src/HOL/Tools/meson.ML
author wenzelm
Fri Aug 17 00:03:50 2007 +0200 (2007-08-17)
changeset 24300 e170cee91c66
parent 24040 0d5cf52ebf87
child 24742 73b8b42a36b6
permissions -rw-r--r--
proper signature for Meson;
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(*  Title:      HOL/Tools/meson.ML
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    ID:         $Id$
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    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
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    Copyright   1992  University of Cambridge
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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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NEED TO SORT LITERALS BY # OF VARS, USING ==>I/E.  ELIMINATES NEED FOR
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FUNCTION nodups -- if done to goal clauses too!
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*)
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signature MESON =
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sig
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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 flexflex_first_order: thm -> thm
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  val size_of_subgoals: thm -> int
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  val make_cnf: thm list -> thm -> thm list
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  val finish_cnf: thm list -> thm list
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  val generalize: thm -> thm
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  val make_nnf: thm -> thm
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  val make_nnf1: thm -> thm
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  val skolemize: thm -> thm
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  val is_fol_term: theory -> term -> bool
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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: thm list -> int -> tactic
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  val MESON: (thm list -> thm list) -> (thm list -> tactic) -> int -> tactic
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  val best_meson_tac: (thm -> int) -> int -> tactic
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  val safe_best_meson_tac: int -> tactic
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  val depth_meson_tac: 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: 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_claset_tac: thm list -> claset -> int -> tactic
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  val meson_tac: int -> tactic
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  val negate_head: thm -> thm
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  val select_literal: int -> thm -> thm
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  val skolemize_tac: int -> tactic
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end
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structure Meson: MESON =
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struct
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val not_conjD = thm "meson_not_conjD";
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val not_disjD = thm "meson_not_disjD";
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val not_notD = thm "meson_not_notD";
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val not_allD = thm "meson_not_allD";
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val not_exD = thm "meson_not_exD";
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val imp_to_disjD = thm "meson_imp_to_disjD";
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val not_impD = thm "meson_not_impD";
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val iff_to_disjD = thm "meson_iff_to_disjD";
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val not_iffD = thm "meson_not_iffD";
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val conj_exD1 = thm "meson_conj_exD1";
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val conj_exD2 = thm "meson_conj_exD2";
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val disj_exD = thm "meson_disj_exD";
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val disj_exD1 = thm "meson_disj_exD1";
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val disj_exD2 = thm "meson_disj_exD2";
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val disj_assoc = thm "meson_disj_assoc";
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val disj_comm = thm "meson_disj_comm";
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val disj_FalseD1 = thm "meson_disj_FalseD1";
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val disj_FalseD2 = thm "meson_disj_FalseD2";
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(**** Operators for forward proof ****)
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(** First-order Resolution **)
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fun typ_pair_of (ix, (sort,ty)) = (TVar (ix,sort), ty);
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fun term_pair_of (ix, (ty,t)) = (Var (ix,ty), t);
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val Envir.Envir {asol = tenv0, iTs = tyenv0, ...} = Envir.empty 0
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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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  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 (tyenv,tenv) = Pattern.first_order_match thy (tmB,tmA) (tyenv0,tenv0)
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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
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  handle _ => raise THM ("first_order_resolve", 0, [thA,thB]);
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fun flexflex_first_order th =
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  case (tpairs_of th) of
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      [] => th
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    | pairs =>
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        let val thy = theory_of_thm th
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            val (tyenv,tenv) =
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                  foldl (uncurry (Pattern.first_order_match thy)) (tyenv0,tenv0) pairs
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            val t_pairs = map term_pair_of (Vartab.dest tenv)
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            val th' = Thm.instantiate ([], map (pairself (cterm_of thy)) t_pairs) th
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        in  th'  end
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        handle THM _ => th;
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(*raises exception if no rules apply -- unlike RL*)
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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) = (th RS 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 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 ("Bad proof state in forward_res, please inform lcp@cl.cam.ac.uk:\n" ^
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                   string_of_thm st ^
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                   "\nPremises:\n" ^
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                   cat_lines (map string_of_thm prems))
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  in
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    case Seq.pull (ALLGOALS (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(a,_)) = false
