X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2Fsoftware%2Fcomponents%2Fng_refiner%2FnCicUnification.ml;h=291dcabdde30c808b88db0c362bc09fbefa1e0b6;hb=7ca0a000878e864c92d94f77900bc2ca0ac143b9;hp=54b8218f5912e08f0b805f2718db8489e37e5799;hpb=7bc72d8afaebb1d2070a26b07f9bf4242b648e2c;p=helm.git

diff --git a/helm/software/components/ng_refiner/nCicUnification.ml b/helm/software/components/ng_refiner/nCicUnification.ml
index 54b8218f5..291dcabdd 100644
--- a/helm/software/components/ng_refiner/nCicUnification.ml
+++ b/helm/software/components/ng_refiner/nCicUnification.ml
@@ -36,56 +36,85 @@ let mk_appl ~upto hd tl =
     | _ -> NCic.Appl (hd :: tl))
 ;;
 
-let flexible l = 
-  List.exists 
-    (function 
-       | NCic.Meta _  
-       | NCic.Appl (NCic.Meta _::_) -> true
-       | _ -> false) l
-;;
-
 exception WrongShape;;
 
-let eta_reduce = 
-  let delift_if_not_occur body orig =
+let eta_reduce subst t = 
+  let delift_if_not_occur body =
     try 
-        NCicSubstitution.psubst ~avoid_beta_redexes:true
-          (fun () -> raise WrongShape) [()] body
-    with WrongShape -> orig
+        Some (NCicSubstitution.psubst ~avoid_beta_redexes:true
+          (fun () -> raise WrongShape) [()] body)
+    with WrongShape -> None
+  in 
+  let rec eat_lambdas ctx = function
+    | NCic.Lambda (name, src, tgt) -> 
+        eat_lambdas ((name, src) :: ctx) tgt
+    | NCic.Meta (i,lc) as t->
+        (try 
+          let _,_,t,_ = NCicUtils.lookup_subst i subst in
+          let t = NCicSubstitution.subst_meta lc t in
+          eat_lambdas ctx t
+        with Not_found -> ctx, t)
+    | t -> ctx, t
   in
-  function
-  | NCic.Lambda(_, _, NCic.Appl [hd; NCic.Rel 1]) as orig ->
-      delift_if_not_occur hd orig
-  | NCic.Lambda(_, _, NCic.Appl (hd :: l)) as orig
-    when HExtlib.list_last l = NCic.Rel 1 ->
-       let body = 
-         let args, _ = HExtlib.split_nth (List.length l - 1) l in
-         NCic.Appl (hd::args)
-       in
-       delift_if_not_occur body orig
-  | t -> t
+  let context_body = eat_lambdas [] t in
+  let rec aux = function
+    | [],body -> body
+    | (name, src)::ctx, (NCic.Appl (hd::[NCic.Rel 1]) as bo) -> 
+        (match delift_if_not_occur hd with
+        | None -> aux (ctx,NCic.Lambda(name,src, bo)) 
+        | Some bo -> aux (ctx,bo))
+    | (name, src)::ctx, (NCic.Appl args as bo) 
+      when HExtlib.list_last args = NCic.Rel 1 -> 
+        let args, _ = HExtlib.split_nth (List.length args - 1) args in
+        (match delift_if_not_occur (NCic.Appl args) with
+        | None -> aux (ctx,NCic.Lambda(name,src, bo)) 
+        | Some bo -> aux (ctx,bo))
+    | (name, src) :: ctx, t ->
+        aux (ctx,NCic.Lambda(name,src, t)) 
+  in
+    aux context_body
 ;;
- 
+
 module C = NCic;;
 module Ref = NReference;;
 
+let debug = false;;
 let indent = ref "";;
-let inside c = indent := !indent ^ String.make 1 c;;
-let outside () = indent := String.sub !indent 0 (String.length !indent -1);;
+let pp =
+ if debug then
+  fun s -> prerr_endline (Printf.sprintf "%-20s" !indent ^ " " ^ Lazy.force s)
+ else 
+  fun _ -> ()
+;;
+let inside c =
+ indent := !indent ^ String.make 1 c;
+ if debug then prerr_endline ("{{{" ^ !indent ^ " ")
+;;
+let outside ok =
+ if debug then prerr_endline "}}}";
+ if not ok then pp (lazy "exception raised!");
+ try
+  indent := String.sub !indent 0 (String.length !indent -1)
+ with
+  Invalid_argument _ -> indent := "??"; ()
+;;
 
-let pp s = 
-  prerr_endline (Printf.sprintf "%-20s" !indent ^ " " ^ Lazy.force s)
-;;  
+let ppcontext ~metasenv ~subst c = 
+      "\nctx:\n"^ NCicPp.ppcontext ~metasenv ~subst c
+;;
+let ppmetasenv ~subst m = "\nmenv:\n" ^ NCicPp.ppmetasenv ~subst m;;
 
