src/HOL/Tools/Sledgehammer/sledgehammer_fact_preprocessor.ML
author blanchet
Wed Jun 23 10:20:33 2010 +0200 (2010-06-23)
changeset 37512 ff72d3ddc898
parent 37511 26afa11a1fb2
child 37518 efb0923cc098
permissions -rw-r--r--
this looks like the most appropriate place to do the beta-eta-contraction
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(*  Title:      HOL/Tools/Sledgehammer/sledgehammer_fact_preprocessor.ML
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    Author:     Jia Meng, Cambridge University Computer Laboratory
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    Author:     Jasmin Blanchette, TU Muenchen
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Transformation of axiom rules (elim/intro/etc) into CNF forms.
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*)
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signature SLEDGEHAMMER_FACT_PREPROCESSOR =
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sig
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  type cnf_thm = thm * ((string * int) * thm)
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  val chained_prefix: string
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  val trace: bool Unsynchronized.ref
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  val trace_msg: (unit -> string) -> unit
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  val skolem_theory_name: string
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  val skolem_prefix: string
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  val skolem_infix: string
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  val is_skolem_const_name: string -> bool
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  val cnf_axiom: theory -> thm -> thm list
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  val multi_base_blacklist: string list
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  val is_theorem_bad_for_atps: thm -> bool
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  val type_has_topsort: typ -> bool
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  val cnf_rules_pairs : theory -> (string * thm) list -> cnf_thm list
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  val saturate_skolem_cache: theory -> theory option
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  val auto_saturate_skolem_cache: bool Unsynchronized.ref
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  val neg_clausify: thm -> thm list
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  val neg_conjecture_clauses:
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    Proof.context -> thm -> int -> thm list list * (string * typ) list
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  val setup: theory -> theory
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end;
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structure Sledgehammer_Fact_Preprocessor : SLEDGEHAMMER_FACT_PREPROCESSOR =
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struct
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open Sledgehammer_FOL_Clause
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type cnf_thm = thm * ((string * int) * thm)
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(* Used to label theorems chained into the goal. *)
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val chained_prefix = "Sledgehammer.chained_"
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val trace = Unsynchronized.ref false;
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fun trace_msg msg = if !trace then tracing (msg ()) else ();
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val skolem_theory_name = "Sledgehammer.Sko"
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val skolem_prefix = "sko_"
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val skolem_infix = "$"
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fun freeze_thm th = #1 (Drule.legacy_freeze_thaw th);
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val type_has_topsort = Term.exists_subtype
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  (fn TFree (_, []) => true
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    | TVar (_, []) => true
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    | _ => false);
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(**** Transformation of Elimination Rules into First-Order Formulas****)
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val cfalse = cterm_of @{theory HOL} HOLogic.false_const;
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val ctp_false = cterm_of @{theory HOL} (HOLogic.mk_Trueprop HOLogic.false_const);
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(*Converts an elim-rule into an equivalent theorem that does not have the
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  predicate variable.  Leaves other theorems unchanged.  We simply instantiate the
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  conclusion variable to False.*)
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fun transform_elim th =
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  case concl_of th of    (*conclusion variable*)
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       @{const Trueprop} $ (v as Var (_, @{typ bool})) =>
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           Thm.instantiate ([], [(cterm_of @{theory HOL} v, cfalse)]) th
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    | v as Var(_, @{typ prop}) =>
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           Thm.instantiate ([], [(cterm_of @{theory HOL} v, ctp_false)]) th
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    | _ => th;
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(*To enforce single-threading*)
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exception Clausify_failure of theory;
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(**** SKOLEMIZATION BY INFERENCE (lcp) ****)
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(*Keep the full complexity of the original name*)
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fun flatten_name s = space_implode "_X" (Long_Name.explode s);
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fun skolem_name thm_name j var_name =
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  skolem_prefix ^ thm_name ^ "_" ^ Int.toString j ^
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  skolem_infix ^ (if var_name = "" then "g" else flatten_name var_name)
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(* Hack: Could return false positives (e.g., a user happens to declare a
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   constant called "SomeTheory.sko_means_shoe_in_$wedish". *)
