1 (* Copyright (C) 2000, HELM Team.
3 * This file is part of HELM, an Hypertextual, Electronic
4 * Library of Mathematics, developed at the Computer Science
5 * Department, University of Bologna, Italy.
7 * HELM is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; either version 2
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13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
17 * You should have received a copy of the GNU General Public License
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19 * Foundation, Inc., 59 Temple Place - Suite 330, Boston,
22 * For details, see the HELM World-Wide-Web page,
23 * http://cs.unibo.it/helm/.
26 exception UnificationFailed;;
28 exception OccurCheck;;
29 exception RelToHiddenHypothesis;;
34 (* the delift function takes in input an ordered list of optional terms *)
35 (* [t1,...,tn] and a term t, and substitutes every tk = Some (rel(nk)) with *)
36 (* rel(k). Typically, the list of optional terms is the explicit substitution *)(* that is applied to a metavariable occurrence and the result of the delift *)
37 (* function is a term the implicit variable can be substituted with to make *)
38 (* the term [t] unifiable with the metavariable occurrence. *)
39 (* In general, the problem is undecidable if we consider equivalence in place *)
40 (* of alpha convertibility. Our implementation, though, is even weaker than *)
41 (* alpha convertibility, since it replace the term [tk] if and only if [tk] *)
42 (* is a Rel (missing all the other cases). Does this matter in practice? *)
44 exception NotInTheList;;
49 [] -> raise NotInTheList
50 | (Some (Cic.Rel m))::_ when m=n -> k
51 | _::tl -> aux (k+1) tl in
55 (*CSC: this restriction function is utterly wrong, since it does not check *)
56 (*CSC: that the variable that is going to be restricted does not occur free *)
57 (*CSC: in a part of the sequent that is not going to be restricted. *)
58 (*CSC: In particular, the whole approach is wrong; if restriction can fail *)
59 (*CSC: (as indeed it is the case), we can not collect all the restrictions *)
60 (*CSC: and restrict everything at the end ;-( *)
61 let restrict to_be_restricted =
65 | _::tl when List.mem (n,i) to_be_restricted ->
66 None::(erase (i+1) n tl)
67 | he::tl -> he::(erase (i+1) n tl) in
71 | (n,context,t)::tl -> (n,erase 1 n context,t)::(aux tl) in
76 (*CSC: maybe we should rename delift in abstract, as I did in my dissertation *)
77 let delift context metasenv l t =
78 let module S = CicSubstitution in
79 let to_be_restricted = ref [] in
85 C.Rel m (*CSC: che succede se c'e' un Def? Dovrebbe averlo gia' *)
86 (*CSC: deliftato la regola per il LetIn *)
87 (*CSC: FALSO! La regola per il LetIn non lo fa *)
89 (match List.nth context (m-k-1) with
90 Some (_,C.Def (t,_)) ->
91 (*CSC: Hmmm. This bit of reduction is not in the spirit of *)
92 (*CSC: first order unification. Does it help or does it harm? *)
93 deliftaux k (S.lift m t)
94 | Some (_,C.Decl t) ->
95 (* It may augment to_be_restricted *)
96 (*CSC: Really? Even in the case of well-typed terms? *)
97 (*CSC: I am no longer sure of the usefulness of the check *)
98 ignore (deliftaux k (S.lift m t)) ;
99 C.Rel ((position (m-k) l) + k)
100 | None -> raise RelToHiddenHypothesis)
101 | C.Var (uri,exp_named_subst) ->
102 let exp_named_subst' =
103 List.map (function (uri,t) -> uri,deliftaux k t) exp_named_subst
105 C.Var (uri,exp_named_subst')
106 | C.Meta (i, l1) as t ->
110 | None::tl -> None::(deliftl (j+1) tl)