-let pp _ = ();;
+let ppcontext ~metasenv:_metasenv ~subst:_subst _context = "";;
+let ppmetasenv ~subst:_subst _metasenv = "";;
 
-let fix_sorts swap metasenv subst context meta t =
+let fix_sorts swap exc t =
   let rec aux () = function
     | NCic.Sort (NCic.Type u) as orig ->
         if swap then
          match NCicEnvironment.sup u with
-         | None -> prerr_endline "no sup for" ;
-            raise (fail_exc metasenv subst context meta t)
+         | None ->
+            prerr_endline ("no sup for " ^ NCicPp.ppterm ~metasenv:[] ~subst:[] ~context:[] orig) ;
+            raise exc
          | Some u1 -> if u = u1 then orig else NCic.Sort (NCic.Type u1)
         else
          NCic.Sort (NCic.Type (
@@ -98,98 +127,133 @@ let fix_sorts swap metasenv subst context meta t =
     aux () t
 ;;
 
-let rec beta_expand hdb num test_eq_only swap metasenv subst context t arg =
-  let rec aux (n,context,test_eq_only as k) (metasenv, subst as acc) t' =
+let is_locked n subst =
    try
-    let metasenv, subst =
-     if swap then
-      unify hdb test_eq_only metasenv subst context t' (NCicSubstitution.lift n arg)
-     else
-      unify hdb test_eq_only metasenv subst context (NCicSubstitution.lift n arg) t'
-    in
-     (metasenv, subst), NCic.Rel (1 + n)
-   with Uncertain _ | UnificationFailure _ ->
-       match t' with
-       | NCic.Rel m as orig -> 
-           (metasenv, subst), if m <= n then orig else NCic.Rel (m+1)
-       (* andrea: in general, beta_expand can create badly typed
-        terms. This happens quite seldom in practice, UNLESS we
-        iterate on the local context. For this reason, we renounce
-        to iterate and just lift *)
-       | NCic.Meta (i,(shift,lc)) ->
-           (metasenv,subst), NCic.Meta (i,(shift+1,lc))
-       | NCic.Prod (name, src, tgt) as orig ->
-           let (metasenv, subst), src1 = aux (n,context,true) acc src in 
-           let k = n+1, (name, NCic.Decl src) :: context, test_eq_only in
-           let ms, tgt1 = aux k (metasenv, subst) tgt in 
-           if src == src1 && tgt == tgt1 then ms, orig else
-           ms, NCic.Prod (name, src1, tgt1)
-       | t -> 
-           NCicUntrusted.map_term_fold_a 
-             (fun e (n,ctx,teq) -> n+1,e::ctx,teq) k aux acc t
+     match NCicUtils.lookup_subst n subst with
+     | Some tag, _,_,_ when NCicMetaSubst.is_out_scope_tag tag -> true
+     | _ -> false
+   with NCicUtils.Subst_not_found _ -> false
+;;
 
-  in
-  let argty = NCicTypeChecker.typeof ~metasenv ~subst context arg in
-  let fresh_name = "Hbeta" ^ string_of_int num in
-  let (metasenv,subst), t1 = 
-    aux (0, context, test_eq_only) (metasenv, subst) t in
-  let t2 = eta_reduce (NCic.Lambda (fresh_name,argty,t1)) in
-  try 
-    ignore(NCicTypeChecker.typeof ~metasenv ~subst context t2);
-    metasenv, subst, t2
-  with NCicTypeChecker.TypeCheckerFailure _ -> 
-    metasenv, subst, NCic.Lambda ("_", argty, NCicSubstitution.lift 1 arg)
-
-and beta_expand_many hdb test_equality_only swap metasenv subst context t args =
-(* (*D*)  inside 'B'; try let rc = *)
-  pp (lazy (String.concat ", "
-     (List.map (NCicPp.ppterm ~metasenv ~subst ~context)
-     args) ^ " ∈ " ^ NCicPp.ppterm ~metasenv ~subst ~context t));
-  let _, subst, metasenv, hd =
-    List.fold_right
-      (fun arg (num,subst,metasenv,t) ->
-         let metasenv, subst, t =
-           beta_expand hdb num test_equality_only swap metasenv subst context t arg
-         in
-           num+1,subst,metasenv,t)
-      args (1,subst,metasenv,t) 
-  in
-  pp (lazy ("Head syntesized by b-exp: " ^ 
-    NCicPp.ppterm ~metasenv ~subst ~context hd));
-    metasenv, subst, hd
-(* (*D*)  in outside (); rc with exn -> outside (); raise exn *)
+let rec mk_irl =
+ function
+    0 -> []
+  | n -> NCic.Rel n :: mk_irl (n-1)
+;;
 
