src/HOL/Tools/meson.ML
author wenzelm
Sat Jan 20 14:09:14 2007 +0100 (2007-01-20)
changeset 22130 0906fd95e0b5
parent 21999 0cf192e489e2
child 22360 26ead7ed4f4b
permissions -rw-r--r--
Output.debug: non-strict;
renamed Output.show_debug_msgs to Output.debugging (coincides with Toplevel.debug);
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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 BASIC_MESON =
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sig
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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 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 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 -> 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 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 =
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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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val depth_limit = ref 2000;
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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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      fun match pat = Pattern.first_order_match thy (pat,tmA) (tyenv0,tenv0)
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      val Const("==>",_) $ tmB $ _ = prop_of thB
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      val (tyenv,tenv) = match tmB
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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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(*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, 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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  presumably to instantiate a Boolean variable.*)
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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","Code_Generator.eq_class","ProtoPure.term"?*)
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val has_meta_conn = 
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    exists_Const (fn (c,_) => c mem_string ["==", "==>", "all", "prop"]);
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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 |", _) => (*disjunction*)
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	      let val tac =
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		  (METAHYPS (resop cnf_nil) 1) THEN
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		   (fn st' => st' |> METAHYPS (resop cnf_nil) 1)
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	      in  Seq.list_of (tac (th RS disj_forward)) @ ths  end 
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	  | _ => (*no work to do*) th::ths 
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      and cnf_nil th = cnf_aux (th,[])
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  in 
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    if too_many_clauses (concl_of th) 
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    then (Output.debug (fn () => ("cnf is ignoring: " ^ string_of_thm th)); ths)
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    else cnf_aux (th,ths)
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  end;
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(*Convert all suitable free variables to schematic variables, 
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  but don't discharge assumptions.*)
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fun generalize th = Thm.varifyT (forall_elim_vars 0 (forall_intr_frees th));
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fun make_cnf skoths th = cnf skoths (th, []);
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(*Generalization, removal of redundant equalities, removal of tautologies.*)
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fun finish_cnf ths = filter (not o is_taut) (map (refl_clause o generalize) ths);
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   286
paulson@9840
   287
paulson@15579
   288
(**** Removal of duplicate literals ****)
paulson@9840
   289
paulson@15579
   290
(*Forward proof, passing extra assumptions as theorems to the tactic*)
paulson@15579
   291
fun forward_res2 nf hyps st =
paulson@15579
   292
  case Seq.pull
paulson@15579
   293
	(REPEAT
paulson@15579
   294
	 (METAHYPS (fn major::minors => rtac (nf (minors@hyps) major) 1) 1)
paulson@15579
   295
	 st)
paulson@15579
   296
  of SOME(th,_) => th
paulson@15579
   297
   | NONE => raise THM("forward_res2", 0, [st]);
