2 ||M|| This file is part of HELM, an Hypertextual, Electronic
3 ||A|| Library of Mathematics, developed at the Computer Science
4 ||T|| Department, University of Bologna, Italy.
6 ||T|| HELM is free software; you can redistribute it and/or
7 ||A|| modify it under the terms of the GNU General Public License
8 \ / version 2 or (at your option) any later version.
9 \ / This software is distributed as is, NO WARRANTY.
10 V_______________________________________________________________ *)
12 (* $Id: index.mli 9822 2009-06-03 15:37:06Z tassi $ *)
14 module Superposition (B : Terms.Blob) =
16 module IDX = Index.Index(B)
17 module Unif = FoUnif.Founif(B)
18 module Subst = FoSubst
19 module Order = Orderings.Orderings(B)
20 module Utils = FoUtils.Utils(B)
23 exception Success of B.t Terms.bag * int * B.t Terms.unit_clause
25 let debug s = prerr_endline s;;
28 let rec list_first f = function
30 | x::tl -> match f x with Some _ as x -> x | _ -> list_first f tl
33 let first_position pos ctx t f =
34 let rec aux pos ctx = function
35 | Terms.Leaf _ as t -> f t pos ctx
38 match f t pos ctx with
41 let rec first pre post = function
44 let newctx = fun x -> ctx (Terms.Node (pre@[x]@post)) in
45 match aux (List.length pre :: pos) newctx t with
48 if post = [] then None (* tl is also empty *)
49 else first (pre @ [t]) (List.tl post) tl
51 first [] (List.tl l) l
56 let all_positions pos ctx t f =
57 let rec aux pos ctx = function
58 | Terms.Leaf _ as t -> f t pos ctx
63 (fun (acc,pre,post) t -> (* Invariant: pre @ [t] @ post = l *)
64 let newctx = fun x -> ctx (Terms.Node (pre@[x]@post)) in
65 let acc = aux (List.length pre :: pos) newctx t @ acc in
66 if post = [] then acc, l, []
67 else acc, pre @ [t], List.tl post)
68 (f t pos ctx, [], List.tl l) l
76 let rec aux acc = function
78 | Terms.Var i -> if (List.mem i acc) then acc else i::acc
79 | Terms.Node l -> List.fold_left aux acc l
83 let build_clause bag filter rule t subst vl id id2 pos dir =
84 let proof = Terms.Step(rule,id,id2,dir,pos,subst) in
85 let t = Subst.apply_subst subst t in
89 | Terms.Node [ Terms.Leaf eq ; ty; l; r ] when B.eq B.eqP eq ->
90 let o = Order.compare_terms l r in
91 Terms.Equation (l, r, ty, o)
92 | t -> Terms.Predicate t
95 Terms.add_to_bag (0, literal, vars_of_term t, proof) bag
99 ((*prerr_endline ("Filtering: " ^ Pp.pp_foterm t);*)None)
103 (* ============ simplification ================= *)
105 let demod table varlist subterm pos context =
106 let cands = IDX.DT.retrieve_generalizations table subterm in
108 (fun (dir, (id,lit,vl,_)) ->
110 | Terms.Predicate _ -> assert false
111 | Terms.Equation (l,r,_,o) ->
112 let side, newside = if dir=Terms.Left2Right then l,r else r,l in
115 Unif.unification (varlist@vl) varlist subterm side
117 if o = Terms.Incomparable then
118 let side = Subst.apply_subst subst side in
119 let newside = Subst.apply_subst subst newside in
120 let o = Order.compare_terms newside side in
121 (* Riazanov, pp. 45 (ii) *)
123 Some (context newside, subst, varlist, id, pos, dir)
125 ((*prerr_endline ("Filtering: " ^
126 Pp.pp_foterm side ^ " =(< || =)" ^
127 Pp.pp_foterm newside ^ " coming from " ^
128 Pp.pp_unit_clause uc );*)None)
130 Some (context newside, subst, varlist, id, pos, dir)
131 with FoUnif.UnificationFailure _ -> None)
132 (IDX.ClauseSet.elements cands)
135 let demodulate_once ~jump_to_right bag (id, literal, vl, pr) table =
137 | Terms.Predicate t -> assert false
138 | Terms.Equation (l,r,ty,_) ->
139 let left_position = if jump_to_right then None else
141 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; x; r ]) l
144 match left_position with