-and instantiate hdb test_eq_only metasenv subst context n lc t swap =
+(* the argument must be a term in whd *)
+let rec could_reduce =
+ function
+  | C.Meta _ -> true
+  | C.Appl (C.Const (Ref.Ref (_,Ref.Fix (_,recno,_)))::args)
+     when List.length args > recno -> could_reduce (List.nth args recno)
+  | C.Match (_,_,arg,_) -> could_reduce arg
+  | C.Appl (he::_) -> could_reduce he
+  | C.Sort _ | C.Rel _ | C.Prod _ | C.Lambda _ | C.Const _ -> false
+  | C.Appl [] | C.LetIn _ | C.Implicit _ -> assert false
+;;
+
+let rec lambda_intros rdb metasenv subst context t args =
+ let tty = NCicTypeChecker.typeof ~metasenv ~subst context t in
+ let argsty =
+  List.map
+  (fun arg -> arg, NCicTypeChecker.typeof ~metasenv ~subst context arg) args in
+ let context_of_args = context in
+ let rec mk_lambda metasenv subst context n processed_args = function
+   | [] ->
+       let metasenv, _, bo, _ = 
+         NCicMetaSubst.mk_meta metasenv context 
+           (`WithType (NCicSubstitution.lift n tty))
+       in
+       metasenv, subst, bo
+   | (arg,ty)::tail ->
+       pp(lazy("arg{ " ^ 
+         NCicPp.ppterm ~metasenv ~subst ~context:context_of_args arg ^  ":" ^
+         NCicPp.ppterm ~metasenv ~subst ~context:context_of_args ty));
+       let metasenv, subst, telescopic_ty = 
+         if processed_args = [] then metasenv, subst, ty else
+         let _ = pp(lazy("delift")) in
+         delift_type_wrt_terms rdb metasenv subst context_of_args ty 
+           (List.rev processed_args)
+       in
+       pp(lazy("arg}"));
+       let name = "HBeta"^string_of_int n in
+       let metasenv, subst, bo =
+        mk_lambda metasenv subst ((name,NCic.Decl telescopic_ty)::context) (n+1)
+         (arg::processed_args) tail
+       in
+        metasenv, subst, NCic.Lambda (name, telescopic_ty, bo)
+ in
+ pp(lazy("LAMBDA_INTROS{ " ^ 
+   NCicPp.ppterm ~metasenv ~subst ~context t ^  ":" ^
+   NCicPp.ppterm ~metasenv ~subst ~context tty ^ " over " ^ 
+   String.concat "," (List.map (NCicPp.ppterm ~metasenv ~subst ~context)args)));
+ let rc = mk_lambda metasenv subst context 0 [] argsty in
+ pp(lazy("LAMBDA_INTROS}"));
+ rc
+
+and instantiate rdb test_eq_only metasenv subst context n lc t swap =
  (*D*)  inside 'I'; try let rc =  
          pp (lazy(string_of_int n ^ " :=?= "^
            NCicPp.ppterm ~metasenv ~subst ~context t));
   let unify test_eq_only m s c t1 t2 = 
-    if swap then unify hdb test_eq_only m s c t2 t1 
-    else unify hdb test_eq_only m s c t1 t2
+    if swap then unify rdb test_eq_only m s c t2 t1 
+    else unify rdb test_eq_only m s c t1 t2
   in
   let name, ctx, ty = NCicUtils.lookup_meta n metasenv in
   let metasenv, subst, t = 
     match ty with 
-    | NCic.Implicit (`Typeof _) -> 
-       metasenv,subst, t
-         (* fix_sorts swap metasenv subst context (NCic.Meta(n,lc)) t *)
+    | NCic.Implicit (`Typeof _) ->
+       (match NCicReduction.whd ~subst context t with
+          NCic.Sort _ -> metasenv,subst,t
+        | NCic.Meta (i,_) when
+           let _,_,ty = NCicUtils.lookup_meta i metasenv in
+            (match ty with
+                NCic.Implicit (`Typeof _) -> true
+              | _ -> false)
+           -> metasenv,subst,t
+        | NCic.Meta (i,_) ->
+           let rec remove_and_hope i =
+            let _,ctx,ty = NCicUtils.lookup_meta i metasenv in
+            match ty with
+               NCic.Implicit _ -> List.filter (fun i',_ -> i <> i') metasenv
+             | _ ->
+               match NCicReduction.whd ~subst ctx ty with
+                  NCic.Meta (j,_) ->
+                   let metasenv = remove_and_hope j in
+                    List.filter (fun i',_ -> i <> i') metasenv
+                | _ -> assert false (* NON POSSO RESTRINGERE *)
+           in
+           let metasenv = remove_and_hope i in
+           let metasenv =
+            (i,(None,[],NCic.Implicit (`Typeof i)))::
+             List.filter (fun i',_ -> i <> i') metasenv
+           in
+            metasenv,subst,t
+        | NCic.Appl (NCic.Meta _::_) ->
+           raise (Uncertain (lazy "Trying to instantiate a metavariable that represents a sort with a term"))
+        | t when could_reduce t -> 
+           raise (Uncertain (lazy "Trying to instantiate a metavariable that represents a sort with a term"))
+        | _ ->
+           raise (UnificationFailure (lazy "Trying to instantiate a metavariable that represents a sort with a term")))
