src/HOL/Tools/Meson/meson.ML
author blanchet
Thu Apr 14 11:24:04 2011 +0200 (2011-04-14)
changeset 42335 cb8aa792d138
parent 40724 d01a1b3ab23d
child 42346 be52d9bed9f6
permissions -rw-r--r--
experiment with definitional CNF
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(*  Title:      HOL/Tools/Meson/meson.ML
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    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
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    Author:     Jasmin Blanchette, TU Muenchen
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The MESON resolution proof procedure for HOL.
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When making clauses, avoids using the rewriter -- instead uses RS recursively.
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*)
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signature MESON =
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sig
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  val trace : bool Config.T
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  val max_clauses : int Config.T
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  val term_pair_of: indexname * (typ * 'a) -> term * 'a
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  val size_of_subgoals: thm -> int
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  val has_too_many_clauses: Proof.context -> term -> bool
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  val make_cnf: thm list -> thm -> Proof.context -> thm list * Proof.context
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  val make_xxx_skolem: Proof.context -> thm list -> thm -> thm
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  val finish_cnf: thm list -> thm list
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  val presimplify: thm -> thm
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  val make_nnf: Proof.context -> thm -> thm
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  val choice_theorems : theory -> thm list
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  val skolemize_with_choice_theorems : Proof.context -> thm list -> thm -> thm
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  val skolemize : Proof.context -> thm -> thm
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  val is_fol_term: theory -> term -> bool
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  val make_clauses_unsorted: thm list -> thm list
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  val make_clauses: thm list -> thm list
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  val make_horns: thm list -> thm list
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  val best_prolog_tac: (thm -> int) -> thm list -> tactic
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  val depth_prolog_tac: thm list -> tactic
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  val gocls: thm list -> thm list
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  val skolemize_prems_tac : Proof.context -> thm list -> int -> tactic
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  val MESON:
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    tactic -> (thm list -> thm list) -> (thm list -> tactic) -> Proof.context
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    -> int -> tactic
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  val best_meson_tac: (thm -> int) -> Proof.context -> int -> tactic
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  val safe_best_meson_tac: Proof.context -> int -> tactic
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  val depth_meson_tac: Proof.context -> int -> tactic
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  val prolog_step_tac': thm list -> int -> tactic
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  val iter_deepen_prolog_tac: thm list -> tactic
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  val iter_deepen_meson_tac: Proof.context -> thm list -> int -> tactic
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  val make_meta_clause: thm -> thm
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  val make_meta_clauses: thm list -> thm list
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  val meson_tac: Proof.context -> thm list -> int -> tactic
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  val setup : theory -> theory
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end
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structure Meson : MESON =
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struct
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val (trace, trace_setup) = Attrib.config_bool "meson_trace" (K false)
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fun trace_msg ctxt msg = if Config.get ctxt trace then tracing (msg ()) else ()
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val max_clauses_default = 60
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val (max_clauses, max_clauses_setup) =
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  Attrib.config_int "meson_max_clauses" (K max_clauses_default)
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(*No known example (on 1-5-2007) needs even thirty*)
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val iter_deepen_limit = 50;
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val disj_forward = @{thm disj_forward};
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val disj_forward2 = @{thm disj_forward2};
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val make_pos_rule = @{thm make_pos_rule};
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val make_pos_rule' = @{thm make_pos_rule'};
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val make_pos_goal = @{thm make_pos_goal};
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val make_neg_rule = @{thm make_neg_rule};
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val make_neg_rule' = @{thm make_neg_rule'};
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val make_neg_goal = @{thm make_neg_goal};
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val conj_forward = @{thm conj_forward};
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val all_forward = @{thm all_forward};
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val ex_forward = @{thm ex_forward};
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val not_conjD = @{thm not_conjD};
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val not_disjD = @{thm not_disjD};
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val not_notD = @{thm not_notD};
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val not_allD = @{thm not_allD};
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val not_exD = @{thm not_exD};
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val imp_to_disjD = @{thm imp_to_disjD};
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val not_impD = @{thm not_impD};
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val iff_to_disjD = @{thm iff_to_disjD};
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val not_iffD = @{thm not_iffD};
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val conj_exD1 = @{thm conj_exD1};
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val conj_exD2 = @{thm conj_exD2};
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val disj_exD = @{thm disj_exD};
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val disj_exD1 = @{thm disj_exD1};
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val disj_exD2 = @{thm disj_exD2};
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val disj_assoc = @{thm disj_assoc};
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val disj_comm = @{thm disj_comm};
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val disj_FalseD1 = @{thm disj_FalseD1};
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val disj_FalseD2 = @{thm disj_FalseD2};
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(**** Operators for forward proof ****)
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(** First-order Resolution **)
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fun term_pair_of (ix, (ty,t)) = (Var (ix,ty), t);
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(*FIXME: currently does not "rename variables apart"*)
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fun first_order_resolve thA thB =
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  (case
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    try (fn () =>
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      let val thy = theory_of_thm thA
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          val tmA = concl_of thA
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          val Const("==>",_) $ tmB $ _ = prop_of thB
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          val tenv =
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            Pattern.first_order_match thy (tmB, tmA)
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                                          (Vartab.empty, Vartab.empty) |> snd
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          val ct_pairs = map (pairself (cterm_of thy) o term_pair_of) (Vartab.dest tenv)
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      in  thA RS (cterm_instantiate ct_pairs thB)  end) () of
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    SOME th => th
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  | NONE => raise THM ("first_order_resolve", 0, [thA, thB]))
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(* Hack to make it less likely that we lose our precious bound variable names in
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   "rename_bound_vars_RS" below, because of a clash. *)
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val protect_prefix = "Meson_xyzzy"
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fun protect_bound_var_names (t $ u) =