145 | Some (newt, subst, varlist, id2, pos, dir) ->
147 match build_clause bag (fun _ -> true) Terms.Demodulation
148 newt subst varlist id id2 pos dir
150 | None -> assert false
151 | Some x -> Some (x,false)
155 [3] (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; l; x ]) r
159 | Some (newt, subst, varlist, id2, pos, dir) ->
160 match build_clause bag (fun _ -> true)
161 Terms.Demodulation newt subst varlist id id2 pos dir
163 | None -> assert false
164 | Some x -> Some (x,true)
167 let rec demodulate ~jump_to_right bag clause table =
168 match demodulate_once ~jump_to_right bag clause table with
169 | None -> bag, clause
170 | Some ((bag, clause),r) -> demodulate ~jump_to_right:r
174 let demodulate bag clause table = demodulate ~jump_to_right:false
179 let is_identity_clause ~unify = function
180 | _, Terms.Equation (_,_,_,Terms.Eq), _, _ -> true
181 | _, Terms.Equation (l,r,_,_), vl, proof when unify ->
182 (try ignore(Unif.unification vl [] l r); true
183 with FoUnif.UnificationFailure _ -> false)
184 | _, Terms.Equation (_,_,_,_), _, _ -> false
185 | _, Terms.Predicate _, _, _ -> assert false
188 let build_new_clause bag maxvar filter rule t subst vl id id2 pos dir =
189 let maxvar, vl, relocsubst = Utils.relocate maxvar vl in
190 let subst = Subst.concat relocsubst subst in
191 match build_clause bag filter rule t subst vl id id2 pos dir with
192 | Some (bag, c) -> Some ((bag, maxvar), c)
196 let fold_build_new_clause bag maxvar id rule filter res =
197 let (bag, maxvar), res =
198 HExtlib.filter_map_acc
199 (fun (bag, maxvar) (t,subst,vl,id2,pos,dir) ->
200 build_new_clause bag maxvar filter rule t subst vl id id2 pos dir)
207 let rewrite_eq ~unify l r ty vl table =
208 let retrieve = if unify then IDX.DT.retrieve_unifiables
209 else IDX.DT.retrieve_generalizations in
210 let lcands = retrieve table l in
211 let rcands = retrieve table r in
213 let id, dir, l, r, vl =
215 | (d, (id,Terms.Equation (l,r,ty,_),vl,_))-> id, d, l, r, vl
218 let reverse = (dir = Terms.Left2Right) = b in
219 let l, r, proof_rewrite_dir = if reverse then l,r,Terms.Left2Right
220 else r,l, Terms.Right2Left in
221 (id,proof_rewrite_dir,Terms.Node [ Terms.Leaf B.eqP; ty; l; r ], vl)
223 let cands1 = List.map (f true) (IDX.ClauseSet.elements lcands) in
224 let cands2 = List.map (f false) (IDX.ClauseSet.elements rcands) in
225 let t = Terms.Node [ Terms.Leaf B.eqP; ty; l; r ] in
226 let locked_vars = if unify then [] else vl in
227 let rec aux = function
229 | (id2,dir,c,vl1)::tl ->
231 let subst,vl1 = Unif.unification (vl@vl1) locked_vars c t in
232 Some (id2, dir, subst)
233 with FoUnif.UnificationFailure _ -> aux tl
235 aux (cands1 @ cands2)
238 let is_subsumed ~unify bag maxvar (id, lit, vl, _) table =
240 | Terms.Predicate _ -> assert false
241 | Terms.Equation (l,r,ty,_) ->
242 match rewrite_eq ~unify l r ty vl table with
244 | Some (id2, dir, subst) ->
245 let id_t = Terms.Node [ Terms.Leaf B.eqP; ty; r; r ] in
246 build_new_clause bag maxvar (fun _ -> true)
247 Terms.Superposition id_t subst [] id id2 [2] dir
249 (* id refers to a clause proving contextl l = contextr r *)
251 let rec deep_eq ~unify l r ty pos contextl contextr table acc =
254 | Some(bag,maxvar,(id,lit,vl,p),subst) ->
255 let l = Subst.apply_subst subst l in
256 let r = Subst.apply_subst subst r in
258 let subst1,vl1 = Unif.unification vl [] l r in
260 match lit with Terms.Predicate _ -> assert false
261 | Terms.Equation (l,r,ty,o) ->
262 Terms.Equation (FoSubst.apply_subst subst1 l,
263 FoSubst.apply_subst subst1 r, ty, o)
265 Some(bag,maxvar,(id,lit,vl1,p),Subst.concat subst1 subst)
266 with FoUnif.UnificationFailure _ ->