     | _ ->
        pp (lazy (
-         "typeof: " ^ NCicPp.ppterm ~metasenv ~subst ~context t ^ "\nctx:\n"^
-          NCicPp.ppcontext ~metasenv ~subst context ^ "\nmenv:\n"^
-          NCicPp.ppmetasenv ~subst metasenv));
+               "typeof: " ^ NCicPp.ppterm ~metasenv ~subst ~context t ^
+          ppcontext ~metasenv ~subst context ^ 
+          ppmetasenv ~subst metasenv));
+       let exc_to_be = fail_exc metasenv subst context (NCic.Meta (n,lc)) t in
        let t, ty_t = 
          try t, NCicTypeChecker.typeof ~subst ~metasenv context t 
          with 
          | NCicTypeChecker.AssertFailure msg -> 
            (pp (lazy "fine typeof (fallimento)");
-           let ft=fix_sorts swap metasenv subst context (NCic.Meta (n,lc)) t in
+           let ft = fix_sorts swap exc_to_be t in
            if ft == t then 
              (prerr_endline ( ("ILLTYPED: " ^ 
                 NCicPp.ppterm ~metasenv ~subst ~context t
-            ^ "\nBECAUSE:" ^ Lazy.force msg ^ "\nCONTEXT:\n" ^
-            NCicPp.ppcontext ~metasenv ~subst context ^ "\nMENV:\n" ^
-            NCicPp.ppmetasenv ~subst metasenv
+            ^ "\nBECAUSE:" ^ Lazy.force msg ^ 
+            ppcontext ~metasenv ~subst context ^ 
+            ppmetasenv ~subst metasenv
             ));
                      assert false)
            else
@@ -201,20 +265,44 @@ and instantiate hdb test_eq_only metasenv subst context n lc t swap =
               assert false)
          | NCicTypeChecker.TypeCheckerFailure msg ->
               prerr_endline (Lazy.force msg);
+       prerr_endline (
+               "typeof: " ^ NCicPp.ppterm ~metasenv ~subst ~context t ^
+          ppcontext ~metasenv ~subst context ^ 
+          ppmetasenv ~subst metasenv);
               pp msg; assert false
        in
        let lty = NCicSubstitution.subst_meta lc ty in
-       pp (lazy ("On the types: " ^
-        NCicPp.ppterm ~metasenv ~subst ~context:ctx ty ^ " ~~~ " ^
-        NCicPp.ppterm ~metasenv ~subst ~context lty ^ " === "
-         ^ NCicPp.ppterm ~metasenv ~subst ~context ty_t)); 
-       let metasenv,subst= unify test_eq_only metasenv subst context lty ty_t in
-       metasenv, subst, t
+       match ty_t with
+       | NCic.Implicit _ -> 
+           raise (UnificationFailure 
+             (lazy "trying to unify a term with a type"))
+       | ty_t -> 
+          pp (lazy ("On the types: " ^
+           NCicPp.ppterm ~metasenv ~subst ~context:ctx ty ^ " ~~~ " ^
+           NCicPp.ppterm ~metasenv ~subst ~context lty ^ " === "
+            ^ NCicPp.ppterm ~metasenv ~subst ~context ty_t)); 
+          let metasenv,subst = 
+           try
+            unify test_eq_only metasenv subst context lty ty_t
+           with NCicEnvironment.BadConstraint _ as exc ->
+            let ty_t = fix_sorts swap exc_to_be ty_t in 
+             try unify test_eq_only metasenv subst context lty ty_t
+             with _ -> raise exc in
+          metasenv, subst, t
   in
          pp (lazy(string_of_int n ^ " := 111 = "^
            NCicPp.ppterm ~metasenv ~subst ~context t));
   let (metasenv, subst), t = 
-    try NCicMetaSubst.delift metasenv subst context n lc t
+    try 
+      NCicMetaSubst.delift 
+       ~unify:(fun m s c t1 t2 -> 
+         let ind = !indent in
+         let res = 
+           try Some (unify test_eq_only m s c t1 t2 )
+           with UnificationFailure _ | Uncertain _ -> None
+         in
+         indent := ind; res) 
+       metasenv subst context n lc t
     with NCicMetaSubst.Uncertain msg -> 
          pp (lazy ("delift fails: " ^ Lazy.force msg));
          raise (Uncertain msg)
@@ -224,7 +312,7 @@ and instantiate hdb test_eq_only metasenv subst context n lc t swap =
   in
          pp (lazy(string_of_int n ^ " := 222 = "^
            NCicPp.ppterm ~metasenv ~subst ~context:ctx t
-         ^ "\n" ^ NCicPp.ppmetasenv ~subst metasenv));
+         ^ ppmetasenv ~subst metasenv));
   (* Unifying the types may have already instantiated n. *)
   try
     let _, _,oldt,_ = NCicUtils.lookup_subst n subst in
@@ -242,14 +330,14 @@ and instantiate hdb test_eq_only metasenv subst context n lc t swap =
       List.filter (fun (m,_) -> not (n = m)) metasenv 
     in
     metasenv, subst
- (*D*)  in outside(); rc with exn -> outside (); raise exn 
+ (*D*)  in outside true; rc with exn -> outside false; raise exn 
 
