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 (*.Subst(B)*)
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
26 () (* prerr_endline s *)
29 let rec list_first f = function
31 | x::tl -> match f x with Some _ as x -> x | _ -> list_first f tl
34 let first_position pos ctx t f =
35 let rec aux pos ctx = function
36 | Terms.Leaf _ as t -> f t pos ctx
39 match f t pos ctx with
42 let rec first pre post = function
45 let newctx = fun x -> ctx (Terms.Node (pre@[x]@post)) in
46 match aux (List.length pre :: pos) newctx t with
49 if post = [] then None (* tl is also empty *)
50 else first (pre @ [t]) (List.tl post) tl
52 first [] (List.tl l) l
57 let all_positions pos ctx t f =
58 let rec aux pos ctx = function
59 | Terms.Leaf _ as t -> f t pos ctx
64 (fun (acc,pre,post) t -> (* Invariant: pre @ [t] @ post = l *)
65 let newctx = fun x -> ctx (Terms.Node (pre@[x]@post)) in
66 let acc = aux (List.length pre :: pos) newctx t @ acc in
67 if post = [] then acc, l, []
68 else acc, pre @ [t], List.tl post)
69 (f t pos ctx, [], List.tl l) l
77 let rec aux acc = function
79 | Terms.Var i -> if (List.mem i acc) then acc else i::acc
80 | Terms.Node l -> List.fold_left aux acc l
84 let build_clause bag filter rule t subst vl id id2 pos dir =
85 let proof = Terms.Step(rule,id,id2,dir,pos,subst) in
86 let t = Subst.apply_subst subst t in
90 | Terms.Node [ Terms.Leaf eq ; ty; l; r ] when B.eq B.eqP eq ->
91 let o = Order.compare_terms l r in
92 Terms.Equation (l, r, ty, o)
93 | t -> Terms.Predicate t
96 Utils.add_to_bag bag (0, literal, vars_of_term t, proof)
100 ((*prerr_endline ("Filtering: " ^ Pp.pp_foterm t);*)None)
104 (* ============ simplification ================= *)
106 let demod table varlist subterm pos context =
107 let cands = IDX.DT.retrieve_generalizations table subterm in
109 (fun (dir, (id,lit,vl,_)) ->
111 | Terms.Predicate _ -> assert false
112 | Terms.Equation (l,r,_,o) ->
113 let side, newside = if dir=Terms.Left2Right then l,r else r,l in
116 Unif.unification (varlist@vl) varlist subterm side
118 if o = Terms.Incomparable then
119 let side = Subst.apply_subst subst side in
120 let newside = Subst.apply_subst subst newside in
121 let o = Order.compare_terms newside side in
122 (* Riazanov, pp. 45 (ii) *)
124 Some (context newside, subst, varlist, id, pos, dir)
126 ((*prerr_endline ("Filtering: " ^
127 Pp.pp_foterm side ^ " =(< || =)" ^
128 Pp.pp_foterm newside ^ " coming from " ^
129 Pp.pp_unit_clause uc );*)None)
131 Some (context newside, subst, varlist, id, pos, dir)
132 with FoUnif.UnificationFailure _ -> None)
133 (IDX.ClauseSet.elements cands)
136 let demodulate_once ~jump_to_right bag (id, literal, vl, pr) table =
137 (* debug ("Demodulating : " ^ (Pp.pp_unit_clause (id, literal, vl, pr)));*)
139 | Terms.Predicate t -> assert false
140 | Terms.Equation (l,r,ty,_) ->
141 let left_position = if jump_to_right then None else
143 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; x; r ]) l
146 match left_position with
147 | Some (newt, subst, varlist, id2, pos, dir) ->
149 match build_clause bag (fun _ -> true) Terms.Demodulation
150 newt subst varlist id id2 pos dir
152 | None -> assert false
153 | Some x -> Some (x,false)
157 [3] (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; l; x ]) r
161 | Some (newt, subst, varlist, id2, pos, dir) ->
162 match build_clause bag (fun _ -> true)
163 Terms.Demodulation newt subst varlist id id2 pos dir
165 | None -> assert false
166 | Some x -> Some (x,true)
169 let rec demodulate ~jump_to_right bag clause table =
170 match demodulate_once ~jump_to_right bag clause table with
171 | None -> bag, clause
172 | Some ((bag, clause),r) -> demodulate ~jump_to_right:r
176 let demodulate bag clause table = demodulate ~jump_to_right:false
181 let is_identity_clause = function
182 | _, Terms.Equation (_,_,_,Terms.Eq), _, _ -> true
183 | _, Terms.Equation (l,r,_,_), vl, proof ->
184 (try ignore(Unif.unification vl [] l r); true
185 with FoUnif.UnificationFailure _ -> false)
