src/HOL/Tools/Nitpick/nitpick_preproc.ML

fixed a few bugs in Nitpick and removed unreferenced variables

(*  Title:      HOL/Tools/Nitpick/nitpick_preproc.ML
    Author:     Jasmin Blanchette, TU Muenchen
    Copyright   2008, 2009, 2010

Nitpick's HOL preprocessor.
*)

signature NITPICK_PREPROC =
sig
  type hol_context = Nitpick_HOL.hol_context
  val preprocess_term :
    hol_context -> term
    -> ((term list * term list) * (bool * bool)) * term * bool
end

structure Nitpick_Preproc : NITPICK_PREPROC =
struct

open Nitpick_Util
open Nitpick_HOL

(* polarity -> string -> bool *)
fun is_positive_existential polar quant_s =
  (polar = Pos andalso quant_s = @{const_name Ex}) orelse
  (polar = Neg andalso quant_s <> @{const_name Ex})

(** Binary coding of integers **)

(* If a formula contains a numeral whose absolute value is more than this
   threshold, the unary coding is likely not to work well and we prefer the
   binary coding. *)
val binary_int_threshold = 3

(* term -> bool *)
fun may_use_binary_ints (t1 $ t2) =
    may_use_binary_ints t1 andalso may_use_binary_ints t2
  | may_use_binary_ints (t as Const (s, _)) =
    t <> @{const Suc} andalso
    not (member (op =) [@{const_name Abs_Frac}, @{const_name Rep_Frac},
                        @{const_name nat_gcd}, @{const_name nat_lcm},
                        @{const_name Frac}, @{const_name norm_frac}] s)
  | may_use_binary_ints (Abs (_, _, t')) = may_use_binary_ints t'
  | may_use_binary_ints _ = true
fun should_use_binary_ints (t1 $ t2) =
    should_use_binary_ints t1 orelse should_use_binary_ints t2
  | should_use_binary_ints (Const (s, T)) =
    ((s = @{const_name times} orelse s = @{const_name div}) andalso
     is_integer_type (body_type T)) orelse
    (String.isPrefix numeral_prefix s andalso
     let val n = the (Int.fromString (unprefix numeral_prefix s)) in
       n < ~ binary_int_threshold orelse n > binary_int_threshold
     end)
  | should_use_binary_ints (Abs (_, _, t')) = should_use_binary_ints t'
  | should_use_binary_ints _ = false

(** Uncurrying **)

(* theory -> term -> int Termtab.tab -> int Termtab.tab *)
fun add_to_uncurry_table thy t =
  let
    (* term -> term list -> int Termtab.tab -> int Termtab.tab *)
    fun aux (t1 $ t2) args table =
        let val table = aux t2 [] table in aux t1 (t2 :: args) table end
      | aux (Abs (_, _, t')) _ table = aux t' [] table
      | aux (t as Const (x as (s, _))) args table =
        if is_built_in_const thy [(NONE, true)] true x orelse
           is_constr_like thy x orelse
           is_sel s orelse s = @{const_name Sigma} then
          table
        else
          Termtab.map_default (t, 65536) (curry Int.min (length args)) table
      | aux _ _ table = table
  in aux t [] end

(* int -> int -> string *)
fun uncurry_prefix_for k j =
  uncurry_prefix ^ string_of_int k ^ "@" ^ string_of_int j ^ name_sep

(* int Termtab.tab term -> term *)
fun uncurry_term table t =
  let
    (* term -> term list -> term *)
    fun aux (t1 $ t2) args = aux t1 (aux t2 [] :: args)
      | aux (Abs (s, T, t')) args = betapplys (Abs (s, T, aux t' []), args)
      | aux (t as Const (s, T)) args =
        (case Termtab.lookup table t of
           SOME n =>
           if n >= 2 then
             let
               val arg_Ts = strip_n_binders n T |> fst
               val j =
                 if is_iterator_type (hd arg_Ts) then
                   1
                 else case find_index (not_equal bool_T) arg_Ts of
                   ~1 => n
                 | j => j
               val ((before_args, tuple_args), after_args) =
                 args |> chop n |>> chop j
               val ((before_arg_Ts, tuple_arg_Ts), rest_T) =
                 T |> strip_n_binders n |>> chop j
               val tuple_T = HOLogic.mk_tupleT tuple_arg_Ts
             in
               if n - j < 2 then
                 betapplys (t, args)
               else
                 betapplys (Const (uncurry_prefix_for (n - j) j ^ s,
                                   before_arg_Ts ---> tuple_T --> rest_T),
                            before_args @ [mk_flat_tuple tuple_T tuple_args] @
                            after_args)
             end
           else
             betapplys (t, args)
         | NONE => betapplys (t, args))
      | aux t args = betapplys (t, args)
  in aux t [] end

(** Boxing **)

(* hol_context -> typ -> term -> term *)
fun constr_expand (hol_ctxt as {thy, stds, ...}) T t =
  (case head_of t of
     Const x => if is_constr_like thy x then t else raise SAME ()
   | _ => raise SAME ())
  handle SAME () =>
         let
           val x' as (_, T') =
             if is_pair_type T then
               let val (T1, T2) = HOLogic.dest_prodT T in
                 (@{const_name Pair}, T1 --> T2 --> T)
               end
             else
               datatype_constrs hol_ctxt T |> hd
           val arg_Ts = binder_types T'
         in
           list_comb (Const x', map2 (select_nth_constr_arg thy stds x' t)
                                     (index_seq 0 (length arg_Ts)) arg_Ts)
         end