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        | has (Const("Trueprop",_) $ p) = has p
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        | has (Const("Not",_) $ p) = has p
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        | has (Const("op |",_) $ p $ q) = member (op =) bs "op |" orelse has p orelse has q
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        | has (Const("op &",_) $ p $ q) = member (op =) bs "op &" orelse has p orelse has q
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        | has (Const("All",_) $ Abs(_,_,p)) = member (op =) bs "All" orelse has p
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        | has (Const("Ex",_) $ Abs(_,_,p)) = member (op =) bs "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("Trueprop",_) $ P) = literals P
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  | literals (Const("op |",_) $ P $ Q) = literals P @ literals Q
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  | literals (Const("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 ("op |", _) $ 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("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("op =",_) $ t $ u) = t aconv u
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  | taut_poslit (Const("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"meson_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 ("op |", _) $ (Const ("op |", _) $ _ $ _) $ _) =>
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            refl_clause_aux n (th RS disj_assoc)    (*isolate an atom as first disjunct*)
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        | (Const ("op |", _) $ (Const("Not",_) $ (Const("op =",_) $ 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 ("op |", _) $ _ $ _) => 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 ("op |", _) $ P $ Q) =
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      notequal_lits_count P + notequal_lits_count Q
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  | notequal_lits_count (Const("Not",_) $ (Const("op =",_) $ _ $ _)) = 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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(*** The basic CNF transformation ***)
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val max_clauses = ref 40;
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fun sum x y = if x < !max_clauses andalso y < !max_clauses then x+y else !max_clauses;
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fun prod x y = if x < !max_clauses andalso y < !max_clauses then x*y else !max_clauses;
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(*Estimate the number of clauses in order to detect infeasible theorems*)
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fun signed_nclauses b (Const("Trueprop",_) $ t) = signed_nclauses b t
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  | signed_nclauses b (Const("Not",_) $ t) = signed_nclauses (not b) t
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  | signed_nclauses b (Const("op &",_) $ t $ u) =
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      if b then sum (signed_nclauses b t) (signed_nclauses b u)
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           else prod (signed_nclauses b t) (signed_nclauses b u)
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  | signed_nclauses b (Const("op |",_) $ t $ u) =
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      if b then prod (signed_nclauses b t) (signed_nclauses b u)
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           else sum (signed_nclauses b t) (signed_nclauses b u)
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  | signed_nclauses b (Const("op -->",_) $ t $ u) =
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      if b then prod (signed_nclauses (not b) t) (signed_nclauses b u)
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           else sum (signed_nclauses (not b) t) (signed_nclauses b u)
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  | signed_nclauses b (Const("op =", Type ("fun", [T, _])) $ t $ u) =
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      if T = HOLogic.boolT then (*Boolean equality is if-and-only-if*)
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          if b then sum (prod (signed_nclauses (not b) t) (signed_nclauses b u))
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                        (prod (signed_nclauses (not b) u) (signed_nclauses b t))
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               else sum (prod (signed_nclauses b t) (signed_nclauses b u))
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                        (prod (signed_nclauses (not b) t) (signed_nclauses (not b) u))
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      else 1
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  | signed_nclauses b (Const("Ex", _) $ Abs (_,_,t)) = signed_nclauses b t
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  | signed_nclauses b (Const("All",_) $ Abs (_,_,t)) = signed_nclauses b t
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  | signed_nclauses _ _ = 1; (* literal *)
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val nclauses = signed_nclauses true;
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fun too_many_clauses t = nclauses t >= !max_clauses;
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(*Replaces universally quantified variables by FREE variables -- because
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  assumptions may not contain scheme variables.  Later, we call "generalize". *)
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fun freeze_spec th =
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  let val newname = gensym "mes_"
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      val spec' = read_instantiate [("x", newname)] spec
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  in  th RS spec'  end;
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(*Used with METAHYPS below. There is one assumption, which gets bound to prem
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  and then normalized via function nf. The normal form is given to resolve_tac,
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  instantiate a Boolean variable created by resolution with disj_forward. Since
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  (nf prem) returns a LIST of theorems, we can backtrack to get all combinations.*)
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fun resop nf [prem] = resolve_tac (nf prem) 1;
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(*Any need to extend this list with
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  "HOL.type_class","HOL.eq_class","ProtoPure.term"?*)
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val has_meta_conn =
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    exists_Const (member (op =) ["==", "==>", "all", "prop"] o #1);
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fun apply_skolem_ths (th, rls) =
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  let fun tryall [] = raise THM("apply_skolem_ths", 0, th::rls)
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        | tryall (rl::rls) = (first_order_resolve th rl handle THM _ => tryall rls)
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  in  tryall rls  end;
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(*Conjunctive normal form, adding clauses from th in front of ths (for foldr).
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  Strips universal quantifiers and breaks up conjunctions.
