high(cur: BINTREE): INTEGER
            local
                h_left: INTEGER
                h_right: INTEGER
            do
                if Current.value = Current.value.min_value then
                    Result := 0
                else
                    if cur.left /= Void then
                        h_left := high(cur.left)
                    end

                    if cur.right /= Void then
                        h_right := high(cur.right)
                    end

                    Result := h_left.max (h_right) + 1
                end
            end