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    protect_bound_var_names t $ protect_bound_var_names u
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  | protect_bound_var_names (Abs (s, T, t')) =
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    Abs (protect_prefix ^ s, T, protect_bound_var_names t')
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  | protect_bound_var_names t = t
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fun fix_bound_var_names old_t new_t =
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  let
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    fun quant_of @{const_name All} = SOME true
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      | quant_of @{const_name Ball} = SOME true
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      | quant_of @{const_name Ex} = SOME false
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      | quant_of @{const_name Bex} = SOME false
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      | quant_of _ = NONE
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    val flip_quant = Option.map not
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    fun some_eq (SOME x) (SOME y) = x = y
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      | some_eq _ _ = false
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    fun add_names quant (Const (quant_s, _) $ Abs (s, _, t')) =
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        add_names quant t' #> some_eq quant (quant_of quant_s) ? cons s
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      | add_names quant (@{const Not} $ t) = add_names (flip_quant quant) t
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      | add_names quant (@{const implies} $ t1 $ t2) =
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        add_names (flip_quant quant) t1 #> add_names quant t2
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      | add_names quant (t1 $ t2) = fold (add_names quant) [t1, t2]
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      | add_names _ _ = I
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    fun lost_names quant =
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      subtract (op =) (add_names quant new_t []) (add_names quant old_t [])
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    fun aux ((t1 as Const (quant_s, _)) $ (Abs (s, T, t'))) =
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      t1 $ Abs (s |> String.isPrefix protect_prefix s
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                   ? perhaps (try (fn _ => hd (lost_names (quant_of quant_s)))),
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                T, aux t')
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      | aux (t1 $ t2) = aux t1 $ aux t2
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      | aux t = t
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  in aux new_t end
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(* Forward proof while preserving bound variables names *)
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fun rename_bound_vars_RS th rl =
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  let
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    val t = concl_of th
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    val r = concl_of rl
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    val th' = th RS Thm.rename_boundvars r (protect_bound_var_names r) rl
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    val t' = concl_of th'
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  in Thm.rename_boundvars t' (fix_bound_var_names t t') th' end
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(*raises exception if no rules apply*)
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fun tryres (th, rls) =
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  let fun tryall [] = raise THM("tryres", 0, th::rls)
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        | tryall (rl::rls) =
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          (rename_bound_vars_RS th rl handle THM _ => tryall rls)
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  in  tryall rls  end;
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(*Permits forward proof from rules that discharge assumptions. The supplied proof state st,
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  e.g. from conj_forward, should have the form
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    "[| P' ==> ?P; Q' ==> ?Q |] ==> ?P & ?Q"
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  and the effect should be to instantiate ?P and ?Q with normalized versions of P' and Q'.*)
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fun forward_res ctxt nf st =
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  let fun forward_tacf [prem] = rtac (nf prem) 1
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        | forward_tacf prems =
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            error (cat_lines
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              ("Bad proof state in forward_res, please inform lcp@cl.cam.ac.uk:" ::
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                Display.string_of_thm ctxt st ::
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                "Premises:" :: map (Display.string_of_thm ctxt) prems))
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  in
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    case Seq.pull (ALLGOALS (Misc_Legacy.METAHYPS forward_tacf) st)
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    of SOME(th,_) => th
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     | NONE => raise THM("forward_res", 0, [st])
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  end;
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(*Are any of the logical connectives in "bs" present in the term?*)
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fun has_conns bs =
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  let fun has (Const _) = false
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        | has (Const(@{const_name Trueprop},_) $ p) = has p
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        | has (Const(@{const_name Not},_) $ p) = has p
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        | has (Const(@{const_name HOL.disj},_) $ p $ q) = member (op =) bs @{const_name HOL.disj} orelse has p orelse has q
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        | has (Const(@{const_name HOL.conj},_) $ p $ q) = member (op =) bs @{const_name HOL.conj} orelse has p orelse has q
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        | has (Const(@{const_name All},_) $ Abs(_,_,p)) = member (op =) bs @{const_name All} orelse has p
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        | has (Const(@{const_name Ex},_) $ Abs(_,_,p)) = member (op =) bs @{const_name Ex} orelse has p
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        | has _ = false
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  in  has  end;
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(**** Clause handling ****)
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fun literals (Const(@{const_name Trueprop},_) $ P) = literals P
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  | literals (Const(@{const_name HOL.disj},_) $ P $ Q) = literals P @ literals Q
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  | literals (Const(@{const_name Not},_) $ P) = [(false,P)]
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  | literals P = [(true,P)];
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(*number of literals in a term*)
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val nliterals = length o literals;
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(*** Tautology Checking ***)
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fun signed_lits_aux (Const (@{const_name HOL.disj}, _) $ P $ Q) (poslits, neglits) =
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      signed_lits_aux Q (signed_lits_aux P (poslits, neglits))
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  | signed_lits_aux (Const(@{const_name Not},_) $ P) (poslits, neglits) = (poslits, P::neglits)
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  | signed_lits_aux P (poslits, neglits) = (P::poslits, neglits);
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fun signed_lits th = signed_lits_aux (HOLogic.dest_Trueprop (concl_of th)) ([],[]);
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(*Literals like X=X are tautologous*)
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fun taut_poslit (Const(@{const_name HOL.eq},_) $ t $ u) = t aconv u
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  | taut_poslit (Const(@{const_name True},_)) = true
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  | taut_poslit _ = false;
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fun is_taut th =
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  let val (poslits,neglits) = signed_lits th
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  in  exists taut_poslit poslits
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      orelse
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      exists (member (op aconv) neglits) (HOLogic.false_const :: poslits)
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  end
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  handle TERM _ => false;       (*probably dest_Trueprop on a weird theorem*)
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(*** To remove trivial negated equality literals from clauses ***)
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(*They are typically functional reflexivity axioms and are the converses of
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  injectivity equivalences*)