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  Eliminates existential quantifiers using skoths: Skolemization theorems.*)
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fun cnf skoths (th,ths) =
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  let fun cnf_aux (th,ths) =
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        if not (can HOLogic.dest_Trueprop (prop_of th)) then ths (*meta-level: ignore*)
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        else if not (has_conns ["All","Ex","op &"] (prop_of th))
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        then th::ths (*no work to do, terminate*)
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        else case head_of (HOLogic.dest_Trueprop (concl_of th)) of
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            Const ("op &", _) => (*conjunction*)
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                cnf_aux (th RS conjunct1, cnf_aux (th RS conjunct2, ths))
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          | Const ("All", _) => (*universal quantifier*)
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                cnf_aux (freeze_spec th, ths)
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          | Const ("Ex", _) =>
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              (*existential quantifier: Insert Skolem functions*)
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              cnf_aux (apply_skolem_ths (th,skoths), ths)
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          | Const ("op |", _) =>
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              (*Disjunction of P, Q: Create new goal of proving ?P | ?Q and solve it using
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                all combinations of converting P, Q to CNF.*)
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              let val tac =
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                  (METAHYPS (resop cnf_nil) 1) THEN
wenzelm@24300
   288
                   (fn st' => st' |> METAHYPS (resop cnf_nil) 1)
wenzelm@24300
   289
              in  Seq.list_of (tac (th RS disj_forward)) @ ths  end
wenzelm@24300
   290
          | _ => (*no work to do*) th::ths
paulson@19154
   291
      and cnf_nil th = cnf_aux (th,[])
wenzelm@24300
   292
  in
wenzelm@24300
   293
    if too_many_clauses (concl_of th)
wenzelm@22130
   294
    then (Output.debug (fn () => ("cnf is ignoring: " ^ string_of_thm th)); ths)
paulson@19894
   295
    else cnf_aux (th,ths)
paulson@15998
   296
  end;
paulson@9840
   297
paulson@22515
   298
fun all_names (Const ("all", _) $ Abs(x,_,P)) = x :: all_names P
paulson@22515
   299
  | all_names _ = [];
paulson@22515
   300
paulson@22515
   301
fun new_names n [] = []
wenzelm@24300
   302
  | new_names n (x::xs) =
paulson@22515
   303
      if String.isPrefix "mes_" x then (x, radixstring(26,"A",n)) :: new_names (n+1) xs
paulson@22515
   304
      else new_names n xs;
paulson@22515
   305
paulson@22515
   306
(*The gensym names are ugly, so don't let the user see them. When forall_elim_vars
paulson@22515
   307
  is called, it will ensure that no name clauses ensue.*)
paulson@22515
   308
fun nice_names th =
paulson@22515
   309
  let val old_names = all_names (prop_of th)
paulson@22515
   310
  in  Drule.rename_bvars (new_names 0 old_names) th  end;
paulson@22515
   311
wenzelm@24300
   312
(*Convert all suitable free variables to schematic variables,
paulson@16012
   313
  but don't discharge assumptions.*)
paulson@22515
   314
fun generalize th = Thm.varifyT (forall_elim_vars 0 (nice_names (forall_intr_frees th)));
paulson@16012
   315
paulson@20417
   316
fun make_cnf skoths th = cnf skoths (th, []);
paulson@20417
   317
paulson@20417
   318
(*Generalization, removal of redundant equalities, removal of tautologies.*)
paulson@20417
   319
fun finish_cnf ths = filter (not o is_taut) (map (refl_clause o generalize) ths);
paulson@15998
   320
paulson@9840
   321
paulson@15579
   322
(**** Removal of duplicate literals ****)
paulson@9840
   323
paulson@15579
   324
(*Forward proof, passing extra assumptions as theorems to the tactic*)
paulson@15579
   325
fun forward_res2 nf hyps st =
