module Order = Orderings.Orderings(B)
module Utils = FoUtils.Utils(B)
module Pp = Pp.Pp(B)
+
+ exception Success of B.t Terms.bag * int * B.t Terms.unit_clause
+
+ let debug s =
+ ()(* prerr_endline s *)
+ ;;
let rec list_first f = function
| [] -> None
if o = Terms.Incomparable then
let side = Subst.apply_subst subst side in
let newside = Subst.apply_subst subst newside in
- let o = Order.compare_terms side newside in
+ let o = Order.compare_terms newside side in
(* Riazanov, pp. 45 (ii) *)
if o = Terms.Lt then
Some (context newside, subst, varlist, id, pos, dir)
(* XXX: possible optimization, if the literal has a "side" already
* in normal form we should not traverse it again *)
- let demodulate_once bag (id, literal, vl, _) table =
+ let demodulate_once bag (id, literal, vl, pr) table =
+ debug ("Demodulating : " ^ (Pp.pp_unit_clause (id, literal, vl, pr)));
let t =
match literal with
| Terms.Predicate t -> t
| _ -> false
;;
- let is_subsumed (id, lit, vl, _) table =
+ let is_subsumed ~unify (id, lit, vl, _) table =
match lit with
| Terms.Predicate _ -> assert false
| Terms.Equation (l,r,ty,_) ->
- let lcands = IDX.DT.retrieve_generalizations table l in
- let rcands = IDX.DT.retrieve_generalizations table l in
+ let retrieve = if unify then IDX.DT.retrieve_unifiables
+ else IDX.DT.retrieve_generalizations in
+ let lcands = retrieve table l in
+ let rcands = retrieve table r in
let f b c =
let dir, l, r, vl =
match c with
let cands1 = List.map (f true) (IDX.ClauseSet.elements lcands) in
let cands2 = List.map (f false) (IDX.ClauseSet.elements rcands) in
let t = Terms.Node [ Terms.Leaf B.eqP; ty; l; r ] in
- List.exists
- (fun (c, vl1) ->
- try ignore(Unif.unification (vl@vl1) vl c t); true
- with FoUnif.UnificationFailure _ -> false)
- (cands1 @ cands2)
+ let locked_vars = if unify then [] else vl in
+ List.exists
+ (fun (c, vl1) ->
+ try ignore(Unif.unification (vl@vl1) locked_vars c t); true
+ with FoUnif.UnificationFailure _ -> false)
+ (cands1 @ cands2)
;;
(* demodulate and check for subsumption *)
let bag, clause = demodulate bag clause table in
if is_identity_clause clause then None
else
- if is_subsumed clause table then None
+ if is_subsumed ~unify:false clause table then None
else Some (bag, clause)
;;
+ (* this is like forward_simplify but raises Success *)
+ let backward_simplify maxvar table bag clause =
+ let bag, clause = demodulate bag clause table in
+ if (is_identity_clause clause) || (is_subsumed ~unify:true clause table)
+ then raise (Success (bag, maxvar, clause))
+ else bag, clause
+ ;;
+
(* =================== inference ===================== *)
- let superposition_right table varlist subterm pos context =
+ (* this is OK for both the sup_left and sup_right inference steps *)
+ let superposition table varlist subterm pos context =
let cands = IDX.DT.retrieve_unifiables table subterm in
HExtlib.filter_map
(fun (dir, (id,lit,vl,_ (*as uc*))) ->
bag, maxvar, res
;;
- let superposition_right_with_table bag maxvar (id,selected,vl,_) table =
+ (* Superposes selected equation with equalities in table *)
+ let superposition_with_table bag maxvar (id,selected,vl,_) table =
match selected with
| Terms.Predicate _ -> assert false
| Terms.Equation (l,r,ty,Terms.Lt) ->
- fold_build_new_clause bag maxvar id Terms.SuperpositionRight
+ fold_build_new_clause bag maxvar id Terms.Superposition
(fun _ -> true)
(all_positions [3]
(fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; l; x ])
- r (superposition_right table vl))
+ r (superposition table vl))
| Terms.Equation (l,r,ty,Terms.Gt) ->
- fold_build_new_clause bag maxvar id Terms.SuperpositionRight
+ fold_build_new_clause bag maxvar id Terms.Superposition
(fun _ -> true)
(all_positions [2]
(fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; x; r ])
- l (superposition_right table vl))
+ l (superposition table vl))
| Terms.Equation (l,r,ty,Terms.Incomparable) ->
- fold_build_new_clause bag maxvar id Terms.SuperpositionRight
+ fold_build_new_clause bag maxvar id Terms.Superposition
(function (* Riazanov: p.33 condition (iv) *)
| Terms.Node [Terms.Leaf eq; ty; l; r ] when B.eq B.eqP eq ->
Order.compare_terms l r <> Terms.Eq
| _ -> assert false)
((all_positions [3]
(fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; l; x ])
- r (superposition_right table vl)) @
+ r (superposition table vl)) @
(all_positions [2]
(fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; x; r ])
- l (superposition_right table vl)))
+ l (superposition table vl)))
| _ -> assert false
;;
(* the current equation is normal w.r.t. demodulation with atable
* (and is not the identity) *)
let infer_right bag maxvar current (alist,atable) =
+ (* We demodulate actives clause with current *)
let ctable = IDX.index_unit_clause IDX.DT.empty current in
+ let bag, (alist, atable) =
+ let bag, alist =
+ HExtlib.filter_map_acc (forward_simplify ctable) bag alist
+ in
+ bag, (alist, List.fold_left IDX.index_unit_clause IDX.DT.empty alist)
+ in
+ debug "Simplified active clauses with fact";
+ (* We superpose active clauses with current *)
let bag, maxvar, new_clauses =
List.fold_left
(fun (bag, maxvar, acc) active ->
let bag, maxvar, newc =
- superposition_right_with_table bag maxvar active ctable
+ superposition_with_table bag maxvar active ctable
in
bag, maxvar, newc @ acc)
(bag, maxvar, []) alist
in
+ debug "First superpositions";
+ (* We add current to active clauses so that it can be *
+ * superposed with itself *)
let alist, atable =
current :: alist, IDX.index_unit_clause atable current
in
+ debug "Indexed";
let fresh_current, maxvar = Utils.fresh_unit_clause maxvar current in
+ (* We need to put fresh_current into the bag so that all *
+ * variables clauses refer to are known. *)
+ let bag, fresh_current = Utils.add_to_bag bag fresh_current in
+ (* We superpose current with active clauses *)
let bag, maxvar, additional_new_clauses =
- superposition_right_with_table bag maxvar fresh_current atable
+ superposition_with_table bag maxvar fresh_current atable
in
+ debug "Another superposition";
let new_clauses = new_clauses @ additional_new_clauses in
let bag, new_clauses =
HExtlib.filter_map_acc (forward_simplify atable) bag new_clauses
in
+ debug "Demodulated new clauses";
bag, maxvar, (alist, atable), new_clauses
;;
+ let infer_left bag maxvar goal (_alist, atable) =
+ (* We superpose the goal with active clauses *)
+ let bag, maxvar, new_goals =
+ superposition_with_table bag maxvar goal atable
+ in
+ (* We demodulate the goal with active clauses *)
+ let bag, new_goals =
+ List.fold_left
+ (fun (bag, acc) g ->
+ let bag, g = demodulate bag g atable in
+ bag, g :: acc)
+ (bag, []) new_goals
+ in
+ bag, maxvar, List.rev new_goals
+ ;;
+
end
projects / helm.git / blobdiff