However, in some cases, you will need to read cursors both forward and backward, in which case you should use scrollable cursor.
但某些情况下，您需要游标既能向前又能向后，此时需要使用可滚动游标。
That veil is lifting as you read this, however, as telescopic vision extends ever backward in time and data is fed into powerful new computer models.
无论如何，正如你读到的这样，随着望远镜的视线拓展和计算机模式的数据处理能力日益更新和强大，面纱正在被揭开。
Some read the sequence backward, thus requiring bidirectional iterators.
一些算法反向读取序列，所以要求双向迭代器。
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