internal _ExpandStream(Stream <S> source, _stream._Transformation <S, IEnumerable <T> > expand) : base(source) { _expand = expand; }
Stream <S> expand <S>(_stream._Transformation <T, IEnumerable <S> > convert) { return(new _ExpandStream <T, S>(this, convert)); }
internal _MapStream(Stream <S> source, Func <S, T> transform) : base(source) { _transform = d => transform(d); }