112 let l1' = (deliftl (j+1) tl) in
114 Some (deliftaux k t)::l1'
116 RelToHiddenHypothesis
118 to_be_restricted := (i,j)::!to_be_restricted ; None::l1'
120 let l' = deliftl 1 l1 in
123 | C.Implicit as t -> t
124 | C.Cast (te,ty) -> C.Cast (deliftaux k te, deliftaux k ty)
125 | C.Prod (n,s,t) -> C.Prod (n, deliftaux k s, deliftaux (k+1) t)
126 | C.Lambda (n,s,t) -> C.Lambda (n, deliftaux k s, deliftaux (k+1) t)
127 | C.LetIn (n,s,t) -> C.LetIn (n, deliftaux k s, deliftaux (k+1) t)
128 | C.Appl l -> C.Appl (List.map (deliftaux k) l)
129 | C.Const (uri,exp_named_subst) ->
130 let exp_named_subst' =
131 List.map (function (uri,t) -> uri,deliftaux k t) exp_named_subst
133 C.Const (uri,exp_named_subst')
134 | C.MutInd (uri,typeno,exp_named_subst) ->
135 let exp_named_subst' =
136 List.map (function (uri,t) -> uri,deliftaux k t) exp_named_subst
138 C.MutInd (uri,typeno,exp_named_subst')
139 | C.MutConstruct (uri,typeno,consno,exp_named_subst) ->
140 let exp_named_subst' =
141 List.map (function (uri,t) -> uri,deliftaux k t) exp_named_subst
143 C.MutConstruct (uri,typeno,consno,exp_named_subst')
144 | C.MutCase (sp,i,outty,t,pl) ->
145 C.MutCase (sp, i, deliftaux k outty, deliftaux k t,
146 List.map (deliftaux k) pl)
148 let len = List.length fl in
151 (fun (name, i, ty, bo) ->
152 (name, i, deliftaux k ty, deliftaux (k+len) bo))
157 let len = List.length fl in
160 (fun (name, ty, bo) -> (name, deliftaux k ty, deliftaux (k+len) bo))
163 C.CoFix (i, liftedfl)
170 (* This is the case where we fail even first order unification. *)
171 (* The reason is that our delift function is weaker than first *)
172 (* order (in the sense of alpha-conversion). See comment above *)
173 (* related to the delift function. *)
174 prerr_endline "!!!!!!!!!!! First Order UnificationFailed, but maybe it could have been successful even in a first order setting (no conversion, only alpha convertibility)! Please, implement a better delift function !!!!!!!!!!!!!!!!" ;
175 raise UnificationFailed
177 res, restrict !to_be_restricted metasenv
180 (**** END OF DELIFT ****)
182 type substitution = (int * Cic.term) list
184 (* NUOVA UNIFICAZIONE *)
185 (* A substitution is a (int * Cic.term) list that associates a
186 metavariable i with its body.
187 A metaenv is a (int * Cic.term) list that associate a metavariable
189 fo_unif_new takes a metasenv, a context, two terms t1 and t2 and gives back
190 a new substitution which is _NOT_ unwinded. It must be unwinded before
193 let rec fo_unif_subst subst context metasenv t1 t2 =
194 let module C = Cic in
195 let module R = CicReduction in
196 let module S = CicSubstitution in
198 (C.Meta (n,ln), C.Meta (m,lm)) when n=m ->
206 | Some t1', Some t2' ->
207 (* First possibility: restriction *)
208 (* Second possibility: unification *)
209 (* Third possibility: convertibility *)
210 R.are_convertible context t1' t2'
213 if ok then subst,metasenv else raise UnificationFailed
214 | (C.Meta (n,l), C.Meta (m,_)) when n>m ->
215 fo_unif_subst subst context metasenv t2 t1
217 | (t, C.Meta (n,l)) ->
218 let subst',metasenv' =
220 let oldt = (List.assoc n subst) in
221 let lifted_oldt = S.lift_meta l oldt in
222 fo_unif_subst subst context metasenv lifted_oldt t
224 let t',metasenv' = delift context metasenv l t in
225 (n, t')::subst, metasenv'
227 let (_,_,meta_type) =
228 List.find (function (m,_,_) -> m=n) metasenv' in
229 let tyt = CicTypeChecker.type_of_aux' metasenv' context t in