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val is_skolem_const_name =
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  Long_Name.base_name
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  #> String.isPrefix skolem_prefix andf String.isSubstring skolem_infix
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fun rhs_extra_types lhsT rhs =
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  let val lhs_vars = Term.add_tfreesT lhsT []
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      fun add_new_TFrees (TFree v) =
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            if member (op =) lhs_vars v then I else insert (op =) (TFree v)
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        | add_new_TFrees _ = I
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      val rhs_consts = fold_aterms (fn Const c => insert (op =) c | _ => I) rhs []
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  in fold (#2 #> Term.fold_atyps add_new_TFrees) rhs_consts [] end;
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fun skolem_type_and_args bound_T body =
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  let
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    val args1 = OldTerm.term_frees body
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    val Ts1 = map type_of args1
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    val Ts2 = rhs_extra_types (Ts1 ---> bound_T) body
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    val args2 = map (fn T => Free (gensym "vsk", T)) Ts2
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  in (Ts2 ---> Ts1 ---> bound_T, args2 @ args1) end
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(* Traverse a theorem, declaring Skolem function definitions. String "s" is the
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   suggested prefix for the Skolem constants. *)
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fun declare_skolem_funs s th thy =
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  let
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    val skolem_count = Unsynchronized.ref 0    (* FIXME ??? *)
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    fun dec_sko (Const (@{const_name Ex}, _) $ (body as Abs (s', T, p)))
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                (axs, thy) =
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        (*Existential: declare a Skolem function, then insert into body and continue*)
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        let
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          val id = skolem_name s (Unsynchronized.inc skolem_count) s'
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          val (cT, args) = skolem_type_and_args T body
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          val rhs = list_abs_free (map dest_Free args,
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                                   HOLogic.choice_const T $ body)
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                  (*Forms a lambda-abstraction over the formal parameters*)
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          val (c, thy) =
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            Sign.declare_const ((Binding.conceal (Binding.name id), cT), NoSyn) thy
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          val cdef = id ^ "_def"
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          val ((_, ax), thy) =
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            Thm.add_def true false (Binding.name cdef, Logic.mk_equals (c, rhs)) thy
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          val ax' = Drule.export_without_context ax
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        in dec_sko (subst_bound (list_comb (c, args), p)) (ax' :: axs, thy) end
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      | dec_sko (Const (@{const_name All}, _) $ (Abs (a, T, p))) thx =
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        (*Universal quant: insert a free variable into body and continue*)
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        let val fname = Name.variant (OldTerm.add_term_names (p, [])) a
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        in dec_sko (subst_bound (Free (fname, T), p)) thx end
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      | dec_sko (@{const "op &"} $ p $ q) thx = dec_sko q (dec_sko p thx)
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      | dec_sko (@{const "op |"} $ p $ q) thx = dec_sko q (dec_sko p thx)
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      | dec_sko (@{const Trueprop} $ p) thx = dec_sko p thx
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      | dec_sko _ thx = thx
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  in dec_sko (prop_of th) ([], thy) end
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fun mk_skolem_id t =
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  let val T = fastype_of t in
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    Const (@{const_name skolem_id}, T --> T) $ t
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  end
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fun quasi_beta_eta_contract (Abs (s, T, t')) =
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    Abs (s, T, quasi_beta_eta_contract t')
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  | quasi_beta_eta_contract t = Envir.beta_eta_contract t
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(*Traverse a theorem, accumulating Skolem function definitions.*)
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fun assume_skolem_funs inline s th =
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  let
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    val skolem_count = Unsynchronized.ref 0   (* FIXME ??? *)
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    fun dec_sko (Const (@{const_name Ex}, _) $ (body as Abs (s', T, p))) defs =
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        (*Existential: declare a Skolem function, then insert into body and continue*)
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        let
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          val skos = map (#1 o Logic.dest_equals) defs  (*existing sko fns*)
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          val args = subtract (op =) skos (OldTerm.term_frees body) (*the formal parameters*)
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          val Ts = map type_of args
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          val cT = Ts ---> T (* FIXME: use "skolem_type_and_args" *)