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val not_refl_disj_D = @{thm not_refl_disj_D};
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(*Is either term a Var that does not properly occur in the other term?*)
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fun eliminable (t as Var _, u) = t aconv u orelse not (Logic.occs(t,u))
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  | eliminable (u, t as Var _) = t aconv u orelse not (Logic.occs(t,u))
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  | eliminable _ = false;
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fun refl_clause_aux 0 th = th
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  | refl_clause_aux n th =
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       case HOLogic.dest_Trueprop (concl_of th) of
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          (Const (@{const_name HOL.disj}, _) $ (Const (@{const_name HOL.disj}, _) $ _ $ _) $ _) =>
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            refl_clause_aux n (th RS disj_assoc)    (*isolate an atom as first disjunct*)
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        | (Const (@{const_name HOL.disj}, _) $ (Const(@{const_name Not},_) $ (Const(@{const_name HOL.eq},_) $ t $ u)) $ _) =>
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            if eliminable(t,u)
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            then refl_clause_aux (n-1) (th RS not_refl_disj_D)  (*Var inequation: delete*)
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            else refl_clause_aux (n-1) (th RS disj_comm)  (*not between Vars: ignore*)
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        | (Const (@{const_name HOL.disj}, _) $ _ $ _) => refl_clause_aux n (th RS disj_comm)
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        | _ => (*not a disjunction*) th;
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fun notequal_lits_count (Const (@{const_name HOL.disj}, _) $ P $ Q) =
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      notequal_lits_count P + notequal_lits_count Q
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  | notequal_lits_count (Const(@{const_name Not},_) $ (Const(@{const_name HOL.eq},_) $ _ $ _)) = 1
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  | notequal_lits_count _ = 0;
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(*Simplify a clause by applying reflexivity to its negated equality literals*)
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fun refl_clause th =
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  let val neqs = notequal_lits_count (HOLogic.dest_Trueprop (concl_of th))
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  in  zero_var_indexes (refl_clause_aux neqs th)  end
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  handle TERM _ => th;  (*probably dest_Trueprop on a weird theorem*)
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(*** Removal of duplicate literals ***)
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(*Forward proof, passing extra assumptions as theorems to the tactic*)
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fun forward_res2 nf hyps st =
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  case Seq.pull
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        (REPEAT
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         (Misc_Legacy.METAHYPS (fn major::minors => rtac (nf (minors@hyps) major) 1) 1)
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         st)
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  of SOME(th,_) => th
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   | NONE => raise THM("forward_res2", 0, [st]);
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(*Remove duplicates in P|Q by assuming ~P in Q
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  rls (initially []) accumulates assumptions of the form P==>False*)
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fun nodups_aux ctxt rls th = nodups_aux ctxt rls (th RS disj_assoc)
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    handle THM _ => tryres(th,rls)
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    handle THM _ => tryres(forward_res2 (nodups_aux ctxt) rls (th RS disj_forward2),
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                           [disj_FalseD1, disj_FalseD2, asm_rl])
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    handle THM _ => th;
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(*Remove duplicate literals, if there are any*)
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fun nodups ctxt th =
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  if has_duplicates (op =) (literals (prop_of th))
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    then nodups_aux ctxt [] th
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    else th;
paulson@24937
   292
paulson@24937
   293
paulson@18389
   294
(*** The basic CNF transformation ***)
paulson@18389
   295
blanchet@39328
   296
fun estimated_num_clauses bound t =
paulson@26562
   297
 let
blanchet@39269
   298
  fun sum x y = if x < bound andalso y < bound then x+y else bound
blanchet@39269
   299
  fun prod x y = if x < bound andalso y < bound then x*y else bound
paulson@26562
   300
  
paulson@26562
   301
  (*Estimate the number of clauses in order to detect infeasible theorems*)
haftmann@38557
   302
  fun signed_nclauses b (Const(@{const_name Trueprop},_) $ t) = signed_nclauses b t
haftmann@38557
   303
    | signed_nclauses b (Const(@{const_name Not},_) $ t) = signed_nclauses (not b) t
haftmann@38795
   304
    | signed_nclauses b (Const(@{const_name HOL.conj},_) $ t $ u) =
wenzelm@32960
   305
        if b then sum (signed_nclauses b t) (signed_nclauses b u)
wenzelm@32960
   306
             else prod (signed_nclauses b t) (signed_nclauses b u)
haftmann@38795
   307
    | signed_nclauses b (Const(@{const_name HOL.disj},_) $ t $ u) =
wenzelm@32960
   308
        if b then prod (signed_nclauses b t) (signed_nclauses b u)
wenzelm@32960
   309
             else sum (signed_nclauses b t) (signed_nclauses b u)
haftmann@38786
   310
    | signed_nclauses b (Const(@{const_name HOL.implies},_) $ t $ u) =
wenzelm@32960
   311
        if b then prod (signed_nclauses (not b) t) (signed_nclauses b u)
wenzelm@32960
   312
             else sum (signed_nclauses (not b) t) (signed_nclauses b u)
haftmann@38864
   313
    | signed_nclauses b (Const(@{const_name HOL.eq}, Type ("fun", [T, _])) $ t $ u) =
wenzelm@32960
   314
        if T = HOLogic.boolT then (*Boolean equality is if-and-only-if*)
wenzelm@32960
   315
            if b then sum (prod (signed_nclauses (not b) t) (signed_nclauses b u))
wenzelm@32960
   316
                          (prod (signed_nclauses (not b) u) (signed_nclauses b t))
wenzelm@32960
   317
                 else sum (prod (signed_nclauses b t) (signed_nclauses b u))
wenzelm@32960
   318
                          (prod (signed_nclauses (not b) t) (signed_nclauses (not b) u))
wenzelm@32960
   319
        else 1
haftmann@38557
   320
    | signed_nclauses b (Const(@{const_name Ex}, _) $ Abs (_,_,t)) = signed_nclauses b t
haftmann@38557
   321
    | signed_nclauses b (Const(@{const_name All},_) $ Abs (_,_,t)) = signed_nclauses b t
paulson@26562
   322
    | signed_nclauses _ _ = 1; (* literal *)
blanchet@39269
   323
 in signed_nclauses true t end
blanchet@39269
   324
blanchet@39269
   325
fun has_too_many_clauses ctxt t =
blanchet@39269
   326
  let val max_cl = Config.get ctxt max_clauses in
blanchet@39328
   327
    estimated_num_clauses (max_cl + 1) t > max_cl
blanchet@39269
   328
  end
paulson@19894
   329
paulson@15579
   330
(*Replaces universally quantified variables by FREE variables -- because
paulson@24937
   331
  assumptions may not contain scheme variables.  Later, generalize using Variable.export. *)
paulson@24937
   332
local  
paulson@24937
   333
  val spec_var = Thm.dest_arg (Thm.dest_arg (#2 (Thm.dest_implies (Thm.cprop_of spec))));
paulson@24937
   334
  val spec_varT = #T (Thm.rep_cterm spec_var);
haftmann@38557
   335
  fun name_of (Const (@{const_name All}, _) $ Abs(x,_,_)) = x | name_of _ = Name.uu;
paulson@24937
   336
in  
paulson@24937
   337
  fun freeze_spec th ctxt =
paulson@24937
   338
    let
paulson@24937
   339
      val cert = Thm.cterm_of (ProofContext.theory_of ctxt);
paulson@24937
   340
      val ([x], ctxt') = Variable.variant_fixes [name_of (HOLogic.dest_Trueprop (concl_of th))] ctxt;
paulson@24937
   341
      val spec' = Thm.instantiate ([], [(spec_var, cert (Free (x, spec_varT)))]) spec;
paulson@24937
   342
    in (th RS spec', ctxt') end
paulson@24937
   343
end;
paulson@9840
   344
paulson@15998
   345
(*Used with METAHYPS below. There is one assumption, which gets bound to prem
paulson@15998
   346
  and then normalized via function nf. The normal form is given to resolve_tac,
paulson@22515
   347
  instantiate a Boolean variable created by resolution with disj_forward. Since
paulson@22515
   348
  (nf prem) returns a LIST of theorems, we can backtrack to get all combinations.*)
paulson@15579
   349
fun resop nf [prem] = resolve_tac (nf prem) 1;
paulson@9840
   350
blanchet@39037
   351
(* Any need to extend this list with "HOL.type_class", "HOL.eq_class",
blanchet@39037
   352
   and "Pure.term"? *)
haftmann@38557
   353
val has_meta_conn = exists_Const (member (op =) ["==", "==>", "=simp=>", "all", "prop"] o #1);
paulson@20417
   354
blanchet@37410
   355
fun apply_skolem_theorem (th, rls) =
blanchet@37398
   356
  let
blanchet@37410
   357
    fun tryall [] = raise THM ("apply_skolem_theorem", 0, th::rls)
blanchet@37398
   358
      | tryall (rl :: rls) =
blanchet@37398
   359
        first_order_resolve th rl handle THM _ => tryall rls
blanchet@37398
   360
  in tryall rls end
paulson@22515
   361
blanchet@37410
   362
(* Conjunctive normal form, adding clauses from th in front of ths (for foldr).
