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)
198 let fold_build_new_clause bag maxvar id rule filter res =
199 let (bag, maxvar), res =
200 HExtlib.filter_map_acc
201 (fun (bag, maxvar) (t,subst,vl,id2,pos,dir) ->
202 build_new_clause bag maxvar filter rule t subst vl id id2 pos dir)
208 let is_subsumed ~unify bag maxvar (id, lit, vl, _) table =
210 | Terms.Predicate _ -> assert false
211 | Terms.Equation (l,r,ty,_) ->
212 let retrieve = if unify then IDX.DT.retrieve_unifiables
213 else IDX.DT.retrieve_generalizations in
214 let lcands = retrieve table l in
215 let rcands = retrieve table r in
217 let id, dir, l, r, vl =
219 | (d, (id,Terms.Equation (l,r,ty,_),vl,_))-> id, d, l, r, vl
222 let reverse = (dir = Terms.Left2Right) = b in
223 let l, r, proof_rewrite_dir = if reverse then l,r,Terms.Left2Right
224 else r,l, Terms.Right2Left in
225 (id,proof_rewrite_dir,Terms.Node [ Terms.Leaf B.eqP; ty; l; r ], vl)
227 let cands1 = List.map (f true) (IDX.ClauseSet.elements lcands) in
228 let cands2 = List.map (f false) (IDX.ClauseSet.elements rcands) in
229 let t = Terms.Node [ Terms.Leaf B.eqP; ty; l; r ] in
230 let locked_vars = if unify then [] else vl in
231 let rec aux = function
233 | (id2,dir,c,vl1)::tl ->
235 let subst,vl1 = Unif.unification (vl@vl1) locked_vars c t in
236 let id_t = Terms.Node [ Terms.Leaf B.eqP; ty; r; r ] in
237 build_new_clause bag maxvar (fun _ -> true)
238 Terms.Superposition id_t subst [] id id2 [2] dir
239 with FoUnif.UnificationFailure _ -> aux tl
241 aux (cands1 @ cands2)
244 (* demodulate and check for subsumption *)
245 let simplify table maxvar bag clause =
246 let bag, clause = demodulate bag clause table in
247 if is_identity_clause clause then None
249 match is_subsumed ~unify:false bag maxvar clause table with
250 | None -> Some (bag, clause)
254 let one_pass_simplification new_clause (alist,atable) bag maxvar =
255 match simplify atable maxvar bag new_clause with
256 | None -> None (* new_clause has been discarded *)
257 | Some (bag, clause) ->
258 let ctable = IDX.index_unit_clause IDX.DT.empty clause in
259 let bag, alist, atable =
261 (fun (bag, alist, atable as acc) c ->
262 match simplify ctable maxvar bag c with
263 |None -> acc (* an active clause as been discarded *)
265 bag, c :: alist, IDX.index_unit_clause atable c)
266 (bag,[],IDX.DT.empty) alist
268 Some (clause, bag, (alist,atable))
271 let simplification_step ~new_cl cl (alist,atable) bag maxvar new_clause =
273 if new_cl then atable else
274 IDX.index_unit_clause atable cl
276 (* Simplification of new_clause with : *
277 * - actives and cl if new_clause is not cl *
278 * - only actives otherwise *)
279 match simplify atable1 maxvar bag new_clause with
280 | None -> (Some cl, None) (* new_clause has been discarded *)
281 | Some (bag, clause) ->
282 (* Simplification of each active clause with clause *
283 * which is the simplified form of new_clause *)
284 let ctable = IDX.index_unit_clause IDX.DT.empty clause in
285 let bag, newa, alist, atable =
287 (fun (bag, newa, alist, atable as acc) c ->
288 match simplify ctable maxvar bag c with
289 |None -> acc (* an active clause as been discarded *)
292 bag, newa, c :: alist,
293 IDX.index_unit_clause atable c
295 bag, c1 :: newa, alist, atable)
296 (bag,[],[],IDX.DT.empty) alist
299 (Some cl, Some (clause, (alist,atable), newa, bag))
301 (* if new_clause is not cl, we simplify cl with clause *)
302 match simplify ctable maxvar bag cl with
304 (* cl has been discarded *)
305 (None, Some (clause, (alist,atable), newa, bag))
307 (Some cl1, Some (clause, (alist,atable), newa, bag))
310 let keep_simplified cl (alist,atable) bag maxvar =
311 let rec keep_simplified_aux ~new_cl cl (alist,atable) bag newc =
313 match simplification_step ~new_cl cl (alist,atable) bag maxvar cl with
314 | (None, _) -> assert false
315 | (Some _, None) -> None
316 | (Some _, Some (clause, (alist,atable), newa, bag)) ->
317 keep_simplified_aux ~new_cl:(cl!=clause) clause (alist,atable)
321 | [] -> Some (cl, bag, (alist,atable))
323 match simplification_step ~new_cl cl
324 (alist,atable) bag maxvar hd with
325 | (None,None) -> assert false
327 keep_simplified_aux ~new_cl cl (alist,atable) bag tl
328 | (None, Some _) -> None
329 | (Some cl1, Some (clause, (alist,atable), newa, bag)) ->
331 (clause::alist, IDX.index_unit_clause atable clause)
333 keep_simplified_aux ~new_cl:(cl!=cl1) cl1 (alist,atable)
336 keep_simplified_aux ~new_cl:true cl (alist,atable) bag []
339 let are_alpha_eq cl1 cl2 =
340 let get_term (_,lit,_,_) =
342 | Terms.Predicate _ -> assert false
343 | Terms.Equation (l,r,ty,_) ->
344 Terms.Node [Terms.Leaf B.eqP; ty; l ; r]
346 try ignore(Unif.alpha_eq (get_term cl1) (get_term cl2)) ; true
347 with FoUnif.UnificationFailure _ -> false
350 (* this is like simplify but raises Success *)
351 let simplify_goal maxvar table bag g_actives clause =