-and unify hdb test_eq_only metasenv subst context t1 t2 =
+and unify rdb test_eq_only metasenv subst context t1 t2 =
  (*D*) inside 'U'; try let rc =
    let fo_unif test_eq_only metasenv subst t1 t2 =
     (*D*) inside 'F'; try let rc =  
      pp (lazy("  " ^ NCicPp.ppterm ~metasenv ~subst ~context t1 ^ " ==?== " ^ 
-         NCicPp.ppterm ~metasenv ~subst ~context t2 ^ "\n" ^ NCicPp.ppmetasenv
+         NCicPp.ppterm ~metasenv ~subst ~context t2 ^ ppmetasenv
          ~subst metasenv));
      if t1 === t2 then
        metasenv, subst
@@ -271,13 +359,13 @@ and unify hdb test_eq_only metasenv subst context t1 t2 =
 
        | (C.Lambda (name1,s1,t1), C.Lambda(_,s2,t2)) 
        | (C.Prod (name1,s1,t1), C.Prod(_,s2,t2)) ->
-           let metasenv, subst = unify hdb true metasenv subst context s1 s2 in
-           unify hdb test_eq_only metasenv subst ((name1, C.Decl s1)::context) t1 t2
+           let metasenv, subst = unify rdb true metasenv subst context s1 s2 in
+           unify rdb test_eq_only metasenv subst ((name1, C.Decl s1)::context) t1 t2
        | (C.LetIn (name1,ty1,s1,t1), C.LetIn(_,ty2,s2,t2)) ->
-           let metasenv,subst=unify hdb test_eq_only metasenv subst context ty1 ty2 in
-           let metasenv,subst=unify hdb test_eq_only metasenv subst context s1 s2 in
+           let metasenv,subst=unify rdb test_eq_only metasenv subst context ty1 ty2 in
+           let metasenv,subst=unify rdb test_eq_only metasenv subst context s1 s2 in
            let context = (name1, C.Def (s1,ty1))::context in
-           unify hdb test_eq_only metasenv subst context t1 t2
+           unify rdb test_eq_only metasenv subst context t1 t2
 