paulson@15579
   326
  case Seq.pull
wenzelm@24300
   327
        (REPEAT
wenzelm@24300
   328
         (METAHYPS (fn major::minors => rtac (nf (minors@hyps) major) 1) 1)
wenzelm@24300
   329
         st)
paulson@15579
   330
  of SOME(th,_) => th
paulson@15579
   331
   | NONE => raise THM("forward_res2", 0, [st]);
paulson@9840
   332
paulson@15579
   333
(*Remove duplicates in P|Q by assuming ~P in Q
paulson@15579
   334
  rls (initially []) accumulates assumptions of the form P==>False*)
paulson@15579
   335
fun nodups_aux rls th = nodups_aux rls (th RS disj_assoc)
paulson@15579
   336
    handle THM _ => tryres(th,rls)
paulson@15579
   337
    handle THM _ => tryres(forward_res2 nodups_aux rls (th RS disj_forward2),
wenzelm@24300
   338
                           [disj_FalseD1, disj_FalseD2, asm_rl])
paulson@15579
   339
    handle THM _ => th;
paulson@9840
   340
paulson@15579
   341
(*Remove duplicate literals, if there are any*)
paulson@15579
   342
fun nodups th =
haftmann@20972
   343
  if has_duplicates (op =) (literals (prop_of th))
haftmann@20972
   344
    then nodups_aux [] th
haftmann@20972
   345
    else th;
paulson@9840
   346
paulson@9840
   347
paulson@15579
   348
(**** Generation of contrapositives ****)
paulson@9840
   349
wenzelm@24300
   350
fun is_left (Const ("Trueprop", _) $
paulson@21102
   351
               (Const ("op |", _) $ (Const ("op |", _) $ _ $ _) $ _)) = true
paulson@21102
   352
  | is_left _ = false;
wenzelm@24300
   353
paulson@15579
   354
(*Associate disjuctions to right -- make leftmost disjunct a LITERAL*)
wenzelm@24300
   355
fun assoc_right th =
paulson@21102
   356
  if is_left (prop_of th) then assoc_right (th RS disj_assoc)
paulson@21102
   357
  else th;
paulson@9840
   358
paulson@15579
   359
(*Must check for negative literal first!*)
paulson@15579
   360
val clause_rules = [disj_assoc, make_neg_rule, make_pos_rule];
paulson@9840
   361
paulson@15579
   362
(*For ordinary resolution. *)
paulson@15579
   363
val resolution_clause_rules = [disj_assoc, make_neg_rule', make_pos_rule'];
paulson@9840
   364
paulson@15579
   365
(*Create a goal or support clause, conclusing False*)
paulson@15579
   366
fun make_goal th =   (*Must check for negative literal first!*)
paulson@15579
   367
    make_goal (tryres(th, clause_rules))
paulson@15579
   368
  handle THM _ => tryres(th, [make_neg_goal, make_pos_goal]);
paulson@9840
   369
paulson@15579
   370
(*Sort clauses by number of literals*)
paulson@15579
   371
fun fewerlits(th1,th2) = nliterals(prop_of th1) < nliterals(prop_of th2);
paulson@9840
   372
paulson@18389
   373
fun sort_clauses ths = sort (make_ord fewerlits) ths;
paulson@9840
   374
paulson@15581
   375
(*True if the given type contains bool anywhere*)
paulson@15581
   376
fun has_bool (Type("bool",_)) = true
paulson@15581
   377
  | has_bool (Type(_, Ts)) = exists has_bool Ts
paulson@15581
   378
  | has_bool _ = false;
wenzelm@24300
   379
wenzelm@24300
   380
(*Is the string the name of a connective? Really only | and Not can remain,
wenzelm@24300
   381
  since this code expects to be called on a clause form.*)
wenzelm@19875
   382
val is_conn = member (op =)
wenzelm@24300
   383
    ["Trueprop", "op &", "op |", "op -->", "Not",
paulson@15613
   384
     "All", "Ex", "Ball", "Bex"];
paulson@15613
   385
wenzelm@24300
   386
(*True if the term contains a function--not a logical connective--where the type
paulson@20524
   387
  of any argument contains bool.*)
wenzelm@24300
   388
val has_bool_arg_const =
paulson@15613
   389
    exists_Const
paulson@15613
   390
      (fn (c,T) => not(is_conn c) andalso exists (has_bool) (binder_types T));
paulson@22381
   391
wenzelm@24300
   392
(*A higher-order instance of a first-order constant? Example is the definition of
paulson@22381
   393
  HOL.one, 1, at a function type in theory SetsAndFunctions.*)
wenzelm@24300
   394
fun higher_inst_const thy (c,T) =
paulson@22381
   395
  case binder_types T of
paulson@22381
   396
      [] => false (*not a function type, OK*)
paulson@22381
   397
    | Ts => length (binder_types (Sign.the_const_type thy c)) <> length Ts;
paulson@22381
   398
wenzelm@24300
   399
(*Raises an exception if any Vars in the theorem mention type bool.
