+ let create a =
+ let dummy5 = N5.create a in
+ N1.create dummy5
+
+ let add a i j k l m n v =
+ let line = N1.find a i in
+ if line == N1.dummy a then
+ let nline = N5.create (N5.dummy line) in
+ N1.add a i nline;
+ N5.add nline j k l m n v
+ else
+ N5.add line j k l m n v
+
+ let find a i j k l m n =
+ let v = N1.find a i in
+ if v == N1.dummy a then N5.dummy v
+ else N5.find v j k l m n
+
+
+ let dummy a = N5.dummy (N1.dummy a)
+ let iteri f a =
+ N1.iteri (fun i v _ ->
+ N5.iteri (fun j k l m n v2 b -> f i j k l m n v2 b) v
+ ) a