paulson@9840
   298
paulson@15579
   299
(*Remove duplicates in P|Q by assuming ~P in Q
paulson@15579
   300
  rls (initially []) accumulates assumptions of the form P==>False*)
paulson@15579
   301
fun nodups_aux rls th = nodups_aux rls (th RS disj_assoc)
paulson@15579
   302
    handle THM _ => tryres(th,rls)
paulson@15579
   303
    handle THM _ => tryres(forward_res2 nodups_aux rls (th RS disj_forward2),
paulson@15579
   304
			   [disj_FalseD1, disj_FalseD2, asm_rl])
paulson@15579
   305
    handle THM _ => th;
paulson@9840
   306
paulson@15579
   307
(*Remove duplicate literals, if there are any*)
paulson@15579
   308
fun nodups th =
haftmann@20972
   309
  if has_duplicates (op =) (literals (prop_of th))
haftmann@20972
   310
    then nodups_aux [] th
haftmann@20972
   311
    else th;
paulson@9840
   312
paulson@9840
   313
paulson@15579
   314
(**** Generation of contrapositives ****)
paulson@9840
   315
paulson@21102
   316
fun is_left (Const ("Trueprop", _) $ 
paulson@21102
   317
               (Const ("op |", _) $ (Const ("op |", _) $ _ $ _) $ _)) = true
paulson@21102
   318
  | is_left _ = false;
paulson@21102
   319
               
paulson@15579
   320
(*Associate disjuctions to right -- make leftmost disjunct a LITERAL*)
paulson@21102
   321
fun assoc_right th = 
paulson@21102
   322
  if is_left (prop_of th) then assoc_right (th RS disj_assoc)
paulson@21102
   323
  else th;
paulson@9840
   324
paulson@15579
   325
(*Must check for negative literal first!*)
paulson@15579
   326
val clause_rules = [disj_assoc, make_neg_rule, make_pos_rule];
paulson@9840
   327
paulson@15579
   328
(*For ordinary resolution. *)
paulson@15579
   329
val resolution_clause_rules = [disj_assoc, make_neg_rule', make_pos_rule'];
paulson@9840
   330
paulson@15579
   331
(*Create a goal or support clause, conclusing False*)
paulson@15579
   332
fun make_goal th =   (*Must check for negative literal first!*)
paulson@15579
   333
    make_goal (tryres(th, clause_rules))
paulson@15579
   334
  handle THM _ => tryres(th, [make_neg_goal, make_pos_goal]);
paulson@9840
   335
paulson@15579
   336
(*Sort clauses by number of literals*)
paulson@15579
   337
fun fewerlits(th1,th2) = nliterals(prop_of th1) < nliterals(prop_of th2);
paulson@9840
   338
paulson@18389
   339
fun sort_clauses ths = sort (make_ord fewerlits) ths;
paulson@9840
   340
paulson@15581
   341
(*True if the given type contains bool anywhere*)
paulson@15581
   342
fun has_bool (Type("bool",_)) = true
paulson@15581
   343
  | has_bool (Type(_, Ts)) = exists has_bool Ts
paulson@15581
   344
  | has_bool _ = false;
paulson@15581
   345
  
paulson@20524
   346
(*Is the string the name of a connective? Really only | and Not can remain, 
paulson@20524
   347
  since this code expects to be called on a clause form.*)  
wenzelm@19875
   348
val is_conn = member (op =)
paulson@20524
   349
    ["Trueprop", "op &", "op |", "op -->", "Not", 
paulson@15613
   350
     "All", "Ex", "Ball", "Bex"];
paulson@15613
   351
paulson@20524
   352
(*True if the term contains a function--not a logical connective--where the type 
paulson@20524
   353
  of any argument contains bool.*)
paulson@15613
   354
val has_bool_arg_const = 
paulson@15613
   355
    exists_Const
paulson@15613
   356
      (fn (c,T) => not(is_conn c) andalso exists (has_bool) (binder_types T));
paulson@15908
   357
      
paulson@21102
   358
(*Raises an exception if any Vars in the theorem mention type bool. 
paulson@21102
   359
  Also rejects functions whose arguments are Booleans or other functions.*)
paulson@19204
   360
fun is_fol_term t =
paulson@19204
   361
    not (exists (has_bool o fastype_of) (term_vars t)  orelse
paulson@19204
   362
	 not (Term.is_first_order ["all","All","Ex"] t) orelse
paulson@19204
   363
	 has_bool_arg_const t  orelse  
paulson@19204
   364
	 has_meta_conn t);
paulson@19204
   365
paulson@21102
   366
fun rigid t = not (is_Var (head_of t));
paulson@21102
   367
paulson@21102
   368
fun ok4horn (Const ("Trueprop",_) $ (Const ("op |", _) $ t $ _)) = rigid t
paulson@21102
   369
  | ok4horn (Const ("Trueprop",_) $ t) = rigid t
paulson@21102
   370
  | ok4horn _ = false;
paulson@21102
   371
paulson@15579
   372
(*Create a meta-level Horn clause*)
paulson@21102
   373
fun make_horn crules th = 
paulson@21102
   374
  if ok4horn (concl_of th) 
paulson@21102
   375
  then make_horn crules (tryres(th,crules)) handle THM _ => th
paulson@21102
   376
  else th;
paulson@9840
   377
paulson@16563
   378
