1 files changed, 4 insertions, 0 deletions
diff --git a/tree.sml b/tree.sml
index 678ebe8..ee82485 100644
--- a/tree.sml
+++ b/tree.sml
@@ -82,6 +82,10 @@ structure Tree: TREE = struct
     assemble' buf n
   end
 
+  (* f accepts previous value (NONE if not present) and returns
+   * (res, v' option). Res will be returned by lookup2. 'v if present, will
+   * be new value in place of the old one
+   *)
   fun lookup' buf _ Empty k f =
   let
     val (res, newV) = f NONE