anchor.diff:                      // The prefixes disagree.
                       PatriciaSet.Join (p, s, q, t)
   
  -        | (Br (p, m, s0, s1) as s), (Lf k as t) ->
  +        | Br (p, m, s0, s1), Lf k ->
               if matchPrefix (k, p, m) then
                   if zeroBit (k, m) then
                       let left = PatriciaSet.Add (k, s0)
  
positive.code:         checkNonNull "set1" set1
          checkNonNull "set2" set2
  
          set1.IsSuperset set2
  
      /// <summary>
      /// Evaluates to &quot;true&quot; if all elements of the second set are in the first,
  
negative.code:                 else
                      Empty
  
          | Br (_, m, s0, s1), Lf k ->
              let s' = if zeroBit (k, m) then s0 else s1
              if PatriciaSet.Contains (k, s') then t
              else Empty
  