(* hol_context -> bool -> term -> term *)
fun box_fun_and_pair_in_term (hol_ctxt as {thy, stds, fast_descrs, ...}) def
                             orig_t =
  let
    (* typ -> typ *)
    fun box_relational_operator_type (Type ("fun", Ts)) =
        Type ("fun", map box_relational_operator_type Ts)
      | box_relational_operator_type (Type ("*", Ts)) =
        Type ("*", map (box_type hol_ctxt InPair) Ts)
      | box_relational_operator_type T = T
    (* (term -> term) -> int -> term -> term *)
    fun coerce_bound_no f j t =
      case t of
        t1 $ t2 => coerce_bound_no f j t1 $ coerce_bound_no f j t2
      | Abs (s, T, t') => Abs (s, T, coerce_bound_no f (j + 1) t')
      | Bound j' => if j' = j then f t else t
      | _ => t
    (* typ -> typ -> term -> term *)
    fun coerce_bound_0_in_term new_T old_T =
      old_T <> new_T ? coerce_bound_no (coerce_term [new_T] old_T new_T) 0
    (* typ list -> typ -> term -> term *)
    and coerce_term Ts new_T old_T t =
      if old_T = new_T then
        t
      else
        case (new_T, old_T) of
          (Type (new_s, new_Ts as [new_T1, new_T2]),
           Type ("fun", [old_T1, old_T2])) =>
          (case eta_expand Ts t 1 of
             Abs (s, _, t') =>
             Abs (s, new_T1,
                  t' |> coerce_bound_0_in_term new_T1 old_T1
                     |> coerce_term (new_T1 :: Ts) new_T2 old_T2)
             |> Envir.eta_contract
             |> new_s <> "fun"
                ? construct_value thy stds
                      (@{const_name FunBox}, Type ("fun", new_Ts) --> new_T)
                      o single
           | t' => raise TERM ("Nitpick_Preproc.box_fun_and_pair_in_term.\
                               \coerce_term", [t']))
        | (Type (new_s, new_Ts as [new_T1, new_T2]),
           Type (old_s, old_Ts as [old_T1, old_T2])) =>
          if old_s = @{type_name fun_box} orelse
             old_s = @{type_name pair_box} orelse old_s = "*" then
            case constr_expand hol_ctxt old_T t of
              Const (@{const_name FunBox}, _) $ t1 =>
              if new_s = "fun" then
                coerce_term Ts new_T (Type ("fun", old_Ts)) t1
              else
                construct_value thy stds
                    (@{const_name FunBox}, Type ("fun", new_Ts) --> new_T)
                    [coerce_term Ts (Type ("fun", new_Ts))
                                 (Type ("fun", old_Ts)) t1]
            | Const _ $ t1 $ t2 =>
              construct_value thy stds
                  (if new_s = "*" then @{const_name Pair}
                   else @{const_name PairBox}, new_Ts ---> new_T)
                  [coerce_term Ts new_T1 old_T1 t1,
                   coerce_term Ts new_T2 old_T2 t2]
            | t' => raise TERM ("Nitpick_Preproc.box_fun_and_pair_in_term.\
                                \coerce_term", [t'])
          else
            raise TYPE ("coerce_term", [new_T, old_T], [t])
        | _ => raise TYPE ("coerce_term", [new_T, old_T], [t])
    (* indexname * typ -> typ * term -> typ option list -> typ option list *)
    fun add_boxed_types_for_var (z as (_, T)) (T', t') =
      case t' of
        Var z' => z' = z ? insert (op =) T'
      | Const (@{const_name Pair}, _) $ t1 $ t2 =>
        (case T' of
           Type (_, [T1, T2]) =>
           fold (add_boxed_types_for_var z) [(T1, t1), (T2, t2)]
         | _ => raise TYPE ("Nitpick_Preproc.box_fun_and_pair_in_term.\
                            \add_boxed_types_for_var", [T'], []))
      | _ => exists_subterm (curry (op =) (Var z)) t' ? insert (op =) T
    (* typ list -> typ list -> term -> indexname * typ -> typ *)
    fun box_var_in_def new_Ts old_Ts t (z as (_, T)) =
      case t of
        @{const Trueprop} $ t1 => box_var_in_def new_Ts old_Ts t1 z
      | Const (s0, _) $ t1 $ _ =>
        if s0 = @{const_name "=="} orelse s0 = @{const_name "op ="} then
          let
            val (t', args) = strip_comb t1
            val T' = fastype_of1 (new_Ts, do_term new_Ts old_Ts Neut t')
          in
            case fold (add_boxed_types_for_var z)
                      (fst (strip_n_binders (length args) T') ~~ args) [] of
              [T''] => T''
            | _ => T
          end
        else
          T
      | _ => T
    (* typ list -> typ list -> polarity -> string -> typ -> string -> typ
       -> term -> term *)
    and do_quantifier new_Ts old_Ts polar quant_s quant_T abs_s abs_T t =
      let
        val abs_T' =
          if polar = Neut orelse is_positive_existential polar quant_s then
            box_type hol_ctxt InFunLHS abs_T
          else
            abs_T
        val body_T = body_type quant_T
      in
        Const (quant_s, (abs_T' --> body_T) --> body_T)
        $ Abs (abs_s, abs_T',
               t |> do_term (abs_T' :: new_Ts) (abs_T :: old_Ts) polar)
      end
    (* typ list -> typ list -> string -> typ -> term -> term -> term *)
    and do_equals new_Ts old_Ts s0 T0 t1 t2 =
      let
        val (t1, t2) = pairself (do_term new_Ts old_Ts Neut) (t1, t2)
        val (T1, T2) = pairself (curry fastype_of1 new_Ts) (t1, t2)
        val T = [T1, T2] |> sort TermOrd.typ_ord |> List.last
      in
        list_comb (Const (s0, T --> T --> body_type T0),
                   map2 (coerce_term new_Ts T) [T1, T2] [t1, t2])
      end
    (* string -> typ -> term *)
    and do_description_operator s T =
      let val T1 = box_type hol_ctxt InFunLHS (range_type T) in
        Const (s, (T1 --> bool_T) --> T1)
      end
    (* typ list -> typ list -> polarity -> term -> term *)
    and do_term new_Ts old_Ts polar t =
      case t of
        Const (s0 as @{const_name all}, T0) $ Abs (s1, T1, t1) =>
        do_quantifier new_Ts old_Ts polar s0 T0 s1 T1 t1
      | Const (s0 as @{const_name "=="}, T0) $ t1 $ t2 =>
        do_equals new_Ts old_Ts s0 T0 t1 t2
      | @{const "==>"} $ t1 $ t2 =>
        @{const "==>"} $ do_term new_Ts old_Ts (flip_polarity polar) t1
        $ do_term new_Ts old_Ts polar t2
      | @{const Pure.conjunction} $ t1 $ t2 =>
        @{const Pure.conjunction} $ do_term new_Ts old_Ts polar t1
        $ do_term new_Ts old_Ts polar t2
      | @{const Trueprop} $ t1 =>
        @{const Trueprop} $ do_term new_Ts old_Ts polar t1
      | @{const Not} $ t1 =>
        @{const Not} $ do_term new_Ts old_Ts (flip_polarity polar) t1
      | Const (s0 as @{const_name All}, T0) $ Abs (s1, T1, t1) =>
        do_quantifier new_Ts old_Ts polar s0 T0 s1 T1 t1
      | Const (s0 as @{const_name Ex}, T0) $ Abs (s1, T1, t1) =>
        do_quantifier new_Ts old_Ts polar s0 T0 s1 T1 t1
      | Const (s0 as @{const_name "op ="}, T0) $ t1 $ t2 =>
        do_equals new_Ts old_Ts s0 T0 t1 t2
      | @{const "op &"} $ t1 $ t2 =>
        @{const "op &"} $ do_term new_Ts old_Ts polar t1
        $ do_term new_Ts old_Ts polar t2
      | @{const "op |"} $ t1 $ t2 =>
        @{const "op |"} $ do_term new_Ts old_Ts polar t1
        $ do_term new_Ts old_Ts polar t2
      | @{const "op -->"} $ t1 $ t2 =>
        @{const "op -->"} $ do_term new_Ts old_Ts (flip_polarity polar) t1
        $ do_term new_Ts old_Ts polar t2
      | Const (s as @{const_name The}, T) => do_description_operator s T
      | Const (s as @{const_name Eps}, T) => do_description_operator s T
      | Const (@{const_name quot_normal}, Type ("fun", [_, T2])) =>
        let val T' = box_type hol_ctxt InSel T2 in
          Const (@{const_name quot_normal}, T' --> T')
        end
      | Const (s as @{const_name Tha}, T) => do_description_operator s T
      | Const (x as (s, T)) =>
        Const (s, if s = @{const_name converse} orelse
                     s = @{const_name trancl} then
                    box_relational_operator_type T
                  else if is_built_in_const thy stds fast_descrs x orelse
                          s = @{const_name Sigma} then
                    T
                  else if is_constr_like thy x then
                    box_type hol_ctxt InConstr T
                  else if is_sel s
                       orelse is_rep_fun thy x then
                    box_type hol_ctxt InSel T
                  else
                    box_type hol_ctxt InExpr T)
      | t1 $ Abs (s, T, t2') =>
        let
          val t1 = do_term new_Ts old_Ts Neut t1
          val T1 = fastype_of1 (new_Ts, t1)
          val (s1, Ts1) = dest_Type T1
          val T' = hd (snd (dest_Type (hd Ts1)))
          val t2 = Abs (s, T', do_term (T' :: new_Ts) (T :: old_Ts) Neut t2')
          val T2 = fastype_of1 (new_Ts, t2)
          val t2 = coerce_term new_Ts (hd Ts1) T2 t2
        in
          betapply (if s1 = "fun" then
                      t1
                    else
                      select_nth_constr_arg thy stds
                          (@{const_name FunBox}, Type ("fun", Ts1) --> T1) t1 0
                          (Type ("fun", Ts1)), t2)
        end
      | t1 $ t2 =>
        let
          val t1 = do_term new_Ts old_Ts Neut t1
          val T1 = fastype_of1 (new_Ts, t1)
          val (s1, Ts1) = dest_Type T1
          val t2 = do_term new_Ts old_Ts Neut t2
          val T2 = fastype_of1 (new_Ts, t2)
          val t2 = coerce_term new_Ts (hd Ts1) T2 t2
        in
          betapply (if s1 = "fun" then
                      t1
                    else
                      select_nth_constr_arg thy stds
                          (@{const_name FunBox}, Type ("fun", Ts1) --> T1) t1 0
                          (Type ("fun", Ts1)), t2)
        end
      | Free (s, T) => Free (s, box_type hol_ctxt InExpr T)
      | Var (z as (x, T)) =>
        Var (x, if def then box_var_in_def new_Ts old_Ts orig_t z
                else box_type hol_ctxt InExpr T)
      | Bound _ => t
      | Abs (s, T, t') =>
        Abs (s, T, do_term (T :: new_Ts) (T :: old_Ts) Neut t')
  in do_term [] [] Pos orig_t end