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          val id = skolem_name s (Unsynchronized.inc skolem_count) s'
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          val c = Free (id, cT)
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          (* Forms a lambda-abstraction over the formal parameters *)
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          val rhs =
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            list_abs_free (map dest_Free args,
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                           HOLogic.choice_const T
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                           $ quasi_beta_eta_contract body)
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            |> inline ? mk_skolem_id
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          val def = Logic.mk_equals (c, rhs)
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          val comb = list_comb (if inline then rhs else c, args)
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        in dec_sko (subst_bound (comb, p)) (def :: defs) end
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      | dec_sko (Const (@{const_name All},_) $ Abs (a, T, p)) defs =
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        (*Universal quant: insert a free variable into body and continue*)
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        let val fname = Name.variant (OldTerm.add_term_names (p,[])) a
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        in dec_sko (subst_bound (Free(fname,T), p)) defs end
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      | dec_sko (@{const "op &"} $ p $ q) defs = dec_sko q (dec_sko p defs)
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      | dec_sko (@{const "op |"} $ p $ q) defs = dec_sko q (dec_sko p defs)
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      | dec_sko (@{const Trueprop} $ p) defs = dec_sko p defs
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      | dec_sko _ defs = defs
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  in  dec_sko (prop_of th) []  end;
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(**** REPLACING ABSTRACTIONS BY COMBINATORS ****)
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(*Returns the vars of a theorem*)
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fun vars_of_thm th =
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  map (Thm.cterm_of (theory_of_thm th) o Var) (Thm.fold_terms Term.add_vars th []);
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(*Make a version of fun_cong with a given variable name*)
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local
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    val fun_cong' = fun_cong RS asm_rl; (*renumber f, g to prevent clashes with (a,0)*)
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    val cx = hd (vars_of_thm fun_cong');
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    val ty = typ_of (ctyp_of_term cx);
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    val thy = theory_of_thm fun_cong;
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    fun mkvar a = cterm_of thy (Var((a,0),ty));
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in
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fun xfun_cong x = Thm.instantiate ([], [(cx, mkvar x)]) fun_cong'
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end;
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(*Removes the lambdas from an equation of the form t = (%x. u).  A non-negative n,
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  serves as an upper bound on how many to remove.*)
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fun strip_lambdas 0 th = th
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  | strip_lambdas n th =
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      case prop_of th of
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          _ $ (Const (@{const_name "op ="}, _) $ _ $ Abs (x, _, _)) =>
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              strip_lambdas (n-1) (freeze_thm (th RS xfun_cong x))
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        | _ => th;
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fun is_quasi_lambda_free (Const (@{const_name skolem_id}, _) $ _) = true
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  | is_quasi_lambda_free (t1 $ t2) =
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    is_quasi_lambda_free t1 andalso is_quasi_lambda_free t2
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  | is_quasi_lambda_free (Abs _) = false
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  | is_quasi_lambda_free _ = true
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val [f_B,g_B] = map (cterm_of @{theory}) (OldTerm.term_vars (prop_of @{thm abs_B}));
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val [g_C,f_C] = map (cterm_of @{theory}) (OldTerm.term_vars (prop_of @{thm abs_C}));
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val [f_S,g_S] = map (cterm_of @{theory}) (OldTerm.term_vars (prop_of @{thm abs_S}));
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(*FIXME: requires more use of cterm constructors*)
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fun abstract ct =
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  let
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      val thy = theory_of_cterm ct
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      val Abs(x,_,body) = term_of ct
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      val Type(@{type_name fun}, [xT,bodyT]) = typ_of (ctyp_of_term ct)
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      val cxT = ctyp_of thy xT and cbodyT = ctyp_of thy bodyT
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      fun makeK() = instantiate' [SOME cxT, SOME cbodyT] [SOME (cterm_of thy body)] @{thm abs_K}
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  in
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      case body of
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          Const _ => makeK()
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        | Free _ => makeK()
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        | Var _ => makeK()  (*though Var isn't expected*)
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        | Bound 0 => instantiate' [SOME cxT] [] @{thm abs_I} (*identity: I*)
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        | rator$rand =>
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            if loose_bvar1 (rator,0) then (*C or S*)