(*Generate Horn clauses for all contrapositives of a clause. The input, th,
paulson@16563
   379
  is a HOL disjunction.*)
paulson@15579
   380
fun add_contras crules (th,hcs) =
paulson@15579
   381
  let fun rots (0,th) = hcs
paulson@15579
   382
	| rots (k,th) = zero_var_indexes (make_horn crules th) ::
paulson@15579
   383
			rots(k-1, assoc_right (th RS disj_comm))
paulson@15862
   384
  in case nliterals(prop_of th) of
paulson@15579
   385
	1 => th::hcs
paulson@15579
   386
      | n => rots(n, assoc_right th)
paulson@15579
   387
  end;
paulson@9840
   388
paulson@15579
   389
(*Use "theorem naming" to label the clauses*)
paulson@15579
   390
fun name_thms label =
paulson@15579
   391
    let fun name1 (th, (k,ths)) =
wenzelm@21646
   392
	  (k-1, PureThy.put_name_hint (label ^ string_of_int k) th :: ths)
paulson@15579
   393
    in  fn ths => #2 (foldr name1 (length ths, []) ths)  end;
paulson@9840
   394
paulson@16563
   395
(*Is the given disjunction an all-negative support clause?*)
paulson@15579
   396
fun is_negative th = forall (not o #1) (literals (prop_of th));
paulson@9840
   397
paulson@15579
   398
val neg_clauses = List.filter is_negative;
paulson@9840
   399
paulson@9840
   400
paulson@15579
   401
(***** MESON PROOF PROCEDURE *****)
paulson@9840
   402
paulson@15579
   403
fun rhyps (Const("==>",_) $ (Const("Trueprop",_) $ A) $ phi,
paulson@15579
   404
	   As) = rhyps(phi, A::As)
paulson@15579
   405
  | rhyps (_, As) = As;
paulson@9840
   406
paulson@15579
   407
(** Detecting repeated assumptions in a subgoal **)
paulson@9840
   408
paulson@15579
   409
(*The stringtree detects repeated assumptions.*)
wenzelm@16801
   410
fun ins_term (net,t) = Net.insert_term (op aconv) (t,t) net;
paulson@9840
   411
paulson@15579
   412
(*detects repetitions in a list of terms*)
paulson@15579
   413
fun has_reps [] = false
paulson@15579
   414
  | has_reps [_] = false
paulson@15579
   415
  | has_reps [t,u] = (t aconv u)
paulson@15579
   416
  | has_reps ts = (Library.foldl ins_term (Net.empty, ts);  false)
wenzelm@19875
   417
		  handle Net.INSERT => true;
paulson@9840
   418
paulson@15579
   419
(*Like TRYALL eq_assume_tac, but avoids expensive THEN calls*)
paulson@18508
   420
fun TRYING_eq_assume_tac 0 st = Seq.single st
paulson@18508
   421
  | TRYING_eq_assume_tac i st =
paulson@18508
   422
       TRYING_eq_assume_tac (i-1) (eq_assumption i st)
paulson@18508
   423
       handle THM _ => TRYING_eq_assume_tac (i-1) st;
paulson@18508
   424
paulson@18508
   425
fun TRYALL_eq_assume_tac st = TRYING_eq_assume_tac (nprems_of st) st;
paulson@9840
   426
paulson@15579
   427
(*Loop checking: FAIL if trying to prove the same thing twice
paulson@15579
   428
  -- if *ANY* subgoal has repeated literals*)
paulson@15579
   429
fun check_tac st =
paulson@15579
   430
  if exists (fn prem => has_reps (rhyps(prem,[]))) (prems_of st)
paulson@15579
   431
  then  Seq.empty  else  Seq.single st;
paulson@9840
   432
paulson@9840
   433
paulson@15579
   434
(* net_resolve_tac actually made it slower... *)
paulson@15579
   435
fun prolog_step_tac horns i =
paulson@15579
   436
    (assume_tac i APPEND resolve_tac horns i) THEN check_tac THEN
paulson@18508
   437
    TRYALL_eq_assume_tac;
paulson@9840
   438
paulson@9840
   439
(*Sums the sizes of the subgoals, ignoring hypotheses (ancestors)*)
paulson@15579
   440
fun addconcl(prem,sz) = size_of_term(Logic.strip_assums_concl prem) + sz
paulson@15579
   441
paulson@15579
   442
fun size_of_subgoals st = foldr addconcl 0 (prems_of st);
paulson@15579
   443
paulson@9840
   444
paulson@9840
   445
(*Negation Normal Form*)
paulson@9840
   446
val nnf_rls = [imp_to_disjD, iff_to_disjD, not_conjD, not_disjD,
wenzelm@9869
   447
               not_impD, not_iffD, not_allD, not_exD, not_notD];
paulson@15581
   448
paulson@21102
   449
fun ok4nnf (Const ("Trueprop",_) $ (Const ("Not", _) $ t)) = rigid t
paulson@21102
   450
  | ok4nnf (Const ("Trueprop",_) $ t) = rigid t
paulson@21102
   451
  | ok4nnf _ = false;
paulson@21102
   452
paulson@21102
   453
fun make_nnf1 th = 
paulson@21102
   454
  if ok4nnf (concl_of th) 
paulson@21102
   455
  then make_nnf1 (tryres(th, nnf_rls))
wenzelm@9869
   456
    handle THM _ =>
paulson@15581
   457
        forward_res make_nnf1
wenzelm@9869
   458
           (tryres(th, [conj_forward,disj_forward,all_forward,ex_forward]))
paulson@21102
   459
    handle THM _ => th
paulson@21102
   460
  else th;
paulson@9840
   461
paulson@20018
   462
(*The simplification removes defined quantifiers and occurrences of True and False. 