paulson@21102
   400
  Also rejects functions whose arguments are Booleans or other functions.*)
paulson@22381
   401
fun is_fol_term thy t =
paulson@22381
   402
    Term.is_first_order ["all","All","Ex"] t andalso
paulson@19204
   403
    not (exists (has_bool o fastype_of) (term_vars t)  orelse
wenzelm@24300
   404
         has_bool_arg_const t  orelse
wenzelm@24300
   405
         exists_Const (higher_inst_const thy) t orelse
wenzelm@24300
   406
         has_meta_conn t);
paulson@19204
   407
paulson@21102
   408
fun rigid t = not (is_Var (head_of t));
paulson@21102
   409
paulson@21102
   410
fun ok4horn (Const ("Trueprop",_) $ (Const ("op |", _) $ t $ _)) = rigid t
paulson@21102
   411
  | ok4horn (Const ("Trueprop",_) $ t) = rigid t
paulson@21102
   412
  | ok4horn _ = false;
paulson@21102
   413
paulson@15579
   414
(*Create a meta-level Horn clause*)
wenzelm@24300
   415
fun make_horn crules th =
wenzelm@24300
   416
  if ok4horn (concl_of th)
paulson@21102
   417
  then make_horn crules (tryres(th,crules)) handle THM _ => th
paulson@21102
   418
  else th;
paulson@9840
   419
paulson@16563
   420
(*Generate Horn clauses for all contrapositives of a clause. The input, th,
paulson@16563
   421
  is a HOL disjunction.*)
paulson@15579
   422
fun add_contras crules (th,hcs) =
paulson@15579
   423
  let fun rots (0,th) = hcs
wenzelm@24300
   424
        | rots (k,th) = zero_var_indexes (make_horn crules th) ::
wenzelm@24300
   425
                        rots(k-1, assoc_right (th RS disj_comm))
paulson@15862
   426
  in case nliterals(prop_of th) of
wenzelm@24300
   427
        1 => th::hcs
paulson@15579
   428
      | n => rots(n, assoc_right th)
paulson@15579
   429
  end;
paulson@9840
   430
paulson@15579
   431
(*Use "theorem naming" to label the clauses*)
paulson@15579
   432
fun name_thms label =
paulson@15579
   433
    let fun name1 (th, (k,ths)) =
wenzelm@24300
   434
          (k-1, PureThy.put_name_hint (label ^ string_of_int k) th :: ths)
paulson@15579
   435
    in  fn ths => #2 (foldr name1 (length ths, []) ths)  end;
paulson@9840
   436
paulson@16563
   437
(*Is the given disjunction an all-negative support clause?*)
paulson@15579
   438
fun is_negative th = forall (not o #1) (literals (prop_of th));
paulson@9840
   439
paulson@15579
   440
val neg_clauses = List.filter is_negative;
paulson@9840
   441
paulson@9840
   442
paulson@15579
   443
(***** MESON PROOF PROCEDURE *****)
paulson@9840
   444
paulson@15579
   445
fun rhyps (Const("==>",_) $ (Const("Trueprop",_) $ A) $ phi,
wenzelm@24300
   446
           As) = rhyps(phi, A::As)
paulson@15579
   447
  | rhyps (_, As) = As;
paulson@9840
   448
paulson@15579
   449
(** Detecting repeated assumptions in a subgoal **)
paulson@9840
   450
paulson@15579
   451
(*The stringtree detects repeated assumptions.*)
wenzelm@16801
   452
fun ins_term (net,t) = Net.insert_term (op aconv) (t,t) net;
paulson@9840
   453
paulson@15579
   454
(*detects repetitions in a list of terms*)
paulson@15579
   455
fun has_reps [] = false
paulson@15579
   456
  | has_reps [_] = false
paulson@15579
   457
  | has_reps [t,u] = (t aconv u)
paulson@15579
   458
  | has_reps ts = (Library.foldl ins_term (Net.empty, ts);  false)
wenzelm@24300
   459
                  handle Net.INSERT => true;
paulson@9840
   460
paulson@15579
   461
(*Like TRYALL eq_assume_tac, but avoids expensive THEN calls*)
paulson@18508
   462
fun TRYING_eq_assume_tac 0 st = Seq.single st
paulson@18508
   463
  | TRYING_eq_assume_tac i st =
paulson@18508
   464
       TRYING_eq_assume_tac (i-1) (eq_assumption i st)
paulson@18508
   465
       handle THM _ => TRYING_eq_assume_tac (i-1) st;
paulson@18508
   466
paulson@18508
   467
fun TRYALL_eq_assume_tac st = TRYING_eq_assume_tac (nprems_of st) st;
paulson@9840
   468
paulson@15579
   469
(*Loop checking: FAIL if trying to prove the same thing twice
paulson@15579
   470
  -- if *ANY* subgoal has repeated literals*)
paulson@15579
   471
fun check_tac st =
paulson@15579
   472
  if exists (fn prem => has_reps (rhyps(prem,[]))) (prems_of st)
paulson@15579
   473
  then  Seq.empty  else  Seq.single st;
paulson@9840
   474
paulson@9840
   475
paulson@15579
   476
(* net_resolve_tac actually made it slower... *)
paulson@15579
   477
fun prolog_step_tac horns i =
paulson@15579
   478
    (assume_tac i APPEND resolve_tac horns i) THEN check_tac THEN
paulson@18508
   479
    TRYALL_eq_assume_tac;
paulson@9840
   480
paulson@9840
   481
(*Sums the sizes of the subgoals, ignoring hypotheses (ancestors)*)
paulson@15579
   482
fun addconcl(prem,sz) = size_of_term(Logic.strip_assums_concl prem) + sz
paulson@15579
   483
paulson@15579
   484
fun size_of_subgoals st = foldr addconcl 0 (prems_of st);
paulson@15579
   485
paulson@9840
   486
paulson@9840
   487
(*Negation Normal Form*)
paulson@9840
   488
val nnf_rls = [imp_to_disjD, iff_to_disjD, not_conjD, not_disjD,
wenzelm@9869
   489
               not_impD, not_iffD, not_allD, not_exD, not_notD];
paulson@15581
   490
paulson@21102
   491
fun ok4nnf (Const ("Trueprop",_) $ (Const ("Not", _) $ t)) = rigid t
paulson@21102
   492
  | ok4nnf (Const ("Trueprop",_) $ t) = rigid t
paulson@21102
   493
  | ok4nnf _ = false;
paulson@21102
   494
wenzelm@24300
   495
fun make_nnf1 th =
wenzelm@24300
   496
  if ok4nnf (concl_of th)
paulson@21102
   497
  then make_nnf1 (tryres(th, nnf_rls))
wenzelm@9869
   498
    handle THM _ =>
paulson@15581
   499
        forward_res make_nnf1
wenzelm@9869
   500
           (tryres(th, [conj_forward,disj_forward,all_forward,ex_forward]))
paulson@21102
   501
    handle THM _ => th
paulson@21102
   502
  else th;
paulson@9840
   503
wenzelm@24300
   504
(*The simplification removes defined quantifiers and occurrences of True and False.
