src/HOL/Tools/Meson/meson.ML
author blanchet
Tue May 22 16:59:27 2012 +0200 (2012-05-22)
changeset 47956 2a420750248b
parent 47954 aada9fd08b58
child 50695 cace30ea5a2c
permissions -rw-r--r--
don't apply "ext_cong_neq" to biimplications
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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 first_order_resolve : thm -> thm -> thm
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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:
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    thm list -> thm -> Proof.context
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    -> Proof.context -> thm list * Proof.context
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  val finish_cnf: thm list -> thm list
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  val presimplified_consts : string 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 cong_extensionalize_thm : theory -> thm -> thm
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  val abs_extensionalize_conv : Proof.context -> conv
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  val abs_extensionalize_thm : Proof.context -> thm -> thm
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  val make_clauses_unsorted: Proof.context -> thm list -> thm list
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  val make_clauses: Proof.context -> 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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end
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structure Meson : MESON =
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struct
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val trace = Attrib.setup_config_bool @{binding 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 = Attrib.setup_config_int @{binding meson_max_clauses} (K 60)
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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) (@{term False} :: 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))
wenzelm@32262
   292
    then nodups_aux ctxt [] th
paulson@24937
   293
    else th;
paulson@24937
   294
paulson@24937
   295
paulson@18389
   296
(*** The basic CNF transformation ***)
paulson@18389
   297
blanchet@39328
   298
fun estimated_num_clauses bound t =
paulson@26562
   299
 let
blanchet@39269
   300
  fun sum x y = if x < bound andalso y < bound then x+y else bound
blanchet@39269
   301
  fun prod x y = if x < bound andalso y < bound then x*y else bound
paulson@26562
   302
  
paulson@26562
   303
  (*Estimate the number of clauses in order to detect infeasible theorems*)
haftmann@38557
   304
  fun signed_nclauses b (Const(@{const_name Trueprop},_) $ t) = signed_nclauses b t
haftmann@38557
   305
    | signed_nclauses b (Const(@{const_name Not},_) $ t) = signed_nclauses (not b) t
haftmann@38795
   306
    | signed_nclauses b (Const(@{const_name HOL.conj},_) $ t $ u) =
wenzelm@32960
   307
        if b then sum (signed_nclauses b t) (signed_nclauses b u)
wenzelm@32960
   308
             else prod (signed_nclauses b t) (signed_nclauses b u)
haftmann@38795
   309
    | signed_nclauses b (Const(@{const_name HOL.disj},_) $ t $ u) =
wenzelm@32960
   310
        if b then prod (signed_nclauses b t) (signed_nclauses b u)
wenzelm@32960
   311
             else sum (signed_nclauses b t) (signed_nclauses b u)
haftmann@38786
   312
    | signed_nclauses b (Const(@{const_name HOL.implies},_) $ t $ u) =
wenzelm@32960
   313
        if b then prod (signed_nclauses (not b) t) (signed_nclauses b u)
wenzelm@32960
   314
             else sum (signed_nclauses (not b) t) (signed_nclauses b u)
haftmann@38864
   315
    | signed_nclauses b (Const(@{const_name HOL.eq}, Type ("fun", [T, _])) $ t $ u) =
wenzelm@32960
   316
        if T = HOLogic.boolT then (*Boolean equality is if-and-only-if*)
wenzelm@32960
   317
            if b then sum (prod (signed_nclauses (not b) t) (signed_nclauses b u))
wenzelm@32960
   318
                          (prod (signed_nclauses (not b) u) (signed_nclauses b t))
wenzelm@32960
   319
                 else sum (prod (signed_nclauses b t) (signed_nclauses b u))
