4 exception AssertFailure of string
5 exception MetaSubstFailure of string
7 let debug_print = prerr_endline
9 type substitution = (int * Cic.term) list
14 (fun (idx, term) -> Printf.sprintf "?%d := %s" idx (CicPp.ppterm term))
18 (* the delift function takes in input a metavariable index, an ordered list of
19 * optional terms [t1,...,tn] and a term t, and substitutes every tk = Some
20 * (rel(nk)) with rel(k). Typically, the list of optional terms is the explicit
21 * substitution that is applied to a metavariable occurrence and the result of
22 * the delift function is a term the implicit variable can be substituted with
23 * to make the term [t] unifiable with the metavariable occurrence. In general,
24 * the problem is undecidable if we consider equivalence in place of alpha
25 * convertibility. Our implementation, though, is even weaker than alpha
26 * convertibility, since it replace the term [tk] if and only if [tk] is a Rel
27 * (missing all the other cases). Does this matter in practice?
28 * The metavariable index is the index of the metavariable that must not occur
29 * in the term (for occur check).
32 exception NotInTheList;;
37 [] -> raise NotInTheList
38 | (Some (Cic.Rel m))::_ when m=n -> k
39 | _::tl -> aux (k+1) tl in
45 let rec force_does_not_occur subst to_be_restricted t =
47 let more_to_be_restricted = ref [] in
48 let rec aux k = function
49 C.Rel r when List.mem (r+k) to_be_restricted -> raise Occur
52 | C.Implicit -> assert false
54 (* we do not retrieve the term associated to ?n in subst since *)
55 (* in this way we can restrict if something goes wrong *)
66 more_to_be_restricted := (n,!i) :: !more_to_be_restricted;
71 | C.Cast (te,ty) -> C.Cast (aux k te, aux k ty)
72 | C.Prod (name,so,dest) -> C.Prod (name, aux k so, aux (k+1) dest)
73 | C.Lambda (name,so,dest) -> C.Lambda (name, aux k so, aux (k+1) dest)
74 | C.LetIn (name,so,dest) -> C.LetIn (name, aux k so, aux (k+1) dest)
75 | C.Appl l -> C.Appl (List.map (aux k) l)
76 | C.Var (uri,exp_named_subst) ->
77 let exp_named_subst' =
78 List.map (fun (uri,t) -> (uri, aux k t)) exp_named_subst
80 C.Var (uri, exp_named_subst')
81 | C.Const (uri, exp_named_subst) ->
82 let exp_named_subst' =
83 List.map (fun (uri,t) -> (uri, aux k t)) exp_named_subst
85 C.Const (uri, exp_named_subst')
86 | C.MutInd (uri,tyno,exp_named_subst) ->
87 let exp_named_subst' =
88 List.map (fun (uri,t) -> (uri, aux k t)) exp_named_subst
90 C.MutInd (uri, tyno, exp_named_subst')
91 | C.MutConstruct (uri,tyno,consno,exp_named_subst) ->
92 let exp_named_subst' =
93 List.map (fun (uri,t) -> (uri, aux k t)) exp_named_subst
95 C.MutConstruct (uri, tyno, consno, exp_named_subst')
96 | C.MutCase (uri,tyno,out,te,pl) ->
97 C.MutCase (uri, tyno, aux k out, aux k te, List.map (aux k) pl)
99 let len = List.length fl in
100 let k_plus_len = k + len in
103 (fun (name,j,ty,bo) -> (name, j, aux k ty, aux k_plus_len bo)) fl
107 let len = List.length fl in
108 let k_plus_len = k + len in
111 (fun (name,ty,bo) -> (name, aux k ty, aux k_plus_len bo)) fl
116 (!more_to_be_restricted, res)
118 let rec restrict subst to_be_restricted metasenv =
119 let names_of_context_indexes context indexes =
