// assumed to be comparer
// i.e. comp(x,x)=0, and comp(x,y)>0 then comp(y,x)<0, and comp(x,y)>0 & comp(y,z)>0 then comp(x,z)>0
public AVLTree(Comparison <T> comp)
{
sentinel = new AVLNode(this);
sentinel.ResetAsSentinel();
this.comp = comp ?? DefaultComparison <T>();
if (typeof(T).IsValueType)
{
equals = (x, y) => x.Equals(y);
}
else
{
equals = (x, y) => ReferenceEquals(x, y);
}
count = 0;
}
public void Clear()
{
sentinel.Left = sentinel; count = 0; sentinel.ResetAsSentinel();
}