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
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 Utils.add_to_bag bag (0, literal, vars_of_term t, proof)
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 =
136 (* debug ("Demodulating : " ^ (Pp.pp_unit_clause (id, literal, vl, pr)));*)
138 | Terms.Predicate t -> assert false
139 | Terms.Equation (l,r,ty,_) ->
140 let left_position = if jump_to_right then None else
142 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; x; r ]) l
145 match left_position with
146 | Some (newt, subst, varlist, id2, pos, dir) ->
148 match build_clause bag (fun _ -> true) Terms.Demodulation
149 newt subst varlist id id2 pos dir
151 | None -> assert false
152 | Some x -> Some (x,false)
156 [3] (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; l; x ]) r
160 | Some (newt, subst, varlist, id2, pos, dir) ->
161 match build_clause bag (fun _ -> true)
162 Terms.Demodulation newt subst varlist id id2 pos dir
164 | None -> assert false
165 | Some x -> Some (x,true)
168 let rec demodulate ~jump_to_right bag clause table =
169 match demodulate_once ~jump_to_right bag clause table with
170 | None -> bag, clause
171 | Some ((bag, clause),r) -> demodulate ~jump_to_right:r
175 let demodulate bag clause table = demodulate ~jump_to_right:false
180 let is_identity_clause ~unify = function
181 | _, Terms.Equation (_,_,_,Terms.Eq), _, _ -> true
182 | _, Terms.Equation (l,r,_,_), vl, proof when unify ->
183 (try ignore(Unif.unification vl [] l r); true
184 with FoUnif.UnificationFailure _ -> false)
185 | _, Terms.Equation (_,_,_,_), _, _ -> 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 let rec orphan_murder bag acc i =
299 match Terms.M.find i bag with
300 | (_,_,_,Terms.Exact _),discarded -> (discarded,acc)
301 | (_,_,_,Terms.Step (_,i1,i2,_,_,_)),true -> (true,acc)
302 | (_,_,_,Terms.Step (_,i1,i2,_,_,_)),false ->
303 if (List.mem i acc) then (false,acc)
304 else match orphan_murder bag acc i1 with
305 | (true,acc) -> (true,acc)
307 let (res,acc) = orphan_murder bag acc i2 in
308 if res then res,acc else res,i::acc
311 let orphan_murder bag cl =
312 let (id,_,_,_) = cl in
313 let (res,_) = orphan_murder bag [] id in
314 if res then debug "Orphan murdered"; res
317 (* demodulate and check for subsumption *)
318 let simplify table maxvar bag clause =
319 if is_identity_clause ~unify:false clause then bag,None
320 (* else if orphan_murder bag clause then bag,None *)
321 else let bag, clause = demodulate bag clause table in
322 if is_identity_clause ~unify:false clause then bag,None
324 match is_subsumed ~unify:false bag maxvar clause table with
325 | None -> bag, Some clause
326 | Some _ -> bag, None
329 let simplify table maxvar bag clause =
330 match simplify table maxvar bag clause with
331 | bag, None -> let (id,_,_,_) = clause in
332 Terms.M.add id (clause,true) bag, None
333 | bag, Some clause -> bag, Some clause
336 let one_pass_simplification new_clause (alist,atable) bag maxvar =
337 match simplify atable maxvar bag new_clause with
338 | bag,None -> bag,None (* new_clause has been discarded *)
339 | bag,(Some clause) ->
340 let ctable = IDX.index_unit_clause IDX.DT.empty clause in
341 let bag, alist, atable =
343 (fun (bag, alist, atable) c ->
344 match simplify ctable maxvar bag c with
345 |bag,None -> (bag,alist,atable)
346 (* an active clause as been discarded *)
348 bag, c :: alist, IDX.index_unit_clause atable c)
349 (bag,[],IDX.DT.empty) alist
351 bag, Some (clause, (alist,atable))
354 let simplification_step ~new_cl cl (alist,atable) bag maxvar new_clause =
356 if new_cl then atable else
357 IDX.index_unit_clause atable cl
359 (* Simplification of new_clause with : *
360 * - actives and cl if new_clause is not cl *
361 * - only actives otherwise *)