123 match List.nth context i with
124 | None -> assert false
125 | Some (n, _) -> CicPp.ppname n)
128 let force_does_not_occur_in_context to_be_restricted = function
130 | Some (name, Cic.Decl t) ->
131 let (more_to_be_restricted, t') =
132 force_does_not_occur subst to_be_restricted t
134 more_to_be_restricted, Some (name, Cic.Decl t)
135 | Some (name, Cic.Def (bo, ty)) ->
136 let (more_to_be_restricted, bo') =
137 force_does_not_occur subst to_be_restricted bo
139 let more_to_be_restricted, ty' =
141 | None -> more_to_be_restricted, None
143 let more_to_be_restricted', ty' =
144 force_does_not_occur subst to_be_restricted ty
146 more_to_be_restricted @ more_to_be_restricted',
149 more_to_be_restricted, Some (name, Cic.Def (bo', ty'))
151 let rec erase i to_be_restricted n = function
152 | [] -> [], to_be_restricted, []
154 let restrict_me = List.mem i to_be_restricted in
156 let more_to_be_restricted, restricted, new_tl =
157 erase (i+1) (i :: to_be_restricted) n tl
159 more_to_be_restricted, restricted, None :: new_tl
162 let more_to_be_restricted, hd' =
163 force_does_not_occur_in_context to_be_restricted hd
165 let more_to_be_restricted', restricted, tl' =
166 erase (i+1) to_be_restricted n tl
168 more_to_be_restricted @ more_to_be_restricted',
169 restricted, hd' :: tl'
171 let more_to_be_restricted, restricted, tl' =
172 erase (i+1) (i :: to_be_restricted) n tl
174 more_to_be_restricted, restricted, None :: tl')
176 let (more_to_be_restricted, metasenv, subst) =
178 (fun (n, context, t) (more, metasenv, subst) ->
179 let to_be_restricted =
180 List.map snd (List.filter (fun (m, _) -> m = n) to_be_restricted)
182 let (more_to_be_restricted, restricted, context') =
183 erase 1 to_be_restricted n context
186 let more_to_be_restricted', t' =
187 force_does_not_occur subst restricted t
189 let metasenv' = (n, context', t') :: metasenv in
191 let s = List.assoc n subst in
193 let more_to_be_restricted'', s' =
194 force_does_not_occur subst restricted s
196 let subst' = (n, s') :: (List.remove_assoc n subst) in
198 more @ more_to_be_restricted @ more_to_be_restricted' @
199 more_to_be_restricted''
201 (more, metasenv', subst')
203 raise (MetaSubstFailure (sprintf
204 "Cannot restrict the context of the metavariable ?%d over the hypotheses %s since ?%d is already instantiated with %s and at least one of the hypotheses occurs in the substituted term"
205 n (names_of_context_indexes context to_be_restricted) n
207 with Not_found -> (more @ more_to_be_restricted @ more_to_be_restricted', metasenv', subst))
209 raise (MetaSubstFailure (sprintf
210 "Cannot restrict the context of the metavariable ?%d over the hypotheses %s since metavariable's type depends on at least one of them"
211 n (names_of_context_indexes context to_be_restricted))))
212 metasenv ([], [], subst)
214 match more_to_be_restricted with
215 | [] -> (metasenv, subst)
216 | _ -> restrict subst more_to_be_restricted metasenv
219 (*CSC: maybe we should rename delift in abstract, as I did in my dissertation *)
220 let delift n subst context metasenv l t =
221 let module S = CicSubstitution in
222 let to_be_restricted = ref [] in
223 let rec deliftaux k =
224 let module C = Cic in
