anchor.diff:          | Tip(ky, y) -> Some(ky, y)
           | Bin(_, _, _, r) -> unsafeFindMax r
   
  +    ///O(log n). Find largest key smaller than the given one and return the corresponding (key, value) pair.  Credit: Haskell.org
       let tryFindLT k t =
           let rec go def =
               function
  
positive.code:         | Tip(kx, x) -> None
          | Nil -> None
  
      let rec exists k =
          function
          | Bin(p, m, l, r) when nomatch k p m -> false
  
negative.code:         | Tip(ky, _) -> (None, join k (Tip(k, x)) ky t)
          | Nil -> (None, Tip(k, x))
  
      ///O(min(n,W)). Delete a key and its value from the map. When the key is not a member of the map, the original map is returned. Credit: Haskell.org
      let rec delete k t =
          match t with
          | Bin(p, m, l, r) when nomatch k p m -> t
  