(** Destruction of constructors **)

val val_var_prefix = nitpick_prefix ^ "v"

(* typ list -> int -> int -> int -> term -> term *)
fun fresh_value_var Ts k n j t =
  Var ((val_var_prefix ^ nat_subscript (n - j), k), fastype_of1 (Ts, t))

(* typ list -> term -> bool *)
fun has_heavy_bounds_or_vars Ts t =
  let
    (* typ list -> bool *)
    fun aux [] = false
      | aux [T] = is_fun_type T orelse is_pair_type T
      | aux _ = true
  in aux (map snd (Term.add_vars t []) @ map (nth Ts) (loose_bnos t)) end

(* hol_context -> typ list -> bool -> int -> int -> term -> term list
   -> term list -> term * term list *)
fun pull_out_constr_comb ({thy, stds, ...} : hol_context) Ts relax k level t
                         args seen =
  let val t_comb = list_comb (t, args) in
    case t of
      Const x =>
      if not relax andalso is_constr thy stds x andalso
         not (is_fun_type (fastype_of1 (Ts, t_comb))) andalso
         has_heavy_bounds_or_vars Ts t_comb andalso
         not (loose_bvar (t_comb, level)) then
        let
          val (j, seen) = case find_index (curry (op =) t_comb) seen of
                            ~1 => (0, t_comb :: seen)
                          | j => (j, seen)
        in (fresh_value_var Ts k (length seen) j t_comb, seen) end
      else
        (t_comb, seen)
    | _ => (t_comb, seen)
  end

(* (term -> term) -> typ list -> int -> term list -> term list *)
fun equations_for_pulled_out_constrs mk_eq Ts k seen =
  let val n = length seen in
    map2 (fn j => fn t => mk_eq (fresh_value_var Ts k n j t, t))
         (index_seq 0 n) seen
  end

(* hol_context -> bool -> term -> term *)
fun pull_out_universal_constrs hol_ctxt def t =
  let
    val k = maxidx_of_term t + 1
    (* typ list -> bool -> term -> term list -> term list -> term * term list *)
    fun do_term Ts def t args seen =
      case t of
        (t0 as Const (@{const_name "=="}, _)) $ t1 $ t2 =>
        do_eq_or_imp Ts true def t0 t1 t2 seen
      | (t0 as @{const "==>"}) $ t1 $ t2 =>
        if def then (t, []) else do_eq_or_imp Ts false def t0 t1 t2 seen
      | (t0 as Const (@{const_name "op ="}, _)) $ t1 $ t2 =>
        do_eq_or_imp Ts true def t0 t1 t2 seen
      | (t0 as @{const "op -->"}) $ t1 $ t2 =>
        do_eq_or_imp Ts false def t0 t1 t2 seen
      | Abs (s, T, t') =>
        let val (t', seen) = do_term (T :: Ts) def t' [] seen in
          (list_comb (Abs (s, T, t'), args), seen)
        end
      | t1 $ t2 =>
        let val (t2, seen) = do_term Ts def t2 [] seen in
          do_term Ts def t1 (t2 :: args) seen
        end
      | _ => pull_out_constr_comb hol_ctxt Ts def k 0 t args seen
    (* typ list -> bool -> bool -> term -> term -> term -> term list
       -> term * term list *)
    and do_eq_or_imp Ts eq def t0 t1 t2 seen =
      let
        val (t2, seen) = if eq andalso def then (t2, seen)
                         else do_term Ts false t2 [] seen
        val (t1, seen) = do_term Ts false t1 [] seen
      in (t0 $ t1 $ t2, seen) end
    val (concl, seen) = do_term [] def t [] []
  in
    Logic.list_implies (equations_for_pulled_out_constrs Logic.mk_equals [] k
                                                         seen, concl)
  end

(* term -> term -> term *)
fun mk_exists v t =
  HOLogic.exists_const (fastype_of v) $ lambda v (incr_boundvars 1 t)

(* hol_context -> term -> term *)
fun pull_out_existential_constrs hol_ctxt t =
  let
    val k = maxidx_of_term t + 1
    (* typ list -> int -> term -> term list -> term list -> term * term list *)
    fun aux Ts num_exists t args seen =
      case t of
        (t0 as Const (@{const_name Ex}, _)) $ Abs (s1, T1, t1) =>
        let
          val (t1, seen') = aux (T1 :: Ts) (num_exists + 1) t1 [] []
          val n = length seen'
          (* unit -> term list *)
          fun vars () = map2 (fresh_value_var Ts k n) (index_seq 0 n) seen'
        in
          (equations_for_pulled_out_constrs HOLogic.mk_eq Ts k seen'
           |> List.foldl s_conj t1 |> fold mk_exists (vars ())
           |> curry3 Abs s1 T1 |> curry (op $) t0, seen)
        end
      | t1 $ t2 =>
        let val (t2, seen) = aux Ts num_exists t2 [] seen in
          aux Ts num_exists t1 (t2 :: args) seen
        end
      | Abs (s, T, t') =>
        let
          val (t', seen) = aux (T :: Ts) 0 t' [] (map (incr_boundvars 1) seen)
        in (list_comb (Abs (s, T, t'), args), map (incr_boundvars ~1) seen) end
      | _ =>
        if num_exists > 0 then
          pull_out_constr_comb hol_ctxt Ts false k num_exists t args seen
        else
          (list_comb (t, args), seen)
  in aux [] 0 t [] [] |> fst end

(* hol_context -> bool -> term -> term *)
fun destroy_pulled_out_constrs (hol_ctxt as {thy, stds, ...}) axiom t =
  let
    (* styp -> int *)
    val num_occs_of_var =
      fold_aterms (fn Var z => (fn f => fn z' => f z' |> z = z' ? Integer.add 1)
                    | _ => I) t (K 0)
    (* bool -> term -> term *)
    fun aux careful ((t0 as Const (@{const_name "=="}, _)) $ t1 $ t2) =
        aux_eq careful true t0 t1 t2
      | aux careful ((t0 as @{const "==>"}) $ t1 $ t2) =
        t0 $ aux false t1 $ aux careful t2
      | aux careful ((t0 as Const (@{const_name "op ="}, _)) $ t1 $ t2) =
        aux_eq careful true t0 t1 t2
      | aux careful ((t0 as @{const "op -->"}) $ t1 $ t2) =
        t0 $ aux false t1 $ aux careful t2
      | aux careful (Abs (s, T, t')) = Abs (s, T, aux careful t')
      | aux careful (t1 $ t2) = aux careful t1 $ aux careful t2
      | aux _ t = t
    (* bool -> bool -> term -> term -> term -> term *)
    and aux_eq careful pass1 t0 t1 t2 =
      ((if careful then
          raise SAME ()
        else if axiom andalso is_Var t2 andalso
                num_occs_of_var (dest_Var t2) = 1 then
          @{const True}
        else case strip_comb t2 of
          (* The first case is not as general as it could be. *)
          (Const (@{const_name PairBox}, _),
                  [Const (@{const_name fst}, _) $ Var z1,
                   Const (@{const_name snd}, _) $ Var z2]) =>
          if z1 = z2 andalso num_occs_of_var z1 = 2 then @{const True}
          else raise SAME ()
        | (Const (x as (s, T)), args) =>
          let val arg_Ts = binder_types T in
            if length arg_Ts = length args andalso
               (is_constr thy stds x orelse s = @{const_name Pair}) andalso
               (not careful orelse not (is_Var t1) orelse
                String.isPrefix val_var_prefix (fst (fst (dest_Var t1)))) then
              discriminate_value hol_ctxt x t1 ::
              map3 (sel_eq x t1) (index_seq 0 (length args)) arg_Ts args
              |> foldr1 s_conj
            else
              raise SAME ()
          end
        | _ => raise SAME ())
       |> body_type (type_of t0) = prop_T ? HOLogic.mk_Trueprop)
      handle SAME () => if pass1 then aux_eq careful false t0 t2 t1
                        else t0 $ aux false t2 $ aux false t1
    (* styp -> term -> int -> typ -> term -> term *)
    and sel_eq x t n nth_T nth_t =
      HOLogic.eq_const nth_T $ nth_t
                             $ select_nth_constr_arg thy stds x t n nth_T
      |> aux false
  in aux axiom t end

