep_inverse: thm,
  Abs_inverse: thm, Rep_inject: thm, Abs_inject: thm, Rep_cases: thm,
  Abs_cases: thm, Rep_induct: thm, Abs_induct: thm};

structure TypedefData = TheoryDataFun
(
  type T = info Symtab.table;
  val empty = Symtab.empty;
  val copy = I;
  val extend = I;
  fun merge _ tabs : T = Symtab.merge (K true) tabs;
);

val get_info = Symtab.lookup o TypedefData.get;
fun put_info name info = TypedefData.map (Symtab.update (name, info));


(* prepare_typedef *)

fun err_in_typedef msg name =
  cat_error msg ("The error(s) above occurred in typedef " ^ quote name);

fun declare_type_name a = Variable.declare_constraints (Logic.mk_type (TFree (a, dummyS)));

fun prepare_typedef prep_term def name (t, vs, mx) raw_set opt_morphs thy =
  let
    val _ = Theory.requires thy "Typedef" "typedefs";
    val ctxt = ProofContext.init thy;
    val full = Sign.full_name thy;

    (*rhs*)
    val full_name = full name;
    val set = prep_term (ctxt |> fold declare_type_name vs) raw_set;
    val setT = Term.fastype_of set;
    val rhs_tfrees = Term.add_tfrees set [];
    val rhs_tfreesT = Term.add_tfreesT setT [];
    val oldT = HOLogic.dest_setT setT handle TYPE _ =>
      error ("Not a set type: " ^ quote (Syntax.string_of_typ ctxt setT));
    fun mk_nonempty A =
      HOLogic.mk_Trueprop (HOLogic.mk_exists ("x", oldT, HOLogic.mk_mem (Free ("x", oldT), A)));
    val goal = mk_nonempty set;
    val goal_pat = mk_nonempty (Var (the_default (name, 0) (Syntax.read_variable name), setT));

    (*lhs*)
    val defS = Sign.defaultS thy;
    val lhs_tfrees = map (fn v => (v, the_default defS (AList.lookup (op =) rhs_tfrees v))) vs;
    val args_setT = lhs_tfrees
      |> filter (member (op =) rhs_tfrees andf (not o member (op =) rhs_tfreesT))
      |> map TFree;

    val tname = Syntax.type_name t mx;
    val full_tname = full tname;
    val newT = Type (full_tname, map TFree lhs_tfrees);

    val (Rep_name, Abs_name) = the_default ("Rep_" ^ name, "Abs_" ^ name) opt_morphs;
    val setT' = map Term.itselfT args_setT ---> setT;
    val setC = Term.list_comb (Const (full_name, setT'), map Logic.mk_type args_setT);
    val RepC = Const (full Rep_name, newT --> oldT);
    val AbsC = Const (full Abs_name, oldT --> newT);
    val x_new = Free ("x", newT);
    val y_old = Free ("y", oldT);

    val set' = if def then setC else set;

    val typedef_name = "type_definition_" ^ name;
    val typedefC =
      Const (type_definitionN, (newT --> oldT) --> (oldT --> newT) --> setT --> HOLogic.boolT);
    val typedef_prop =
      Logic.mk_implies (goal, HOLogic.mk_Trueprop (typedefC $ RepC $ AbsC $ set'));
    val typedef_deps = Term.fold_aterms (fn Const c => insert (op =) c | _ => I) set' [];

    fun add_def eq thy =
      if def then
        thy
        |> PureThy.add_defs_i false [Thm.no_attributes eq]
        |-> (fn [th] => pair (SOME th))
      else (NONE, thy);

    fun typedef_result nonempty =
      add_typedecls [(t, vs, mx)]
      #> Sign.add_consts_i
       ((if def then [(name, setT', NoSyn)] else []) @
        [(Rep_name, newT --> oldT, NoSyn),
         (Abs_name, oldT --> newT, NoSyn)])
      #> add_def (PrimitiveDefs.mk_defpair (setC, set))
      ##>> PureThy.add_axioms_i [((typedef_name, typedef_prop),
          [apsnd (fn cond_axm => nonempty RS cond_axm)])]
      ##> Theory.add_deps "" (dest_Const RepC) typedef_deps
      ##> Theory.add_deps "" (dest_Const AbsC) typedef_deps
      #-> (fn (set_def, [type_definition]) => fn thy1 =>
        let
          fun make th = Drule.standard (th OF [type_definition]);
          val abs_inject = make Abs_inject;
          val abs_inverse = make Abs_inverse;
          val ([Rep, Rep_inverse, Abs_inverse, Rep_inject, Abs_inject,
              Rep_cases, Abs_cases, Rep_induct, Abs_induct], thy2) =
            thy1
            |> Sign.add_path name
            |> PureThy.add_thms
              ([((Rep_name, make Rep), []),
                ((Rep_name ^ "_inverse", make Rep_inverse), []),
                ((Abs_name ^ "_inverse", abs_inverse), []),
                ((Rep_name ^ "_inject", make Rep_inject), []),
                ((Abs_name ^ "_inject", abs_inject), []),
                ((Rep_name ^ "_cases", make Rep_cases),
                  [RuleCases.case_names [Rep_name], Induct.cases_pred full_name]),
                ((Abs_name ^ "_cases", make Abs_cases),
                  [RuleCases.case_names [Abs_name], Induct.cases_type full_tname]),
                ((Rep_name ^ "_induct", make Rep_induct),
                  [RuleCases.case_names [Rep_name], Induct.induct_pred full_name]),
                ((Abs_name ^ "_induct", make Abs_induct),
                  [RuleCases.case_names [Abs_name], Induct.induct_type full_tname])])
            ||> Sign.parent_path;
          val info = {rep_type = oldT, abs_type = newT,
            Rep_name = full Rep_name, Abs_name = full Abs_name,
              type_definition = type_definition, set_def = set_def,
              Rep = Rep, Rep_inverse = Rep_inverse, Abs_inverse = Abs_inverse,
              Rep_inject = Rep_inject, Abs_inject = Abs_inject, Rep_cases = Rep_cases,
            Abs_cases = Abs_cases, Rep_induct = Rep_induct, Abs_induct = Abs_induct};
          val thy3 = thy2 |> put_info full_tname info;
        in ((full_tname, info), thy3) end);