paulson@20018
   463
  nnf_ss also includes the one-point simprocs,
paulson@18405
   464
  which are needed to avoid the various one-point theorems from generating junk clauses.*)
paulson@19894
   465
val nnf_simps =
paulson@20018
   466
     [simp_implies_def, Ex1_def, Ball_def, Bex_def, if_True, 
paulson@19894
   467
      if_False, if_cancel, if_eq_cancel, cases_simp];
paulson@19894
   468
val nnf_extra_simps =
paulson@19894
   469
      thms"split_ifs" @ ex_simps @ all_simps @ simp_thms;
paulson@18405
   470
paulson@18405
   471
val nnf_ss =
paulson@19894
   472
    HOL_basic_ss addsimps nnf_extra_simps 
paulson@19894
   473
                 addsimprocs [defALL_regroup,defEX_regroup,neq_simproc,let_simproc];
paulson@15872
   474
paulson@21050
   475
fun make_nnf th = case prems_of th of
paulson@21050
   476
    [] => th |> rewrite_rule (map safe_mk_meta_eq nnf_simps)
paulson@21102
   477
	     |> simplify nnf_ss  
paulson@21050
   478
	     |> make_nnf1
paulson@21050
   479
  | _ => raise THM ("make_nnf: premises in argument", 0, [th]);
paulson@15581
   480
paulson@15965
   481
(*Pull existential quantifiers to front. This accomplishes Skolemization for
paulson@15965
   482
  clauses that arise from a subgoal.*)
wenzelm@9869
   483
fun skolemize th =
paulson@20134
   484
  if not (has_conns ["Ex"] (prop_of th)) then th
quigley@15773
   485
  else (skolemize (tryres(th, [choice, conj_exD1, conj_exD2,
quigley@15679
   486
                              disj_exD, disj_exD1, disj_exD2])))
wenzelm@9869
   487
    handle THM _ =>
wenzelm@9869
   488
        skolemize (forward_res skolemize
wenzelm@9869
   489
                   (tryres (th, [conj_forward, disj_forward, all_forward])))
paulson@9840
   490
    handle THM _ => forward_res skolemize (th RS ex_forward);
paulson@9840
   491
paulson@9840
   492
paulson@9840
   493
(*Make clauses from a list of theorems, previously Skolemized and put into nnf.
paulson@9840
   494
  The resulting clauses are HOL disjunctions.*)
wenzelm@9869
   495
fun make_clauses ths =
paulson@15998
   496
    (sort_clauses (map (generalize o nodups) (foldr (cnf[]) [] ths)));
quigley@15773
   497
paulson@16563
   498
(*Convert a list of clauses (disjunctions) to Horn clauses (contrapositives)*)
wenzelm@9869
   499
fun make_horns ths =
paulson@9840
   500
    name_thms "Horn#"
wenzelm@19046
   501
      (distinct Drule.eq_thm_prop (foldr (add_contras clause_rules) [] ths));
paulson@9840
   502
paulson@9840
   503
(*Could simply use nprems_of, which would count remaining subgoals -- no
paulson@9840
   504
  discrimination as to their size!  With BEST_FIRST, fails for problem 41.*)
paulson@9840
   505
wenzelm@9869
   506
fun best_prolog_tac sizef horns =
paulson@9840
   507
    BEST_FIRST (has_fewer_prems 1, sizef) (prolog_step_tac horns 1);
paulson@9840
   508
wenzelm@9869
   509
fun depth_prolog_tac horns =
paulson@9840
   510
    DEPTH_FIRST (has_fewer_prems 1) (prolog_step_tac horns 1);
paulson@9840
   511
paulson@9840
   512
(*Return all negative clauses, as possible goal clauses*)
paulson@9840
   513
fun gocls cls = name_thms "Goal#" (map make_goal (neg_clauses cls));
paulson@9840
   514
paulson@15008
   515
fun skolemize_prems_tac prems =
paulson@9840
   516
    cut_facts_tac (map (skolemize o make_nnf) prems)  THEN'
paulson@9840
   517
    REPEAT o (etac exE);
paulson@9840
   518
paulson@18141
   519
(*Expand all definitions (presumably of Skolem functions) in a proof state.*)
paulson@18141
   520
fun expand_defs_tac st =
paulson@18141
   521
  let val defs = filter (can dest_equals) (#hyps (crep_thm st))
wenzelm@21678