wenzelm@32960
   320
                          (prod (signed_nclauses (not b) t) (signed_nclauses (not b) u))
wenzelm@32960
   321
        else 1
haftmann@38557
   322
    | signed_nclauses b (Const(@{const_name Ex}, _) $ Abs (_,_,t)) = signed_nclauses b t
haftmann@38557
   323
    | signed_nclauses b (Const(@{const_name All},_) $ Abs (_,_,t)) = signed_nclauses b t
paulson@26562
   324
    | signed_nclauses _ _ = 1; (* literal *)
blanchet@39269
   325
 in signed_nclauses true t end
blanchet@39269
   326
blanchet@39269
   327
fun has_too_many_clauses ctxt t =
blanchet@39269
   328
  let val max_cl = Config.get ctxt max_clauses in
blanchet@39328
   329
    estimated_num_clauses (max_cl + 1) t > max_cl
blanchet@39269
   330
  end
paulson@19894
   331
paulson@15579
   332
(*Replaces universally quantified variables by FREE variables -- because
paulson@24937
   333
  assumptions may not contain scheme variables.  Later, generalize using Variable.export. *)
paulson@24937
   334
local  
paulson@24937
   335
  val spec_var = Thm.dest_arg (Thm.dest_arg (#2 (Thm.dest_implies (Thm.cprop_of spec))));
paulson@24937
   336
  val spec_varT = #T (Thm.rep_cterm spec_var);
haftmann@38557
   337
  fun name_of (Const (@{const_name All}, _) $ Abs(x,_,_)) = x | name_of _ = Name.uu;
paulson@24937
   338
in  
paulson@24937
   339
  fun freeze_spec th ctxt =
paulson@24937
   340
    let
wenzelm@42361
   341
      val cert = Thm.cterm_of (Proof_Context.theory_of ctxt);
paulson@24937
   342
      val ([x], ctxt') = Variable.variant_fixes [name_of (HOLogic.dest_Trueprop (concl_of th))] ctxt;
paulson@24937
   343
      val spec' = Thm.instantiate ([], [(spec_var, cert (Free (x, spec_varT)))]) spec;
paulson@24937
   344
    in (th RS spec', ctxt') end
paulson@24937
   345
end;
paulson@9840
   346
paulson@15998
   347
(*Used with METAHYPS below. There is one assumption, which gets bound to prem
paulson@15998
   348
  and then normalized via function nf. The normal form is given to resolve_tac,
paulson@22515
   349
  instantiate a Boolean variable created by resolution with disj_forward. Since
paulson@22515
   350
  (nf prem) returns a LIST of theorems, we can backtrack to get all combinations.*)
paulson@15579
   351
fun resop nf [prem] = resolve_tac (nf prem) 1;
paulson@9840
   352
blanchet@37410
   353
fun apply_skolem_theorem (th, rls) =
blanchet@37398
   354
  let
blanchet@37410
   355
    fun tryall [] = raise THM ("apply_skolem_theorem", 0, th::rls)
blanchet@37398
   356
      | tryall (rl :: rls) =
blanchet@37398
   357
        first_order_resolve th rl handle THM _ => tryall rls
blanchet@37398
   358
  in tryall rls end
paulson@22515
   359
blanchet@37410
   360
(* Conjunctive normal form, adding clauses from th in front of ths (for foldr).
blanchet@37410
   361
   Strips universal quantifiers and breaks up conjunctions.
blanchet@37410
   362
   Eliminates existential quantifiers using Skolemization theorems. *)
blanchet@43964
   363
fun cnf old_skolem_ths ctxt ctxt0 (th, ths) =
blanchet@43964
   364
  let val ctxt0r = Unsynchronized.ref ctxt0   (* FIXME ??? *)
paulson@24937
   365
      fun cnf_aux (th,ths) =
wenzelm@24300
   366
        if not (can HOLogic.dest_Trueprop (prop_of th)) then ths (*meta-level: ignore*)
haftmann@38795
   367
        else if not (has_conns [@{const_name All}, @{const_name Ex}, @{const_name HOL.conj}] (prop_of th))
blanchet@43964
   368
        then nodups ctxt0 th :: ths (*no work to do, terminate*)
wenzelm@24300
   369
        else case head_of (HOLogic.dest_Trueprop (concl_of th)) of
haftmann@38795
   370
            Const (@{const_name HOL.conj}, _) => (*conjunction*)
wenzelm@24300
   371
                cnf_aux (th RS conjunct1, cnf_aux (th RS conjunct2, ths))
haftmann@38557
   372
          | Const (@{const_name All}, _) => (*universal quantifier*)
blanchet@43964
   373
                let val (th',ctxt0') = freeze_spec th (!ctxt0r)
blanchet@43964
   374
                in  ctxt0r := ctxt0'; cnf_aux (th', ths) end
haftmann@38557
   375
          | Const (@{const_name Ex}, _) =>
wenzelm@24300
   376
