anchor.diff:          // Return the taken elements and the remaining part of the list.
           takenElements, list
   
  +/// <summary>
   /// Applies a function to each element of the collection and the element which
   /// follows it, threading an accumulator argument through the computation.
  +/// </summary>
  +/// <param name="folder"></param>
  +/// <param name="state"></param>
  +/// <param name="list"></param>
  +/// <returns></returns>
   [<CompiledName("FoldPairwise")>]
   let foldPairwise (folder : 'State -> 'T -> 'T -> 'State) state list =
       // Preconditions
  
positive.code: 
      list |> List.mapi (fun i x -> i, x)
  
  /// Applies a function to each element of the array, returning a new array whose elements are
  /// tuples of the original element and the function result for that element.
  [<CompiledName("ProjectValues")>]
  let projectValues (projection : 'Key -> 'T) (list : 'Key list) =
      // Preconditions
  
negative.code:     | hd :: _ ->
          Some hd
  
  /// <summary>Create a list containing the given value.</summary>
  /// <param name="value"></param>
  /// <returns></returns>
  [<CompiledName("Singleton")>]
  let inline singleton (value : 'T) =
      [value]
  
  /// <summary>Builds a list from the given option value.</summary>
  /// <param name="value"></param>
  /// <returns></returns>
  [<CompiledName("OfOption")>]
  let inline ofOption (value : 'T option) =
      match value with
      | None -> []
      | Some x -> [x]
  
  /// <summary>Builds a list from the given string.</summary>
  /// <param name="str"></param>
  /// <returns></returns>
  [<CompiledName("OfString")>]
  let ofString (str : string) : char list =
      // Preconditions
  