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               if loose_bvar1 (rand,0) then (*S*)
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                 let val crator = cterm_of thy (Abs(x,xT,rator))
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                     val crand = cterm_of thy (Abs(x,xT,rand))
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                     val abs_S' = cterm_instantiate [(f_S,crator),(g_S,crand)] @{thm abs_S}
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                     val (_,rhs) = Thm.dest_equals (cprop_of abs_S')
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                 in
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                   Thm.transitive abs_S' (Conv.binop_conv abstract rhs)
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                 end
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               else (*C*)
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                 let val crator = cterm_of thy (Abs(x,xT,rator))
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                     val abs_C' = cterm_instantiate [(f_C,crator),(g_C,cterm_of thy rand)] @{thm abs_C}
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                     val (_,rhs) = Thm.dest_equals (cprop_of abs_C')
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                 in
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                   Thm.transitive abs_C' (Conv.fun_conv (Conv.arg_conv abstract) rhs)
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                 end
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            else if loose_bvar1 (rand,0) then (*B or eta*)
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               if rand = Bound 0 then Thm.eta_conversion ct
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               else (*B*)
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                 let val crand = cterm_of thy (Abs(x,xT,rand))
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                     val crator = cterm_of thy rator
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                     val abs_B' = cterm_instantiate [(f_B,crator),(g_B,crand)] @{thm abs_B}
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                     val (_,rhs) = Thm.dest_equals (cprop_of abs_B')
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                 in Thm.transitive abs_B' (Conv.arg_conv abstract rhs) end
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            else makeK()
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        | _ => raise Fail "abstract: Bad term"
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  end;
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(* Traverse a theorem, remplacing lambda-abstractions with combinators. *)
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fun do_introduce_combinators ct =
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  if is_quasi_lambda_free (term_of ct) then
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    Thm.reflexive ct
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  else case term_of ct of
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    Abs _ =>
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    let
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      val (cv, cta) = Thm.dest_abs NONE ct
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      val (v, _) = dest_Free (term_of cv)
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      val u_th = do_introduce_combinators cta
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      val cu = Thm.rhs_of u_th
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      val comb_eq = abstract (Thm.cabs cv cu)
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    in Thm.transitive (Thm.abstract_rule v cv u_th) comb_eq end
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  | _ $ _ =>
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    let val (ct1, ct2) = Thm.dest_comb ct in
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        Thm.combination (do_introduce_combinators ct1)
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                        (do_introduce_combinators ct2)
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    end
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fun introduce_combinators th =
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  if is_quasi_lambda_free (prop_of th) then
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    th
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  else
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    let
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      val th = Drule.eta_contraction_rule th
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      val eqth = do_introduce_combinators (cprop_of th)
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    in Thm.equal_elim eqth th end
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    handle THM (msg, _, _) =>
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           (warning ("Error in the combinator translation of " ^
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                     Display.string_of_thm_without_context th ^
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                     "\nException message: " ^ msg ^ ".");
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            (* A type variable of sort "{}" will make abstraction fail. *)
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            TrueI)
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(*cterms are used throughout for efficiency*)
wenzelm@29064
   294
val cTrueprop = Thm.cterm_of @{theory HOL} HOLogic.Trueprop;
paulson@16009
   295
paulson@16009
   296
(*cterm version of mk_cTrueprop*)
paulson@16009
   297
fun c_mkTrueprop A = Thm.capply cTrueprop A;
paulson@16009
   298
paulson@16009
   299
(*Given an abstraction over n variables, replace the bound variables by free
paulson@16009
   300
  ones. Return the body, along with the list of free variables.*)
wenzelm@20461
   301
fun c_variant_abs_multi (ct0, vars) =
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   302
      let val (cv,ct) = Thm.dest_abs NONE ct0
paulson@16009
   303
      in  c_variant_abs_multi (ct, cv::vars)  end
paulson@16009
   304
      handle CTERM _ => (ct0, rev vars);
paulson@16009
   305
wenzelm@20461
   306
(*Given the definition of a Skolem function, return a theorem to replace
wenzelm@20461
   307
  an existential formula by a use of that function.
