fact: Fixpoint add (k : key) (x : elt) (s : t elt) : t elt := match s with | nil => (k,x) :: nil | (k',y) :: l => match X.compare k k' with | Lt => (k,x)::s | Eq => (k,x)::l | Gt => (k',y) :: add k x l end end.
imports: Coq(OrdersFacts OrdersLists)