362 match simplify atable1 maxvar bag new_clause with
363 | bag,None -> bag,(Some cl, None) (* new_clause has been discarded *)
365 (* Simplification of each active clause with clause *
366 * which is the simplified form of new_clause *)
367 let ctable = IDX.index_unit_clause IDX.DT.empty clause in
368 let bag, newa, alist, atable =
370 (fun (bag, newa, alist, atable) c ->
371 match simplify ctable maxvar bag c with
372 |bag,None -> (bag, newa, alist, atable)
373 (* an active clause as been discarded *)
376 bag, newa, c :: alist,
377 IDX.index_unit_clause atable c
379 bag, c1 :: newa, alist, atable)
380 (bag,[],[],IDX.DT.empty) alist
383 bag, (Some cl, Some (clause, (alist,atable), newa))
385 (* if new_clause is not cl, we simplify cl with clause *)
386 match simplify ctable maxvar bag cl with
388 (* cl has been discarded *)
389 bag,(None, Some (clause, (alist,atable), newa))
391 bag,(Some cl1, Some (clause, (alist,atable), newa))
394 let keep_simplified cl (alist,atable) bag maxvar =
395 let rec keep_simplified_aux ~new_cl cl (alist,atable) bag newc =
397 match simplification_step ~new_cl cl (alist,atable) bag maxvar cl with
398 | _,(None, _) -> assert false
399 | bag,(Some _, None) -> bag,None
400 | bag,(Some _, Some (clause, (alist,atable), newa)) ->
401 keep_simplified_aux ~new_cl:(cl!=clause) clause (alist,atable)
405 | [] -> bag, Some (cl, (alist,atable))
407 match simplification_step ~new_cl cl
408 (alist,atable) bag maxvar hd with
409 | _,(None,None) -> assert false
410 | bag,(Some _,None) ->
411 keep_simplified_aux ~new_cl cl (alist,atable) bag tl
412 | bag,(None, Some _) -> bag,None
413 | bag,(Some cl1, Some (clause, (alist,atable), newa)) ->
415 (clause::alist, IDX.index_unit_clause atable clause)
417 keep_simplified_aux ~new_cl:(cl!=cl1) cl1 (alist,atable)
420 keep_simplified_aux ~new_cl:true cl (alist,atable) bag []
423 let are_alpha_eq cl1 cl2 =
424 let get_term (_,lit,_,_) =
426 | Terms.Predicate _ -> assert false
427 | Terms.Equation (l,r,ty,_) ->
428 Terms.Node [Terms.Leaf B.eqP; ty; l ; r]
430 try ignore(Unif.alpha_eq (get_term cl1) (get_term cl2)) ; true
431 with FoUnif.UnificationFailure _ -> false
434 (* this is like simplify but raises Success *)
435 let simplify_goal maxvar table bag g_actives clause =
436 let bag, clause = demodulate bag clause table in
437 if (is_identity_clause ~unify:true clause)
438 then raise (Success (bag, maxvar, clause))
441 let (id,lit,vl,_) = clause in
444 | Terms.Equation(l,r,ty,_) -> l,r,ty
447 match deep_eq ~unify:true l r ty [] (fun x -> x) (fun x -> x)
448 table (Some(bag,maxvar,[clause],Subst.id_subst)) with
450 if List.exists (are_alpha_eq clause) g_actives then None
451 else Some (bag, clause)
452 | Some (bag,maxvar,cl,subst) ->
453 debug "Goal subsumed";
454 raise (Success (bag,maxvar,List.hd cl))
456 else match is_subsumed ~unify:true bag maxvar clause table with
458 if List.exists (are_alpha_eq clause) g_actives then None
459 else Some (bag, clause)
460 | Some ((bag,maxvar),c) ->
461 debug "Goal subsumed";
462 raise (Success (bag,maxvar,c))
465 (* =================== inference ===================== *)
467 (* this is OK for both the sup_left and sup_right inference steps *)
468 let superposition table varlist subterm pos context =
469 let cands = IDX.DT.retrieve_unifiables table subterm in
471 (fun (dir, (id,lit,vl,_ (*as uc*))) ->
473 | Terms.Predicate _ -> assert false
474 | Terms.Equation (l,r,_,o) ->
475 let side, newside = if dir=Terms.Left2Right then l,r else r,l in
478 Unif.unification (varlist@vl) [] subterm side
480 if o = Terms.Incomparable then
481 let side = Subst.apply_subst subst side in
482 let newside = Subst.apply_subst subst newside in
483 let o = Order.compare_terms side newside in
484 (* XXX: check Riazanov p. 33 (iii) *)