267 match rewrite_eq ~unify l r ty vl table with
268 | Some (id2, dir, subst1) ->
269 let newsubst = Subst.concat subst1 subst in
271 FoSubst.apply_subst newsubst
272 (Terms.Node[Terms.Leaf B.eqP;ty;contextl r;contextr r])
275 build_new_clause bag maxvar (fun _ -> true)
276 Terms.Superposition id_t
277 subst1 [] id id2 (pos@[2]) dir
279 | Some ((bag, maxvar), c) ->
280 Some(bag,maxvar,c,newsubst)
281 | None -> assert false)
284 | Terms.Node (a::la), Terms.Node (b::lb) when
285 a = b && List.length la = List.length lb ->
288 (fun (acc,pre,postl,postr) a b ->
290 fun x -> contextl(Terms.Node (pre@(x::postl))) in
292 fun x -> contextr(Terms.Node (pre@(x::postr))) in
293 let newpos = List.length pre::pos in
295 if l = [] then [] else List.tl l in
296 (deep_eq ~unify a b ty
297 newpos newcl newcr table acc,pre@[b],
298 footail postl, footail postr))
299 (acc,[a],List.tl la,List.tl lb) la lb
304 let rec orphan_murder bag acc i =
305 match Terms.get_from_bag i bag with
306 | (_,_,_,Terms.Exact _),discarded -> (discarded,acc)
307 | (_,_,_,Terms.Step (_,i1,i2,_,_,_)),true -> (true,acc)
308 | (_,_,_,Terms.Step (_,i1,i2,_,_,_)),false ->
309 if (List.mem i acc) then (false,acc)
310 else match orphan_murder bag acc i1 with
311 | (true,acc) -> (true,acc)
313 let (res,acc) = orphan_murder bag acc i2 in
314 if res then res,acc else res,i::acc
317 let orphan_murder bag actives cl =
318 let (id,_,_,_) = cl in
319 let actives = List.map (fun (i,_,_,_) -> i) actives in
320 let (res,_) = orphan_murder bag actives id in
321 if res then debug "Orphan murdered"; res
324 (* demodulate and check for subsumption *)
325 let simplify table maxvar bag clause =
326 if is_identity_clause ~unify:false clause then bag,None
327 (* else if orphan_murder bag actives clause then bag,None *)
328 else let bag, clause = demodulate bag clause table in
329 if is_identity_clause ~unify:false clause then bag,None
331 match is_subsumed ~unify:false bag maxvar clause table with
332 | None -> bag, Some clause
333 | Some _ -> bag, None
336 let simplify table maxvar bag clause =
337 match simplify table maxvar bag clause with
339 Terms.replace_in_bag (clause,true) bag, None
340 | bag, Some clause -> bag, Some clause
341 (*let (id,_,_,_) = clause in
342 if orphan_murder bag clause then
343 Terms.M.add id (clause,true) bag, Some clause
344 else bag, Some clause*)
347 let one_pass_simplification new_clause (alist,atable) bag maxvar =
348 match simplify atable maxvar bag new_clause with
349 | bag,None -> bag,None (* new_clause has been discarded *)
350 | bag,(Some clause) ->
351 let ctable = IDX.index_unit_clause IDX.DT.empty clause in
352 let bag, alist, atable =
354 (fun (bag, alist, atable) c ->
355 match simplify ctable maxvar bag c with
356 |bag,None -> (bag,alist,atable)
357 (* an active clause as been discarded *)
359 bag, c :: alist, IDX.index_unit_clause atable c)
360 (bag,[],IDX.DT.empty) alist
362 bag, Some (clause, (alist,atable))
365 let simplification_step ~new_cl cl (alist,atable) bag maxvar new_clause =
367 if new_cl then atable else
368 IDX.index_unit_clause atable cl
370 (* Simplification of new_clause with : *
371 * - actives and cl if new_clause is not cl *
372 * - only actives otherwise *)
374 simplify atable1 maxvar bag new_clause with
375 | bag,None -> bag,(Some cl, None) (* new_clause has been discarded *)
377 (* Simplification of each active clause with clause *
378 * which is the simplified form of new_clause *)
379 let ctable = IDX.index_unit_clause IDX.DT.empty clause in
380 let bag, newa, alist, atable =
382 (fun (bag, newa, alist, atable) c ->
383 match simplify ctable maxvar bag c with