blanchet@37410
   363
   Strips universal quantifiers and breaks up conjunctions.
blanchet@37410
   364
   Eliminates existential quantifiers using Skolemization theorems. *)
blanchet@39886
   365
fun cnf old_skolem_ths ctxt (th, ths) =
wenzelm@33222
   366
  let val ctxtr = Unsynchronized.ref ctxt   (* FIXME ??? *)
paulson@24937
   367
      fun cnf_aux (th,ths) =
wenzelm@24300
   368
        if not (can HOLogic.dest_Trueprop (prop_of th)) then ths (*meta-level: ignore*)
haftmann@38795
   369
        else if not (has_conns [@{const_name All}, @{const_name Ex}, @{const_name HOL.conj}] (prop_of th))
wenzelm@32262
   370
        then nodups ctxt th :: ths (*no work to do, terminate*)
wenzelm@24300
   371
        else case head_of (HOLogic.dest_Trueprop (concl_of th)) of
haftmann@38795
   372
            Const (@{const_name HOL.conj}, _) => (*conjunction*)
wenzelm@24300
   373
                cnf_aux (th RS conjunct1, cnf_aux (th RS conjunct2, ths))
haftmann@38557
   374
          | Const (@{const_name All}, _) => (*universal quantifier*)
paulson@24937
   375
                let val (th',ctxt') = freeze_spec th (!ctxtr)
paulson@24937
   376
                in  ctxtr := ctxt'; cnf_aux (th', ths) end
haftmann@38557
   377
          | Const (@{const_name Ex}, _) =>
wenzelm@24300
   378
              (*existential quantifier: Insert Skolem functions*)
blanchet@39886
   379
              cnf_aux (apply_skolem_theorem (th, old_skolem_ths), ths)
haftmann@38795
   380
          | Const (@{const_name HOL.disj}, _) =>
wenzelm@24300
   381
              (*Disjunction of P, Q: Create new goal of proving ?P | ?Q and solve it using
wenzelm@24300
   382
                all combinations of converting P, Q to CNF.*)
wenzelm@24300
   383
              let val tac =
wenzelm@37781
   384
                  Misc_Legacy.METAHYPS (resop cnf_nil) 1 THEN
wenzelm@37781
   385
                   (fn st' => st' |> Misc_Legacy.METAHYPS (resop cnf_nil) 1)
wenzelm@24300
   386
              in  Seq.list_of (tac (th RS disj_forward)) @ ths  end
wenzelm@32262
   387
          | _ => nodups ctxt th :: ths  (*no work to do*)
paulson@19154
   388
      and cnf_nil th = cnf_aux (th,[])
blanchet@39269
   389
      val cls =
blanchet@39269
   390
            if has_too_many_clauses ctxt (concl_of th)
blanchet@39979
   391
            then (trace_msg ctxt (fn () => "cnf is ignoring: " ^ Display.string_of_thm ctxt th); ths)
wenzelm@32960
   392
            else cnf_aux (th,ths)
paulson@24937
   393
  in  (cls, !ctxtr)  end;
paulson@22515
   394
blanchet@39886
   395
fun make_cnf old_skolem_ths th ctxt = cnf old_skolem_ths ctxt (th, [])
paulson@20417
   396
blanchet@42335
   397
val disj_imp_cong =
blanchet@42335
   398
  @{lemma "[| P --> P'; Q --> Q'; P | Q |] ==> P' | Q'" by auto}
blanchet@42335
   399
blanchet@42335
   400
val impI = @{thm impI}
blanchet@42335
   401
blanchet@42335
   402
(* ### *)
blanchet@42335
   403
(* Match untyped terms. *)
blanchet@42335
   404
fun untyped_aconv (Const (a, _)) (Const(b, _)) = (a = b)
blanchet@42335
   405
  | untyped_aconv (Free (a, _)) (Free (b, _)) = (a = b)
blanchet@42335
   406
  | untyped_aconv (Var ((a, _), _)) (Var ((b, _), _)) = true
blanchet@42335
   407
  | untyped_aconv (Free (a, _)) (Var ((b, _), _)) = true
blanchet@42335
   408
  | untyped_aconv (Var ((a, _), _)) (Free (b, _)) = true
blanchet@42335
   409
  | untyped_aconv (Bound i) (Bound j) = (i = j)
blanchet@42335
   410
  | untyped_aconv (Abs (_, _, t)) (Abs (_, _, u)) = untyped_aconv t u
blanchet@42335
   411
  | untyped_aconv (t1 $ t2) (u1 $ u2) =
blanchet@42335
   412
    untyped_aconv t1 u1 andalso untyped_aconv t2 u2
blanchet@42335
   413
  | untyped_aconv _ _ = false
blanchet@42335
   414
blanchet@42335
   415
fun make_xxx_skolem ctxt skolem_ths th =
blanchet@42335
   416
  let
blanchet@42335
   417
    val thy = ProofContext.theory_of ctxt
blanchet@42335
   418
    fun do_connective fwd_thm t1 t2 =
blanchet@42335
   419
      do_formula t1
blanchet@42335
   420
      COMP rotate_prems 1 (do_formula t2 COMP (rotate_prems 2 fwd_thm))
blanchet@42335
   421
    and do_formula t =
blanchet@42335
   422
      case t of
blanchet@42335
   423
        @{const Trueprop} $ t' => do_formula t'
blanchet@42335
   424
      | @{const conj} $ t1 $ t2 => do_connective @{thm conj_forward} t1 t2
blanchet@42335
   425
      | @{const disj} $ t1 $ t2 => do_connective @{thm disj_forward} t1 t2
