- (* this easy_case handles "(? ?) =?= (f a)", same number of
- * args, preferring the instantiation "f" over "\_.f a" for the
- * metavariable in head position. Since the arguments of the meta
- * are flexible, delift would ignore them generating a constant
- * function even in the easy case above *)
- let easy_case =
- match t2 with
- | NCic.Appl (f :: f_args)
- when
- List.exists (NCicMetaSubst.is_flexible context ~subst) args ->
- let mlen = List.length args in
- let flen = List.length f_args in
- let min_len = min mlen flen in
- let mhe,margs = HExtlib.split_nth (mlen - min_len) args in
- let fhe,fargs = HExtlib.split_nth (flen - min_len) f_args in
- (try
- Some (List.fold_left2
- (fun (m, s) t1 t2 ->
- unify rdb test_eq_only m s context t1 t2 swap
- ) (metasenv,subst)
- ((NCicUntrusted.mk_appl meta mhe)::margs)
- ((NCicUntrusted.mk_appl f fhe)::fargs))
- with UnificationFailure _ | Uncertain _ | KeepReducing _ ->
- None)
- | _ -> None
- in
- (match easy_case with
- | Some ms -> ms
- | None ->
- (* This case handles "(?_f ..ti..) =?= t2", abstracting every
- * non flexible ti (delift skips local context items that are
- * flexible) from t2 in two steps:
- * 1) ?_f := \..xi.. .?
- * 2) ?_f ..ti.. =?= t2 --unif_machines-->
- ?_f[..ti..] =?= t2 --instantiate-->
- delift [..ti..] t2 *)
- let metasenv, lambda_Mj =
- lambda_intros rdb metasenv subst context (List.length args)
- (NCicTypeChecker.typeof ~metasenv ~subst context meta)
- in
- let metasenv, subst =
- unify rdb test_eq_only metasenv subst context
- (C.Meta (i,l)) lambda_Mj swap
- in
- let metasenv, subst =
- unify rdb test_eq_only metasenv subst context t1 t2 swap
- in
- (try
- let name, ctx, term, ty = NCicUtils.lookup_subst i subst in
- let term = eta_reduce subst term in
- let subst = List.filter (fun (j,_) -> j <> i) subst in
- metasenv, ((i, (name, ctx, term, ty)) :: subst)
- with Not_found -> assert false))
-
+ let metasenv, lambda_Mj =
+ lambda_intros rdb metasenv subst context (List.length args)
+ (NCicTypeChecker.typeof ~metasenv ~subst context meta)
+ in
+ let metasenv, subst =
+ try
+ unify rdb test_eq_only metasenv subst context
+ (C.Meta (i,l)) lambda_Mj swap
+ with UnificationFailure msg | Uncertain msg when not norm2->
+ (* failure: let's try again argument vs argument *)
+ raise (KeepReducing msg)
+ in
+ let metasenv, subst =
+ unify rdb test_eq_only metasenv subst context t1 t2 swap
+ in
+ (try
+ let name, ctx, term, ty = NCicUtils.lookup_subst i subst in
+ let term = eta_reduce subst term in
+ let subst = List.filter (fun (j,_) -> j <> i) subst in
+ metasenv, ((i, (name, ctx, term, ty)) :: subst)
+ with Not_found -> assert false)