              (*existential quantifier: Insert Skolem functions*)
blanchet@39886
   377
              cnf_aux (apply_skolem_theorem (th, old_skolem_ths), ths)
haftmann@38795
   378
          | Const (@{const_name HOL.disj}, _) =>
wenzelm@24300
   379
              (*Disjunction of P, Q: Create new goal of proving ?P | ?Q and solve it using
wenzelm@24300
   380
                all combinations of converting P, Q to CNF.*)
wenzelm@24300
   381
              let val tac =
wenzelm@37781
   382
                  Misc_Legacy.METAHYPS (resop cnf_nil) 1 THEN
wenzelm@37781
   383
                   (fn st' => st' |> Misc_Legacy.METAHYPS (resop cnf_nil) 1)
wenzelm@24300
   384
              in  Seq.list_of (tac (th RS disj_forward)) @ ths  end
blanchet@43964
   385
          | _ => nodups ctxt0 th :: ths  (*no work to do*)
paulson@19154
   386
      and cnf_nil th = cnf_aux (th,[])
blanchet@39269
   387
      val cls =
blanchet@43964
   388
        if has_too_many_clauses ctxt (concl_of th) then
blanchet@43964
   389
          (trace_msg ctxt (fn () =>
blanchet@43964
   390
               "cnf is ignoring: " ^ Display.string_of_thm ctxt0 th); ths)
blanchet@43964
   391
        else
blanchet@43964
   392
          cnf_aux (th, ths)
blanchet@43964
   393
  in (cls, !ctxt0r) end
blanchet@43964
   394
fun make_cnf old_skolem_ths th ctxt ctxt0 =
blanchet@43964
   395
  cnf old_skolem_ths ctxt ctxt0 (th, [])
paulson@20417
   396
paulson@20417
   397
(*Generalization, removal of redundant equalities, removal of tautologies.*)
paulson@24937
   398
fun finish_cnf ths = filter (not o is_taut) (map refl_clause ths);
paulson@9840
   399
paulson@9840
   400
paulson@15579
   401
(**** Generation of contrapositives ****)
paulson@9840
   402
haftmann@38557
   403
fun is_left (Const (@{const_name Trueprop}, _) $
haftmann@38795
   404
               (Const (@{const_name HOL.disj}, _) $ (Const (@{const_name HOL.disj}, _) $ _ $ _) $ _)) = true
paulson@21102
   405
  | is_left _ = false;
wenzelm@24300
   406
paulson@15579
   407
(*Associate disjuctions to right -- make leftmost disjunct a LITERAL*)
wenzelm@24300
   408
fun assoc_right th =
paulson@21102
   409
  if is_left (prop_of th) then assoc_right (th RS disj_assoc)
paulson@21102
   410
  else th;
paulson@9840
   411
paulson@15579
   412
(*Must check for negative literal first!*)
paulson@15579
   413
val clause_rules = [disj_assoc, make_neg_rule, make_pos_rule];
paulson@9840
   414
paulson@15579
   415
(*For ordinary resolution. *)
paulson@15579
   416
val resolution_clause_rules = [disj_assoc, make_neg_rule', make_pos_rule'];
paulson@9840
   417
paulson@15579
   418
(*Create a goal or support clause, conclusing False*)
paulson@15579
   419
fun make_goal th =   (*Must check for negative literal first!*)
paulson@15579
   420
    make_goal (tryres(th, clause_rules))
paulson@15579
   421
  handle THM _ => tryres(th, [make_neg_goal, make_pos_goal]);
paulson@9840
   422
paulson@21102
   423
fun rigid t = not (is_Var (head_of t));
paulson@21102
   424
haftmann@38795
   425
fun ok4horn (Const (@{const_name Trueprop},_) $ (Const (@{const_name HOL.disj}, _) $ t $ _)) = rigid t
haftmann@38557
   426
  | ok4horn (Const (@{const_name Trueprop},_) $ t) = rigid t
paulson@21102
   427
  | ok4horn _ = false;
paulson@21102
   428
paulson@15579
   429
(*Create a meta-level Horn clause*)
wenzelm@24300
   430
fun make_horn crules th =
wenzelm@24300
   431
  if ok4horn (concl_of th)
paulson@21102
   432
  then make_horn crules (tryres(th,crules)) handle THM _ => th
paulson@21102
   433
  else th;
paulson@9840
   434
paulson@16563
   435
(*Generate Horn clauses for all contrapositives of a clause. The input, th,
paulson@16563
   436
  is a HOL disjunction.*)
wenzelm@33339
   437
fun add_contras crules th hcs =
blanchet@39328
   438
  let fun rots (0,_) = hcs
wenzelm@24300
   439
        | rots (k,th) = zero_var_indexes (make_horn crules th) ::
wenzelm@24300
   440
                        rots(k-1, assoc_right (th RS disj_comm))
paulson@15862
   441
  in case nliterals(prop_of th) of
wenzelm@24300
   442
        1 => th::hcs
paulson@15579
   443
      | n => rots(n, assoc_right th)
