/// <summary>
/// Filters the specified sorted sequence on the specified predicate.
/// </summary>
public static ISortedEnumerable <TSource> WhereSorted <TSource>(this ISortedEnumerable <TSource> sequence, Func <TSource, bool> predicate)
{
Contract.Requires(sequence != null);
Contract.Requires(predicate != null);
return(new SortedEnumerable <TSource>(sequence.Where(predicate), sequence.Comparer));
}