230 fo_unif_subst subst' context metasenv' (S.lift_meta l meta_type) tyt
231 | (C.Var (uri1,exp_named_subst1),C.Var (uri2,exp_named_subst2))
232 | (C.Const (uri1,exp_named_subst1),C.Const (uri2,exp_named_subst2)) ->
233 if UriManager.eq uri1 uri2 then
234 fo_unif_subst_exp_named_subst subst context metasenv
235 exp_named_subst1 exp_named_subst2
237 raise UnificationFailed
238 | C.MutInd (uri1,i1,exp_named_subst1),C.MutInd (uri2,i2,exp_named_subst2) ->
239 if UriManager.eq uri1 uri2 && i1 = i2 then
240 fo_unif_subst_exp_named_subst subst context metasenv
241 exp_named_subst1 exp_named_subst2
243 raise UnificationFailed
244 | C.MutConstruct (uri1,i1,j1,exp_named_subst1),
245 C.MutConstruct (uri2,i2,j2,exp_named_subst2) ->
246 if UriManager.eq uri1 uri2 && i1 = i2 && j1 = j2 then
247 fo_unif_subst_exp_named_subst subst context metasenv
248 exp_named_subst1 exp_named_subst2
250 raise UnificationFailed
257 if R.are_convertible context t1 t2 then
260 raise UnificationFailed
261 | (C.Cast (te,ty), t2) -> fo_unif_subst subst context metasenv te t2
262 | (t1, C.Cast (te,ty)) -> fo_unif_subst subst context metasenv t1 te
263 | (C.Prod (n1,s1,t1), C.Prod (_,s2,t2)) ->
264 let subst',metasenv' = fo_unif_subst subst context metasenv s1 s2 in
265 fo_unif_subst subst' ((Some (n1,(C.Decl s1)))::context) metasenv' t1 t2
266 | (C.Lambda (n1,s1,t1), C.Lambda (_,s2,t2)) ->
267 let subst',metasenv' = fo_unif_subst subst context metasenv s1 s2 in
268 fo_unif_subst subst' ((Some (n1,(C.Decl s1)))::context) metasenv' t1 t2
269 | (C.LetIn (_,s1,t1), t2)
270 | (t2, C.LetIn (_,s1,t1)) ->
271 fo_unif_subst subst context metasenv t2 (S.subst s1 t1)
272 | (C.Appl l1, C.Appl l2) ->
273 let lr1 = List.rev l1 in
274 let lr2 = List.rev l2 in
275 let rec fo_unif_l subst metasenv =
278 | _,[] -> assert false
280 fo_unif_subst subst context metasenv h1 h2
283 fo_unif_subst subst context metasenv h (C.Appl (List.rev l))
284 | ((h1::l1),(h2::l2)) ->
285 let subst', metasenv' =
286 fo_unif_subst subst context metasenv h1 h2
288 fo_unif_l subst' metasenv' (l1,l2)
290 fo_unif_l subst metasenv (lr1, lr2)
295 | (C.MutConstruct _, _)
296 | (_, C.MutConstruct _) ->
297 if R.are_convertible context t1 t2 then
300 raise UnificationFailed
301 | (C.MutCase (_,_,outt1,t1,pl1), C.MutCase (_,_,outt2,t2,pl2))->
302 let subst', metasenv' =
303 fo_unif_subst subst context metasenv outt1 outt2 in
304 let subst'',metasenv'' =
305 fo_unif_subst subst' context metasenv' t1 t2 in
307 (function (subst,metasenv) ->
308 fo_unif_subst subst context metasenv
309 ) (subst'',metasenv'') pl1 pl2
314 if R.are_convertible context t1 t2 then
317 raise UnificationFailed
319 if R.are_convertible context t1 t2 then
322 raise UnificationFailed
324 and fo_unif_subst_exp_named_subst subst context metasenv
325 exp_named_subst1 exp_named_subst2
329 (fun (subst,metasenv) (uri1,t1) (uri2,t2) ->
331 fo_unif_subst subst context metasenv t1 t2
332 ) (subst,metasenv) exp_named_subst1 exp_named_subst2
335 let uri = UriManager.uri_of_string "cic:/dummy.var" in
336 prerr_endline ("@@@: " ^ CicPp.ppterm (Cic.Var (uri,exp_named_subst1)) ^
337 " <==> " ^ CicPp.ppterm (Cic.Var (uri,exp_named_subst2))) ; raise e
340 let unwind metasenv subst unwinded t =
341 let unwinded = ref unwinded in
342 let frozen = ref [] in
343 let rec um_aux metasenv =
344 let module C = Cic in
345 let module S = CicSubstitution in
347 C.Rel _ as t -> t,metasenv
348 | C.Var _ as t -> t,metasenv
351 S.lift_meta l (List.assoc i !unwinded), metasenv
