anchor.diff:          | Nil, Nil -> EQ
           | Nil, _ -> LT
   
  +    ///O(n+m). Is this a proper submap? (ie. a submap but not equal). The expression (isProperSubmapOfBy f m1 m2) returns True when m1 and m2 are not equal, all keys in m1 are in m2, and when f returns True when applied to their respective values.  Credit: Haskell.org
       let isProperSubmapOfBy predicate t1 t2 =
           match submapCmp predicate t1 t2 with
           | LT -> true
           | _ -> false
   
  +    ///O(n+m). Is this a proper submap? (ie. a submap but not equal). Defined as (isProperSubmapOf = isProperSubmapOfBy (==)). Credit: Haskell.org
       let isProperSubmapOf m1 m2 = isProperSubmapOfBy (=) m1 m2
   
       let monoid<'a> = 
  
positive.code:             | Bin(_, m, l, r) -> go (go z l) r
              | _ -> go z t
  
      let inline foldBackWithKey f z = fun (t: _ IntMap) -> t.FoldBackWithKey f z
  
      let foldWithKey f z =
          let rec go z =
              function
  
negative.code:         | Tip(kx, x) -> notFound()
          | Nil -> notFound()
  
      ///O(min(n,W)). The expression (findWithDefault def k map) returns the value at key k or returns def when the key is not an element of the map.  Credit: Haskell.org
      let rec findWithDefault def k =
          function
          | Bin(p, m, l, r) when nomatch k p m -> def
  