   522
  in  PRIMITIVE (LocalDefs.expand defs) st  end;
paulson@18141
   523
paulson@16588
   524
(*Basis of all meson-tactics.  Supplies cltac with clauses: HOL disjunctions*)
paulson@16588
   525
fun MESON cltac i st = 
paulson@16588
   526
  SELECT_GOAL
paulson@18141
   527
    (EVERY [rtac ccontr 1,
paulson@16588
   528
	    METAHYPS (fn negs =>
paulson@16588
   529
		      EVERY1 [skolemize_prems_tac negs,
paulson@18141
   530
			      METAHYPS (cltac o make_clauses)]) 1,
paulson@18141
   531
            expand_defs_tac]) i st
paulson@20417
   532
  handle THM _ => no_tac st;	(*probably from make_meta_clause, not first-order*)		      
paulson@9840
   533
paulson@9840
   534
(** Best-first search versions **)
paulson@9840
   535
paulson@16563
   536
(*ths is a list of additional clauses (HOL disjunctions) to use.*)
wenzelm@9869
   537
fun best_meson_tac sizef =
wenzelm@9869
   538
  MESON (fn cls =>
paulson@9840
   539
         THEN_BEST_FIRST (resolve_tac (gocls cls) 1)
paulson@9840
   540
                         (has_fewer_prems 1, sizef)
paulson@9840
   541
                         (prolog_step_tac (make_horns cls) 1));
paulson@9840
   542
paulson@9840
   543
(*First, breaks the goal into independent units*)
paulson@9840
   544
val safe_best_meson_tac =
wenzelm@9869
   545
     SELECT_GOAL (TRY Safe_tac THEN
paulson@9840
   546
                  TRYALL (best_meson_tac size_of_subgoals));
paulson@9840
   547
paulson@9840
   548
(** Depth-first search version **)
paulson@9840
   549
paulson@9840
   550
val depth_meson_tac =
wenzelm@9869
   551
     MESON (fn cls => EVERY [resolve_tac (gocls cls) 1,
paulson@9840
   552
                             depth_prolog_tac (make_horns cls)]);
paulson@9840
   553
paulson@9840
   554
paulson@9840
   555
(** Iterative deepening version **)
paulson@9840
   556
paulson@9840
   557
(*This version does only one inference per call;
paulson@9840
   558
  having only one eq_assume_tac speeds it up!*)
wenzelm@9869
   559
fun prolog_step_tac' horns =
paulson@9840
   560
    let val (horn0s, hornps) = (*0 subgoals vs 1 or more*)
paulson@9840
   561
            take_prefix Thm.no_prems horns
paulson@9840
   562
        val nrtac = net_resolve_tac horns
paulson@9840
   563
    in  fn i => eq_assume_tac i ORELSE
paulson@9840
   564
                match_tac horn0s i ORELSE  (*no backtracking if unit MATCHES*)
paulson@9840
   565
                ((assume_tac i APPEND nrtac i) THEN check_tac)
paulson@9840
   566
    end;
paulson@9840
   567
wenzelm@9869
   568
fun iter_deepen_prolog_tac horns =
paulson@9840
   569
    ITER_DEEPEN (has_fewer_prems 1) (prolog_step_tac' horns);
paulson@9840
   570
paulson@21095
   571
fun iter_deepen_meson_tac ths = MESON 
paulson@21095
   572
 (fn cls =>
paulson@21095
   573
      case (gocls (cls@ths)) of
paulson@21095
   574
	   [] => no_tac  (*no goal clauses*)
paulson@21095
   575
	 | goes => 
paulson@21095
   576
	     let val horns = make_horns (cls@ths)
wenzelm@22130
   577
	         val _ =
wenzelm@22130
   578
	             Output.debug (fn () => ("meson method called:\n" ^ 
paulson@21095
   579
	     	                  space_implode "\n" (map string_of_thm (cls@ths)) ^ 
paulson@21095
   580
	     	                  "\nclauses:\n" ^ 
wenzelm@22130
   581
	     	                  space_implode "\n" (map string_of_thm horns)))
paulson@21095
   582
	     in THEN_ITER_DEEPEN (resolve_tac goes 1) (has_fewer_prems 1) (prolog_step_tac' horns)
paulson@21095
   583
	     end
paulson@21095
   584
 );
paulson@9840
   585
paulson@16563
   586
fun meson_claset_tac ths cs =
paulson@16563
   587