paulson@18141
   308
   Example: "EX x. x : A & x ~: B ==> sko A B : A & sko A B ~: B"  [.] *)
blanchet@37399
   309
fun skolem_theorem_of_def inline def =
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   310
  let
blanchet@37410
   311
      val (c, rhs) = Thm.dest_equals (cprop_of (freeze_thm def))
blanchet@37410
   312
      val rhs' = rhs |> inline ? (snd o Thm.dest_comb)
blanchet@37410
   313
      val (ch, frees) = c_variant_abs_multi (rhs', [])
blanchet@37410
   314
      val (chilbert, cabs) = ch |> Thm.dest_comb
wenzelm@26627
   315
      val thy = Thm.theory_of_cterm chilbert
wenzelm@26627
   316
      val t = Thm.term_of chilbert
blanchet@37399
   317
      val T =
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   318
        case t of
blanchet@37410
   319
          Const (@{const_name Eps}, Type (@{type_name fun}, [_, T])) => T
blanchet@37410
   320
        | _ => raise TERM ("skolem_theorem_of_def: expected \"Eps\"", [t])
wenzelm@22596
   321
      val cex = Thm.cterm_of thy (HOLogic.exists_const T)
paulson@16009
   322
      val ex_tm = c_mkTrueprop (Thm.capply cex cabs)
blanchet@37399
   323
      and conc =
blanchet@37399
   324
        Drule.list_comb (if inline then rhs else c, frees)
blanchet@37399
   325
        |> Drule.beta_conv cabs |> c_mkTrueprop
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   326
      fun tacf [prem] =
blanchet@37410
   327
        (if inline then rewrite_goals_tac @{thms skolem_id_def_raw}
blanchet@37410
   328
         else rewrite_goals_tac [def])
blanchet@37410
   329
        THEN rtac ((prem |> inline ? rewrite_rule @{thms skolem_id_def_raw})
blanchet@37410
   330
                   RS @{thm someI_ex}) 1
wenzelm@23352
   331
  in  Goal.prove_internal [ex_tm] conc tacf
paulson@18141
   332
       |> forall_intr_list frees
wenzelm@26653
   333
       |> Thm.forall_elim_vars 0  (*Introduce Vars, but don't discharge defs.*)
wenzelm@35845
   334
       |> Thm.varifyT_global
paulson@18141
   335
  end;
paulson@16009
   336
paulson@24742
   337
paulson@20863
   338
(*Converts an Isabelle theorem (intro, elim or simp format, even higher-order) into NNF.*)
paulson@24937
   339
fun to_nnf th ctxt0 =
wenzelm@27179
   340
  let val th1 = th |> transform_elim |> zero_var_indexes
wenzelm@32262
   341
      val ((_, [th2]), ctxt) = Variable.import true [th1] ctxt0
wenzelm@32262
   342
      val th3 = th2
wenzelm@35625
   343
        |> Conv.fconv_rule Object_Logic.atomize
wenzelm@32262
   344
        |> Meson.make_nnf ctxt |> strip_lambdas ~1
paulson@24937
   345
  in  (th3, ctxt)  end;
paulson@16009
   346
paulson@18141
   347
(*Generate Skolem functions for a theorem supplied in nnf*)
blanchet@37399
   348
fun skolem_theorems_of_assume inline s th =
blanchet@37399
   349
  map (skolem_theorem_of_def inline o Thm.assume o cterm_of (theory_of_thm th))
blanchet@37399
   350
      (assume_skolem_funs inline s th)
paulson@18141
   351
paulson@25007
   352
blanchet@37349
   353
(*** Blacklisting (more in "Sledgehammer_Fact_Filter") ***)
paulson@25007
   354
blanchet@37348
   355
val max_lambda_nesting = 3
wenzelm@27184
   356
blanchet@37348
   357
fun term_has_too_many_lambdas max (t1 $ t2) =
blanchet@37348
   358
    exists (term_has_too_many_lambdas max) [t1, t2]
blanchet@37348
   359
  | term_has_too_many_lambdas max (Abs (_, _, t)) =
blanchet@37348
   360
    max = 0 orelse term_has_too_many_lambdas (max - 1) t
blanchet@37348
   361
  | term_has_too_many_lambdas _ _ = false
paulson@25007
   362
blanchet@37348
   363
fun is_formula_type T = (T = HOLogic.boolT orelse T = propT)