(** Destruction of universal and existential equalities **)

(* term -> term *)
fun curry_assms (@{const "==>"} $ (@{const Trueprop}
                                   $ (@{const "op &"} $ t1 $ t2)) $ t3) =
    curry_assms (Logic.list_implies ([t1, t2] |> map HOLogic.mk_Trueprop, t3))
  | curry_assms (@{const "==>"} $ t1 $ t2) =
    @{const "==>"} $ curry_assms t1 $ curry_assms t2
  | curry_assms t = t

(* term -> term *)
val destroy_universal_equalities =
  let
    (* term list -> (indexname * typ) list -> term -> term *)
    fun aux prems zs t =
      case t of
        @{const "==>"} $ t1 $ t2 => aux_implies prems zs t1 t2
      | _ => Logic.list_implies (rev prems, t)
    (* term list -> (indexname * typ) list -> term -> term -> term *)
    and aux_implies prems zs t1 t2 =
      case t1 of
        Const (@{const_name "=="}, _) $ Var z $ t' => aux_eq prems zs z t' t1 t2
      | @{const Trueprop} $ (Const (@{const_name "op ="}, _) $ Var z $ t') =>
        aux_eq prems zs z t' t1 t2
      | @{const Trueprop} $ (Const (@{const_name "op ="}, _) $ t' $ Var z) =>
        aux_eq prems zs z t' t1 t2
      | _ => aux (t1 :: prems) (Term.add_vars t1 zs) t2
    (* term list -> (indexname * typ) list -> indexname * typ -> term -> term
       -> term -> term *)
    and aux_eq prems zs z t' t1 t2 =
      if not (member (op =) zs z) andalso
         not (exists_subterm (curry (op =) (Var z)) t') then
        aux prems zs (subst_free [(Var z, t')] t2)
      else
        aux (t1 :: prems) (Term.add_vars t1 zs) t2
  in aux [] [] end

(* theory -> (typ option * bool) list -> int -> term list -> term list
   -> (term * term list) option *)
fun find_bound_assign thy stds j =
  let
    (* term list -> term list -> (term * term list) option *)
    fun do_term _ [] = NONE
      | do_term seen (t :: ts) =
        let
          (* bool -> term -> term -> (term * term list) option *)
          fun do_eq pass1 t1 t2 =
            (if loose_bvar1 (t2, j) then
               if pass1 then do_eq false t2 t1 else raise SAME ()
             else case t1 of
               Bound j' => if j' = j then SOME (t2, ts @ seen) else raise SAME ()
             | Const (s, Type ("fun", [T1, T2])) $ Bound j' =>
               if j' = j andalso
                  s = nth_sel_name_for_constr_name @{const_name FunBox} 0 then
                 SOME (construct_value thy stds (@{const_name FunBox}, T2 --> T1)
                                       [t2], ts @ seen)
               else
                 raise SAME ()
             | _ => raise SAME ())
            handle SAME () => do_term (t :: seen) ts
        in
          case t of
            Const (@{const_name "op ="}, _) $ t1 $ t2 => do_eq true t1 t2
          | _ => do_term (t :: seen) ts
        end
  in do_term end

(* int -> term -> term -> term *)
fun subst_one_bound j arg t =
  let
    (* term * int -> term *)
    fun aux (Bound i, lev) =
        if i < lev then raise SAME ()
        else if i = lev then incr_boundvars (lev - j) arg
        else Bound (i - 1)
      | aux (Abs (a, T, body), lev) = Abs (a, T, aux (body, lev + 1))
      | aux (f $ t, lev) =
        (aux (f, lev) $ (aux (t, lev) handle SAME () => t)
         handle SAME () => f $ aux (t, lev))
      | aux _ = raise SAME ()
  in aux (t, j) handle SAME () => t end

(* hol_context -> term -> term *)
fun destroy_existential_equalities ({thy, stds, ...} : hol_context) =
  let
    (* string list -> typ list -> term list -> term *)
    fun kill [] [] ts = foldr1 s_conj ts
      | kill (s :: ss) (T :: Ts) ts =
        (case find_bound_assign thy stds (length ss) [] ts of
           SOME (_, []) => @{const True}
         | SOME (arg_t, ts) =>
           kill ss Ts (map (subst_one_bound (length ss)
                                (incr_bv (~1, length ss + 1, arg_t))) ts)
         | NONE =>
           Const (@{const_name Ex}, (T --> bool_T) --> bool_T)
           $ Abs (s, T, kill ss Ts ts))
      | kill _ _ _ = raise UnequalLengths
    (* string list -> typ list -> term -> term *)
    fun gather ss Ts (Const (@{const_name Ex}, _) $ Abs (s1, T1, t1)) =
        gather (ss @ [s1]) (Ts @ [T1]) t1
      | gather [] [] (Abs (s, T, t1)) = Abs (s, T, gather [] [] t1)
      | gather [] [] (t1 $ t2) = gather [] [] t1 $ gather [] [] t2
      | gather [] [] t = t
      | gather ss Ts t = kill ss Ts (conjuncts_of (gather [] [] t))
  in gather [] [] end

(** Skolemization **)

(* int -> int -> string *)
fun skolem_prefix_for k j =
  skolem_prefix ^ string_of_int k ^ "@" ^ string_of_int j ^ name_sep

(* hol_context -> int -> term -> term *)
fun skolemize_term_and_more (hol_ctxt as {thy, def_table, skolems, ...})
                            skolem_depth =
  let
    (* int list -> int list *)
    val incrs = map (Integer.add 1)
    (* string list -> typ list -> int list -> int -> polarity -> term -> term *)
    fun aux ss Ts js depth polar t =
      let
        (* string -> typ -> string -> typ -> term -> term *)
        fun do_quantifier quant_s quant_T abs_s abs_T t =
          if not (loose_bvar1 (t, 0)) then
            aux ss Ts js depth polar (incr_boundvars ~1 t)
          else if depth <= skolem_depth andalso
                  is_positive_existential polar quant_s then
            let
              val j = length (!skolems) + 1
              val sko_s = skolem_prefix_for (length js) j ^ abs_s
              val _ = Unsynchronized.change skolems (cons (sko_s, ss))
              val sko_t = list_comb (Const (sko_s, rev Ts ---> abs_T),
                                     map Bound (rev js))
              val abs_t = Abs (abs_s, abs_T, aux ss Ts (incrs js) depth polar t)
            in
              if null js then betapply (abs_t, sko_t)
              else Const (@{const_name Let}, abs_T --> quant_T) $ sko_t $ abs_t
            end
          else
            Const (quant_s, quant_T)
            $ Abs (abs_s, abs_T,
                   if is_higher_order_type abs_T then
                     t
                   else
                     aux (abs_s :: ss) (abs_T :: Ts) (0 :: incrs js)
                         (depth + 1) polar t)
      in
        case t of
          Const (s0 as @{const_name all}, T0) $ Abs (s1, T1, t1) =>
          do_quantifier s0 T0 s1 T1 t1
        | @{const "==>"} $ t1 $ t2 =>
          @{const "==>"} $ aux ss Ts js depth (flip_polarity polar) t1
          $ aux ss Ts js depth polar t2
        | @{const Pure.conjunction} $ t1 $ t2 =>
          @{const Pure.conjunction} $ aux ss Ts js depth polar t1
          $ aux ss Ts js depth polar t2
        | @{const Trueprop} $ t1 =>
          @{const Trueprop} $ aux ss Ts js depth polar t1
        | @{const Not} $ t1 =>
          @{const Not} $ aux ss Ts js depth (flip_polarity polar) t1
        | Const (s0 as @{const_name All}, T0) $ Abs (s1, T1, t1) =>
          do_quantifier s0 T0 s1 T1 t1
        | Const (s0 as @{const_name Ex}, T0) $ Abs (s1, T1, t1) =>
          do_quantifier s0 T0 s1 T1 t1
        | @{const "op &"} $ t1 $ t2 =>
          @{const "op &"} $ aux ss Ts js depth polar t1
          $ aux ss Ts js depth polar t2
        | @{const "op |"} $ t1 $ t2 =>
          @{const "op |"} $ aux ss Ts js depth polar t1
          $ aux ss Ts js depth polar t2
        | @{const "op -->"} $ t1 $ t2 =>
          @{const "op -->"} $ aux ss Ts js depth (flip_polarity polar) t1
          $ aux ss Ts js depth polar t2
        | (t0 as Const (@{const_name Let}, _)) $ t1 $ t2 =>
          t0 $ t1 $ aux ss Ts js depth polar t2
        | Const (x as (s, T)) =>
          if is_inductive_pred hol_ctxt x andalso
             not (is_well_founded_inductive_pred hol_ctxt x) then
            let
              val gfp = (fixpoint_kind_of_const thy def_table x = Gfp)
              val (pref, connective, set_oper) =
                if gfp then
                  (lbfp_prefix, @{const "op |"},
                   @{const_name semilattice_sup_class.sup})
                else
                  (ubfp_prefix, @{const "op &"},
                   @{const_name semilattice_inf_class.inf})
              (* unit -> term *)
              fun pos () = unrolled_inductive_pred_const hol_ctxt gfp x
                           |> aux ss Ts js depth polar
              fun neg () = Const (pref ^ s, T)
            in
              (case polar |> gfp ? flip_polarity of
                 Pos => pos ()
               | Neg => neg ()
               | Neut =>
                 if is_fun_type T then
                   let
                     val ((trunk_arg_Ts, rump_arg_T), body_T) =
                       T |> strip_type |>> split_last
                     val set_T = rump_arg_T --> body_T
                     (* (unit -> term) -> term *)
                     fun app f =
                       list_comb (f (),
                                  map Bound (length trunk_arg_Ts - 1 downto 0))
                   in
                     List.foldr absdummy
                                (Const (set_oper, set_T --> set_T --> set_T)
                                        $ app pos $ app neg) trunk_arg_Ts
                   end
                 else
                   connective $ pos () $ neg ())
            end
          else
            Const x
        | t1 $ t2 =>
          betapply (aux ss Ts [] (skolem_depth + 1) polar t1,
                    aux ss Ts [] depth Neut t2)
        | Abs (s, T, t1) => Abs (s, T, aux ss Ts (incrs js) depth polar t1)
        | _ => t
      end
  in aux [] [] [] 0 Pos end