  SELECT_GOAL (TRY (safe_tac cs) THEN TRYALL (iter_deepen_meson_tac ths));
wenzelm@9869
   588
paulson@16563
   589
val meson_tac = CLASET' (meson_claset_tac []);
wenzelm@9869
   590
wenzelm@9869
   591
paulson@14813
   592
(**** Code to support ordinary resolution, rather than Model Elimination ****)
paulson@14744
   593
paulson@15008
   594
(*Convert a list of clauses (disjunctions) to meta-level clauses (==>), 
paulson@15008
   595
  with no contrapositives, for ordinary resolution.*)
paulson@14744
   596
paulson@14744
   597
(*Rules to convert the head literal into a negated assumption. If the head
paulson@14744
   598
  literal is already negated, then using notEfalse instead of notEfalse'
paulson@14744
   599
  prevents a double negation.*)
paulson@14744
   600
val notEfalse = read_instantiate [("R","False")] notE;
paulson@14744
   601
val notEfalse' = rotate_prems 1 notEfalse;
paulson@14744
   602
paulson@15448
   603
fun negated_asm_of_head th = 
paulson@14744
   604
    th RS notEfalse handle THM _ => th RS notEfalse';
paulson@14744
   605
paulson@14744
   606
(*Converting one clause*)
paulson@15581
   607
fun make_meta_clause th = 
paulson@21102
   608
  negated_asm_of_head (make_horn resolution_clause_rules th);
paulson@21102
   609
  
paulson@14744
   610
fun make_meta_clauses ths =
paulson@14744
   611
    name_thms "MClause#"
wenzelm@19046
   612
      (distinct Drule.eq_thm_prop (map make_meta_clause ths));
paulson@14744
   613
paulson@14744
   614
(*Permute a rule's premises to move the i-th premise to the last position.*)
paulson@14744
   615
fun make_last i th =
paulson@14744
   616
  let val n = nprems_of th 
paulson@14744
   617
  in  if 1 <= i andalso i <= n 
paulson@14744
   618
      then Thm.permute_prems (i-1) 1 th
paulson@15118
   619
      else raise THM("select_literal", i, [th])
paulson@14744
   620
  end;
paulson@14744
   621
paulson@14744
   622
(*Maps a rule that ends "... ==> P ==> False" to "... ==> ~P" while suppressing
paulson@14744
   623
  double-negations.*)
paulson@14744
   624
val negate_head = rewrite_rule [atomize_not, not_not RS eq_reflection];
paulson@14744
   625
paulson@14744
   626
(*Maps the clause  [P1,...Pn]==>False to [P1,...,P(i-1),P(i+1),...Pn] ==> ~P*)
paulson@14744
   627
fun select_literal i cl = negate_head (make_last i cl);
paulson@14744
   628
paulson@18508
   629
paulson@14813
   630
(*Top-level Skolemization. Allows part of the conversion to clauses to be
paulson@14813
   631
  expressed as a tactic (or Isar method).  Each assumption of the selected 
paulson@14813
   632
  goal is converted to NNF and then its existential quantifiers are pulled
paulson@14813
   633
  to the front. Finally, all existential quantifiers are eliminated, 
paulson@14813
   634
  leaving !!-quantified variables. Perhaps Safe_tac should follow, but it
paulson@14813
   635
  might generate many subgoals.*)
mengj@18194
   636
paulson@19204
   637
fun skolemize_tac i st = 
paulson@19204
   638
  let val ts = Logic.strip_assums_hyp (List.nth (prems_of st, i-1))
paulson@19204
   639
  in 
paulson@19204
   640
     EVERY' [METAHYPS
quigley@15773
   641
	    (fn hyps => (cut_facts_tac (map (skolemize o make_nnf) hyps) 1
paulson@14813
   642
                         THEN REPEAT (etac exE 1))),
paulson@19204
   643
            REPEAT_DETERM_N (length ts) o (etac thin_rl)] i st
paulson@19204
   644
  end
paulson@19204
   645
  handle Subscript => Seq.empty;
mengj@18194
   646
paulson@9840
   647
end;
wenzelm@9869
   648
paulson@15579
   649
structure BasicMeson: BASIC_MESON = Meson;
paulson@15579
   650
open BasicMeson;