384 |bag,None -> (bag, newa, alist, atable)
385 (* an active clause as been discarded *)
388 bag, newa, c :: alist,
389 IDX.index_unit_clause atable c
391 bag, c1 :: newa, alist, atable)
392 (bag,[],[],IDX.DT.empty) alist
395 bag, (Some cl, Some (clause, (alist,atable), newa))
397 (* if new_clause is not cl, we simplify cl with clause *)
398 match simplify ctable maxvar bag cl with
400 (* cl has been discarded *)
401 bag,(None, Some (clause, (alist,atable), newa))
403 bag,(Some cl1, Some (clause, (alist,atable), newa))
406 let keep_simplified cl (alist,atable) bag maxvar =
407 let rec keep_simplified_aux ~new_cl cl (alist,atable) bag newc =
409 match simplification_step ~new_cl cl (alist,atable) bag maxvar cl with
410 | _,(None, _) -> assert false
411 | bag,(Some _, None) -> bag,None
412 | bag,(Some _, Some (clause, (alist,atable), newa)) ->
413 keep_simplified_aux ~new_cl:(cl!=clause) clause (alist,atable)
417 | [] -> bag, Some (cl, (alist,atable))
419 match simplification_step ~new_cl cl
420 (alist,atable) bag maxvar hd with
421 | _,(None,None) -> assert false
422 | bag,(Some _,None) ->
423 keep_simplified_aux ~new_cl cl (alist,atable) bag tl
424 | bag,(None, Some _) -> bag,None
425 | bag,(Some cl1, Some (clause, (alist,atable), newa)) ->
427 (clause::alist, IDX.index_unit_clause atable clause)
429 keep_simplified_aux ~new_cl:(cl!=cl1) cl1 (alist,atable)
432 keep_simplified_aux ~new_cl:true cl (alist,atable) bag []
435 let are_alpha_eq cl1 cl2 =
436 let get_term (_,lit,_,_) =
438 | Terms.Predicate _ -> assert false
439 | Terms.Equation (l,r,ty,_) ->
440 Terms.Node [Terms.Leaf B.eqP; ty; l ; r]
442 try ignore(Unif.alpha_eq (get_term cl1) (get_term cl2)) ; true
443 with FoUnif.UnificationFailure _ -> false
446 (* this is like simplify but raises Success *)
447 let simplify_goal ~no_demod maxvar table bag g_actives clause =
449 if no_demod then bag, clause else demodulate bag clause table
451 if List.exists (are_alpha_eq clause) g_actives then None else
452 if (is_identity_clause ~unify:true clause)
453 then raise (Success (bag, maxvar, clause))
455 let (id,lit,vl,_) = clause in
456 if vl = [] then Some (bag,clause)
460 | Terms.Equation(l,r,ty,_) -> l,r,ty
463 match deep_eq ~unify:true l r ty [] (fun x -> x) (fun x -> x)
464 table (Some(bag,maxvar,clause,Subst.id_subst)) with
465 | None -> Some (bag,clause)
466 | Some (bag,maxvar,cl,subst) ->
467 prerr_endline "Goal subsumed";
468 raise (Success (bag,maxvar,cl))
470 else match is_subsumed ~unify:true bag maxvar clause table with
471 | None -> Some (bag, clause)
472 | Some ((bag,maxvar),c) ->
473 prerr_endline "Goal subsumed";
474 raise (Success (bag,maxvar,c))
478 (* =================== inference ===================== *)
480 (* this is OK for both the sup_left and sup_right inference steps *)
481 let superposition table varlist subterm pos context =
482 let cands = IDX.DT.retrieve_unifiables table subterm in
484 (fun (dir, (id,lit,vl,_ (*as uc*))) ->
486 | Terms.Predicate _ -> assert false
487 | Terms.Equation (l,r,_,o) ->
488 let side, newside = if dir=Terms.Left2Right then l,r else r,l in
491 Unif.unification (varlist@vl) [] subterm side
493 if o = Terms.Incomparable then
494 let side = Subst.apply_subst subst side in
495 let newside = Subst.apply_subst subst newside in
496 let o = Order.compare_terms side newside in
497 (* XXX: check Riazanov p. 33 (iii) *)
498 if o <> Terms.Lt && o <> Terms.Eq then
499 Some (context newside, subst, varlist, id, pos, dir)
501 ((*prerr_endline ("Filtering: " ^
502 Pp.pp_foterm side ^ " =(< || =)" ^
503 Pp.pp_foterm newside ^ " coming from " ^
504 Pp.pp_unit_clause uc );*)None)