        | (C.Meta (n1,(s1,l1 as lc1)),C.Meta (n2,(s2,l2 as lc2))) when n1 = n2 ->
           (try 
@@ -288,7 +376,7 @@ and unify hdb test_eq_only metasenv subst context t1 t2 =
              (fun t1 t2 (metasenv, subst, to_restrict, i) -> 
                 try 
                   let metasenv, subst = 
-                   unify hdb test_eq_only metasenv subst context 
+                   unify rdb test_eq_only metasenv subst context 
                     (NCicSubstitution.lift s1 t1) (NCicSubstitution.lift s2 t2)
                   in
                   metasenv, subst, to_restrict, i-1  
@@ -309,37 +397,80 @@ and unify hdb test_eq_only metasenv subst context t1 t2 =
                 let _,_,term,_ = NCicUtils.lookup_subst n1 subst in
                 let term1 = NCicSubstitution.subst_meta lc1 term in
                 let term2 = NCicSubstitution.subst_meta lc2 term in
-                  unify hdb test_eq_only metasenv subst context term1 term2
+                  unify rdb test_eq_only metasenv subst context term1 term2
               with NCicUtils.Subst_not_found _-> raise (UnificationFailure msg))
+       
+       | _, NCic.Meta (n, _) when is_locked n subst ->
+           (let (metasenv, subst), i = 
+              match NCicReduction.whd ~subst context t1 with
+              | NCic.Appl (NCic.Meta (i,l)::args) ->
+                 let metasenv, subst, lambda_Mj =
+                   lambda_intros rdb metasenv subst context t1 args
+                 in
+                   unify rdb test_eq_only metasenv subst context 
+                    (C.Meta (i,l)) lambda_Mj,
+                   i
+              | NCic.Meta (i,_) -> (metasenv, subst), i
+              | _ ->
+                 raise (UnificationFailure (lazy "Locked term vs non
+                  flexible term; probably not saturated enough yet!"))
+             in
+              let t1 = NCicReduction.whd ~subst context t1 in
+              let j, lj = 
+                match t1 with NCic.Meta (j,l) -> j, l | _ -> assert false
+              in
+              let metasenv, subst = 
+                instantiate rdb test_eq_only metasenv subst context j lj t2 true
+              in
+              (* We need to remove the out_scope_tags to avoid propagation of
+                 them that triggers again the ad-hoc case *)
+              let subst =
+               List.map (fun (i,(tag,ctx,bo,ty)) ->
+                let tag =
+                 match tag with
+                    Some tag when
+                        tag = NCicMetaSubst.in_scope_tag
+                     || NCicMetaSubst.is_out_scope_tag tag -> None
+                  | _ -> tag
+                in
+                  i,(tag,ctx,bo,ty)
+                ) subst
+              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))
 
        | C.Meta (n,lc), t -> 
            (try 
              let _,_,term,_ = NCicUtils.lookup_subst n subst in
              let term = NCicSubstitution.subst_meta lc term in
-               unify hdb test_eq_only metasenv subst context term t
+               unify rdb test_eq_only metasenv subst context term t
            with NCicUtils.Subst_not_found _-> 
-             instantiate hdb test_eq_only metasenv subst context n lc 
+             instantiate rdb test_eq_only metasenv subst context n lc 
                (NCicReduction.head_beta_reduce ~subst t) false)
 
        | t, C.Meta (n,lc) -> 
            (try 
              let _,_,term,_ = NCicUtils.lookup_subst n subst in
              let term = NCicSubstitution.subst_meta lc term in
-               unify hdb test_eq_only metasenv subst context t term
+               unify rdb test_eq_only metasenv subst context t term
            with NCicUtils.Subst_not_found _-> 
-             instantiate hdb test_eq_only metasenv subst context n lc 
+             instantiate rdb test_eq_only metasenv subst context n lc 
               (NCicReduction.head_beta_reduce ~subst t) true)
 
        | NCic.Appl (NCic.Meta (i,l)::args), _ when List.mem_assoc i subst ->
             let _,_,term,_ = NCicUtils.lookup_subst i subst in
             let term = NCicSubstitution.subst_meta l term in
-              unify hdb test_eq_only metasenv subst context 
+              unify rdb test_eq_only metasenv subst context 
                 (mk_appl ~upto:(List.length args) term args) t2
 
        | _, NCic.Appl (NCic.Meta (i,l)::args) when List.mem_assoc i subst ->
             let _,_,term,_ = NCicUtils.lookup_subst i subst in
             let term = NCicSubstitution.subst_meta l term in
-              unify hdb test_eq_only metasenv subst context t1 
+              unify rdb test_eq_only metasenv subst context t1 
                 (mk_appl ~upto:(List.length args) term args)
 
        |  NCic.Appl (NCic.Meta (i,_)::_ as l1),
@@ -347,30 +478,46 @@ and unify hdb test_eq_only metasenv subst context t1 t2 =
             (try
               List.fold_left2 
                 (fun (metasenv, subst) t1 t2 ->
-                  unify hdb test_eq_only metasenv subst context t1 t2)
+                  unify rdb test_eq_only metasenv subst context t1 t2)
                 (metasenv,subst) l1 l2
             with Invalid_argument _ -> 
               raise (fail_exc metasenv subst context t1 t2))
 