paulson@25007
   364
blanchet@37348
   365
(* Don't count nested lambdas at the level of formulas, since they are
blanchet@37348
   366
   quantifiers. *)
blanchet@37348
   367
fun formula_has_too_many_lambdas Ts (Abs (_, T, t)) =
blanchet@37348
   368
    formula_has_too_many_lambdas (T :: Ts) t
blanchet@37348
   369
  | formula_has_too_many_lambdas Ts t =
blanchet@37348
   370
    if is_formula_type (fastype_of1 (Ts, t)) then
blanchet@37348
   371
      exists (formula_has_too_many_lambdas Ts) (#2 (strip_comb t))
blanchet@37348
   372
    else
blanchet@37348
   373
      term_has_too_many_lambdas max_lambda_nesting t
paulson@25007
   374
blanchet@37348
   375
(* The max apply depth of any "metis" call in "Metis_Examples" (on 31-10-2007)
blanchet@37348
   376
   was 11. *)
blanchet@37348
   377
val max_apply_depth = 15
wenzelm@27184
   378
blanchet@37348
   379
fun apply_depth (f $ t) = Int.max (apply_depth f, apply_depth t + 1)
blanchet@37348
   380
  | apply_depth (Abs (_, _, t)) = apply_depth t
blanchet@37348
   381
  | apply_depth _ = 0
paulson@25256
   382
blanchet@37348
   383
fun is_formula_too_complex t =
blanchet@37348
   384
  apply_depth t > max_apply_depth orelse Meson.too_many_clauses NONE t orelse
blanchet@37348
   385
  formula_has_too_many_lambdas [] t
wenzelm@27184
   386
paulson@25243
   387
fun is_strange_thm th =
paulson@25243
   388
  case head_of (concl_of th) of
blanchet@35963
   389
      Const (a, _) => (a <> @{const_name Trueprop} andalso
blanchet@35963
   390
                       a <> @{const_name "=="})
paulson@25243
   391
    | _ => false;
paulson@25243
   392
blanchet@37348
   393
fun is_theorem_bad_for_atps thm =
blanchet@37348
   394
  let val t = prop_of thm in
blanchet@37348
   395
    is_formula_too_complex t orelse exists_type type_has_topsort t orelse
blanchet@37348
   396
    is_strange_thm thm
blanchet@37348
   397
  end
paulson@25243
   398
blanchet@35963
   399
(* FIXME: put other record thms here, or declare as "no_atp" *)
paulson@25007
   400
val multi_base_blacklist =
blanchet@35963
   401
  ["defs", "select_defs", "update_defs", "induct", "inducts", "split", "splits",
blanchet@35963
   402
   "split_asm", "cases", "ext_cases"];
paulson@25007
   403
paulson@22731
   404
fun fake_name th =
wenzelm@27865
   405
  if Thm.has_name_hint th then flatten_name (Thm.get_name_hint th)
paulson@22731
   406
  else gensym "unknown_thm_";
paulson@22731
   407
wenzelm@27184
   408
(*Skolemize a named theorem, with Skolem functions as additional premises.*)
blanchet@37399
   409
fun skolemize_theorem s th =
blanchet@37345
   410
  if member (op =) multi_base_blacklist (Long_Name.base_name s) orelse
blanchet@37348
   411
     is_theorem_bad_for_atps th then
blanchet@37345
   412
    []
wenzelm@27184
   413
  else
wenzelm@27184
   414
    let
wenzelm@36603
   415
      val ctxt0 = Variable.global_thm_context th
blanchet@37349
   416
      val (nnfth, ctxt) = to_nnf th ctxt0
blanchet@37399
   417
      val inline = exists_type (exists_subtype (can dest_TFree)) (prop_of nnfth)
blanchet@37399
   418
      val defs = skolem_theorems_of_assume inline s nnfth
blanchet@37349
   419
      val (cnfs, ctxt) = Meson.make_cnf defs nnfth ctxt
blanchet@37349
   420
    in
blanchet@37349
   421
      cnfs |> map introduce_combinators
blanchet@37349
   422
           |> Variable.export ctxt ctxt0
blanchet@37349
   423
           |> Meson.finish_cnf
blanchet@37349
   424
    end
blanchet@37349
   425
    handle THM _ => []
wenzelm@27184
   426
paulson@24742
   427