    (* errors *)

    fun show_names pairs = commas_quote (map fst pairs);

    val illegal_vars =
      if null (term_vars set) andalso null (term_tvars set) then []
      else ["Illegal schematic variable(s) on rhs"];

    val dup_lhs_tfrees =
      (case duplicates (op =) lhs_tfrees of [] => []
      | dups => ["Duplicate type variables on lhs: " ^ show_names dups]);

    val extra_rhs_tfrees =
      (case fold (remove (op =)) lhs_tfrees rhs_tfrees of [] => []
      | extras => ["Extra type variables on rhs: " ^ show_names extras]);

    val illegal_frees =
      (case term_frees set of [] => []
      | xs => ["Illegal variables on rhs: " ^ show_names (map dest_Free xs)]);

    val errs = illegal_vars @ dup_lhs_tfrees @ extra_rhs_tfrees @ illegal_frees;
    val _ = if null errs then () else error (cat_lines errs);

    (*test theory errors now!*)
    val test_thy = Theory.copy thy;
    val _ = test_thy
      |> typedef_result (setmp quick_and_dirty true (SkipProof.make_thm test_thy) goal);

  in (set, goal, goal_pat, typedef_result) end
  handle ERROR msg => err_in_typedef msg name;


(* add_typedef interfaces *)

local

fun gen_typedef prep_term def opt_name typ set opt_morphs tac thy =
  let
    val string_of_term = Sign.string_of_term thy;
    val name = the_default (#1 typ) opt_name;
    val (set, goal, _, typedef_result) =
      prepare_typedef prep_term def name typ set opt_morphs thy;
    val _ = message ("Proving non-emptiness of set " ^ quote (string_of_term set) ^ " ...");
    val non_empty = Goal.prove_global thy [] [] goal (K tac) handle ERROR msg =>
      cat_error msg ("Failed to prove non-emptiness of " ^ quote (string_of_term set));
  in typedef_result non_empty thy end;

in

val add_typedef = gen_typedef Syntax.read_term;
val add_typedef_i = gen_typedef Syntax.check_term;

end;


(* Isar typedef interface *)

local

fun gen_typedef prep_term ((def, name), typ, set, opt_morphs) thy =
  let
    val (_, goal, goal_pat, typedef_result) =
      prepare_typedef prep_term def name typ set opt_morphs thy;
    fun after_qed [[th]] = ProofContext.theory (snd o typedef_result th);
  in Proof.theorem_i NONE after_qed [[(goal, [goal_pat])]] (ProofContext.init thy) end;

in

val typedef = gen_typedef Syntax.read_term;
val typedef_i = gen_typedef Syntax.check_term;

end;



(** outer syntax **)

local structure P = OuterParse and K = OuterKeyword in

val _ = OuterSyntax.keywords ["morphisms"];

val _ =
  OuterSyntax.command "typedecl" "type declaration (HOL)" K.thy_decl
    (P.type_args -- P.name -- P.opt_infix >> (fn ((vs, t), mx) =>
      Toplevel.theory (add_typedecls [(t, vs, mx)])));


val typedef_decl =
  Scan.optional (P.$$$ "(" |--
      ((P.$$$ "open" >> K false) -- Scan.option P.name || P.name >> (fn s => (true, SOME s)))
        --| P.$$$ ")") (true, NONE) --
    (P.type_args -- P.name) -- P.opt_infix -- (P.$$$ "=" |-- P.term) --
    Scan.option (P.$$$ "morphisms" |-- P.!!! (P.name -- P.name));

fun mk_typedef ((((((def, opt_name), (vs, t)), mx), A), morphs)) =
  typedef ((def, the_default (Syntax.type_name t mx) opt_name), (t, vs, mx), A, morphs);

val _ =
  OuterSyntax.command "typedef" "HOL type definition (requires non-emptiness proof)" K.thy_goal
    (typedef_decl >> (Toplevel.print oo (Toplevel.theory_to_proof o mk_typedef)));

end;

end;