228 C.Rel m (*CSC: che succede se c'e' un Def? Dovrebbe averlo gia' *)
229 (*CSC: deliftato la regola per il LetIn *)
230 (*CSC: FALSO! La regola per il LetIn non lo fa *)
232 (match List.nth context (m-k-1) with
233 Some (_,C.Def (t,_)) ->
234 (*CSC: Hmmm. This bit of reduction is not in the spirit of *)
235 (*CSC: first order unification. Does it help or does it harm? *)
236 deliftaux k (S.lift m t)
237 | Some (_,C.Decl t) ->
238 (*CSC: The following check seems to be wrong! *)
239 (*CSC: B:Set |- ?2 : Set *)
240 (*CSC: A:Set ; x:?2[A/B] |- ?1[x/A] =?= x *)
241 (*CSC: Why should I restrict ?2 over B? The instantiation *)
242 (*CSC: ?1 := A is perfectly reasonable and well-typed. *)
243 (*CSC: Thus I comment out the following two lines that *)
244 (*CSC: are the incriminated ones. *)
245 (*(* It may augment to_be_restricted *)
246 ignore (deliftaux k (S.lift m t)) ;*)
247 (*CSC: end of bug commented out *)
248 C.Rel ((position (m-k) l) + k)
249 | None -> raise (MetaSubstFailure "RelToHiddenHypothesis"))
250 | C.Var (uri,exp_named_subst) ->
251 let exp_named_subst' =
252 List.map (function (uri,t) -> uri,deliftaux k t) exp_named_subst
254 C.Var (uri,exp_named_subst')
255 | C.Meta (i, l1) as t ->
257 raise (MetaSubstFailure (sprintf
258 "Cannot unify the metavariable ?%d with a term that has as subterm %s in which the same metavariable occurs (occur check)"
261 (* I do not consider the term associated to ?i in subst since *)
262 (* in this way I can restrict if something goes wrong. *)
266 | None::tl -> None::(deliftl (j+1) tl)
268 let l1' = (deliftl (j+1) tl) in
270 Some (deliftaux k t)::l1'
273 | MetaSubstFailure _ ->
274 to_be_restricted := (i,j)::!to_be_restricted ; None::l1'
276 let l' = deliftl 1 l1 in
279 | C.Implicit as t -> t
280 | C.Cast (te,ty) -> C.Cast (deliftaux k te, deliftaux k ty)
281 | C.Prod (n,s,t) -> C.Prod (n, deliftaux k s, deliftaux (k+1) t)
282 | C.Lambda (n,s,t) -> C.Lambda (n, deliftaux k s, deliftaux (k+1) t)
283 | C.LetIn (n,s,t) -> C.LetIn (n, deliftaux k s, deliftaux (k+1) t)
284 | C.Appl l -> C.Appl (List.map (deliftaux k) l)
285 | C.Const (uri,exp_named_subst) ->
286 let exp_named_subst' =
287 List.map (function (uri,t) -> uri,deliftaux k t) exp_named_subst
289 C.Const (uri,exp_named_subst')
290 | C.MutInd (uri,typeno,exp_named_subst) ->
291 let exp_named_subst' =
292 List.map (function (uri,t) -> uri,deliftaux k t) exp_named_subst
294 C.MutInd (uri,typeno,exp_named_subst')
295 | C.MutConstruct (uri,typeno,consno,exp_named_subst) ->
296 let exp_named_subst' =
297 List.map (function (uri,t) -> uri,deliftaux k t) exp_named_subst
299 C.MutConstruct (uri,typeno,consno,exp_named_subst')
300 | C.MutCase (sp,i,outty,t,pl) ->
301 C.MutCase (sp, i, deliftaux k outty, deliftaux k t,
302 List.map (deliftaux k) pl)
304 let len = List.length fl in
307 (fun (name, i, ty, bo) ->
308 (name, i, deliftaux k ty, deliftaux (k+len) bo))
313 let len = List.length fl in
316 (fun (name, ty, bo) -> (name, deliftaux k ty, deliftaux (k+len) bo))
319 C.CoFix (i, liftedfl)
326 (* This is the case where we fail even first order unification. *)
327 (* The reason is that our delift function is weaker than first *)
