public static IEnumerable <Indexed <T> > ToIndexed <T>(this IEnumerable <T> source)
{
int index = 0;
foreach (T t in source)
{
yield return(Indexed.Create(index, t));
index++;
}
}
public Indexed <U> Select <U>(Func <T, U> selector)
{
return(Indexed.Create(Index, selector(Value)));
}