353 if List.mem i !frozen then raise OccurCheck
355 let saved_frozen = !frozen in
356 frozen := i::!frozen ;
359 let t = List.assoc i subst in
360 let t',metasenv' = um_aux metasenv t in
362 let (_,canonical_context,_) =
363 List.find (function (m,_,_) -> m=i) metasenv
365 delift canonical_context metasenv' l t'
367 unwinded := (i,t')::!unwinded ;
368 S.lift_meta l t', metasenv'
371 (* not constrained variable, i.e. free in subst*)
374 (fun t (tl,metasenv) ->
376 None -> None::tl,metasenv
378 let t',metasenv' = um_aux metasenv t in
379 (Some t')::tl, metasenv'
382 C.Meta (i,l'), metasenv'
384 frozen := saved_frozen ;
388 | C.Implicit as t -> t,metasenv
390 let te',metasenv' = um_aux metasenv te in
391 let ty',metasenv'' = um_aux metasenv' ty in
392 C.Cast (te',ty'),metasenv''
394 let s',metasenv' = um_aux metasenv s in
395 let t',metasenv'' = um_aux metasenv' t in
396 C.Prod (n, s', t'), metasenv''
397 | C.Lambda (n,s,t) ->
398 let s',metasenv' = um_aux metasenv s in
399 let t',metasenv'' = um_aux metasenv' t in
400 C.Lambda (n, s', t'), metasenv''
402 let s',metasenv' = um_aux metasenv s in
403 let t',metasenv'' = um_aux metasenv' t in
404 C.LetIn (n, s', t'), metasenv''
408 (fun t (tl,metasenv) ->
409 let t',metasenv' = um_aux metasenv t in
414 match um_aux metasenv' he with
415 (C.Appl l, metasenv'') -> C.Appl (l@tl'),metasenv''
416 | (he', metasenv'') -> C.Appl (he'::tl'),metasenv''
418 | C.Appl _ -> assert false
419 | C.Const (uri,exp_named_subst) ->
420 let exp_named_subst', metasenv' =
422 (fun (uri,t) (tl,metasenv) ->
423 let t',metasenv' = um_aux metasenv t in
424 (uri,t')::tl, metasenv'
425 ) exp_named_subst ([],metasenv)
427 C.Const (uri,exp_named_subst'),metasenv'
428 | C.MutInd (uri,typeno,exp_named_subst) ->
429 let exp_named_subst', metasenv' =
431 (fun (uri,t) (tl,metasenv) ->
432 let t',metasenv' = um_aux metasenv t in
433 (uri,t')::tl, metasenv'
434 ) exp_named_subst ([],metasenv)
436 C.MutInd (uri,typeno,exp_named_subst'),metasenv'
437 | C.MutConstruct (uri,typeno,consno,exp_named_subst) ->
438 let exp_named_subst', metasenv' =
440 (fun (uri,t) (tl,metasenv) ->
441 let t',metasenv' = um_aux metasenv t in
442 (uri,t')::tl, metasenv'
443 ) exp_named_subst ([],metasenv)
445 C.MutConstruct (uri,typeno,consno,exp_named_subst'),metasenv'
446 | C.MutCase (sp,i,outty,t,pl) ->
447 let outty',metasenv' = um_aux metasenv outty in
448 let t',metasenv'' = um_aux metasenv' t in
449 let pl',metasenv''' =
451 (fun p (pl,metasenv) ->
452 let p',metasenv' = um_aux metasenv p in
456 C.MutCase (sp, i, outty', t', pl'),metasenv'''
458 let len = List.length fl in
459 let liftedfl,metasenv' =
461 (fun (name, i, ty, bo) (fl,metasenv) ->
462 let ty',metasenv' = um_aux metasenv ty in
463 let bo',metasenv'' = um_aux metasenv' bo in
464 (name, i, ty', bo')::fl,metasenv''
467 C.Fix (i, liftedfl),metasenv'
469 let len = List.length fl in
470 let liftedfl,metasenv' =
472 (fun (name, ty, bo) (fl,metasenv) ->
473 let ty',metasenv' = um_aux metasenv ty in
474 let bo',metasenv'' = um_aux metasenv' bo in
475 (name, ty', bo')::fl,metasenv''
478 C.CoFix (i, liftedfl),metasenv'
480 let t',metasenv' = um_aux metasenv t in
481 t',metasenv',!unwinded
484 (* apply_subst_reducing subst (Some (mtr,reductions_no)) t *)
485 (* performs as (apply_subst subst t) until it finds an application of *)
486 (* (META [meta_to_reduce]) that, once unwinding is performed, creates *)
487 (* a new beta-redex; in this case up to [reductions_no] consecutive *)