paulson@20018
   505
  nnf_ss also includes the one-point simprocs,
paulson@18405
   506
  which are needed to avoid the various one-point theorems from generating junk clauses.*)
paulson@19894
   507
val nnf_simps =
wenzelm@24300
   508
     [simp_implies_def, Ex1_def, Ball_def, Bex_def, if_True,
paulson@19894
   509
      if_False, if_cancel, if_eq_cancel, cases_simp];
paulson@19894
   510
val nnf_extra_simps =
paulson@19894
   511
      thms"split_ifs" @ ex_simps @ all_simps @ simp_thms;
paulson@18405
   512
paulson@18405
   513
val nnf_ss =
wenzelm@24300
   514
  HOL_basic_ss addsimps nnf_extra_simps
wenzelm@24040
   515
    addsimprocs [defALL_regroup,defEX_regroup, @{simproc neq}, @{simproc let_simp}];
paulson@15872
   516
paulson@21050
   517
fun make_nnf th = case prems_of th of
paulson@21050
   518
    [] => th |> rewrite_rule (map safe_mk_meta_eq nnf_simps)
wenzelm@24300
   519
             |> simplify nnf_ss
wenzelm@24300
   520
             |> make_nnf1
paulson@21050
   521
  | _ => raise THM ("make_nnf: premises in argument", 0, [th]);
paulson@15581
   522
paulson@15965
   523
(*Pull existential quantifiers to front. This accomplishes Skolemization for
paulson@15965
   524
  clauses that arise from a subgoal.*)
wenzelm@9869
   525
fun skolemize th =
paulson@20134
   526
  if not (has_conns ["Ex"] (prop_of th)) then th
quigley@15773
   527
  else (skolemize (tryres(th, [choice, conj_exD1, conj_exD2,
quigley@15679
   528
                              disj_exD, disj_exD1, disj_exD2])))
wenzelm@9869
   529
    handle THM _ =>
wenzelm@9869
   530
        skolemize (forward_res skolemize
wenzelm@9869
   531
                   (tryres (th, [conj_forward, disj_forward, all_forward])))
paulson@9840
   532
    handle THM _ => forward_res skolemize (th RS ex_forward);
paulson@9840
   533
paulson@9840
   534
paulson@9840
   535
(*Make clauses from a list of theorems, previously Skolemized and put into nnf.
paulson@9840
   536
  The resulting clauses are HOL disjunctions.*)
wenzelm@9869
   537
fun make_clauses ths =
paulson@15998
   538
    (sort_clauses (map (generalize o nodups) (foldr (cnf[]) [] ths)));
quigley@15773
   539
paulson@16563
   540
(*Convert a list of clauses (disjunctions) to Horn clauses (contrapositives)*)
wenzelm@9869
   541
fun make_horns ths =
paulson@9840
   542
    name_thms "Horn#"
wenzelm@22360
   543
      (distinct Thm.eq_thm_prop (foldr (add_contras clause_rules) [] ths));
paulson@9840
   544
paulson@9840
   545
(*Could simply use nprems_of, which would count remaining subgoals -- no
paulson@9840
   546
  discrimination as to their size!  With BEST_FIRST, fails for problem 41.*)
paulson@9840
   547
wenzelm@9869
   548
fun best_prolog_tac sizef horns =
paulson@9840
   549
    BEST_FIRST (has_fewer_prems 1, sizef) (prolog_step_tac horns 1);
paulson@9840
   550
wenzelm@9869
   551
fun depth_prolog_tac horns =
paulson@9840
   552
    DEPTH_FIRST (has_fewer_prems 1) (prolog_step_tac horns 1);
paulson@9840
   553
paulson@9840
   554
(*Return all negative clauses, as possible goal clauses*)
paulson@9840
   555
fun gocls cls = name_thms "Goal#" (map make_goal (neg_clauses cls));
paulson@9840
   556
paulson@15008
   557
fun skolemize_prems_tac prems =
paulson@9840
   558
    cut_facts_tac (map (skolemize o make_nnf) prems)  THEN'
paulson@9840
   559
    REPEAT o (etac exE);
paulson@9840
   560
paulson@22546
   561
(*Basis of all meson-tactics.  Supplies cltac with clauses: HOL disjunctions.
