anchor.diff:          | Bin(_, m, l, r) when m < 0 -> if k >= 0 then go Nil l else go l r
           | _ -> go Nil t
   
  +    ///O(log n). Find largest key smaller or equal to the given one and return the corresponding (key, value) pair. Credit: Haskell.org
       let tryFindLE k t =
           let rec go def =
               function
  
positive.code:         | Bin(p, m, l, r) when m < 0 -> let (result, l) = go l in Some(result, bin p m l r)
          | _ -> Some(go t)
  
      let minViewWithKey t =
          let rec go =
              function
  
negative.code:         | Bin(p, m, l, r) when m < 0 -> let (result, r) = go r in Some(result, bin p m l r)
          | _ -> Some(go t)
  
      ///O(log n). Update the value at the maximal key. Credit: Haskell.org
      let updateMax f = updateMaxWithKey (konst f)
  
      ///O(log n). Update the value at the minimal key. Credit: Haskell.org
      let updateMin f = updateMinWithKey (konst f)
  
      let private first f (x, y) = (f x, y)
  
      ///O(min(n,W)). Retrieves the maximal key of the map, and the map stripped of that element, or Nothing if passed an empty map. Credit: Haskell.org
      let maxView t = Option.map (first snd) (maxViewWithKey t)
  
      ///O(min(n,W)). Retrieves the minimal key of the map, and the map stripped of that element, or Nothing if passed an empty map. Credit: Haskell.org
      let minView t = Option.map (first snd) (minViewWithKey t)
  
      ///O(log n). Retrieves the maximal key of the map, and the map stripped from that element. Credit: Haskell.org
      let deleteFindMax t = Option.getOrElseF (fun _ -> failwith "deleteFindMax: empty map has no maximal element") << maxViewWithKey <| t
  
      ///O(log n). Retrieves the minimal key of the map, and the map stripped from that element. Credit: Haskell.org
      let deleteFindMin t = Option.getOrElseF (fun _ -> failwith "deleteFindMin: empty map has no minimal element") << minViewWithKey <| t
  
      ///O(log n). The minimal key of the map. Credit: Haskell.org
      let findMin t =
          let rec go =
              function
  