352 let bag, clause = demodulate bag clause table in
353 if (is_identity_clause clause)
354 then raise (Success (bag, maxvar, clause))
355 else match is_subsumed ~unify:true bag maxvar clause table with
357 if List.exists (are_alpha_eq clause) g_actives then None
358 else Some (bag, clause)
359 | Some ((bag,maxvar),c) ->
360 debug "Goal subsumed";
361 raise (Success (bag,maxvar,c))
364 (* =================== inference ===================== *)
366 (* this is OK for both the sup_left and sup_right inference steps *)
367 let superposition table varlist subterm pos context =
368 let cands = IDX.DT.retrieve_unifiables table subterm in
370 (fun (dir, (id,lit,vl,_ (*as uc*))) ->
372 | Terms.Predicate _ -> assert false
373 | Terms.Equation (l,r,_,o) ->
374 let side, newside = if dir=Terms.Left2Right then l,r else r,l in
377 Unif.unification (varlist@vl) [] subterm side
379 if o = Terms.Incomparable then
380 let side = Subst.apply_subst subst side in
381 let newside = Subst.apply_subst subst newside in
382 let o = Order.compare_terms side newside in
383 (* XXX: check Riazanov p. 33 (iii) *)
384 if o <> Terms.Lt && o <> Terms.Eq then
385 Some (context newside, subst, varlist, id, pos, dir)
387 ((*prerr_endline ("Filtering: " ^
388 Pp.pp_foterm side ^ " =(< || =)" ^
389 Pp.pp_foterm newside ^ " coming from " ^
390 Pp.pp_unit_clause uc );*)None)
392 Some (context newside, subst, varlist, id, pos, dir)
393 with FoUnif.UnificationFailure _ -> None)
394 (IDX.ClauseSet.elements cands)
397 (* Superposes selected equation with equalities in table *)
398 let superposition_with_table bag maxvar (id,selected,vl,_) table =
400 | Terms.Predicate _ -> assert false
401 | Terms.Equation (l,r,ty,Terms.Lt) ->
402 fold_build_new_clause bag maxvar id Terms.Superposition
405 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; l; x ])
406 r (superposition table vl))
407 | Terms.Equation (l,r,ty,Terms.Gt) ->
408 fold_build_new_clause bag maxvar id Terms.Superposition
411 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; x; r ])
412 l (superposition table vl))
413 | Terms.Equation (l,r,ty,Terms.Incomparable) ->
414 fold_build_new_clause bag maxvar id Terms.Superposition
415 (function (* Riazanov: p.33 condition (iv) *)
416 | Terms.Node [Terms.Leaf eq; ty; l; r ] when B.eq B.eqP eq ->
417 Order.compare_terms l r <> Terms.Eq
420 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; l; x ])
421 r (superposition table vl)) @
423 (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; x; r ])
424 l (superposition table vl)))
428 (* the current equation is normal w.r.t. demodulation with atable
429 * (and is not the identity) *)
430 let infer_right bag maxvar current (alist,atable) =
431 (* We demodulate actives clause with current until all *
432 * active clauses are reduced w.r.t each other *)
433 (* let bag, (alist,atable) = keep_simplified (alist,atable) bag [current] in *)
434 let ctable = IDX.index_unit_clause IDX.DT.empty current in
435 (* let bag, (alist, atable) =
437 HExtlib.filter_map_acc (simplify ctable) bag alist
439 bag, (alist, List.fold_left IDX.index_unit_clause IDX.DT.empty alist)
441 debug "Simplified active clauses with fact";
442 (* We superpose active clauses with current *)
443 let bag, maxvar, new_clauses =
445 (fun (bag, maxvar, acc) active ->
446 let bag, maxvar, newc =
447 superposition_with_table bag maxvar active ctable
449 bag, maxvar, newc @ acc)
450 (bag, maxvar, []) alist
452 debug "First superpositions";
453 (* We add current to active clauses so that it can be *
454 * superposed with itself *)
456 current :: alist, IDX.index_unit_clause atable current
459 let fresh_current, maxvar = Utils.fresh_unit_clause maxvar current in
460 (* We need to put fresh_current into the bag so that all *
461 * variables clauses refer to are known. *)
462 let bag, fresh_current = Utils.add_to_bag bag fresh_current in
463 (* We superpose current with active clauses *)
464 let bag, maxvar, additional_new_clauses =
465 superposition_with_table bag maxvar fresh_current atable
467 debug "Another superposition";
468 let new_clauses = new_clauses @ additional_new_clauses in
469 debug (Printf.sprintf "Demodulating %d clauses"
470 (List.length new_clauses));
471 let bag, new_clauses =
472 HExtlib.filter_map_acc (simplify atable maxvar) bag new_clauses
474 debug "Demodulated new clauses";
475 bag, maxvar, (alist, atable), new_clauses
478 let infer_left bag maxvar goal (_alist, atable) =
479 (* We superpose the goal with active clauses *)
480 let bag, maxvar, new_goals =
481 superposition_with_table bag maxvar goal atable
483 debug "Superposed goal with active clauses";
484 (* We simplify the new goals with active clauses *)
488 match simplify_goal maxvar atable bag [] g with
489 | None -> assert false
490 | Some (bag,g) -> bag,g::acc)
493 debug "Simplified new goals with active clauses";
494 bag, maxvar, List.rev new_goals