paulson@15579
   444
  end;
paulson@9840
   445
paulson@15579
   446
(*Use "theorem naming" to label the clauses*)
paulson@15579
   447
fun name_thms label =
wenzelm@33339
   448
    let fun name1 th (k, ths) =
wenzelm@27865
   449
          (k-1, Thm.put_name_hint (label ^ string_of_int k) th :: ths)
wenzelm@33339
   450
    in  fn ths => #2 (fold_rev name1 ths (length ths, []))  end;
paulson@9840
   451
paulson@16563
   452
(*Is the given disjunction an all-negative support clause?*)
paulson@15579
   453
fun is_negative th = forall (not o #1) (literals (prop_of th));
paulson@9840
   454
wenzelm@33317
   455
val neg_clauses = filter is_negative;
paulson@9840
   456
paulson@9840
   457
paulson@15579
   458
(***** MESON PROOF PROCEDURE *****)
paulson@9840
   459
haftmann@38557
   460
fun rhyps (Const("==>",_) $ (Const(@{const_name Trueprop},_) $ A) $ phi,
wenzelm@24300
   461
           As) = rhyps(phi, A::As)
paulson@15579
   462
  | rhyps (_, As) = As;
paulson@9840
   463
paulson@15579
   464
(** Detecting repeated assumptions in a subgoal **)
paulson@9840
   465
paulson@15579
   466
(*The stringtree detects repeated assumptions.*)
wenzelm@33245
   467
fun ins_term t net = Net.insert_term (op aconv) (t, t) net;
paulson@9840
   468
paulson@15579
   469
(*detects repetitions in a list of terms*)
paulson@15579
   470
fun has_reps [] = false
paulson@15579
   471
  | has_reps [_] = false
paulson@15579
   472
  | has_reps [t,u] = (t aconv u)
wenzelm@33245
   473
  | has_reps ts = (fold ins_term ts Net.empty; false) handle Net.INSERT => true;
paulson@9840
   474
paulson@15579
   475
(*Like TRYALL eq_assume_tac, but avoids expensive THEN calls*)
paulson@18508
   476
fun TRYING_eq_assume_tac 0 st = Seq.single st
paulson@18508
   477
  | TRYING_eq_assume_tac i st =
wenzelm@31945
   478
       TRYING_eq_assume_tac (i-1) (Thm.eq_assumption i st)
paulson@18508
   479
       handle THM _ => TRYING_eq_assume_tac (i-1) st;
paulson@18508
   480
paulson@18508
   481
fun TRYALL_eq_assume_tac st = TRYING_eq_assume_tac (nprems_of st) st;
paulson@9840
   482
paulson@15579
   483
(*Loop checking: FAIL if trying to prove the same thing twice
paulson@15579
   484
  -- if *ANY* subgoal has repeated literals*)
paulson@15579
   485
fun check_tac st =
paulson@15579
   486
  if exists (fn prem => has_reps (rhyps(prem,[]))) (prems_of st)
paulson@15579
   487
  then  Seq.empty  else  Seq.single st;
paulson@9840
   488
paulson@9840
   489
paulson@15579
   490
(* net_resolve_tac actually made it slower... *)
paulson@15579
   491
fun prolog_step_tac horns i =
paulson@15579
   492
    (assume_tac i APPEND resolve_tac horns i) THEN check_tac THEN
paulson@18508
   493
    TRYALL_eq_assume_tac;
paulson@9840
   494
paulson@9840
   495
(*Sums the sizes of the subgoals, ignoring hypotheses (ancestors)*)
wenzelm@33339
   496
fun addconcl prem sz = size_of_term (Logic.strip_assums_concl prem) + sz;
paulson@15579
   497
wenzelm@33339
   498
fun size_of_subgoals st = fold_rev addconcl (prems_of st) 0;
paulson@15579
   499
paulson@9840
   500
paulson@9840
   501
(*Negation Normal Form*)
paulson@9840
   502
val nnf_rls = [imp_to_disjD, iff_to_disjD, not_conjD, not_disjD,
wenzelm@9869
   503
               not_impD, not_iffD, not_allD, not_exD, not_notD];
paulson@15581
   504
haftmann@38557
   505
fun ok4nnf (Const (@{const_name Trueprop},_) $ (Const (@{const_name Not}, _) $ t)) = rigid t
haftmann@38557
   506
  | ok4nnf (Const (@{const_name Trueprop},_) $ t) = rigid t
paulson@21102
   507
  | ok4nnf _ = false;
paulson@21102
   508
wenzelm@32262
   509
fun make_nnf1 ctxt th =
wenzelm@24300
   510
  if ok4nnf (concl_of th)
wenzelm@32262
   511
  then make_nnf1 ctxt (tryres(th, nnf_rls))
paulson@28174
   512
    handle THM ("tryres", _, _) =>
wenzelm@32262
   513
        forward_res ctxt (make_nnf1 ctxt)
wenzelm@9869
   514
           (tryres(th, [conj_forward,disj_forward,all_forward,ex_forward]))
paulson@28174
   515
    handle THM ("tryres", _, _) => th
blanchet@38608
   516
  else th
paulson@9840
   517
wenzelm@24300
   518
(*The simplification removes defined quantifiers and occurrences of True and False.