(*The cache prevents repeated clausification of a theorem, and also repeated declaration of
paulson@24742
   428
  Skolem functions.*)
wenzelm@33522
   429
structure ThmCache = Theory_Data
wenzelm@22846
   430
(
wenzelm@28544
   431
  type T = thm list Thmtab.table * unit Symtab.table;
wenzelm@28544
   432
  val empty = (Thmtab.empty, Symtab.empty);
wenzelm@26618
   433
  val extend = I;
wenzelm@33522
   434
  fun merge ((cache1, seen1), (cache2, seen2)) : T =
wenzelm@27184
   435
    (Thmtab.merge (K true) (cache1, cache2), Symtab.merge (K true) (seen1, seen2));
wenzelm@22846
   436
);
paulson@22516
   437
wenzelm@27184
   438
val lookup_cache = Thmtab.lookup o #1 o ThmCache.get;
wenzelm@27184
   439
val already_seen = Symtab.defined o #2 o ThmCache.get;
wenzelm@20461
   440
wenzelm@27184
   441
val update_cache = ThmCache.map o apfst o Thmtab.update;
wenzelm@27184
   442
fun mark_seen name = ThmCache.map (apsnd (Symtab.update (name, ())));
paulson@25007
   443
blanchet@36228
   444
(* Convert Isabelle theorems into axiom clauses. *)
wenzelm@27179
   445
fun cnf_axiom thy th0 =
wenzelm@27184
   446
  let val th = Thm.transfer thy th0 in
wenzelm@27184
   447
    case lookup_cache thy th of
blanchet@37416
   448
      SOME cls => cls
blanchet@37416
   449
    | NONE => map Thm.close_derivation (skolemize_theorem (fake_name th) th)
paulson@22516
   450
  end;
paulson@15347
   451
paulson@18141
   452
paulson@22471
   453
(**** Translate a set of theorems into CNF ****)
paulson@15347
   454
paulson@21290
   455
(*The combination of rev and tail recursion preserves the original order*)
blanchet@37416
   456
fun cnf_rules_pairs thy =
blanchet@37416
   457
  let
blanchet@37500
   458
    fun do_one _ [] = []
blanchet@37500
   459
      | do_one ((name, k), th) (cls :: clss) =
blanchet@37500
   460
        (cls, ((name, k), th)) :: do_one ((name, k + 1), th) clss
blanchet@37500
   461
    fun do_all pairs [] = pairs
blanchet@37500
   462
      | do_all pairs ((name, th) :: ths) =
blanchet@37416
   463
        let
blanchet@37500
   464
          val new_pairs = do_one ((name, 0), th) (cnf_axiom thy th)
blanchet@37416
   465
                          handle THM _ => [] |
blanchet@37416
   466
                                 CLAUSE _ => []
blanchet@37500
   467
        in do_all (new_pairs @ pairs) ths end
blanchet@37500
   468
  in do_all [] o rev end
mengj@19353
   469
mengj@19196
   470
blanchet@35865
   471
(**** Convert all facts of the theory into FOL or HOL clauses ****)
paulson@15347
   472
wenzelm@28544
   473
local
wenzelm@28544
   474
wenzelm@28544
   475
fun skolem_def (name, th) thy =
wenzelm@36603
   476
  let val ctxt0 = Variable.global_thm_context th in
blanchet@37348
   477
    case try (to_nnf th) ctxt0 of
wenzelm@28544
   478
      NONE => (NONE, thy)
blanchet@37349
   479
    | SOME (nnfth, ctxt) =>
blanchet@37348
   480
      let val (defs, thy') = declare_skolem_funs (flatten_name name) nnfth thy
blanchet@37349
   481
      in (SOME (th, ctxt0, ctxt, nnfth, defs), thy') end
wenzelm@28544
   482
  end;
paulson@24742
   483
blanchet@37349
   484
fun skolem_cnfs (th, ctxt0, ctxt, nnfth, defs) =
wenzelm@28544
   485
  let
blanchet@37399
   486
    val (cnfs, ctxt) =
blanchet@37399
   487
      Meson.make_cnf (map (skolem_theorem_of_def false) defs) nnfth ctxt
wenzelm@28544
   488
    val cnfs' = cnfs
blanchet@37349
   489
      |> map introduce_combinators
blanchet@37349
   490
      |> Variable.export ctxt ctxt0
wenzelm@28544
   491
      |> Meson.finish_cnf
wenzelm@28544
   492
      |> map Thm.close_derivation;