blanchet@42335
   426
      | Const (@{const_name Ex}, _) $ Abs _ =>
blanchet@42335
   427
        let
blanchet@42335
   428
          val th =
blanchet@42335
   429
            find_first (fn sko_th => (untyped_aconv (Logic.nth_prem (1, prop_of sko_th)) (HOLogic.mk_Trueprop t)))
blanchet@42335
   430
                       skolem_ths |> the
blanchet@42335
   431
        in
blanchet@42335
   432
          th
blanchet@42335
   433
          RS
blanchet@42335
   434
          do_formula (Logic.strip_imp_concl (prop_of th))
blanchet@42335
   435
        end
blanchet@42335
   436
      | _ => Thm.trivial (cterm_of thy (HOLogic.mk_Trueprop t))
blanchet@42335
   437
  in th COMP do_formula (HOLogic.dest_Trueprop (prop_of th)) end
blanchet@42335
   438
paulson@20417
   439
(*Generalization, removal of redundant equalities, removal of tautologies.*)
paulson@24937
   440
fun finish_cnf ths = filter (not o is_taut) (map refl_clause ths);
paulson@9840
   441
paulson@9840
   442
paulson@15579
   443
(**** Generation of contrapositives ****)
paulson@9840
   444
haftmann@38557
   445
fun is_left (Const (@{const_name Trueprop}, _) $
haftmann@38795
   446
               (Const (@{const_name HOL.disj}, _) $ (Const (@{const_name HOL.disj}, _) $ _ $ _) $ _)) = true
paulson@21102
   447
  | is_left _ = false;
wenzelm@24300
   448
paulson@15579
   449
(*Associate disjuctions to right -- make leftmost disjunct a LITERAL*)
wenzelm@24300
   450
fun assoc_right th =
paulson@21102
   451
  if is_left (prop_of th) then assoc_right (th RS disj_assoc)
paulson@21102
   452
  else th;
paulson@9840
   453
paulson@15579
   454
(*Must check for negative literal first!*)
paulson@15579
   455
val clause_rules = [disj_assoc, make_neg_rule, make_pos_rule];
paulson@9840
   456
paulson@15579
   457
(*For ordinary resolution. *)
paulson@15579
   458
val resolution_clause_rules = [disj_assoc, make_neg_rule', make_pos_rule'];
paulson@9840
   459
paulson@15579
   460
(*Create a goal or support clause, conclusing False*)
paulson@15579
   461
fun make_goal th =   (*Must check for negative literal first!*)
paulson@15579
   462
    make_goal (tryres(th, clause_rules))
paulson@15579
   463
  handle THM _ => tryres(th, [make_neg_goal, make_pos_goal]);
paulson@9840
   464
paulson@15579
   465
(*Sort clauses by number of literals*)
paulson@15579
   466
fun fewerlits(th1,th2) = nliterals(prop_of th1) < nliterals(prop_of th2);
paulson@9840
   467
paulson@18389
   468
fun sort_clauses ths = sort (make_ord fewerlits) ths;
paulson@9840
   469
blanchet@38099
   470
fun has_bool @{typ bool} = true
blanchet@38099
   471
  | has_bool (Type (_, Ts)) = exists has_bool Ts
blanchet@38099
   472
  | has_bool _ = false
blanchet@38099
   473
blanchet@38099
   474
fun has_fun (Type (@{type_name fun}, _)) = true
blanchet@38099
   475
  | has_fun (Type (_, Ts)) = exists has_fun Ts
blanchet@38099
   476
  | has_fun _ = false
wenzelm@24300
   477
wenzelm@24300
   478
(*Is the string the name of a connective? Really only | and Not can remain,
wenzelm@24300
   479
  since this code expects to be called on a clause form.*)
wenzelm@19875
   480
val is_conn = member (op =)
haftmann@38795
   481
    [@{const_name Trueprop}, @{const_name HOL.conj}, @{const_name HOL.disj},
haftmann@38786
   482
     @{const_name HOL.implies}, @{const_name Not},
haftmann@38557
   483
     @{const_name All}, @{const_name Ex}, @{const_name Ball}, @{const_name Bex}];
paulson@15613
   484
wenzelm@24300
   485
(*True if the term contains a function--not a logical connective--where the type
paulson@20524
   486
  of any argument contains bool.*)
wenzelm@24300
   487
val has_bool_arg_const =
paulson@15613
   488
    exists_Const
blanchet@38099
   489
      (fn (c,T) => not(is_conn c) andalso exists has_bool (binder_types T));
paulson@22381
   490
wenzelm@24300
   491
(*A higher-order instance of a first-order constant? Example is the definition of
haftmann@38622
   492
  one, 1, at a function type in theory Function_Algebras.*)
wenzelm@24300
   493
fun higher_inst_const thy (c,T) =
paulson@22381
   494
  case binder_types T of
paulson@22381
   495
      [] => false (*not a function type, OK*)
paulson@22381
   496
    | Ts => length (binder_types (Sign.the_const_type thy c)) <> length Ts;
paulson@22381
   497
paulson@24742
   498
(*Returns false if any Vars in the theorem mention type bool.