-       | NCic.Appl (NCic.Meta (i,l)::args), _ when not (flexible args) ->
-           (* we verify that none of the args is a Meta, 
-              since beta expanding w.r.t a metavariable makes no sense  *)
-              let metasenv, subst, beta_expanded =
-                beta_expand_many hdb 
-                  test_eq_only false 
-                  metasenv subst context t2 args
-              in
-                unify hdb test_eq_only metasenv subst context 
-                  (C.Meta (i,l)) beta_expanded 
-
-       | _, NCic.Appl (NCic.Meta (i,l)::args) when not(flexible args) ->
-              let metasenv, subst, beta_expanded =
-                beta_expand_many hdb 
-                  test_eq_only true 
-                  metasenv subst context t1 args
-              in
-                unify hdb test_eq_only metasenv subst context 
-                  beta_expanded (C.Meta (i,l))
+       | NCic.Appl (NCic.Meta (i,l)::args), _ ->
+          let metasenv, subst, lambda_Mj =
+            lambda_intros rdb metasenv subst context t1 args
+          in
+          let metasenv, subst = 
+            unify rdb test_eq_only metasenv subst context 
+              (C.Meta (i,l)) lambda_Mj
+          in
+          let metasenv, subst = 
+            unify rdb test_eq_only metasenv subst context t1 t2 
+          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)
+
+       | _, NCic.Appl (NCic.Meta (i,l)::args) ->
+         let metasenv, subst, lambda_Mj =
+           lambda_intros rdb metasenv subst context t2 args
+         in
+         let metasenv, subst =
+           unify rdb test_eq_only metasenv subst context 
+            lambda_Mj (C.Meta (i,l))
+         in
+         let metasenv, subst = 
+           unify rdb test_eq_only metasenv subst context t1 t2 
+         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)
 