328 (* order (in the sense of alpha-conversion). See comment above *)
329 (* related to the delift function. *)
330 debug_print "!!!!!!!!!!! First Order UnificationFailure, but maybe it could have been successful even in a first order setting (no conversion, only alpha convertibility)! Please, implement a better delift function !!!!!!!!!!!!!!!!" ;
331 raise (MetaSubstFailure (sprintf
332 "Error trying to abstract %s over [%s]: the algorithm only tried to abstract over bound variables"
336 (function Some t -> CicPp.ppterm t | None -> "_")
339 let (metasenv, subst) = restrict subst !to_be_restricted metasenv in
343 (**** END OF DELIFT ****)
345 let apply_subst_gen ~appl_fun subst term =
347 let module C = Cic in
348 let module S = CicSubstitution in
354 let t = List.assoc i subst in
355 um_aux (S.lift_meta l t)
356 with Not_found -> (* not constrained variable, i.e. free in subst*)
358 List.map (function None -> None | Some t -> Some (um_aux t)) l
362 | C.Implicit -> assert false
363 | C.Cast (te,ty) -> C.Cast (um_aux te, um_aux ty)
364 | C.Prod (n,s,t) -> C.Prod (n, um_aux s, um_aux t)
365 | C.Lambda (n,s,t) -> C.Lambda (n, um_aux s, um_aux t)
366 | C.LetIn (n,s,t) -> C.LetIn (n, um_aux s, um_aux t)
367 | C.Appl (hd :: tl) -> appl_fun um_aux hd tl
368 | C.Appl _ -> assert false
369 | C.Const (uri,exp_named_subst) ->
370 let exp_named_subst' =
371 List.map (fun (uri, t) -> (uri, um_aux t)) exp_named_subst
373 C.Const (uri, exp_named_subst')
374 | C.MutInd (uri,typeno,exp_named_subst) ->
375 let exp_named_subst' =
376 List.map (fun (uri, t) -> (uri, um_aux t)) exp_named_subst
378 C.MutInd (uri,typeno,exp_named_subst')
379 | C.MutConstruct (uri,typeno,consno,exp_named_subst) ->
380 let exp_named_subst' =
381 List.map (fun (uri, t) -> (uri, um_aux t)) exp_named_subst
383 C.MutConstruct (uri,typeno,consno,exp_named_subst')
384 | C.MutCase (sp,i,outty,t,pl) ->
385 let pl' = List.map um_aux pl in
386 C.MutCase (sp, i, um_aux outty, um_aux t, pl')
389 List.map (fun (name, i, ty, bo) -> (name, i, um_aux ty, um_aux bo)) fl
394 List.map (fun (name, ty, bo) -> (name, um_aux ty, um_aux bo)) fl
401 let appl_fun um_aux he tl =
402 let tl' = List.map um_aux tl in
405 Cic.Appl l -> Cic.Appl (l@tl')
406 | he' -> Cic.Appl (he'::tl')
409 apply_subst_gen ~appl_fun
411 let ppterm subst term = CicPp.ppterm (apply_subst subst term)
413 (* apply_subst_reducing subst (Some (mtr,reductions_no)) t *)
414 (* performs as (apply_subst subst t) until it finds an application of *)
415 (* (META [meta_to_reduce]) that, once unwinding is performed, creates *)
416 (* a new beta-redex; in this case up to [reductions_no] consecutive *)
417 (* beta-reductions are performed. *)
418 (* Hint: this function is usually called when [reductions_no] *)
419 (* eta-expansions have been performed and the head of the new *)
420 (* application has been unified with (META [meta_to_reduce]): *)
421 (* during the unwinding the eta-expansions are undone. *)
423 let apply_subst_reducing meta_to_reduce =
424 let appl_fun um_aux he tl =
425 let tl' = List.map um_aux tl in
428 Cic.Appl l -> Cic.Appl (l@tl')
429 | he' -> Cic.Appl (he'::tl')
432 match meta_to_reduce, he with