186 | _, Terms.Predicate _, _, _ -> assert false
189 let build_new_clause bag maxvar filter rule t subst vl id id2 pos dir =
190 let maxvar, vl, relocsubst = Utils.relocate maxvar vl in
191 let subst = Subst.concat relocsubst subst in
192 match build_clause bag filter rule t subst vl id id2 pos dir with
193 | Some (bag, c) -> Some ((bag, maxvar), c)
197 let fold_build_new_clause bag maxvar id rule filter res =
198 let (bag, maxvar), res =
199 HExtlib.filter_map_acc
200 (fun (bag, maxvar) (t,subst,vl,id2,pos,dir) ->
201 build_new_clause bag maxvar filter rule t subst vl id id2 pos dir)
208 let rewrite_eq ~unify l r ty vl table =
209 let retrieve = if unify then IDX.DT.retrieve_unifiables
210 else IDX.DT.retrieve_generalizations in
211 let lcands = retrieve table l in
212 let rcands = retrieve table r in
214 let id, dir, l, r, vl =
216 | (d, (id,Terms.Equation (l,r,ty,_),vl,_))-> id, d, l, r, vl
219 let reverse = (dir = Terms.Left2Right) = b in
220 let l, r, proof_rewrite_dir = if reverse then l,r,Terms.Left2Right
221 else r,l, Terms.Right2Left in
222 (id,proof_rewrite_dir,Terms.Node [ Terms.Leaf B.eqP; ty; l; r ], vl)
224 let cands1 = List.map (f true) (IDX.ClauseSet.elements lcands) in
225 let cands2 = List.map (f false) (IDX.ClauseSet.elements rcands) in
226 let t = Terms.Node [ Terms.Leaf B.eqP; ty; l; r ] in
227 let locked_vars = if unify then [] else vl in
228 let rec aux = function
230 | (id2,dir,c,vl1)::tl ->
232 let subst,vl1 = Unif.unification (vl@vl1) locked_vars c t in
233 Some (id2, dir, subst)
234 with FoUnif.UnificationFailure _ -> aux tl
236 aux (cands1 @ cands2)
239 let is_subsumed ~unify bag maxvar (id, lit, vl, _) table =
241 | Terms.Predicate _ -> assert false
242 | Terms.Equation (l,r,ty,_) ->
243 match rewrite_eq ~unify l r ty vl table with
245 | Some (id2, dir, subst) ->
246 let id_t = Terms.Node [ Terms.Leaf B.eqP; ty; r; r ] in
247 build_new_clause bag maxvar (fun _ -> true)
248 Terms.Superposition id_t subst [] id id2 [2] dir
250 (* id refers to a clause proving contextl l = contextr r *)
252 let rec deep_eq ~unify l r ty pos contextl contextr table acc =
255 | Some(bag,maxvar,[],subst) -> assert false
256 | Some(bag,maxvar,(id,_,vl,_)::clauses,subst) ->
257 let l = Subst.apply_subst subst l in
258 let r = Subst.apply_subst subst r in
260 let subst1,vl1 = Unif.unification vl [] l r in
261 Some(bag,maxvar,clauses,Subst.concat subst1 subst)
262 with FoUnif.UnificationFailure _ ->
263 match rewrite_eq ~unify l r ty vl table with
264 | Some (id2, dir, subst1) ->
266 Terms.Node[Terms.Leaf B.eqP;ty;contextl r;contextr r] in
268 build_new_clause bag maxvar (fun _ -> true)
269 Terms.Superposition id_t subst1 [] id id2 (2::pos) dir
271 | Some ((bag, maxvar), c) ->
272 Some(bag,maxvar,c::clauses,Subst.concat subst1 subst)
273 | None -> assert false)
276 | Terms.Node (a::la), Terms.Node (b::lb) when
277 a = b && List.length la = List.length lb ->
280 (fun (acc,pre,postl,postr) a b ->
282 fun x -> contextl(Terms.Node (pre@(x::postl))) in
284 fun x -> contextr(Terms.Node (pre@(x::postr))) in
285 let newpos = List.length pre::pos in
287 if l = [] then [] else List.tl l in
288 (deep_eq ~unify a b ty
289 newpos newcl newcr table acc,pre@[b],
290 footail postl, footail postr))
291 (acc,[a],List.tl la,List.tl lb) la lb
294 | _, Terms.Var _ -> assert false
298 (* demodulate and check for subsumption *)
299 let simplify table maxvar bag clause =
300 let bag, clause = demodulate bag clause table in
301 if is_identity_clause ~unify:false clause then bag,None
303 match is_subsumed ~unify:false bag maxvar clause table with
304 | None -> bag, Some clause
305 | Some _ -> bag, None
308 let one_pass_simplification new_clause (alist,atable) bag maxvar =
309 match simplify atable maxvar bag new_clause with
310 | bag,None -> None (* new_clause has been discarded *)
311 | bag,(Some clause) ->
312 let ctable = IDX.index_unit_clause IDX.DT.empty clause in
313 let bag, alist, atable =
315 (fun (bag, alist, atable as acc) c ->