        (* processing this case here we avoid a useless small delta step *)
        | (C.Appl ((C.Const r1) as _hd1::tl1), C.Appl (C.Const r2::tl2)) 
@@ -378,7 +525,10 @@ and unify hdb test_eq_only metasenv subst context t1 t2 =
            let relevance = NCicEnvironment.get_relevance r1 in
            let relevance = match r1 with
              | Ref.Ref (_,Ref.Con (_,_,lno)) ->
-                 let _,relevance = HExtlib.split_nth lno relevance in
+                 let relevance =
+                  try snd (HExtlib.split_nth lno relevance)
+                  with Failure _ -> []
+                 in
                    HExtlib.mk_list false lno @ relevance
              | _ -> relevance
            in
@@ -389,7 +539,7 @@ and unify hdb test_eq_only metasenv subst context t1 t2 =
                     let b, relevance = 
                       match relevance with b::tl -> b,tl | _ -> true, [] in
                     let metasenv, subst = 
-                      try unify hdb test_eq_only metasenv subst context t1 t2
+                      try unify rdb test_eq_only metasenv subst context t1 t2
                       with UnificationFailure _ | Uncertain _ when not b ->
                         metasenv, subst
                     in
@@ -421,41 +571,67 @@ and unify hdb test_eq_only metasenv subst context t1 t2 =
              raise (uncert_exc metasenv subst context t1 t2) 
            else
              let metasenv, subst = 
-              unify hdb test_eq_only metasenv subst context outtype1 outtype2 in
+              unify rdb test_eq_only metasenv subst context outtype1 outtype2 in
              let metasenv, subst = 
-               try unify hdb test_eq_only metasenv subst context term1 term2 
+               try unify rdb test_eq_only metasenv subst context term1 term2 
                with UnificationFailure _ | Uncertain _ when is_prop -> 
                  metasenv, subst
              in
              (try
               List.fold_left2 
                (fun (metasenv,subst) -> 
-                  unify hdb test_eq_only metasenv subst context)
+                  unify rdb test_eq_only metasenv subst context)
                (metasenv, subst) pl1 pl2
-             with Invalid_argument _ -> 
-               raise (uncert_exc metasenv subst context t1 t2))
+             with Invalid_argument _ -> assert false)
        | (C.Implicit _, _) | (_, C.Implicit _) -> assert false
        | _ when NCicUntrusted.metas_of_term subst context t1 = [] && 
                 NCicUntrusted.metas_of_term subst context t2 = [] -> 
                   raise (fail_exc metasenv subst context t1 t2)
        | _ -> raise (uncert_exc metasenv subst context t1 t2)
-     (*D*)  in outside(); rc with exn -> outside (); raise exn 
+     (*D*)  in outside true; rc with exn -> outside false; raise exn 
     in
     let try_hints metasenv subst t1 t2 (* exc*) =
+    (*D*) inside 'H'; try let rc =  
+(*
+      prerr_endline ("\nProblema:\n" ^
+        NCicPp.ppterm ~metasenv ~subst ~context t1 ^ " =?= " ^
+        NCicPp.ppterm ~metasenv ~subst ~context t2);
+*)
       let candidates = 
-        NCicUnifHint.look_for_hint hdb metasenv subst context t1 t2
+        NCicUnifHint.look_for_hint rdb metasenv subst context t1 t2
       in
       let rec cand_iter = function
         | [] -> None (* raise exc *)
-        | (metasenv,c1,c2)::tl -> 
+        | (metasenv,(c1,c2),premises)::tl -> 
+            pp (lazy ("\nProvo il candidato:\n" ^ 
+              String.concat "\n"
+                (List.map 
+                  (fun (a,b) ->
+                   NCicPp.ppterm ~metasenv ~subst ~context a ^  " =?= " ^
+                   NCicPp.ppterm ~metasenv ~subst ~context b) premises) ^
+              "\n-------------------------------------------\n"^
+              NCicPp.ppterm ~metasenv ~subst ~context c1 ^  " = " ^
+              NCicPp.ppterm ~metasenv ~subst ~context c2));
             try 
-              let metasenv,subst = fo_unif test_eq_only metasenv subst t1 c1 in
-              let metasenv,subst = fo_unif test_eq_only metasenv subst c2 t2 in
+    (*D*) inside 'K'; try let rc =  
+              let metasenv,subst = 
+                fo_unif test_eq_only metasenv subst t1 c1 in
+              let metasenv,subst = 
+                fo_unif test_eq_only metasenv subst c2 t2 in
+              let metasenv,subst = 
+                List.fold_left 
+                  (fun (metasenv, subst) (x,y) ->
+                     unify rdb test_eq_only metasenv subst context x y)
+                  (metasenv, subst) premises
+              in
               Some (metasenv, subst)
+     (*D*)  in outside true; rc with exn -> outside false; raise exn 
             with
-              UnificationFailure _ | Uncertain _ -> cand_iter tl
+              UnificationFailure _ | Uncertain _ ->
+                cand_iter tl
       in
         cand_iter candidates
+     (*D*)  in outside true; rc with exn -> outside false; raise exn 
     in
     let height_of = function
      | NCic.Const (Ref.Ref (_,Ref.Def h)) 
@@ -500,8 +676,8 @@ pp (lazy (string_of_bool norm1 ^ " ?? " ^ string_of_bool norm2));
             | _ -> [] *) in
           let unif_from_stack t1 t2 b metasenv subst =
               try
-                let t1 = NCicReduction.from_stack t1 in
-                let t2 = NCicReduction.from_stack t2 in
+                let t1 = NCicReduction.from_stack ~delta:max_int t1 in
+                let t2 = NCicReduction.from_stack ~delta:max_int t2 in
                 unif_machines metasenv subst (put_in_whd t1 t2)
               with UnificationFailure _ | Uncertain _ when not b ->
                 metasenv, subst
@@ -524,10 +700,18 @@ pp (lazy (string_of_bool norm1 ^ " ?? " ^ string_of_bool norm2));
           ) (metasenv,subst) todo
         with UnificationFailure _ | Uncertain _ when not (norm1 && norm2) ->
 	    unif_machines metasenv subst (small_delta_step ~subst m1 m2)
-      (*D*)  in outside(); rc with exn -> outside (); raise exn 
+      (*D*)  in outside true; rc with exn -> outside false; raise exn 
      in
      try fo_unif test_eq_only metasenv subst t1 t2
-     with UnificationFailure msg | Uncertain msg as exn -> 
+     with 
+     | UnificationFailure msg as exn ->
+          (try 
+            unif_machines metasenv subst 
+             (put_in_whd (0,[],t1,[]) (0,[],t2,[]))
+          with 
+          | UnificationFailure _ -> raise (UnificationFailure msg)
+          | Uncertain _ -> raise exn)
+     | Uncertain msg as exn -> 
        match try_hints metasenv subst t1 t2 with
        | Some x -> x
        | None -> 
@@ -537,11 +721,29 @@ pp (lazy (string_of_bool norm1 ^ " ?? " ^ string_of_bool norm2));
           with 
           | UnificationFailure _ -> raise (UnificationFailure msg)
           | Uncertain _ -> raise exn
- (*D*)  in outside(); rc with exn -> outside (); raise exn 
+ (*D*)  in outside true; rc with exn -> outside false; raise exn 
+
+and delift_type_wrt_terms rdb metasenv subst context t args =
+  let (metasenv, subst), t =
+   try
+    NCicMetaSubst.delift 
+      ~unify:(fun m s c t1 t2 -> 
+         let ind = !indent in
+         let res = 
+           try Some (unify rdb false m s c t1 t2 )
+           with UnificationFailure _ | Uncertain _ -> None
+         in
+         indent := ind; res)
+      metasenv subst context 0 (0,NCic.Ctx (args @ 
+        List.rev (mk_irl (List.length context)))) t
+   with NCicMetaSubst.MetaSubstFailure _ -> (metasenv, subst), t
+  in
+   metasenv, subst, t
 ;;
 
-let unify hdb = 
-  indent := "";      
-  unify hdb false;;
 
+let unify rdb ?(test_eq_only=false) = 
+  indent := "";      
+  unify rdb test_eq_only;;
 
+let fix_sorts = fix_sorts true (UnificationFailure (lazy "no sup"));;