internal Enumerator(SortedSet <T> set, T lower, T upper)
: this()
{
host = set.tree.GetSuffixEnumerator(lower);
comparer = set.Comparer;
this.upper = upper;
}
internal Enumerator(SortedSet <T> set)
: this()
{
host = set.tree.GetEnumerator();
}