simplify to_string

lab05/kvtree/kvtree.ml

@@ -130,13 +130,10 @@ module Make(Ord: OrderedType) = struct
   (** [to_string f t] takes a function [f] to "convert" a
     * key-value pair to a string, and applies that to all
     * key-value pairs in a given tree [t]. *)
-  let to_string f t =
-    let rec aux t =
+  let rec to_string f t =
     match t with
     | L -> "#"
     | N (k, v, l, r) ->
-        Printf.sprintf "^(%s, %s, %s)" (f (k, v)) (aux l) (aux r)
-    in
-    aux t;;
+      Printf.sprintf "^(%s, %s, %s)" (f (k, v)) (to_string f l) (to_string f r);;
 
 end