paulson@20018
   519
  nnf_ss also includes the one-point simprocs,
paulson@18405
   520
  which are needed to avoid the various one-point theorems from generating junk clauses.*)
paulson@19894
   521
val nnf_simps =
blanchet@37539
   522
  @{thms simp_implies_def Ex1_def Ball_def Bex_def if_True if_False if_cancel
blanchet@37539
   523
         if_eq_cancel cases_simp}
blanchet@37539
   524
val nnf_extra_simps = @{thms split_ifs ex_simps all_simps simp_thms}
paulson@18405
   525
blanchet@43821
   526
(* FIXME: "let_simp" is probably redundant now that we also rewrite with
wenzelm@46904
   527
  "Let_def [abs_def]". *)
paulson@18405
   528
val nnf_ss =
wenzelm@24300
   529
  HOL_basic_ss addsimps nnf_extra_simps
blanchet@43264
   530
    addsimprocs [@{simproc defined_All}, @{simproc defined_Ex}, @{simproc neq},
blanchet@43264
   531
                 @{simproc let_simp}]
blanchet@43264
   532
blanchet@46093
   533
val presimplified_consts =
blanchet@43264
   534
  [@{const_name simp_implies}, @{const_name False}, @{const_name True},
blanchet@43264
   535
   @{const_name Ex1}, @{const_name Ball}, @{const_name Bex}, @{const_name If},
blanchet@43264
   536
   @{const_name Let}]
paulson@15872
   537
blanchet@46093
   538
val presimplify =
blanchet@42750
   539
  rewrite_rule (map safe_mk_meta_eq nnf_simps)
blanchet@42750
   540
  #> simplify nnf_ss
wenzelm@46904
   541
  #> Raw_Simplifier.rewrite_rule @{thms Let_def [abs_def]}
blanchet@38089
   542
wenzelm@32262
   543
fun make_nnf ctxt th = case prems_of th of
blanchet@46093
   544
    [] => th |> presimplify |> make_nnf1 ctxt
paulson@21050
   545
  | _ => raise THM ("make_nnf: premises in argument", 0, [th]);
paulson@15581
   546
blanchet@39950
   547
fun choice_theorems thy =
blanchet@39950
   548
  try (Global_Theory.get_thm thy) "Hilbert_Choice.choice" |> the_list
blanchet@39950
   549
blanchet@39900
   550
(* Pull existential quantifiers to front. This accomplishes Skolemization for
blanchet@39900
   551
   clauses that arise from a subgoal. *)
blanchet@39950
   552
fun skolemize_with_choice_theorems ctxt choice_ths =
blanchet@39900
   553
  let
blanchet@39900
   554
    fun aux th =
blanchet@39900
   555
      if not (has_conns [@{const_name Ex}] (prop_of th)) then
blanchet@39900
   556
        th
blanchet@39900
   557
      else
blanchet@39901
   558
        tryres (th, choice_ths @
blanchet@39900
   559
                    [conj_exD1, conj_exD2, disj_exD, disj_exD1, disj_exD2])
blanchet@39900
   560
        |> aux
blanchet@39900
   561
        handle THM ("tryres", _, _) =>
blanchet@39900
   562
               tryres (th, [conj_forward, disj_forward, all_forward])
blanchet@39900
   563
               |> forward_res ctxt aux
blanchet@39900
   564
               |> aux
blanchet@39900
   565
               handle THM ("tryres", _, _) =>
blanchet@40262
   566
                      rename_bound_vars_RS th ex_forward
blanchet@39900
   567
                      |> forward_res ctxt aux
blanchet@39900
   568
  in aux o make_nnf ctxt end
paulson@29684
   569
blanchet@39950
   570
fun skolemize ctxt =
wenzelm@42361
   571
  let val thy = Proof_Context.theory_of ctxt in
blanchet@39950
   572
    skolemize_with_choice_theorems ctxt (choice_theorems thy)
blanchet@39950
   573
  end
blanchet@39904
   574
blanchet@47954
   575
exception NO_F_PATTERN of unit
blanchet@47954
   576
blanchet@47956
   577
fun get_F_pattern T t u =
blanchet@47954
   578
  let
blanchet@47954
   579
    fun pat t u =
blanchet@47954
   580
      let
blanchet@47954
   581
        val ((head1, args1), (head2, args2)) = (t, u) |> pairself strip_comb
blanchet@47954
   582
      in
blanchet@47954
   583
        if head1 = head2 then
blanchet@47954
   584
          let val pats = map2 pat args1 args2 in
blanchet@47954
   585
            case filter (is_some o fst) pats of
blanchet@47954
   586
              [(SOME T, _)] => (SOME T, list_comb (head1, map snd pats))
blanchet@47954
   587
            | [] => (NONE, t)
blanchet@47954
   588
            | _ => raise NO_F_PATTERN ()
blanchet@47954
   589
          end
blanchet@47954
   590
        else
blanchet@47954
   591
          let val T = fastype_of t in
blanchet@47954
   592
            if can dest_funT T then (SOME T, Bound 0) else raise NO_F_PATTERN ()
blanchet@47954
   593