(** Function specialization **)

(* term -> term list *)
fun params_in_equation (@{const "==>"} $ _ $ t2) = params_in_equation t2
  | params_in_equation (@{const Trueprop} $ t1) = params_in_equation t1
  | params_in_equation (Const (@{const_name "op ="}, _) $ t1 $ _) =
    snd (strip_comb t1)
  | params_in_equation _ = []

(* styp -> styp -> int list -> term list -> term list -> term -> term *)
fun specialize_fun_axiom x x' fixed_js fixed_args extra_args t =
  let
    val k = fold Integer.max (map maxidx_of_term (fixed_args @ extra_args)) 0
            + 1
    val t = map_aterms (fn Var ((s, i), T) => Var ((s, k + i), T) | t' => t') t
    val fixed_params = filter_indices fixed_js (params_in_equation t)
    (* term list -> term -> term *)
    fun aux args (Abs (s, T, t)) = list_comb (Abs (s, T, aux [] t), args)
      | aux args (t1 $ t2) = aux (aux [] t2 :: args) t1
      | aux args t =
        if t = Const x then
          list_comb (Const x', extra_args @ filter_out_indices fixed_js args)
        else
          let val j = find_index (curry (op =) t) fixed_params in
            list_comb (if j >= 0 then nth fixed_args j else t, args)
          end
  in aux [] t end

(* hol_context -> styp -> (int * term option) list *)
fun static_args_in_term ({ersatz_table, ...} : hol_context) x t =
  let
    (* term -> term list -> term list -> term list list *)
    fun fun_calls (Abs (_, _, t)) _ = fun_calls t []
      | fun_calls (t1 $ t2) args = fun_calls t2 [] #> fun_calls t1 (t2 :: args)
      | fun_calls t args =
        (case t of
           Const (x' as (s', T')) =>
           x = x' orelse (case AList.lookup (op =) ersatz_table s' of
                            SOME s'' => x = (s'', T')
                          | NONE => false)
         | _ => false) ? cons args
    (* term list list -> term list list -> term list -> term list list *)
    fun call_sets [] [] vs = [vs]
      | call_sets [] uss vs = vs :: call_sets uss [] []
      | call_sets ([] :: _) _ _ = []
      | call_sets ((t :: ts) :: tss) uss vs =
        OrdList.insert TermOrd.term_ord t vs |> call_sets tss (ts :: uss)
    val sets = call_sets (fun_calls t [] []) [] []
    val indexed_sets = sets ~~ (index_seq 0 (length sets))
  in
    fold_rev (fn (set, j) =>
                 case set of
                   [Var _] => AList.lookup (op =) indexed_sets set = SOME j
                              ? cons (j, NONE)
                 | [t as Const _] => cons (j, SOME t)
                 | [t as Free _] => cons (j, SOME t)
                 | _ => I) indexed_sets []
  end
(* hol_context -> styp -> term list -> (int * term option) list *)
fun static_args_in_terms hol_ctxt x =
  map (static_args_in_term hol_ctxt x)
  #> fold1 (OrdList.inter (prod_ord int_ord (option_ord TermOrd.term_ord)))

(* (int * term option) list -> (int * term) list -> int list *)
fun overlapping_indices [] _ = []
  | overlapping_indices _ [] = []
  | overlapping_indices (ps1 as (j1, t1) :: ps1') (ps2 as (j2, t2) :: ps2') =
    if j1 < j2 then overlapping_indices ps1' ps2
    else if j1 > j2 then overlapping_indices ps1 ps2'
    else overlapping_indices ps1' ps2' |> the_default t2 t1 = t2 ? cons j1

(* typ list -> term -> bool *)
fun is_eligible_arg Ts t =
  let val bad_Ts = map snd (Term.add_vars t []) @ map (nth Ts) (loose_bnos t) in
    null bad_Ts orelse
    (is_higher_order_type (fastype_of1 (Ts, t)) andalso
     forall (not o is_higher_order_type) bad_Ts)
  end

(* int -> string *)
fun special_prefix_for j = special_prefix ^ string_of_int j ^ name_sep

(* If a constant's definition is picked up deeper than this threshold, we
   prevent excessive specialization by not specializing it. *)
val special_max_depth = 20

val bound_var_prefix = "b"

(* hol_context -> int -> term -> term *)
fun specialize_consts_in_term (hol_ctxt as {specialize, simp_table,
                                            special_funs, ...}) depth t =
  if not specialize orelse depth > special_max_depth then
    t
  else
    let
      val blacklist = if depth = 0 then []
                      else case term_under_def t of Const x => [x] | _ => []
      (* term list -> typ list -> term -> term *)
      fun aux args Ts (Const (x as (s, T))) =
          ((if not (member (op =) blacklist x) andalso not (null args) andalso
               not (String.isPrefix special_prefix s) andalso
               is_equational_fun hol_ctxt x then
              let
                val eligible_args = filter (is_eligible_arg Ts o snd)
                                           (index_seq 0 (length args) ~~ args)
                val _ = not (null eligible_args) orelse raise SAME ()
                val old_axs = equational_fun_axioms hol_ctxt x
                              |> map (destroy_existential_equalities hol_ctxt)
                val static_params = static_args_in_terms hol_ctxt x old_axs
                val fixed_js = overlapping_indices static_params eligible_args
                val _ = not (null fixed_js) orelse raise SAME ()
                val fixed_args = filter_indices fixed_js args
                val vars = fold Term.add_vars fixed_args []
                           |> sort (TermOrd.fast_indexname_ord o pairself fst)
                val bound_js = fold (fn t => fn js => add_loose_bnos (t, 0, js))
                                    fixed_args []
                               |> sort int_ord
                val live_args = filter_out_indices fixed_js args
                val extra_args = map Var vars @ map Bound bound_js @ live_args
                val extra_Ts = map snd vars @ filter_indices bound_js Ts
                val k = maxidx_of_term t + 1
                (* int -> term *)
                fun var_for_bound_no j =
                  Var ((bound_var_prefix ^
                        nat_subscript (find_index (curry (op =) j) bound_js
                                       + 1), k),
                       nth Ts j)
                val fixed_args_in_axiom =
                  map (curry subst_bounds
                             (map var_for_bound_no (index_seq 0 (length Ts))))
                      fixed_args
              in
                case AList.lookup (op =) (!special_funs)
                                  (x, fixed_js, fixed_args_in_axiom) of
                  SOME x' => list_comb (Const x', extra_args)
                | NONE =>
                  let
                    val extra_args_in_axiom =
                      map Var vars @ map var_for_bound_no bound_js
                    val x' as (s', _) =
                      (special_prefix_for (length (!special_funs) + 1) ^ s,
                       extra_Ts @ filter_out_indices fixed_js (binder_types T)
                       ---> body_type T)
                    val new_axs =
                      map (specialize_fun_axiom x x' fixed_js
                               fixed_args_in_axiom extra_args_in_axiom) old_axs
                    val _ =
                      Unsynchronized.change special_funs
                          (cons ((x, fixed_js, fixed_args_in_axiom), x'))
                    val _ = add_simps simp_table s' new_axs
                  in list_comb (Const x', extra_args) end
              end
            else
              raise SAME ())
           handle SAME () => list_comb (Const x, args))
        | aux args Ts (Abs (s, T, t)) =
          list_comb (Abs (s, T, aux [] (T :: Ts) t), args)
        | aux args Ts (t1 $ t2) = aux (aux [] Ts t2 :: args) Ts t1
        | aux args _ t = list_comb (t, args)
    in aux [] [] t end