316 match simplify ctable maxvar bag c with
317 |bag,None -> acc (* an active clause as been discarded *)
319 bag, c :: alist, IDX.index_unit_clause atable c)
320 (bag,[],IDX.DT.empty) alist
322 Some (clause, bag, (alist,atable))
325 let simplification_step ~new_cl cl (alist,atable) bag maxvar new_clause =
327 if new_cl then atable else
328 IDX.index_unit_clause atable cl
330 (* Simplification of new_clause with : *
331 * - actives and cl if new_clause is not cl *
332 * - only actives otherwise *)
333 match simplify atable1 maxvar bag new_clause with
334 | bag,None -> (Some cl, None) (* new_clause has been discarded *)
336 (* Simplification of each active clause with clause *
337 * which is the simplified form of new_clause *)
338 let ctable = IDX.index_unit_clause IDX.DT.empty clause in
339 let bag, newa, alist, atable =
341 (fun (bag, newa, alist, atable as acc) c ->
342 match simplify ctable maxvar bag c with
343 |bag,None -> acc (* an active clause as been discarded *)
346 bag, newa, c :: alist,
347 IDX.index_unit_clause atable c
349 bag, c1 :: newa, alist, atable)
350 (bag,[],[],IDX.DT.empty) alist
353 (Some cl, Some (clause, (alist,atable), newa, bag))
355 (* if new_clause is not cl, we simplify cl with clause *)
356 match simplify ctable maxvar bag cl with
358 (* cl has been discarded *)
359 (None, Some (clause, (alist,atable), newa, bag))
361 (Some cl1, Some (clause, (alist,atable), newa, bag))
364 let keep_simplified cl (alist,atable) bag maxvar =
365 let rec keep_simplified_aux ~new_cl cl (alist,atable) bag newc =
367 match simplification_step ~new_cl cl (alist,atable) bag maxvar cl with
368 | (None, _) -> assert false
369 | (Some _, None) -> None
370 | (Some _, Some (clause, (alist,atable), newa, bag)) ->
371 keep_simplified_aux ~new_cl:(cl!=clause) clause (alist,atable)
375 | [] -> Some (cl, bag, (alist,atable))
377 match simplification_step ~new_cl cl
378 (alist,atable) bag maxvar hd with
379 | (None,None) -> assert false
381 keep_simplified_aux ~new_cl cl (alist,atable) bag tl
382 | (None, Some _) -> None
383 | (Some cl1, Some (clause, (alist,atable), newa, bag)) ->
385 (clause::alist, IDX.index_unit_clause atable clause)
387 keep_simplified_aux ~new_cl:(cl!=cl1) cl1 (alist,atable)
390 keep_simplified_aux ~new_cl:true cl (alist,atable) bag []
393 let are_alpha_eq cl1 cl2 =
394 let get_term (_,lit,_,_) =
396 | Terms.Predicate _ -> assert false
397 | Terms.Equation (l,r,ty,_) ->
398 Terms.Node [Terms.Leaf B.eqP; ty; l ; r]
400 try ignore(Unif.alpha_eq (get_term cl1) (get_term cl2)) ; true
401 with FoUnif.UnificationFailure _ -> false
404 (* this is like simplify but raises Success *)
405 let simplify_goal maxvar table bag g_actives clause =
406 let bag, clause = demodulate bag clause table in
407 if (is_identity_clause clause)
408 then raise (Success (bag, maxvar, clause))
411 let (id,lit,vl,_) = clause in
414 | Terms.Equation(l,r,ty,_) -> l,r,ty
417 match deep_eq ~unify:true l r ty [] (fun x -> x) (fun x -> x)
418 table (Some(bag,maxvar,[clause],Subst.id_subst)) with
420 if List.exists (are_alpha_eq clause) g_actives then None
421 else Some (bag, clause)
422 | Some (bag,maxvar,cl,subst) ->
423 debug "Goal subsumed";
424 raise (Success (bag,maxvar,List.hd cl))
426 else match is_subsumed ~unify:true bag maxvar clause table with
428 if List.exists (are_alpha_eq clause) g_actives then None
429 else Some (bag, clause)
430 | Some ((bag,maxvar),c) ->
431 debug "Goal subsumed";
432 raise (Success (bag,maxvar,c))
435 (* =================== inference ===================== *)
437 (* this is OK for both the sup_left and sup_right inference steps *)
438 let superposition table varlist subterm pos context =
439 let cands = IDX.DT.retrieve_unifiables table subterm in
441 (fun (dir, (id,lit,vl,_ (*as uc*))) ->
443 | Terms.Predicate _ -> assert false
444 | Terms.Equation (l,r,_,o) ->
445 let side, newside = if dir=Terms.Left2Right then l,r else r,l in
448 Unif.unification (varlist@vl) [] subterm side
450 if o = Terms.Incomparable then