wenzelm@28544
   493
    in (th, cnfs') end;
wenzelm@28544
   494
wenzelm@28544
   495
in
paulson@24742
   496
wenzelm@27184
   497
fun saturate_skolem_cache thy =
wenzelm@28544
   498
  let
wenzelm@33306
   499
    val facts = PureThy.facts_of thy;
wenzelm@33306
   500
    val new_facts = (facts, []) |-> Facts.fold_static (fn (name, ths) =>
wenzelm@33306
   501
      if Facts.is_concealed facts name orelse already_seen thy name then I
wenzelm@33306
   502
      else cons (name, ths));
wenzelm@28544
   503
    val new_thms = (new_facts, []) |-> fold (fn (name, ths) =>
blanchet@37399
   504
      if member (op =) multi_base_blacklist (Long_Name.base_name name) then
blanchet@37399
   505
        I
blanchet@37399
   506
      else
blanchet@37399
   507
        fold_index (fn (i, th) =>
blanchet@37410
   508
          if is_theorem_bad_for_atps th orelse
blanchet@37410
   509
             is_some (lookup_cache thy th) then
blanchet@37399
   510
            I
blanchet@37399
   511
          else
blanchet@37399
   512
            cons (name ^ "_" ^ string_of_int (i + 1), Thm.transfer thy th)) ths)
wenzelm@28544
   513
  in
blanchet@37399
   514
    if null new_facts then
blanchet@37399
   515
      NONE
wenzelm@28544
   516
    else
wenzelm@28544
   517
      let
wenzelm@28544
   518
        val (defs, thy') = thy
wenzelm@28544
   519
          |> fold (mark_seen o #1) new_facts
wenzelm@28544
   520
          |> fold_map skolem_def (sort_distinct (Thm.thm_ord o pairself snd) new_thms)
wenzelm@28544
   521
          |>> map_filter I;
wenzelm@29368
   522
        val cache_entries = Par_List.map skolem_cnfs defs;
wenzelm@28544
   523
      in SOME (fold update_cache cache_entries thy') end
wenzelm@28544
   524
  end;
wenzelm@27184
   525
wenzelm@28544
   526
end;
paulson@24854
   527
blanchet@37511
   528
(* For emergency use where the Skolem cache causes problems. *)
blanchet@37498
   529
val auto_saturate_skolem_cache = Unsynchronized.ref true
paulson@20457
   530
blanchet@37498
   531
fun conditionally_saturate_skolem_cache thy =
blanchet@37498
   532
  if !auto_saturate_skolem_cache then saturate_skolem_cache thy else NONE
wenzelm@27179
   533
blanchet@36398
   534
paulson@21999
   535
(*** Converting a subgoal into negated conjecture clauses. ***)
paulson@21999
   536
wenzelm@32262
   537
fun neg_skolemize_tac ctxt =
blanchet@37332
   538
  EVERY' [rtac ccontr, Object_Logic.atomize_prems_tac, Meson.skolemize_tac ctxt]
blanchet@36398
   539
blanchet@35869
   540
val neg_clausify =
blanchet@37349
   541
  single
blanchet@37349
   542
  #> Meson.make_clauses_unsorted
blanchet@37349
   543
  #> map introduce_combinators
blanchet@37349
   544
  #> Meson.finish_cnf
paulson@21999
   545
wenzelm@32257
   546
fun neg_conjecture_clauses ctxt st0 n =
wenzelm@32257
   547
  let
blanchet@37332
   548
    (* "Option" is thrown if the assumptions contain schematic variables. *)
blanchet@37332
   549
    val st = Seq.hd (neg_skolemize_tac ctxt n st0) handle Option.Option => st0
blanchet@37332
   550
    val ({params, prems, ...}, _) =
blanchet@37332
   551
      Subgoal.focus (Variable.set_body false ctxt) n st
blanchet@37332
   552
  in (map neg_clausify prems, map (dest_Free o term_of o #2) params) end
paulson@21999
   553
wenzelm@27184
   554
wenzelm@27184
   555
(** setup **)
wenzelm@27184
   556
wenzelm@27184
   557
val setup =
blanchet@37498
   558
  perhaps conditionally_saturate_skolem_cache
blanchet@37498
   559
  #> Theory.at_end conditionally_saturate_skolem_cache
paulson@18510
   560
wenzelm@20461
   561
end;