paulson@21102
   499
  Also rejects functions whose arguments are Booleans or other functions.*)
paulson@22381
   500
fun is_fol_term thy t =
haftmann@38557
   501
    Term.is_first_order ["all", @{const_name All}, @{const_name Ex}] t andalso
blanchet@38099
   502
    not (exists_subterm (fn Var (_, T) => has_bool T orelse has_fun T
blanchet@38099
   503
                           | _ => false) t orelse
blanchet@38099
   504
         has_bool_arg_const t orelse
wenzelm@24300
   505
         exists_Const (higher_inst_const thy) t orelse
wenzelm@24300
   506
         has_meta_conn t);
paulson@19204
   507
paulson@21102
   508
fun rigid t = not (is_Var (head_of t));
paulson@21102
   509
haftmann@38795
   510
fun ok4horn (Const (@{const_name Trueprop},_) $ (Const (@{const_name HOL.disj}, _) $ t $ _)) = rigid t
haftmann@38557
   511
  | ok4horn (Const (@{const_name Trueprop},_) $ t) = rigid t
paulson@21102
   512
  | ok4horn _ = false;
paulson@21102
   513
paulson@15579
   514
(*Create a meta-level Horn clause*)
wenzelm@24300
   515
fun make_horn crules th =
wenzelm@24300
   516
  if ok4horn (concl_of th)
paulson@21102
   517
  then make_horn crules (tryres(th,crules)) handle THM _ => th
paulson@21102
   518
  else th;
paulson@9840
   519
paulson@16563
   520
(*Generate Horn clauses for all contrapositives of a clause. The input, th,
paulson@16563
   521
  is a HOL disjunction.*)
wenzelm@33339
   522
fun add_contras crules th hcs =
blanchet@39328
   523
  let fun rots (0,_) = hcs
wenzelm@24300
   524
        | rots (k,th) = zero_var_indexes (make_horn crules th) ::
wenzelm@24300
   525
                        rots(k-1, assoc_right (th RS disj_comm))
paulson@15862
   526
  in case nliterals(prop_of th) of
wenzelm@24300
   527
        1 => th::hcs
paulson@15579
   528
      | n => rots(n, assoc_right th)
paulson@15579
   529
  end;
paulson@9840
   530
paulson@15579
   531
(*Use "theorem naming" to label the clauses*)
paulson@15579
   532
fun name_thms label =
wenzelm@33339
   533
    let fun name1 th (k, ths) =
wenzelm@27865
   534
          (k-1, Thm.put_name_hint (label ^ string_of_int k) th :: ths)
wenzelm@33339
   535
    in  fn ths => #2 (fold_rev name1 ths (length ths, []))  end;
paulson@9840
   536
paulson@16563
   537
(*Is the given disjunction an all-negative support clause?*)
paulson@15579
   538
fun is_negative th = forall (not o #1) (literals (prop_of th));
paulson@9840
   539
wenzelm@33317
   540
val neg_clauses = filter is_negative;
paulson@9840
   541
paulson@9840
   542
paulson@15579
   543
(***** MESON PROOF PROCEDURE *****)
paulson@9840
   544
haftmann@38557
   545
fun rhyps (Const("==>",_) $ (Const(@{const_name Trueprop},_) $ A) $ phi,
wenzelm@24300
   546
           As) = rhyps(phi, A::As)
paulson@15579
   547
  | rhyps (_, As) = As;
paulson@9840
   548
paulson@15579
   549
(** Detecting repeated assumptions in a subgoal **)
paulson@9840
   550
paulson@15579
   551
(*The stringtree detects repeated assumptions.*)
wenzelm@33245
   552
fun ins_term t net = Net.insert_term (op aconv) (t, t) net;
paulson@9840
   553
paulson@15579
   554
(*detects repetitions in a list of terms*)
paulson@15579
   555
fun has_reps [] = false
paulson@15579
   556
  | has_reps [_] = false
paulson@15579
   557
  | has_reps [t,u] = (t aconv u)
wenzelm@33245
   558
  | has_reps ts = (fold ins_term ts Net.empty; false) handle Net.INSERT => true;
paulson@9840
   559
paulson@15579
   560
(*Like TRYALL eq_assume_tac, but avoids expensive THEN calls*)
paulson@18508
   561
fun TRYING_eq_assume_tac 0 st = Seq.single st
paulson@18508
   562
  | TRYING_eq_assume_tac i st =
wenzelm@31945
   563
       TRYING_eq_assume_tac (i-1) (Thm.eq_assumption i st)
paulson@18508
   564
       handle THM _ => TRYING_eq_assume_tac (i-1) st;
paulson@18508
   565
paulson@18508
   566
fun TRYALL_eq_assume_tac st = TRYING_eq_assume_tac (nprems_of st) st;
paulson@9840
   567
paulson@15579
   568
(*Loop checking: FAIL if trying to prove the same thing twice
paulson@15579
   569
  -- if *ANY* subgoal has repeated literals*)
paulson@15579
   570
fun check_tac st =
paulson@15579
   571
  if exists (fn prem => has_reps (rhyps(prem,[]))) (prems_of st)
paulson@15579
   572
  then  Seq.empty  else  Seq.single st;
paulson@9840
   573
paulson@9840
   574
paulson@15579
   575
(* net_resolve_tac actually made it slower... *)
paulson@15579
   576
fun prolog_step_tac horns i =
paulson@15579
   577
    (assume_tac i APPEND resolve_tac horns i) THEN check_tac THEN
paulson@18508
   578
    TRYALL_eq_assume_tac;
paulson@9840
   579
paulson@9840
   580
(*Sums the sizes of the subgoals, ignoring hypotheses (ancestors)*)
wenzelm@33339
   581
fun addconcl prem sz = size_of_term (Logic.strip_assums_concl prem) + sz;
paulson@15579
   582
wenzelm@33339
   583
fun size_of_subgoals st = fold_rev addconcl (prems_of st) 0;
paulson@15579
   584
paulson@9840
   585
paulson@9840
   586
(*Negation Normal Form*)
paulson@9840
   587
val nnf_rls = [imp_to_disjD, iff_to_disjD, not_conjD, not_disjD,
wenzelm@9869
   588
               not_impD, not_iffD, not_allD, not_exD, not_notD];
paulson@15581
   589
haftmann@38557
   590
fun ok4nnf (Const (@{const_name Trueprop},_) $ (Const (@{const_name Not}, _) $ t)) = rigid t
haftmann@38557
   591
  | ok4nnf (Const (@{const_name Trueprop},_) $ t) = rigid t
paulson@21102
   592
  | ok4nnf _ = false;
paulson@21102
   593
wenzelm@32262
   594
fun make_nnf1 ctxt th =
wenzelm@24300
   595
  if ok4nnf (concl_of th)
wenzelm@32262
   596
  then make_nnf1 ctxt (tryres(th, nnf_rls))
paulson@28174
   597
    handle THM ("tryres", _, _) =>
wenzelm@32262
   598
        forward_res ctxt (make_nnf1 ctxt)
wenzelm@9869
   599
           (tryres(th, [conj_forward,disj_forward,all_forward,ex_forward]))
paulson@28174
   600
    handle THM ("tryres", _, _) => th
blanchet@38608
   601
  else th
paulson@9840
   602
wenzelm@24300
   603
(*The simplification removes defined quantifiers and occurrences of True and False.