type special_triple = int list * term list * styp

val cong_var_prefix = "c"

(* typ -> special_triple -> special_triple -> term *)
fun special_congruence_axiom T (js1, ts1, x1) (js2, ts2, x2) =
  let
    val (bounds1, bounds2) = pairself (map Var o special_bounds) (ts1, ts2)
    val Ts = binder_types T
    val max_j = fold (fold Integer.max) [js1, js2] ~1
    val (eqs, (args1, args2)) =
      fold (fn j => case pairself (fn ps => AList.lookup (op =) ps j)
                                  (js1 ~~ ts1, js2 ~~ ts2) of
                      (SOME t1, SOME t2) => apfst (cons (t1, t2))
                    | (SOME t1, NONE) => apsnd (apsnd (cons t1))
                    | (NONE, SOME t2) => apsnd (apfst (cons t2))
                    | (NONE, NONE) =>
                      let val v = Var ((cong_var_prefix ^ nat_subscript j, 0),
                                       nth Ts j) in
                        apsnd (pairself (cons v))
                      end) (max_j downto 0) ([], ([], []))
  in
    Logic.list_implies (eqs |> filter_out (op =) |> distinct (op =)
                            |> map Logic.mk_equals,
                        Logic.mk_equals (list_comb (Const x1, bounds1 @ args1),
                                         list_comb (Const x2, bounds2 @ args2)))
    |> close_form (* TODO: needed? *)
  end

(* hol_context -> styp list -> term list *)
fun special_congruence_axioms (hol_ctxt as {special_funs, ...}) xs =
  let
    val groups =
      !special_funs
      |> map (fn ((x, js, ts), x') => (x, (js, ts, x')))
      |> AList.group (op =)
      |> filter_out (is_equational_fun_surely_complete hol_ctxt o fst)
      |> map (fn (x, zs) => (x, zs |> member (op =) xs x ? cons ([], [], x)))
    (* special_triple -> int *)
    fun generality (js, _, _) = ~(length js)
    (* special_triple -> special_triple -> bool *)
    fun is_more_specific (j1, t1, x1) (j2, t2, x2) =
      x1 <> x2 andalso OrdList.subset (prod_ord int_ord TermOrd.term_ord)
                                      (j2 ~~ t2, j1 ~~ t1)
    (* typ -> special_triple list -> special_triple list -> special_triple list
       -> term list -> term list *)
    fun do_pass_1 _ [] [_] [_] = I
      | do_pass_1 T skipped _ [] = do_pass_2 T skipped
      | do_pass_1 T skipped all (z :: zs) =
        case filter (is_more_specific z) all
             |> sort (int_ord o pairself generality) of
          [] => do_pass_1 T (z :: skipped) all zs
        | (z' :: _) => cons (special_congruence_axiom T z z')
                       #> do_pass_1 T skipped all zs
    (* typ -> special_triple list -> term list -> term list *)
    and do_pass_2 _ [] = I
      | do_pass_2 T (z :: zs) =
        fold (cons o special_congruence_axiom T z) zs #> do_pass_2 T zs
  in fold (fn ((_, T), zs) => do_pass_1 T [] zs zs) groups [] end

(** Axiom selection **)

(* Similar to "Refute.specialize_type" but returns all matches rather than only
   the first (preorder) match. *)
(* theory -> styp -> term -> term list *)
fun multi_specialize_type thy slack (s, T) t =
  let
    (* term -> (typ * term) list -> (typ * term) list *)
    fun aux (Const (s', T')) ys =
        if s = s' then
          ys |> (if AList.defined (op =) ys T' then
                   I
                 else
                  cons (T', Refute.monomorphic_term
                                (Sign.typ_match thy (T', T) Vartab.empty) t)
                  handle Type.TYPE_MATCH => I
                       | Refute.REFUTE _ =>
                         if slack then
                           I
                         else
                           raise NOT_SUPPORTED ("too much polymorphism in \
                                                \axiom involving " ^ quote s))
        else
          ys
      | aux _ ys = ys
  in map snd (fold_aterms aux t []) end

(* theory -> bool -> const_table -> styp -> term list *)
fun nondef_props_for_const thy slack table (x as (s, _)) =
  these (Symtab.lookup table s) |> maps (multi_specialize_type thy slack x)

(* 'a Symtab.table -> 'a list *)
fun all_table_entries table = Symtab.fold (append o snd) table []
(* const_table -> string -> const_table *)
fun extra_table table s = Symtab.make [(s, all_table_entries table)]

(* int -> term -> term *)
fun eval_axiom_for_term j t =
  Logic.mk_equals (Const (eval_prefix ^ string_of_int j, fastype_of t), t)

(* term -> bool *)
val is_trivial_equation = the_default false o try (op aconv o Logic.dest_equals)

(* Prevents divergence in case of cyclic or infinite axiom dependencies. *)
val axioms_max_depth = 255