451 let side = Subst.apply_subst subst side in
452 let newside = Subst.apply_subst subst newside in
453 let o = Order.compare_terms side newside in
454 (* XXX: check Riazanov p. 33 (iii) *)
455 if o <> Terms.Lt && o <> Terms.Eq then
456 Some (context newside, subst, varlist, id, pos, dir)
458 ((*prerr_endline ("Filtering: " ^
459 Pp.pp_foterm side ^ " =(< || =)" ^
460 Pp.pp_foterm newside ^ " coming from " ^
461 Pp.pp_unit_clause uc );*)None)
463 Some (context newside, subst, varlist, id, pos, dir)
464 with FoUnif.UnificationFailure _ -> None)
465 (IDX.ClauseSet.elements cands)
468 (* Superposes selected equation with equalities in table *)
469 let superposition_with_table bag maxvar (id,selected,vl,_) table =
471 | Terms.Predicate _ -> assert false
472 | Terms.Equation (l,r,ty,Terms.Lt) ->
473 fold_build_new_clause bag maxvar id Terms.Superposition
476 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; l; x ])
477 r (superposition table vl))
478 | Terms.Equation (l,r,ty,Terms.Gt) ->
479 fold_build_new_clause bag maxvar id Terms.Superposition
482 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; x; r ])
483 l (superposition table vl))
484 | Terms.Equation (l,r,ty,Terms.Incomparable) ->
485 fold_build_new_clause bag maxvar id Terms.Superposition
486 (function (* Riazanov: p.33 condition (iv) *)
487 | Terms.Node [Terms.Leaf eq; ty; l; r ] when B.eq B.eqP eq ->
488 Order.compare_terms l r <> Terms.Eq
491 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; l; x ])
492 r (superposition table vl)) @
494 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; x; r ])
495 l (superposition table vl)))
499 (* the current equation is normal w.r.t. demodulation with atable
500 * (and is not the identity) *)
501 let infer_right bag maxvar current (alist,atable) =
502 (* We demodulate actives clause with current until all *
503 * active clauses are reduced w.r.t each other *)
504 (* let bag, (alist,atable) = keep_simplified (alist,atable) bag [current] in *)
505 let ctable = IDX.index_unit_clause IDX.DT.empty current in
506 (* let bag, (alist, atable) =
508 HExtlib.filter_map_acc (simplify ctable) bag alist
510 bag, (alist, List.fold_left IDX.index_unit_clause IDX.DT.empty alist)
512 debug "Simplified active clauses with fact";
513 (* We superpose active clauses with current *)
514 let bag, maxvar, new_clauses =
516 (fun (bag, maxvar, acc) active ->
517 let bag, maxvar, newc =
518 superposition_with_table bag maxvar active ctable
520 bag, maxvar, newc @ acc)
521 (bag, maxvar, []) alist
523 debug "First superpositions";
524 (* We add current to active clauses so that it can be *
525 * superposed with itself *)
527 current :: alist, IDX.index_unit_clause atable current
530 let fresh_current, maxvar = Utils.fresh_unit_clause maxvar current in
531 (* We need to put fresh_current into the bag so that all *
532 * variables clauses refer to are known. *)
533 let bag, fresh_current = Utils.add_to_bag bag fresh_current in
534 (* We superpose current with active clauses *)
535 let bag, maxvar, additional_new_clauses =
536 superposition_with_table bag maxvar fresh_current atable
538 debug "Another superposition";
539 let new_clauses = new_clauses @ additional_new_clauses in
540 debug (Printf.sprintf "Demodulating %d clauses"
541 (List.length new_clauses));
542 let bag, new_clauses =
543 HExtlib.filter_map_monad (simplify atable maxvar) bag new_clauses
545 debug "Demodulated new clauses";
546 bag, maxvar, (alist, atable), new_clauses
549 let infer_left bag maxvar goal (_alist, atable) =
550 (* We superpose the goal with active clauses *)
551 let bag, maxvar, new_goals =
552 superposition_with_table bag maxvar goal atable
554 debug "Superposed goal with active clauses";
555 (* We simplify the new goals with active clauses *)
559 match simplify_goal maxvar atable bag [] g with
560 | None -> assert false
561 | Some (bag,g) -> bag,g::acc)
564 debug "Simplified new goals with active clauses";
565 bag, maxvar, List.rev new_goals