paulson@20018
   604
  nnf_ss also includes the one-point simprocs,
paulson@18405
   605
  which are needed to avoid the various one-point theorems from generating junk clauses.*)
paulson@19894
   606
val nnf_simps =
blanchet@37539
   607
  @{thms simp_implies_def Ex1_def Ball_def Bex_def if_True if_False if_cancel
blanchet@37539
   608
         if_eq_cancel cases_simp}
blanchet@37539
   609
val nnf_extra_simps = @{thms split_ifs ex_simps all_simps simp_thms}
paulson@18405
   610
paulson@18405
   611
val nnf_ss =
wenzelm@24300
   612
  HOL_basic_ss addsimps nnf_extra_simps
wenzelm@24040
   613
    addsimprocs [defALL_regroup,defEX_regroup, @{simproc neq}, @{simproc let_simp}];
paulson@15872
   614
blanchet@38089
   615
val presimplify =
blanchet@39900
   616
  rewrite_rule (map safe_mk_meta_eq nnf_simps) #> simplify nnf_ss
blanchet@38089
   617
wenzelm@32262
   618
fun make_nnf ctxt th = case prems_of th of
blanchet@38606
   619
    [] => th |> presimplify |> make_nnf1 ctxt
paulson@21050
   620
  | _ => raise THM ("make_nnf: premises in argument", 0, [th]);
paulson@15581
   621
blanchet@39950
   622
fun choice_theorems thy =
blanchet@39950
   623
  try (Global_Theory.get_thm thy) "Hilbert_Choice.choice" |> the_list
blanchet@39950
   624
blanchet@39900
   625
(* Pull existential quantifiers to front. This accomplishes Skolemization for
blanchet@39900
   626
   clauses that arise from a subgoal. *)
blanchet@39950
   627
fun skolemize_with_choice_theorems ctxt choice_ths =
blanchet@39900
   628
  let
blanchet@39900
   629
    fun aux th =
blanchet@39900
   630
      if not (has_conns [@{const_name Ex}] (prop_of th)) then
blanchet@39900
   631
        th
blanchet@39900
   632
      else
blanchet@39901
   633
        tryres (th, choice_ths @
blanchet@39900
   634
                    [conj_exD1, conj_exD2, disj_exD, disj_exD1, disj_exD2])
blanchet@39900
   635
        |> aux
blanchet@39900
   636
        handle THM ("tryres", _, _) =>
blanchet@39900
   637
               tryres (th, [conj_forward, disj_forward, all_forward])
blanchet@39900
   638
               |> forward_res ctxt aux
blanchet@39900
   639
               |> aux
blanchet@39900
   640
               handle THM ("tryres", _, _) =>
blanchet@40262
   641
                      rename_bound_vars_RS th ex_forward
blanchet@39900
   642
                      |> forward_res ctxt aux
blanchet@39900
   643
  in aux o make_nnf ctxt end
paulson@29684
   644
blanchet@39950
   645
fun skolemize ctxt =
blanchet@39950
   646
  let val thy = ProofContext.theory_of ctxt in
blanchet@39950
   647
    skolemize_with_choice_theorems ctxt (choice_theorems thy)
blanchet@39950
   648
  end
blanchet@39904
   649
blanchet@39900
   650
(* "RS" can fail if "unify_search_bound" is too small. *)
blanchet@39900
   651
fun try_skolemize ctxt th =
blanchet@39904
   652
  try (skolemize ctxt) th
blanchet@39979
   653
  |> tap (fn NONE => trace_msg ctxt (fn () => "Failed to skolemize " ^
blanchet@39979
   654
                                              Display.string_of_thm ctxt th)
blanchet@39900
   655
           | _ => ())
paulson@25694
   656
wenzelm@33339
   657
fun add_clauses th cls =
wenzelm@36603
   658
  let val ctxt0 = Variable.global_thm_context th
wenzelm@33339
   659
      val (cnfs, ctxt) = make_cnf [] th ctxt0
paulson@24937
   660
  in Variable.export ctxt ctxt0 cnfs @ cls end;
paulson@9840
   661
paulson@9840
   662
(*Make clauses from a list of theorems, previously Skolemized and put into nnf.
paulson@9840
   663
  The resulting clauses are HOL disjunctions.*)
wenzelm@39235
   664
fun make_clauses_unsorted ths = fold_rev add_clauses ths [];
blanchet@35869
   665
val make_clauses = sort_clauses o make_clauses_unsorted;
quigley@15773
   666
paulson@16563
   667
(*Convert a list of clauses (disjunctions) to Horn clauses (contrapositives)*)
wenzelm@9869
   668
fun make_horns ths =
paulson@9840
   669
    name_thms "Horn#"
wenzelm@33339
   670
      (distinct Thm.eq_thm_prop (fold_rev (add_contras clause_rules) ths []));
paulson@9840
   671
paulson@9840
   672
(*Could simply use nprems_of, which would count remaining subgoals -- no
paulson@9840
   673
  discrimination as to their size!  With BEST_FIRST, fails for problem 41.*)
paulson@9840
   674
wenzelm@9869
   675
fun best_prolog_tac sizef horns =
paulson@9840
   676
    BEST_FIRST (has_fewer_prems 1, sizef) (prolog_step_tac horns 1);
paulson@9840
   677
wenzelm@9869
   678
fun depth_prolog_tac horns =
paulson@9840
   679
    DEPTH_FIRST (has_fewer_prems 1) (prolog_step_tac horns 1);
paulson@9840
   680
paulson@9840
   681
(*Return all negative clauses, as possible goal clauses*)
paulson@9840
   682
fun gocls cls = name_thms "Goal#" (map make_goal (neg_clauses cls));
paulson@9840
   683
wenzelm@32262
   684
fun skolemize_prems_tac ctxt prems =
blanchet@39900
   685
  cut_facts_tac (map_filter (try_skolemize ctxt) prems) THEN' REPEAT o etac exE
paulson@9840
   686
paulson@22546
   687
(*Basis of all meson-tactics.  Supplies cltac with clauses: HOL disjunctions.
