anchor.diff:      [<CompiledName("Tail")>]
       let tail (list : LazyList<'T>) =
           match getCell list with
  -        | CellCons (_, tl) -> tl
  -        | CellEmpty ->
  +        | Cons (_, tl) -> tl
  +        | Empty ->
               invalidArg "s" "The list is empty."
   
       /// Test if a list is empty.
  
positive.code: //
  [<CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
  module LazyList =
      /// Curried form of the CellCons constructor.
      let inline private consc value (list : LazyList<'T>) =
          CellCons (value, list)
  
      //
      let inline private lzy cellCreator : LazyList<'T> =
  
negative.code:     [<CompiledName("Head")>]
      let head (list : LazyList<'T>) =
          match getCell list with
          | Cons (hd, _) -> hd
          | Empty ->
              invalidArg "s" "The list is empty."
  
      /// Return the list corresponding to the remaining items in the sequence.
  