488 (* beta-reductions are performed. *)
489 (* Hint: this function is usually called when [reductions_no] *)
490 (* eta-expansions have been performed and the head of the new *)
491 (* application has been unified with (META [meta_to_reduce]): *)
492 (* during the unwinding the eta-expansions are undone. *)
494 let apply_subst_reducing subst meta_to_reduce t =
495 let unwinded = ref subst in
497 let module C = Cic in
498 let module S = CicSubstitution in
502 | C.Meta (i,l) as t ->
504 S.lift_meta l (List.assoc i !unwinded)
508 | C.Implicit as t -> t
509 | C.Cast (te,ty) -> C.Cast (um_aux te, um_aux ty)
510 | C.Prod (n,s,t) -> C.Prod (n, um_aux s, um_aux t)
511 | C.Lambda (n,s,t) -> C.Lambda (n, um_aux s, um_aux t)
512 | C.LetIn (n,s,t) -> C.LetIn (n, um_aux s, um_aux t)
514 let tl' = List.map um_aux tl in
517 C.Appl l -> C.Appl (l@tl')
518 | _ as he' -> C.Appl (he'::tl')
521 match meta_to_reduce,he with
522 Some (mtr,reductions_no), C.Meta (m,_) when m = mtr ->
523 let rec beta_reduce =
525 (n,(C.Appl (C.Lambda (_,_,t)::he'::tl'))) when n > 0 ->
526 let he'' = CicSubstitution.subst he' t in
530 beta_reduce (n-1,C.Appl(he''::tl'))
533 beta_reduce (reductions_no,t')
536 | C.Appl _ -> assert false
537 | C.Const (uri,exp_named_subst) ->
538 let exp_named_subst' =
539 List.map (function (uri,t) -> (uri,um_aux t)) exp_named_subst
541 C.Const (uri,exp_named_subst')
542 | C.MutInd (uri,typeno,exp_named_subst) ->
543 let exp_named_subst' =
544 List.map (function (uri,t) -> (uri,um_aux t)) exp_named_subst
546 C.MutInd (uri,typeno,exp_named_subst')
547 | C.MutConstruct (uri,typeno,consno,exp_named_subst) ->
548 let exp_named_subst' =
549 List.map (function (uri,t) -> (uri,um_aux t)) exp_named_subst
551 C.MutConstruct (uri,typeno,consno,exp_named_subst')
552 | C.MutCase (sp,i,outty,t,pl) ->
553 C.MutCase (sp, i, um_aux outty, um_aux t,
556 let len = List.length fl in
559 (fun (name, i, ty, bo) -> (name, i, um_aux ty, um_aux bo))
564 let len = List.length fl in
567 (fun (name, ty, bo) -> (name, um_aux ty, um_aux bo))
570 C.CoFix (i, liftedfl)
575 (* UNWIND THE MGU INSIDE THE MGU *)
576 let unwind_subst metasenv subst =
577 let identity_relocation_list_for_metavariable i =
578 let (_,canonical_context,_) =
579 List.find (function (m,_,_) -> m=i) metasenv
581 let canonical_context_length = List.length canonical_context in
584 n when n > canonical_context_length -> []
585 | n -> (Some (Cic.Rel n))::(aux (n+1))
590 (fun (unwinded,metasenv) (i,_) ->
591 let identity_relocation_list =
592 identity_relocation_list_for_metavariable i
594 let (_,metasenv',subst') =
595 unwind metasenv subst unwinded (Cic.Meta (i,identity_relocation_list))
598 ) ([],metasenv) subst
601 let apply_subst subst t =
602 (* metasenv will not be used nor modified. So, let's use a dummy empty one *)
604 let (t',_,_) = unwind metasenv [] subst t in
608 (* A substitution is a (int * Cic.term) list that associates a *)
609 (* metavariable i with its body. *)
610 (* metasenv is of type Cic.metasenv *)
611 (* fo_unif takes a metasenv, a context, two terms t1 and t2 and gives back *)
612 (* a new substitution which is already unwinded and ready to be applied and *)
613 (* a new metasenv in which some hypothesis in the contexts of the *)
614 (* metavariables may have been restricted. *)
615 let fo_unif metasenv context t1 t2 =
616 let subst_to_unwind,metasenv' = fo_unif_subst [] context metasenv t1 t2 in
617 unwind_subst metasenv' subst_to_unwind