506 Some (context newside, subst, varlist, id, pos, dir)
507 with FoUnif.UnificationFailure _ -> None)
508 (IDX.ClauseSet.elements cands)
511 (* Superposes selected equation with equalities in table *)
512 let superposition_with_table bag maxvar (id,selected,vl,_) table =
514 | Terms.Predicate _ -> assert false
515 | Terms.Equation (l,r,ty,Terms.Lt) ->
516 fold_build_new_clause bag maxvar id Terms.Superposition
519 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; l; x ])
520 r (superposition table vl))
521 | Terms.Equation (l,r,ty,Terms.Gt) ->
522 fold_build_new_clause bag maxvar id Terms.Superposition
525 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; x; r ])
526 l (superposition table vl))
527 | Terms.Equation (l,r,ty,Terms.Incomparable) ->
528 fold_build_new_clause bag maxvar id Terms.Superposition
529 (function (* Riazanov: p.33 condition (iv) *)
530 | Terms.Node [Terms.Leaf eq; ty; l; r ] when B.eq B.eqP eq ->
531 Order.compare_terms l r <> Terms.Eq
534 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; l; x ])
535 r (superposition table vl)) @
537 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; x; r ])
538 l (superposition table vl)))
542 (* the current equation is normal w.r.t. demodulation with atable
543 * (and is not the identity) *)
544 let infer_right bag maxvar current (alist,atable) =
545 (* We demodulate actives clause with current until all *
546 * active clauses are reduced w.r.t each other *)
547 (* let bag, (alist,atable) = keep_simplified (alist,atable) bag [current] in *)
548 let ctable = IDX.index_unit_clause IDX.DT.empty current in
549 (* let bag, (alist, atable) =
551 HExtlib.filter_map_acc (simplify ctable) bag alist
553 bag, (alist, List.fold_left IDX.index_unit_clause IDX.DT.empty alist)
555 debug "Simplified active clauses with fact";
556 (* We superpose active clauses with current *)
557 let bag, maxvar, new_clauses =
559 (fun (bag, maxvar, acc) active ->
560 let bag, maxvar, newc =
561 superposition_with_table bag maxvar active ctable
563 bag, maxvar, newc @ acc)
564 (bag, maxvar, []) alist
566 debug "First superpositions";
567 (* We add current to active clauses so that it can be *
568 * superposed with itself *)
570 current :: alist, IDX.index_unit_clause atable current
573 let fresh_current, maxvar = Utils.fresh_unit_clause maxvar current in
574 (* We need to put fresh_current into the bag so that all *
575 * variables clauses refer to are known. *)
576 let bag, fresh_current = Terms.add_to_bag fresh_current bag in
577 (* We superpose current with active clauses *)
578 let bag, maxvar, additional_new_clauses =
579 superposition_with_table bag maxvar fresh_current atable
581 debug "Another superposition";
582 let new_clauses = new_clauses @ additional_new_clauses in
583 debug (Printf.sprintf "Demodulating %d clauses"
584 (List.length new_clauses));
585 let bag, new_clauses =
586 HExtlib.filter_map_monad (simplify atable maxvar) bag new_clauses
588 debug "Demodulated new clauses";
589 bag, maxvar, (alist, atable), new_clauses
592 let infer_left bag maxvar goal (_alist, atable) =
593 (* We superpose the goal with active clauses *)
594 if (match goal with (_,_,[],_) -> true | _ -> false) then bag, maxvar, []
596 let bag, maxvar, new_goals =
597 superposition_with_table bag maxvar goal atable
599 debug "Superposed goal with active clauses";
600 (* We simplify the new goals with active clauses *)
604 match simplify_goal ~no_demod:false maxvar atable bag [] g with
605 | None -> assert false
606 | Some (bag,g) -> bag,g::acc)
609 debug "Simplified new goals with active clauses";
610 bag, maxvar, List.rev new_goals