485 if o <> Terms.Lt && o <> Terms.Eq then
486 Some (context newside, subst, varlist, id, pos, dir)
488 ((*prerr_endline ("Filtering: " ^
489 Pp.pp_foterm side ^ " =(< || =)" ^
490 Pp.pp_foterm newside ^ " coming from " ^
491 Pp.pp_unit_clause uc );*)None)
493 Some (context newside, subst, varlist, id, pos, dir)
494 with FoUnif.UnificationFailure _ -> None)
495 (IDX.ClauseSet.elements cands)
498 (* Superposes selected equation with equalities in table *)
499 let superposition_with_table bag maxvar (id,selected,vl,_) table =
501 | Terms.Predicate _ -> assert false
502 | Terms.Equation (l,r,ty,Terms.Lt) ->
503 fold_build_new_clause bag maxvar id Terms.Superposition
506 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; l; x ])
507 r (superposition table vl))
508 | Terms.Equation (l,r,ty,Terms.Gt) ->
509 fold_build_new_clause bag maxvar id Terms.Superposition
512 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; x; r ])
513 l (superposition table vl))
514 | Terms.Equation (l,r,ty,Terms.Incomparable) ->
515 fold_build_new_clause bag maxvar id Terms.Superposition
516 (function (* Riazanov: p.33 condition (iv) *)
517 | Terms.Node [Terms.Leaf eq; ty; l; r ] when B.eq B.eqP eq ->
518 Order.compare_terms l r <> Terms.Eq
521 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; l; x ])
522 r (superposition table vl)) @
524 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; x; r ])
525 l (superposition table vl)))
529 (* the current equation is normal w.r.t. demodulation with atable
530 * (and is not the identity) *)
531 let infer_right bag maxvar current (alist,atable) =
532 (* We demodulate actives clause with current until all *
533 * active clauses are reduced w.r.t each other *)
534 (* let bag, (alist,atable) = keep_simplified (alist,atable) bag [current] in *)
535 let ctable = IDX.index_unit_clause IDX.DT.empty current in
536 (* let bag, (alist, atable) =
538 HExtlib.filter_map_acc (simplify ctable) bag alist
540 bag, (alist, List.fold_left IDX.index_unit_clause IDX.DT.empty alist)
542 debug "Simplified active clauses with fact";
543 (* We superpose active clauses with current *)
544 let bag, maxvar, new_clauses =
546 (fun (bag, maxvar, acc) active ->
547 let bag, maxvar, newc =
548 superposition_with_table bag maxvar active ctable
550 bag, maxvar, newc @ acc)
551 (bag, maxvar, []) alist
553 debug "First superpositions";
554 (* We add current to active clauses so that it can be *
555 * superposed with itself *)
557 current :: alist, IDX.index_unit_clause atable current
560 let fresh_current, maxvar = Utils.fresh_unit_clause maxvar current in
561 (* We need to put fresh_current into the bag so that all *
562 * variables clauses refer to are known. *)
563 let bag, fresh_current = Utils.add_to_bag bag fresh_current in
564 (* We superpose current with active clauses *)
565 let bag, maxvar, additional_new_clauses =
566 superposition_with_table bag maxvar fresh_current atable
568 debug "Another superposition";
569 let new_clauses = new_clauses @ additional_new_clauses in
570 debug (Printf.sprintf "Demodulating %d clauses"
571 (List.length new_clauses));
572 let bag, new_clauses =
573 HExtlib.filter_map_monad (simplify atable maxvar) bag new_clauses
575 debug "Demodulated new clauses";
576 bag, maxvar, (alist, atable), new_clauses
579 let infer_left bag maxvar goal (_alist, atable) =
580 (* We superpose the goal with active clauses *)
581 let bag, maxvar, new_goals =
582 superposition_with_table bag maxvar goal atable
584 debug "Superposed goal with active clauses";
585 (* We simplify the new goals with active clauses *)
589 match simplify_goal maxvar atable bag [] g with
590 | None -> assert false
591 | Some (bag,g) -> bag,g::acc)
594 debug "Simplified new goals with active clauses";
595 bag, maxvar, List.rev new_goals