+*)
+
+(*
+ * implementazione del comando DIFF
+ *)
+let rec diff_ex rs1 rs2 =
+ match (rs1, rs2) with
+ [],_ -> []
+ | l,[] -> l
+ | (uri1,l)::tl1,(uri2,_)::_ when uri1 < uri2 -> (uri1,l)::(diff_ex tl1 rs2)
+ | (uri1,_)::_,(uri2,_)::tl2 when uri2 < uri1 -> (diff_ex rs1 tl2)
+ | (uri1,_)::tl1, (uri2,_)::tl2 -> (diff_ex tl1 tl2)
+;;