(**** DELIFT ****)
-(* the delift function takes in input an ordered list of integers [n1,...,nk]
- and a term t, and relocates rel(nk) to k. Typically, the list of integers
- is a parameter of a metavariable occurrence. *)
+(* the delift function takes in input an ordered list of optional terms *)
+(* [t1,...,tn] and a term t, and substitutes every tk = Some (rel(nk)) with *)
+(* 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 *)
+(* function is a term the implicit variable can be substituted with to make *)
+(* the term [t] unifiable with the metavariable occurrence. *)
+(* In general, the problem is undecidable if we consider equivalence in place *)
+(* of alpha convertibility. Our implementation, though, is even weaker than *)
+(* alpha convertibility, since it replace the term [tk] if and only if [tk] *)
+(* is a Rel (missing all the other cases). Does this matter in practice? *)
exception NotInTheList;;
;;
+(*CSC: maybe we should rename delift in abstract, as I did in my dissertation *)
let delift context metasenv l t =
let module S = CicSubstitution in
let to_be_restricted = ref [] in
if m <=k then
C.Rel m (*CSC: che succede se c'e' un Def? Dovrebbe averlo gia' *)
(*CSC: deliftato la regola per il LetIn *)
+ (*CSC: FALSO! La regola per il LetIn non lo fa *)
else
(match List.nth context (m-k-1) with
- Some (_,C.Def (t,_)) -> deliftaux k (S.lift m t)
+ Some (_,C.Def (t,_)) ->
+ (*CSC: Hmmm. This bit of reduction is not in the spirit of *)
+ (*CSC: first order unification. Does it help or does it harm? *)
+ deliftaux k (S.lift m t)
| Some (_,C.Decl t) ->
(* It may augment to_be_restricted *)
+ (*CSC: Really? Even in the case of well-typed terms? *)
+ (*CSC: I am no longer sure of the usefulness of the check *)
ignore (deliftaux k (S.lift m t)) ;
C.Rel ((position (m-k) l) + k)
| None -> raise RelToHiddenHypothesis)
in
C.CoFix (i, liftedfl)
in
- let res = deliftaux 0 t in
+ let res =
+ try
+ deliftaux 0 t
+ with
+ NotInTheList ->
+ (* This is the case where we fail even first order unification. *)
+ (* The reason is that our delift function is weaker than first *)
+ (* order (in the sense of alpha-conversion). See comment above *)
+ (* related to the delift function. *)
+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 !!!!!!!!!!!!!!!!" ;
+ raise UnificationFailed
+ in
res, restrict !to_be_restricted metasenv
;;
raise UnificationFailed
| (C.Rel _, _)
| (_, C.Rel _)
- | (C.Var _, _)
- | (_, C.Var _)
| (C.Sort _ ,_)
| (_, C.Sort _)
| (C.Implicit, _)
" <==> " ^ CicPp.ppterm (Cic.Var (uri,exp_named_subst2))) ; raise e
;;
-(*CSC: ???????????????
-(* m is the index of a metavariable to restrict, k is nesting depth
-of the occurrence m, and l is its relocation list. canonical_context
-is the context of the metavariable we are instantiating - containing
-m - Only rel in the domain of canonical_context are accessible.
-This function takes in input a metasenv and gives back a metasenv.
-A rel(j) in the canonical context of m, is rel(List.nth l j) for the
-instance of m under consideration, that is rel (List.nth l j) - k
-in canonical_context. *)
-
-let restrict canonical_context m k l =
- let rec erase i =
- function
- [] -> []
- | None::tl -> None::(erase (i+1) tl)
- | he::tl ->
- let i' = (List.nth l (i-1)) in
- if i' <= k
- then he::(erase (i+1) tl) (* local variable *)
- else
- let acc =
- (try List.nth canonical_context (i'-k-1)
- with Failure _ -> None) in
- if acc = None
- then None::(erase (i+1) tl)
- else he::(erase (i+1) tl) in
- let rec aux =
- function
- [] -> []
- | (n,context,t)::tl when n=m -> (n,erase 1 context,t)::tl
- | hd::tl -> hd::(aux tl)
- in
- aux
-;;
-
-
-let check_accessibility metasenv i =
- let module C = Cic in
- let module S = CicSubstitution in
- let (_,canonical_context,_) =
- List.find (function (m,_,_) -> m=i) metasenv in
- List.map
- (function t ->
- let =
- delift canonical_context metasenv ? t
- ) canonical_context
-CSCSCS
-
-
-
- let rec aux metasenv k =
- function
- C.Rel i ->
- if i <= k then
- metasenv
- else
- (try
- match List.nth canonical_context (i-k-1) with
- Some (_,C.Decl t)
- | Some (_,C.Def t) -> aux metasenv k (S.lift i t)
- | None -> raise RelToHiddenHypothesis
- with
- Failure _ -> raise OpenTerm
- )
- | C.Var _ -> metasenv
- | C.Meta (i,l) -> restrict canonical_context i k l metasenv
- | C.Sort _ -> metasenv
- | C.Implicit -> metasenv
- | C.Cast (te,ty) ->
- let metasenv' = aux metasenv k te in
- aux metasenv' k ty
- | C.Prod (_,s,t)
- | C.Lambda (_,s,t)
- | C.LetIn (_,s,t) ->
- let metasenv' = aux metasenv k s in
- aux metasenv' (k+1) t
- | C.Appl l ->
- List.fold_left
- (function metasenv -> aux metasenv k) metasenv l
- | C.Const _
- | C.MutInd _
- | C.MutConstruct _ -> metasenv
- | C.MutCase (_,_,_,outty,t,pl) ->
- let metasenv' = aux metasenv k outty in
- let metasenv'' = aux metasenv' k t in
- List.fold_left
- (function metasenv -> aux metasenv k) metasenv'' pl
- | C.Fix (i, fl) ->
- let len = List.length fl in
- List.fold_left
- (fun metasenv f ->
- let (_,_,ty,bo) = f in
- let metasenv' = aux metasenv k ty in
- aux metasenv' (k+len) bo
- ) metasenv fl
- | C.CoFix (i, fl) ->
- let len = List.length fl in
- List.fold_left
- (fun metasenv f ->
- let (_,ty,bo) = f in
- let metasenv' = aux metasenv k ty in
- aux metasenv' (k+len) bo
- ) metasenv fl
- in aux metasenv 0
-;;
-*)
-
-
let unwind metasenv subst unwinded t =
let unwinded = ref unwinded in
let frozen = ref [] in
(* a new metasenv in which some hypothesis in the contexts of the *)
(* metavariables may have been restricted. *)
let fo_unif metasenv context t1 t2 =
-prerr_endline "INIZIO FASE 1" ; flush stderr ;
let subst_to_unwind,metasenv' = fo_unif_subst [] context metasenv t1 t2 in
-prerr_endline "FINE FASE 1" ; flush stderr ;
-let res =
unwind_subst metasenv' subst_to_unwind
-in
-prerr_endline "FINE FASE 2" ; flush stderr ; res
;;
projects / helm.git / blobdiff