Why std::queue doesn't implement insert() while std::deque does?

Question

我正在阅读std::queue ，我想知道为什么没有方法可以通过单个操作有效地插入多个元素，而std::deque提供了std::deque::insert吗？

Answer 1

Insert allows insertion into an arbitrary position into the structure.

std::queue is an abstract interface for a FIFO structure. You can only add things to the end. The underlying structure doesn't necessarily have an efficient way to insert into arbitrary position (consider std::vector for example). Therefore std::queue has no general insert member function.

Since the general insertion function requires the iterator position argument, the multiple-insert is provided as a convenience, so that you don't have to keep track of the next iterator position. The push back doesn't have need for this because no iterator tracking is needed and a trivial loop is sufficient.

Answer 2

std::queue is an adapter that is intended to be limited to push/pop interfaces. It will not expose insert even if std::vector is an underlying implementation.

There are no particular performance reasons, merely a design approach: if you feel that your container is a queue, you just do not expose interfaces you don't need.