paulson@22546
   688
  Function mkcl converts theorems to clauses.*)
blanchet@39037
   689
fun MESON preskolem_tac mkcl cltac ctxt i st =
paulson@16588
   690
  SELECT_GOAL
wenzelm@35625
   691
    (EVERY [Object_Logic.atomize_prems_tac 1,
paulson@23552
   692
            rtac ccontr 1,
blanchet@39269
   693
            preskolem_tac,
wenzelm@32283
   694
            Subgoal.FOCUS (fn {context = ctxt', prems = negs, ...} =>
blanchet@39269
   695
                      EVERY1 [skolemize_prems_tac ctxt negs,
wenzelm@32283
   696
                              Subgoal.FOCUS (cltac o mkcl o #prems) ctxt']) ctxt 1]) i st
wenzelm@24300
   697
  handle THM _ => no_tac st;    (*probably from make_meta_clause, not first-order*)
paulson@9840
   698
blanchet@39037
   699
paulson@9840
   700
(** Best-first search versions **)
paulson@9840
   701
paulson@16563
   702
(*ths is a list of additional clauses (HOL disjunctions) to use.*)
wenzelm@9869
   703
fun best_meson_tac sizef =
blanchet@39269
   704
  MESON all_tac make_clauses
paulson@22546
   705
    (fn cls =>
paulson@9840
   706
         THEN_BEST_FIRST (resolve_tac (gocls cls) 1)
paulson@9840
   707
                         (has_fewer_prems 1, sizef)
paulson@9840
   708
                         (prolog_step_tac (make_horns cls) 1));
paulson@9840
   709
paulson@9840
   710
(*First, breaks the goal into independent units*)
wenzelm@32262
   711
fun safe_best_meson_tac ctxt =
wenzelm@32262
   712
     SELECT_GOAL (TRY (safe_tac (claset_of ctxt)) THEN
wenzelm@32262
   713
                  TRYALL (best_meson_tac size_of_subgoals ctxt));
paulson@9840
   714
paulson@9840
   715
(** Depth-first search version **)
paulson@9840
   716
paulson@9840
   717
val depth_meson_tac =
blanchet@39269
   718
  MESON all_tac make_clauses
paulson@22546
   719
    (fn cls => EVERY [resolve_tac (gocls cls) 1, depth_prolog_tac (make_horns cls)]);
paulson@9840
   720
paulson@9840
   721
paulson@9840
   722
(** Iterative deepening version **)
paulson@9840
   723
paulson@9840
   724
(*This version does only one inference per call;
paulson@9840
   725
  having only one eq_assume_tac speeds it up!*)
wenzelm@9869
   726
fun prolog_step_tac' horns =
blanchet@39328
   727
    let val (horn0s, _) = (*0 subgoals vs 1 or more*)
paulson@9840
   728
            take_prefix Thm.no_prems horns
paulson@9840
   729
        val nrtac = net_resolve_tac horns
paulson@9840
   730
    in  fn i => eq_assume_tac i ORELSE
paulson@9840
   731
                match_tac horn0s i ORELSE  (*no backtracking if unit MATCHES*)
paulson@9840
   732
                ((assume_tac i APPEND nrtac i) THEN check_tac)
paulson@9840
   733
    end;
paulson@9840
   734
wenzelm@9869
   735
fun iter_deepen_prolog_tac horns =
wenzelm@38802
   736
    ITER_DEEPEN iter_deepen_limit (has_fewer_prems 1) (prolog_step_tac' horns);
paulson@9840
   737
blanchet@39269
   738
fun iter_deepen_meson_tac ctxt ths = ctxt |> MESON all_tac make_clauses
wenzelm@32091
   739
  (fn cls =>
wenzelm@32091
   740
    (case (gocls (cls @ ths)) of
wenzelm@32091
   741
      [] => no_tac  (*no goal clauses*)
wenzelm@32091
   742
    | goes =>
wenzelm@32091
   743
        let
wenzelm@32091
   744
          val horns = make_horns (cls @ ths)
blanchet@39979
   745
          val _ = trace_msg ctxt (fn () =>
wenzelm@32091
   746
            cat_lines ("meson method called:" ::
wenzelm@32262
   747
              map (Display.string_of_thm ctxt) (cls @ ths) @
wenzelm@32262
   748
              ["clauses:"] @ map (Display.string_of_thm ctxt) horns))
wenzelm@38802
   749
        in
wenzelm@38802
   750
          THEN_ITER_DEEPEN iter_deepen_limit
wenzelm@38802
   751
            (resolve_tac goes 1) (has_fewer_prems 1) (prolog_step_tac' horns)
wenzelm@38802
   752
        end));
paulson@9840
   753
wenzelm@32262
   754
fun meson_tac ctxt ths =
wenzelm@32262
   755
  SELECT_GOAL (TRY (safe_tac (claset_of ctxt)) THEN TRYALL (iter_deepen_meson_tac ctxt ths));
wenzelm@9869
   756
wenzelm@9869
   757
paulson@14813
   758
(**** Code to support ordinary resolution, rather than Model Elimination ****)
paulson@14744
   759
wenzelm@24300
   760
(*Convert a list of clauses (disjunctions) to meta-level clauses (==>),
paulson@15008
   761
  with no contrapositives, for ordinary resolution.*)
paulson@14744
   762
paulson@14744
   763
(*Rules to convert the head literal into a negated assumption. If the head
paulson@14744
   764
  literal is already negated, then using notEfalse instead of notEfalse'
paulson@14744
   765
  prevents a double negation.*)
wenzelm@27239
   766
val notEfalse = read_instantiate @{context} [(("R", 0), "False")] notE;
paulson@14744
   767
val notEfalse' = rotate_prems 1 notEfalse;
paulson@14744
   768
wenzelm@24300
   769
fun negated_asm_of_head th =
paulson@14744
   770
    th RS notEfalse handle THM _ => th RS notEfalse';
paulson@14744
   771
paulson@26066
   772
(*Converting one theorem from a disjunction to a meta-level clause*)
paulson@26066
   773
fun make_meta_clause th =
wenzelm@33832
   774
  let val (fth,thaw) = Drule.legacy_freeze_thaw_robust th
paulson@26066
   775
  in  
wenzelm@35845
   776
      (zero_var_indexes o Thm.varifyT_global o thaw 0 o 
paulson@26066
   777
       negated_asm_of_head o make_horn resolution_clause_rules) fth
paulson@26066
   778
  end;
wenzelm@24300
   779
paulson@14744
   780
fun make_meta_clauses ths =
paulson@14744
   781
    name_thms "MClause#"
wenzelm@22360
   782
      (distinct Thm.eq_thm_prop (map make_meta_clause ths));
paulson@14744
   783
blanchet@39979
   784
val setup =
blanchet@39979
   785
  trace_setup
blanchet@39979
   786
  #> max_clauses_setup
blanchet@39979
   787
paulson@9840
   788
end;