paulson@22546
   562
  Function mkcl converts theorems to clauses.*)
wenzelm@24300
   563
fun MESON mkcl cltac i st =
paulson@16588
   564
  SELECT_GOAL
wenzelm@23590
   565
    (EVERY [ObjectLogic.atomize_prems_tac 1,
paulson@23552
   566
            rtac ccontr 1,
wenzelm@24300
   567
            METAHYPS (fn negs =>
wenzelm@24300
   568
                      EVERY1 [skolemize_prems_tac negs,
wenzelm@24300
   569
                              METAHYPS (cltac o mkcl)]) 1]) i st
wenzelm@24300
   570
  handle THM _ => no_tac st;    (*probably from make_meta_clause, not first-order*)
paulson@9840
   571
paulson@9840
   572
(** Best-first search versions **)
paulson@9840
   573
paulson@16563
   574
(*ths is a list of additional clauses (HOL disjunctions) to use.*)
wenzelm@9869
   575
fun best_meson_tac sizef =
wenzelm@24300
   576
  MESON make_clauses
paulson@22546
   577
    (fn cls =>
paulson@9840
   578
         THEN_BEST_FIRST (resolve_tac (gocls cls) 1)
paulson@9840
   579
                         (has_fewer_prems 1, sizef)
paulson@9840
   580
                         (prolog_step_tac (make_horns cls) 1));
paulson@9840
   581
paulson@9840
   582
(*First, breaks the goal into independent units*)
paulson@9840
   583
val safe_best_meson_tac =
wenzelm@23894
   584
     SELECT_GOAL (TRY (CLASET safe_tac) THEN
paulson@9840
   585
                  TRYALL (best_meson_tac size_of_subgoals));
paulson@9840
   586
paulson@9840
   587
(** Depth-first search version **)
paulson@9840
   588
paulson@9840
   589
val depth_meson_tac =
paulson@22546
   590
  MESON make_clauses
paulson@22546
   591
    (fn cls => EVERY [resolve_tac (gocls cls) 1, depth_prolog_tac (make_horns cls)]);
paulson@9840
   592
paulson@9840
   593
paulson@9840
   594
(** Iterative deepening version **)
paulson@9840
   595
paulson@9840
   596
(*This version does only one inference per call;
paulson@9840
   597
  having only one eq_assume_tac speeds it up!*)
wenzelm@9869
   598
fun prolog_step_tac' horns =
paulson@9840
   599
    let val (horn0s, hornps) = (*0 subgoals vs 1 or more*)
paulson@9840
   600
            take_prefix Thm.no_prems horns
paulson@9840
   601
        val nrtac = net_resolve_tac horns
paulson@9840
   602
    in  fn i => eq_assume_tac i ORELSE
paulson@9840
   603
                match_tac horn0s i ORELSE  (*no backtracking if unit MATCHES*)
paulson@9840
   604
                ((assume_tac i APPEND nrtac i) THEN check_tac)
paulson@9840
   605
    end;
paulson@9840
   606
wenzelm@9869
   607
fun iter_deepen_prolog_tac horns =
paulson@9840
   608
    ITER_DEEPEN (has_fewer_prems 1) (prolog_step_tac' horns);
paulson@9840
   609
wenzelm@24300
   610
fun iter_deepen_meson_tac ths = MESON make_clauses
paulson@21095
   611
 (fn cls =>
paulson@21095
   612
      case (gocls (cls@ths)) of
wenzelm@24300
   613
           [] => no_tac  (*no goal clauses*)
wenzelm@24300
   614
         | goes =>
wenzelm@24300
   615
             let val horns = make_horns (cls@ths)
wenzelm@24300
   616
                 val _ =
wenzelm@24300
   617
                     Output.debug (fn () => ("meson method called:\n" ^
wenzelm@24300
   618
                                  space_implode "\n" (map string_of_thm (cls@ths)) ^
wenzelm@24300
   619
                                  "\nclauses:\n" ^
wenzelm@24300
   620
                                  space_implode "\n" (map string_of_thm horns)))
wenzelm@24300
   621
             in THEN_ITER_DEEPEN (resolve_tac goes 1) (has_fewer_prems 1) (prolog_step_tac' horns)
wenzelm@24300
   622
             end
paulson@21095
   623
 );
paulson@9840