          end
blanchet@47954
   594
      end
blanchet@47954
   595
  in
blanchet@47956
   596
    if T = @{typ bool} then
blanchet@47956
   597
      NONE
blanchet@47956
   598
    else case pat t u of
blanchet@47956
   599
      (SOME T, p as _ $ _) => SOME (Abs (Name.uu, T, p))
blanchet@47956
   600
    | _ => NONE
blanchet@47954
   601
  end
blanchet@47956
   602
  handle NO_F_PATTERN () => NONE
blanchet@47954
   603
blanchet@47954
   604
val ext_cong_neq = @{thm ext_cong_neq}
blanchet@47954
   605
val F_ext_cong_neq =
blanchet@47954
   606
  Term.add_vars (prop_of @{thm ext_cong_neq}) []
blanchet@47954
   607
  |> filter (fn ((s, _), _) => s = "F")
blanchet@47954
   608
  |> the_single |> Var
blanchet@47954
   609
blanchet@47954
   610
(* Strengthens "f g ~= f h" to "f g ~= f h & (EX x. g x ~= h x)". *)
blanchet@47954
   611
fun cong_extensionalize_thm thy th =
blanchet@47954
   612
  case concl_of th of
blanchet@47956
   613
    @{const Trueprop} $ (@{const Not}
blanchet@47956
   614
        $ (Const (@{const_name HOL.eq}, Type (_, [T, _]))
blanchet@47956
   615
           $ (t as _ $ _) $ (u as _ $ _))) =>
blanchet@47956
   616
    (case get_F_pattern T t u of
blanchet@47954
   617
       SOME p =>
blanchet@47954
   618
       let val inst = [pairself (cterm_of thy) (F_ext_cong_neq, p)] in
blanchet@47954
   619
         th RS cterm_instantiate inst ext_cong_neq
blanchet@47954
   620
       end
blanchet@47954
   621
     | NONE => th)
blanchet@47954
   622
  | _ => th
blanchet@47954
   623
blanchet@42760
   624
(* Removes the lambdas from an equation of the form "t = (%x1 ... xn. u)". It
blanchet@42760
   625
   would be desirable to do this symmetrically but there's at least one existing
blanchet@42760
   626
   proof in "Tarski" that relies on the current behavior. *)
blanchet@47953
   627
fun abs_extensionalize_conv ctxt ct =
blanchet@42747
   628
  case term_of ct of
blanchet@42760
   629
    Const (@{const_name HOL.eq}, _) $ _ $ Abs _ =>
blanchet@42760
   630
    ct |> (Conv.rewr_conv @{thm fun_eq_iff [THEN eq_reflection]}
blanchet@47953
   631
           then_conv abs_extensionalize_conv ctxt)
blanchet@47953
   632
  | _ $ _ => Conv.comb_conv (abs_extensionalize_conv ctxt) ct
blanchet@47953
   633
  | Abs _ => Conv.abs_conv (abs_extensionalize_conv o snd) ctxt ct
blanchet@42747
   634
  | _ => Conv.all_conv ct
blanchet@42747
   635
blanchet@47953
   636
val abs_extensionalize_thm = Conv.fconv_rule o abs_extensionalize_conv
blanchet@47953
   637
blanchet@39900
   638
(* "RS" can fail if "unify_search_bound" is too small. *)
blanchet@46071
   639
fun try_skolemize_etc ctxt th =
blanchet@47954
   640
  let
blanchet@47954
   641
    val thy = Proof_Context.theory_of ctxt
blanchet@47954
   642
    val th = th |> cong_extensionalize_thm thy
blanchet@47954
   643
  in
blanchet@47954
   644
    [th]
blanchet@47954
   645
    (* Extensionalize lambdas in "th", because that makes sense and that's what
blanchet@47954
   646
       Sledgehammer does, but also keep an unextensionalized version of "th" for
blanchet@47954
   647
       backward compatibility. *)
blanchet@47954
   648
    |> insert Thm.eq_thm_prop (abs_extensionalize_thm ctxt th)
blanchet@47954
   649
    |> map_filter (fn th => th |> try (skolemize ctxt)
blanchet@47954
   650
                               |> tap (fn NONE =>
blanchet@47954
   651
                                          trace_msg ctxt (fn () =>
blanchet@47954
   652
                                              "Failed to skolemize " ^
blanchet@47954
   653
                                               Display.string_of_thm ctxt th)
blanchet@47954
   654
                                        | _ => ()))
blanchet@47954
   655
  end
paulson@25694
   656
blanchet@43964
   657
fun add_clauses ctxt th cls =
wenzelm@36603
   658
  let val ctxt0 = Variable.global_thm_context th
blanchet@43964
   659
      val (cnfs, ctxt) = make_cnf [] th ctxt ctxt0
paulson@24937
   660
  in Variable.export ctxt ctxt0 cnfs @ cls end;
paulson@9840
   661
blanchet@47035
   662
(*Sort clauses by number of literals*)
blanchet@47035
   663
fun fewerlits (th1, th2) = nliterals (prop_of th1) < nliterals (prop_of th2)
blanchet@47035
   664
paulson@9840
   665
(*Make clauses from a list of theorems, previously Skolemized and put into nnf.
