Biocaml 0.4-dev : Biocaml_iset.mem

let rec mem s (n:int) =

 if is_empty s then false else

  let v1, v2 = root s in

  if n < v1 then mem (left_branch s) n else

   if v1 <= n && n <= v2 then true else

    mem (right_branch s) n