anchor.diff:              | Empty ->
                   Empty
               | Cons (hd, tl) ->
  -                consc (mapping hd) (map mapping tl)
  +                consCell (mapping hd) (map mapping tl)
   
       /// Build a new collection whose elements are the results of applying the given function
       /// to the corresponding elements of the two collections pairwise.
  
positive.code: 
      /// Returns a new LazyListCell created by adding a value to the end of the given LazyList.
      /// This is simply a curried form of the Cons constructor.
      let inline private consc value (list : LazyList<'T>) =
          assert (not <| isNull list)
          Cons (value, list)
  
  
negative.code:             Empty
          | Cons (hd, tl) ->
              if predicate hd then
                  consCell hd (filter predicate tl)
              else
                  filterCell predicate tl
  
  