 where Generator.Element == Elements.Generator.Element,
 Elements.Index : BidirectionalIndexType
 {
+  /// Returns the concatenated results of mapping `transform` over
+  /// `self`.  Equivalent to 
+  ///
+  ///     self.map(transform).flatten
   public func flatMap<
     Intermediate: CollectionType
     where Intermediate.Index : BidirectionalIndexType


extension _prext_LazyCollectionType
where Generator.Element == Elements.Generator.Element{
  public func flatMap<Intermediate: CollectionType>(
    transform: (Generator.Element)->Intermediate
  ) -> _prext_LazyCollection<


extension _prext_LazySequenceType where
Generator.Element == Elements.Generator.Element {
  /// Returns the concatenated results of mapping `transform` over
  /// `self`.  Equivalent to 
  ///
  ///     self.map(transform).flatten
  public func flatMap<Intermediate: SequenceType>(
    transform: (Generator.Element)->Intermediate
  ) -> _prext_LazySequence<