(* hol_context -> term -> (term list * term list) * (bool * bool) *)
fun axioms_for_term
        (hol_ctxt as {thy, max_bisim_depth, stds, user_axioms, fast_descrs,
                      evals, def_table, nondef_table, user_nondefs, ...}) t =
  let
    type accumulator = styp list * (term list * term list)
    (* (term list * term list -> term list)
       -> ((term list -> term list) -> term list * term list
           -> term list * term list)
       -> int -> term -> accumulator -> accumulator *)
    fun add_axiom get app depth t (accum as (xs, axs)) =
      let
        val t = t |> unfold_defs_in_term hol_ctxt
                  |> skolemize_term_and_more hol_ctxt ~1
      in
        if is_trivial_equation t then
          accum
        else
          let val t' = t |> specialize_consts_in_term hol_ctxt depth in
            if exists (member (op aconv) (get axs)) [t, t'] then accum
            else add_axioms_for_term (depth + 1) t' (xs, app (cons t') axs)
          end
      end
    (* int -> term -> accumulator -> accumulator *)
    and add_def_axiom depth = add_axiom fst apfst depth
    and add_nondef_axiom depth = add_axiom snd apsnd depth
    and add_maybe_def_axiom depth t =
      (if head_of t <> @{const "==>"} then add_def_axiom
       else add_nondef_axiom) depth t
    and add_eq_axiom depth t =
      (if is_constr_pattern_formula thy t then add_def_axiom
       else add_nondef_axiom) depth t
    (* int -> term -> accumulator -> accumulator *)
    and add_axioms_for_term depth t (accum as (xs, axs)) =
      case t of
        t1 $ t2 => accum |> fold (add_axioms_for_term depth) [t1, t2]
      | Const (x as (s, T)) =>
        (if member (op =) xs x orelse
            is_built_in_const thy stds fast_descrs x then
           accum
         else
           let val accum = (x :: xs, axs) in
             if depth > axioms_max_depth then
               raise TOO_LARGE ("Nitpick_Preproc.axioms_for_term.\
                                \add_axioms_for_term",
                                "too many nested axioms (" ^
                                string_of_int depth ^ ")")
             else if Refute.is_const_of_class thy x then
               let
                 val class = Logic.class_of_const s
                 val of_class = Logic.mk_of_class (TVar (("'a", 0), [class]),
                                                   class)
                 val ax1 = try (Refute.specialize_type thy x) of_class
                 val ax2 = Option.map (Refute.specialize_type thy x o snd)
                                      (Refute.get_classdef thy class)
               in
                 fold (add_maybe_def_axiom depth) (map_filter I [ax1, ax2])
                      accum
               end
             else if is_constr thy stds x then
               accum
             else if is_equational_fun hol_ctxt x then
               fold (add_eq_axiom depth) (equational_fun_axioms hol_ctxt x)
                    accum
             else if is_abs_fun thy x then
               if is_quot_type thy (range_type T) then
                 raise NOT_SUPPORTED "\"Abs_\" function of quotient type"
               else
                 accum |> fold (add_nondef_axiom depth)
                               (nondef_props_for_const thy false nondef_table x)
                       |> is_funky_typedef thy (range_type T)
                          ? fold (add_maybe_def_axiom depth)
                                 (nondef_props_for_const thy true
                                                    (extra_table def_table s) x)
             else if is_rep_fun thy x then
               if is_quot_type thy (domain_type T) then
                 raise NOT_SUPPORTED "\"Rep_\" function of quotient type"
               else
                 accum |> fold (add_nondef_axiom depth)
                               (nondef_props_for_const thy false nondef_table x)
                       |> is_funky_typedef thy (range_type T)
                          ? fold (add_maybe_def_axiom depth)
                                 (nondef_props_for_const thy true
                                                    (extra_table def_table s) x)
                       |> add_axioms_for_term depth
                                              (Const (mate_of_rep_fun thy x))
                       |> fold (add_def_axiom depth)
                               (inverse_axioms_for_rep_fun thy x)
             else
               accum |> user_axioms <> SOME false
                        ? fold (add_nondef_axiom depth)
                               (nondef_props_for_const thy false nondef_table x)
           end)
        |> add_axioms_for_type depth T
      | Free (_, T) => add_axioms_for_type depth T accum
      | Var (_, T) => add_axioms_for_type depth T accum
      | Bound _ => accum
      | Abs (_, T, t) => accum |> add_axioms_for_term depth t
                               |> add_axioms_for_type depth T
    (* int -> typ -> accumulator -> accumulator *)
    and add_axioms_for_type depth T =
      case T of
        Type ("fun", Ts) => fold (add_axioms_for_type depth) Ts
      | Type ("*", Ts) => fold (add_axioms_for_type depth) Ts
      | @{typ prop} => I
      | @{typ bool} => I
      | @{typ unit} => I
      | TFree (_, S) => add_axioms_for_sort depth T S
      | TVar (_, S) => add_axioms_for_sort depth T S
      | Type (z as (_, Ts)) =>
        fold (add_axioms_for_type depth) Ts
        #> (if is_pure_typedef thy T then
              fold (add_maybe_def_axiom depth) (optimized_typedef_axioms thy z)
            else if is_quot_type thy T then
              fold (add_def_axiom depth) (optimized_quot_type_axioms thy stds z)
            else if max_bisim_depth >= 0 andalso is_codatatype thy T then
              fold (add_maybe_def_axiom depth)
                   (codatatype_bisim_axioms hol_ctxt T)
            else
              I)
    (* int -> typ -> sort -> accumulator -> accumulator *)
    and add_axioms_for_sort depth T S =
      let
        val supers = Sign.complete_sort thy S
        val class_axioms =
          maps (fn class => map prop_of (AxClass.get_info thy class |> #axioms
                                         handle ERROR _ => [])) supers
        val monomorphic_class_axioms =
          map (fn t => case Term.add_tvars t [] of
                         [] => t
                       | [(x, S)] =>
                         Refute.monomorphic_term (Vartab.make [(x, (S, T))]) t
                       | _ => raise TERM ("Nitpick_Preproc.axioms_for_term.\
                                          \add_axioms_for_sort", [t]))
              class_axioms
      in fold (add_nondef_axiom depth) monomorphic_class_axioms end
    val (mono_user_nondefs, poly_user_nondefs) =
      List.partition (null o Term.hidden_polymorphism) user_nondefs
    val eval_axioms = map2 eval_axiom_for_term (index_seq 0 (length evals))
                           evals
    val (xs, (defs, nondefs)) =
      ([], ([], [])) |> add_axioms_for_term 1 t 
                     |> fold_rev (add_def_axiom 1) eval_axioms
                     |> user_axioms = SOME true
                        ? fold (add_nondef_axiom 1) mono_user_nondefs
    val defs = defs @ special_congruence_axioms hol_ctxt xs
  in
    ((defs, nondefs), (user_axioms = SOME true orelse null mono_user_nondefs,
                       null poly_user_nondefs))
  end

(** Simplification of constructor/selector terms **)

(* theory -> term -> term *)
fun simplify_constrs_and_sels thy t =
  let
    (* term -> int -> term *)
    fun is_nth_sel_on t' n (Const (s, _) $ t) =
        (t = t' andalso is_sel_like_and_no_discr s andalso
         sel_no_from_name s = n)
      | is_nth_sel_on _ _ _ = false
    (* term -> term list -> term *)
    fun do_term (Const (@{const_name Rep_Frac}, _)
                 $ (Const (@{const_name Abs_Frac}, _) $ t1)) [] = do_term t1 []
      | do_term (Const (@{const_name Abs_Frac}, _)
                 $ (Const (@{const_name Rep_Frac}, _) $ t1)) [] = do_term t1 []
      | do_term (t1 $ t2) args = do_term t1 (do_term t2 [] :: args)
      | do_term (t as Const (x as (s, T))) (args as _ :: _) =
        ((if is_constr_like thy x then
            if length args = num_binder_types T then
              case hd args of
                Const (_, T') $ t' =>
                if domain_type T' = body_type T andalso
                   forall (uncurry (is_nth_sel_on t'))
                          (index_seq 0 (length args) ~~ args) then
                  t'
                else
                  raise SAME ()
              | _ => raise SAME ()
            else
              raise SAME ()
          else if is_sel_like_and_no_discr s then
            case strip_comb (hd args) of
              (Const (x' as (s', T')), ts') =>
              if is_constr_like thy x' andalso
                 constr_name_for_sel_like s = s' andalso
                 not (exists is_pair_type (binder_types T')) then
                list_comb (nth ts' (sel_no_from_name s), tl args)
              else
                raise SAME ()
            | _ => raise SAME ()
          else
            raise SAME ())
         handle SAME () => betapplys (t, args))
      | do_term (Abs (s, T, t')) args =
        betapplys (Abs (s, T, do_term t' []), args)
      | do_term t args = betapplys (t, args)
  in do_term t [] end

(** Quantifier massaging: Distributing quantifiers **)

(* term -> term *)
fun distribute_quantifiers t =
  case t of
    (t0 as Const (@{const_name All}, T0)) $ Abs (s, T1, t1) =>
    (case t1 of
       (t10 as @{const "op &"}) $ t11 $ t12 =>
       t10 $ distribute_quantifiers (t0 $ Abs (s, T1, t11))
           $ distribute_quantifiers (t0 $ Abs (s, T1, t12))
     | (t10 as @{const Not}) $ t11 =>
       t10 $ distribute_quantifiers (Const (@{const_name Ex}, T0)
                                     $ Abs (s, T1, t11))
     | t1 =>
       if not (loose_bvar1 (t1, 0)) then
         distribute_quantifiers (incr_boundvars ~1 t1)
       else
         t0 $ Abs (s, T1, distribute_quantifiers t1))
  | (t0 as Const (@{const_name Ex}, T0)) $ Abs (s, T1, t1) =>
    (case distribute_quantifiers t1 of
       (t10 as @{const "op |"}) $ t11 $ t12 =>
       t10 $ distribute_quantifiers (t0 $ Abs (s, T1, t11))
           $ distribute_quantifiers (t0 $ Abs (s, T1, t12))
     | (t10 as @{const "op -->"}) $ t11 $ t12 =>
       t10 $ distribute_quantifiers (Const (@{const_name All}, T0)
                                     $ Abs (s, T1, t11))
           $ distribute_quantifiers (t0 $ Abs (s, T1, t12))
     | (t10 as @{const Not}) $ t11 =>
       t10 $ distribute_quantifiers (Const (@{const_name All}, T0)
                                     $ Abs (s, T1, t11))
     | t1 =>
       if not (loose_bvar1 (t1, 0)) then
         distribute_quantifiers (incr_boundvars ~1 t1)
       else
         t0 $ Abs (s, T1, distribute_quantifiers t1))
  | t1 $ t2 => distribute_quantifiers t1 $ distribute_quantifiers t2
  | Abs (s, T, t') => Abs (s, T, distribute_quantifiers t')
  | _ => t