paulson@9840
   666
  The resulting clauses are HOL disjunctions.*)
blanchet@43964
   667
fun make_clauses_unsorted ctxt ths = fold_rev (add_clauses ctxt) ths [];
blanchet@47035
   668
val make_clauses = sort (make_ord fewerlits) oo make_clauses_unsorted;
quigley@15773
   669
paulson@16563
   670
(*Convert a list of clauses (disjunctions) to Horn clauses (contrapositives)*)
wenzelm@9869
   671
fun make_horns ths =
paulson@9840
   672
    name_thms "Horn#"
wenzelm@33339
   673
      (distinct Thm.eq_thm_prop (fold_rev (add_contras clause_rules) ths []));
paulson@9840
   674
paulson@9840
   675
(*Could simply use nprems_of, which would count remaining subgoals -- no
paulson@9840
   676
  discrimination as to their size!  With BEST_FIRST, fails for problem 41.*)
paulson@9840
   677
wenzelm@9869
   678
fun best_prolog_tac sizef horns =
paulson@9840
   679
    BEST_FIRST (has_fewer_prems 1, sizef) (prolog_step_tac horns 1);
paulson@9840
   680
wenzelm@9869
   681
fun depth_prolog_tac horns =
paulson@9840
   682
    DEPTH_FIRST (has_fewer_prems 1) (prolog_step_tac horns 1);
paulson@9840
   683
paulson@9840
   684
(*Return all negative clauses, as possible goal clauses*)
paulson@9840
   685
fun gocls cls = name_thms "Goal#" (map make_goal (neg_clauses cls));
paulson@9840
   686
wenzelm@32262
   687
fun skolemize_prems_tac ctxt prems =
blanchet@42747
   688
  cut_facts_tac (maps (try_skolemize_etc ctxt) prems) THEN' REPEAT o etac exE
paulson@9840
   689
paulson@22546
   690
(*Basis of all meson-tactics.  Supplies cltac with clauses: HOL disjunctions.
paulson@22546
   691
  Function mkcl converts theorems to clauses.*)
blanchet@39037
   692
fun MESON preskolem_tac mkcl cltac ctxt i st =
paulson@16588
   693
  SELECT_GOAL
wenzelm@35625
   694
    (EVERY [Object_Logic.atomize_prems_tac 1,
paulson@23552
   695
            rtac ccontr 1,
blanchet@39269
   696
            preskolem_tac,
wenzelm@32283
   697
            Subgoal.FOCUS (fn {context = ctxt', prems = negs, ...} =>
blanchet@39269
   698
                      EVERY1 [skolemize_prems_tac ctxt negs,
wenzelm@32283
   699
                              Subgoal.FOCUS (cltac o mkcl o #prems) ctxt']) ctxt 1]) i st
wenzelm@24300
   700
  handle THM _ => no_tac st;    (*probably from make_meta_clause, not first-order*)
paulson@9840
   701
blanchet@39037
   702
paulson@9840
   703
(** Best-first search versions **)
paulson@9840
   704
paulson@16563
   705
(*ths is a list of additional clauses (HOL disjunctions) to use.*)
blanchet@43964
   706
fun best_meson_tac sizef ctxt =
blanchet@43964
   707
  MESON all_tac (make_clauses ctxt)
paulson@22546
   708
    (fn cls =>
paulson@9840
   709
         THEN_BEST_FIRST (resolve_tac (gocls cls) 1)
paulson@9840
   710
                         (has_fewer_prems 1, sizef)
blanchet@43964
   711
                         (prolog_step_tac (make_horns cls) 1))
blanchet@43964
   712
    ctxt
paulson@9840
   713
paulson@9840
   714
(*First, breaks the goal into independent units*)
wenzelm@32262
   715
fun safe_best_meson_tac ctxt =
wenzelm@42793
   716
  SELECT_GOAL (TRY (safe_tac ctxt) THEN TRYALL (best_meson_tac size_of_subgoals ctxt));
paulson@9840
   717
paulson@9840
   718
(** Depth-first search version **)
paulson@9840
   719
blanchet@43964
   720
fun depth_meson_tac ctxt =
blanchet@43964
   721
  MESON all_tac (make_clauses ctxt)
blanchet@43964
   722
    (fn cls => EVERY [resolve_tac (gocls cls) 1, depth_prolog_tac (make_horns cls)])
blanchet@43964
   723
    ctxt
paulson@9840
   724
paulson@9840
   725
(** Iterative deepening version **)
