public override ImmutableCollection <T> AddBack(T value)
{
if (m_right.IsFull)
{
return(new NormalCollection(
m_left,
m_middle.AddBack(m_right.RemoveBack()),
new Two(m_right.Back, value)));
}
else
{
return(new NormalCollection(m_left, m_middle, m_right.AddBack(value)));
}
}