(** Quantifier massaging: Pushing quantifiers inward **)

(* int -> int -> (int -> int) -> term -> term *)
fun renumber_bounds j n f t =
  case t of
    t1 $ t2 => renumber_bounds j n f t1 $ renumber_bounds j n f t2
  | Abs (s, T, t') => Abs (s, T, renumber_bounds (j + 1) n f t')
  | Bound j' =>
    Bound (if j' >= j andalso j' < j + n then f (j' - j) + j else j')
  | _ => t

(* Maximum number of quantifiers in a cluster for which the exponential
   algorithm is used. Larger clusters use a heuristic inspired by Claessen &
   Sörensson's polynomial binary splitting procedure (p. 5 of their MODEL 2003
   paper). *)
val quantifier_cluster_threshold = 7

(* term -> term *)
val push_quantifiers_inward =
  let
    (* string -> string list -> typ list -> term -> term *)
    fun aux quant_s ss Ts t =
      (case t of
         Const (s0, _) $ Abs (s1, T1, t1 as _ $ _) =>
         if s0 = quant_s then
           aux s0 (s1 :: ss) (T1 :: Ts) t1
         else if quant_s = "" andalso
                 (s0 = @{const_name All} orelse s0 = @{const_name Ex}) then
           aux s0 [s1] [T1] t1
         else
           raise SAME ()
       | _ => raise SAME ())
      handle SAME () =>
             case t of
               t1 $ t2 =>
               if quant_s = "" then
                 aux "" [] [] t1 $ aux "" [] [] t2
               else
                 let
                   val typical_card = 4
                   (* ('a -> ''b list) -> 'a list -> ''b list *)
                   fun big_union proj ps =
                     fold (fold (insert (op =)) o proj) ps []
                   val (ts, connective) = strip_any_connective t
                   val T_costs =
                     map (bounded_card_of_type 65536 typical_card []) Ts
                   val t_costs = map size_of_term ts
                   val num_Ts = length Ts
                   (* int -> int *)
                   val flip = curry (op -) (num_Ts - 1)
                   val t_boundss = map (map flip o loose_bnos) ts
                   (* (int list * int) list -> int list
                      -> (int list * int) list *)
                   fun merge costly_boundss [] = costly_boundss
                     | merge costly_boundss (j :: js) =
                       let
                         val (yeas, nays) =
                           List.partition (fn (bounds, _) =>
                                              member (op =) bounds j)
                                          costly_boundss
                         val yeas_bounds = big_union fst yeas
                         val yeas_cost = Integer.sum (map snd yeas)
                                         * nth T_costs j
                       in merge ((yeas_bounds, yeas_cost) :: nays) js end
                   (* (int list * int) list -> int list -> int *)
                   val cost = Integer.sum o map snd oo merge
                   (* (int list * int) list -> int list -> int list *)
                   fun heuristically_best_permutation _ [] = []
                     | heuristically_best_permutation costly_boundss js =
                       let
                         val (costly_boundss, (j, js)) =
                           js |> map (`(merge costly_boundss o single))
                              |> sort (int_ord
                                       o pairself (Integer.sum o map snd o fst))
                              |> split_list |>> hd ||> pairf hd tl
                       in
                         j :: heuristically_best_permutation costly_boundss js
                       end
                   val js =
                     if length Ts <= quantifier_cluster_threshold then
                       all_permutations (index_seq 0 num_Ts)
                       |> map (`(cost (t_boundss ~~ t_costs)))
                       |> sort (int_ord o pairself fst) |> hd |> snd
                     else
                       heuristically_best_permutation (t_boundss ~~ t_costs)
                                                      (index_seq 0 num_Ts)
                   val back_js = map (fn j => find_index (curry (op =) j) js)
                                     (index_seq 0 num_Ts)
                   val ts = map (renumber_bounds 0 num_Ts (nth back_js o flip))
                                ts
                   (* (term * int list) list -> term *)
                   fun mk_connection [] =
                       raise ARG ("Nitpick_Preproc.push_quantifiers_inward.aux.\
                                  \mk_connection", "")
                     | mk_connection ts_cum_bounds =
                       ts_cum_bounds |> map fst
                       |> foldr1 (fn (t1, t2) => connective $ t1 $ t2)
                   (* (term * int list) list -> int list -> term *)
                   fun build ts_cum_bounds [] = ts_cum_bounds |> mk_connection
                     | build ts_cum_bounds (j :: js) =
                       let
                         val (yeas, nays) =
                           List.partition (fn (_, bounds) =>
                                              member (op =) bounds j)
                                          ts_cum_bounds
                           ||> map (apfst (incr_boundvars ~1))
                       in
                         if null yeas then
                           build nays js
                         else
                           let val T = nth Ts (flip j) in
                             build ((Const (quant_s, (T --> bool_T) --> bool_T)
                                     $ Abs (nth ss (flip j), T,
                                            mk_connection yeas),
                                      big_union snd yeas) :: nays) js
                           end
                       end
                 in build (ts ~~ t_boundss) js end
             | Abs (s, T, t') => Abs (s, T, aux "" [] [] t')
             | _ => t
  in aux "" [] [] end

(** Preprocessor entry point **)

(* hol_context -> term
   -> ((term list * term list) * (bool * bool)) * term * bool *)
fun preprocess_term (hol_ctxt as {thy, stds, binary_ints, destroy_constrs,
                                  boxes, skolemize, uncurry, ...}) t =
  let
    val skolem_depth = if skolemize then 4 else ~1
    val (((def_ts, nondef_ts), (got_all_mono_user_axioms, no_poly_user_axioms)),
         core_t) = t |> unfold_defs_in_term hol_ctxt
                     |> close_form
                     |> skolemize_term_and_more hol_ctxt skolem_depth
                     |> specialize_consts_in_term hol_ctxt 0
                     |> `(axioms_for_term hol_ctxt)
    val binarize =
      is_standard_datatype thy stds nat_T andalso
      case binary_ints of
        SOME false => false
      | _ => forall may_use_binary_ints (core_t :: def_ts @ nondef_ts) andalso
             (binary_ints = SOME true orelse
              exists should_use_binary_ints (core_t :: def_ts @ nondef_ts))
    val box = exists (not_equal (SOME false) o snd) boxes
    val table =
      Termtab.empty |> uncurry
        ? fold (add_to_uncurry_table thy) (core_t :: def_ts @ nondef_ts)
    (* bool -> term -> term *)
    fun do_rest def =
      binarize ? binarize_nat_and_int_in_term
      #> uncurry ? uncurry_term table
      #> box ? box_fun_and_pair_in_term hol_ctxt def
      #> destroy_constrs ? (pull_out_universal_constrs hol_ctxt def
                            #> pull_out_existential_constrs hol_ctxt
                            #> destroy_pulled_out_constrs hol_ctxt def)
      #> curry_assms
      #> destroy_universal_equalities
      #> destroy_existential_equalities hol_ctxt
      #> simplify_constrs_and_sels thy
      #> distribute_quantifiers
      #> push_quantifiers_inward
      #> close_form
      #> Term.map_abs_vars shortest_name
  in
    (((map (do_rest true) def_ts, map (do_rest false) nondef_ts),
      (got_all_mono_user_axioms, no_poly_user_axioms)),
     do_rest false core_t, binarize)
  end

end;