433 Some (mtr,reductions_no), Cic.Meta (m,_) when m = mtr ->
434 let rec beta_reduce =
436 (n,(Cic.Appl (Cic.Lambda (_,_,t)::he'::tl'))) when n > 0 ->
437 let he'' = CicSubstitution.subst he' t in
441 beta_reduce (n-1,Cic.Appl(he''::tl'))
444 beta_reduce (reductions_no,t')
448 apply_subst_gen ~appl_fun
450 let rec apply_subst_context subst context =
454 | Some (n, Cic.Decl t) ->
455 let t' = apply_subst subst t in
456 Some (n, Cic.Decl t') :: context
457 | Some (n, Cic.Def (t, ty)) ->
461 | Some ty -> Some (apply_subst subst ty)
463 let t' = apply_subst subst t in
464 Some (n, Cic.Def (t', ty')) :: context
465 | None -> None :: context)
468 let apply_subst_metasenv subst metasenv =
470 (fun (n, context, ty) ->
471 (n, apply_subst_context subst context, apply_subst subst ty))
473 (fun (i, _, _) -> not (List.exists (fun (j, _) -> (j = i)) subst))
476 let ppterm subst term = CicPp.ppterm (apply_subst subst term)
478 let ppcontext ?(sep = "\n") subst context =
480 (List.rev_map (function
481 | Some (n, Cic.Decl t) ->
482 sprintf "%s : %s" (CicPp.ppname n) (ppterm subst t)
483 | Some (n, Cic.Def (t, ty)) ->
484 sprintf "%s : %s := %s"
486 (match ty with None -> "_" | Some ty -> ppterm subst ty)
491 let ppmetasenv ?(sep = "\n") metasenv subst =
495 sprintf "%s |- ?%d: %s" (ppcontext ~sep:"; " subst c) i
498 (fun (i, _, _) -> not (List.exists (fun (j, _) -> (j = i)) subst))
501 (* UNWIND THE MGU INSIDE THE MGU *)
503 let unwind_subst metasenv subst =
505 (fun (unwinded,metasenv) (i,_) ->
506 let (_,canonical_context,_) = CicUtil.lookup_meta i metasenv in
507 let identity_relocation_list =
508 CicMkImplicit.identity_relocation_list_for_metavariable canonical_context
510 let (_,metasenv',subst') =
511 unwind metasenv subst unwinded (Cic.Meta (i,identity_relocation_list))
514 ) ([],metasenv) subst
517 (* From now on we recreate a kernel abstraction where substitutions are part of
520 let lift subst n term =
521 let term = apply_subst subst term in
523 CicSubstitution.lift n term
525 raise (MetaSubstFailure ("Lift failure: " ^ Printexc.to_string e))
527 let subst subst t1 t2 =
528 let t1 = apply_subst subst t1 in
529 let t2 = apply_subst subst t2 in
531 CicSubstitution.subst t1 t2
533 raise (MetaSubstFailure ("Subst failure: " ^ Printexc.to_string e))
535 let whd subst context term =
536 let term = apply_subst subst term in
537 let context = apply_subst_context subst context in
539 CicReduction.whd context term
541 raise (MetaSubstFailure ("Weak head reduction failure: " ^
542 Printexc.to_string e))
544 let are_convertible subst context t1 t2 =
545 let context = apply_subst_context subst context in
546 let t1 = apply_subst subst t1 in
547 let t2 = apply_subst subst t2 in
548 CicReduction.are_convertible context t1 t2
550 let type_of_aux' metasenv subst context term =
551 let term = apply_subst subst term in
552 let context = apply_subst_context subst context in
555 (fun (i, c, t) -> (i, apply_subst_context subst c, apply_subst subst t))
557 (fun (i, _, _) -> not (List.exists (fun (j, _) -> (j = i)) subst))
561 CicTypeChecker.type_of_aux' metasenv context term
562 with CicTypeChecker.TypeCheckerFailure msg ->
563 raise (MetaSubstFailure ("Type checker failure: " ^ msg))