   624
paulson@16563
   625
fun meson_claset_tac ths cs =
paulson@16563
   626
  SELECT_GOAL (TRY (safe_tac cs) THEN TRYALL (iter_deepen_meson_tac ths));
wenzelm@9869
   627
paulson@16563
   628
val meson_tac = CLASET' (meson_claset_tac []);
wenzelm@9869
   629
wenzelm@9869
   630
paulson@14813
   631
(**** Code to support ordinary resolution, rather than Model Elimination ****)
paulson@14744
   632
wenzelm@24300
   633
(*Convert a list of clauses (disjunctions) to meta-level clauses (==>),
paulson@15008
   634
  with no contrapositives, for ordinary resolution.*)
paulson@14744
   635
paulson@14744
   636
(*Rules to convert the head literal into a negated assumption. If the head
paulson@14744
   637
  literal is already negated, then using notEfalse instead of notEfalse'
paulson@14744
   638
  prevents a double negation.*)
paulson@14744
   639
val notEfalse = read_instantiate [("R","False")] notE;
paulson@14744
   640
val notEfalse' = rotate_prems 1 notEfalse;
paulson@14744
   641
wenzelm@24300
   642
fun negated_asm_of_head th =
paulson@14744
   643
    th RS notEfalse handle THM _ => th RS notEfalse';
paulson@14744
   644
paulson@14744
   645
(*Converting one clause*)
wenzelm@24300
   646
val make_meta_clause =
paulson@22646
   647
  zero_var_indexes o negated_asm_of_head o make_horn resolution_clause_rules;
wenzelm@24300
   648
paulson@14744
   649
fun make_meta_clauses ths =
paulson@14744
   650
    name_thms "MClause#"
wenzelm@22360
   651
      (distinct Thm.eq_thm_prop (map make_meta_clause ths));
paulson@14744
   652
paulson@14744
   653
(*Permute a rule's premises to move the i-th premise to the last position.*)
paulson@14744
   654
fun make_last i th =
wenzelm@24300
   655
  let val n = nprems_of th
wenzelm@24300
   656
  in  if 1 <= i andalso i <= n
paulson@14744
   657
      then Thm.permute_prems (i-1) 1 th
paulson@15118
   658
      else raise THM("select_literal", i, [th])
paulson@14744
   659
  end;
paulson@14744
   660
paulson@14744
   661
(*Maps a rule that ends "... ==> P ==> False" to "... ==> ~P" while suppressing
paulson@14744
   662
  double-negations.*)
paulson@14744
   663
val negate_head = rewrite_rule [atomize_not, not_not RS eq_reflection];
paulson@14744
   664
paulson@14744
   665
(*Maps the clause  [P1,...Pn]==>False to [P1,...,P(i-1),P(i+1),...Pn] ==> ~P*)
paulson@14744
   666
fun select_literal i cl = negate_head (make_last i cl);
paulson@14744
   667
paulson@18508
   668
paulson@14813
   669
(*Top-level Skolemization. Allows part of the conversion to clauses to be
wenzelm@24300
   670
  expressed as a tactic (or Isar method).  Each assumption of the selected
paulson@14813
   671
  goal is converted to NNF and then its existential quantifiers are pulled
wenzelm@24300
   672
  to the front. Finally, all existential quantifiers are eliminated,
paulson@14813
   673
  leaving !!-quantified variables. Perhaps Safe_tac should follow, but it
paulson@14813
   674
  might generate many subgoals.*)
mengj@18194
   675
wenzelm@24300
   676
fun skolemize_tac i st =
paulson@19204
   677
  let val ts = Logic.strip_assums_hyp (List.nth (prems_of st, i-1))
wenzelm@24300
   678
  in
paulson@19204
   679
     EVERY' [METAHYPS
wenzelm@24300
   680
            (fn hyps => (cut_facts_tac (map (skolemize o make_nnf) hyps) 1
paulson@14813
   681
                         THEN REPEAT (etac exE 1))),
paulson@19204
   682
            REPEAT_DETERM_N (length ts) o (etac thin_rl)] i st
paulson@19204
   683
  end
paulson@19204
   684
  handle Subscript => Seq.empty;
mengj@18194
   685
paulson@9840
   686
end;
wenzelm@9869
   687