/// <summary>
/// Prepends a sequence of elements.
/// </summary>
/// <param name="ts">The sequence of elements to prepend.</param>
/// <returns>The random access sequence consisting of elements of <paramref name="ts"/>
/// and this random access sequence.</returns>
public RandomAccessSequence <T> PrependRange(IEnumerable <T> ts)
{
return(new RandomAccessSequence <T>(_ft.PrependRange(ts.Map(t => new Element(t)))));
}
