class BinaryTree(V)
{
    alias  RB_Node!V  Node;

    Node* root;
    int  _length;

    @property empty()  const { return root is null; }
    @property length() const { return _length;      }

    /*
     * I don kno :<
     */
    void  add( V value )
    {
        Node** ptr = &root;
        Node*  cur =  root;
        while( cur !is null )
        {
            /**/ if( value < cur.value )  ptr = &cur.left;
            else if( value > cur.value )  ptr = &cur.right;
            else break;

            cur = *ptr;
        }

        if( cur !is null )
        {
            // TODO Duplicate
            return;
        }

        auto child = new Node();

        child.parent = cur;
        child.value  = value;

        // Finally attach to the parent
        *ptr = child;
    }

    void printme()
    {
        import shd.output;
        Node* p;

        void loop( const Node* p )
        {
            if( p.left  !is null )  loop( p.left );
            Shdout.print( p.value, ", " );
            if( p.right !is null )  loop( p.right );
        }
        Shdout.print("[ ");
        loop( root );
        Shdout.println("]");
    }
}

void main()
{

    auto tree = new BinaryTree!int;

    foreach( i; [ 1, 4, 8, 10, 3, 7, 20 ] )
        tree.add( i );

    tree.printme;
}

// Output [ 1, 3, 4, 7, 8, 10, 20, ]