paulson@9840
   726
paulson@9840
   727
(*This version does only one inference per call;
paulson@9840
   728
  having only one eq_assume_tac speeds it up!*)
wenzelm@9869
   729
fun prolog_step_tac' horns =
blanchet@39328
   730
    let val (horn0s, _) = (*0 subgoals vs 1 or more*)
paulson@9840
   731
            take_prefix Thm.no_prems horns
paulson@9840
   732
        val nrtac = net_resolve_tac horns
paulson@9840
   733
    in  fn i => eq_assume_tac i ORELSE
paulson@9840
   734
                match_tac horn0s i ORELSE  (*no backtracking if unit MATCHES*)
paulson@9840
   735
                ((assume_tac i APPEND nrtac i) THEN check_tac)
paulson@9840
   736
    end;
paulson@9840
   737
wenzelm@9869
   738
fun iter_deepen_prolog_tac horns =
wenzelm@38802
   739
    ITER_DEEPEN iter_deepen_limit (has_fewer_prems 1) (prolog_step_tac' horns);
paulson@9840
   740
blanchet@43964
   741
fun iter_deepen_meson_tac ctxt ths = ctxt |> MESON all_tac (make_clauses ctxt)
wenzelm@32091
   742
  (fn cls =>
wenzelm@32091
   743
    (case (gocls (cls @ ths)) of
wenzelm@32091
   744
      [] => no_tac  (*no goal clauses*)
wenzelm@32091
   745
    | goes =>
wenzelm@32091
   746
        let
wenzelm@32091
   747
          val horns = make_horns (cls @ ths)
blanchet@39979
   748
          val _ = trace_msg ctxt (fn () =>
wenzelm@32091
   749
            cat_lines ("meson method called:" ::
wenzelm@32262
   750
              map (Display.string_of_thm ctxt) (cls @ ths) @
wenzelm@32262
   751
              ["clauses:"] @ map (Display.string_of_thm ctxt) horns))
wenzelm@38802
   752
        in
wenzelm@38802
   753
          THEN_ITER_DEEPEN iter_deepen_limit
wenzelm@38802
   754
            (resolve_tac goes 1) (has_fewer_prems 1) (prolog_step_tac' horns)
wenzelm@38802
   755
        end));
paulson@9840
   756
wenzelm@32262
   757
fun meson_tac ctxt ths =
wenzelm@42793
   758
  SELECT_GOAL (TRY (safe_tac ctxt) THEN TRYALL (iter_deepen_meson_tac ctxt ths));
wenzelm@9869
   759
wenzelm@9869
   760
paulson@14813
   761
(**** Code to support ordinary resolution, rather than Model Elimination ****)
paulson@14744
   762
wenzelm@24300
   763
(*Convert a list of clauses (disjunctions) to meta-level clauses (==>),
paulson@15008
   764
  with no contrapositives, for ordinary resolution.*)
paulson@14744
   765
paulson@14744
   766
(*Rules to convert the head literal into a negated assumption. If the head
paulson@14744
   767
  literal is already negated, then using notEfalse instead of notEfalse'
paulson@14744
   768
  prevents a double negation.*)
wenzelm@46503
   769
val notEfalse = @{lemma "~ P ==> P ==> False" by (rule notE)};
wenzelm@46503
   770
val notEfalse' = @{lemma "P ==> ~ P ==> False" by (rule notE)};
paulson@14744
   771
wenzelm@24300
   772
fun negated_asm_of_head th =
paulson@14744
   773
    th RS notEfalse handle THM _ => th RS notEfalse';
paulson@14744
   774
paulson@26066
   775
(*Converting one theorem from a disjunction to a meta-level clause*)
paulson@26066
   776
fun make_meta_clause th =
wenzelm@47022
   777
  let val (fth,thaw) = Misc_Legacy.freeze_thaw_robust th
paulson@26066
   778
  in  
wenzelm@35845
   779
      (zero_var_indexes o Thm.varifyT_global o thaw 0 o 
paulson@26066
   780
       negated_asm_of_head o make_horn resolution_clause_rules) fth
paulson@26066
   781
  end;
wenzelm@24300
   782
paulson@14744
   783
fun make_meta_clauses ths =
paulson@14744
   784
    name_thms "MClause#"
wenzelm@22360
   785
      (distinct Thm.eq_thm_prop (map make_meta_clause ths));
paulson@14744
   786
paulson@9840
   787
end;