为什么std :: queue不支持clear（）函数？ [英] why std::queue doesn't support clear() function?

问题描述

我有这样的要求。对于函数，我获得作为数字流的输入。我的意思是，在每次调用中，函数继续使用单个数字调用。我使用队列存储数字流。只有当满足一些条件时，我需要处理一组收集的数字。如果条件不满足，我需要把所有的元素在队列中，然后开始存储新的数字。为了清空队列，我找不到clear（）方法。所以我如下循环。

  while（！q.empty（））
 q.pop 
 

我在

获得了清除队列的高效算法

http://stackoverflow.com/questions/709146/how-do-我的问题是：为什么队列不支持clear（）函数？我的问题是：为什么队列不支持clear（）函数？

当deque和vector支持clear（）方法时，支持队列的技术难度是多少？

还是我上面的usecase非常罕见，因此不支持？
谢谢。

解决方案

根据http://www.cplusplus.com/reference/stl/queue/ ，

队列被实现为容器适配器，它是使用特定容器类的封装对象作为其底层容器的类，提供一组特定的成员函数来访问它的元素。

这意味着队列使用已经存在的容器，并且只是作为FIFO队列的这个容器的接口。

这意味着队列不会被清除。如果您需要清除队列，这意味着您实际上需要使用不是队列的对象，因此您应该使用实际的底层容器类型，默认为deque。

I have requirement like this. For a function, i get input as a stream of numbers. I mean, function keeps on getting called with single number in each call. I am using queue for storing stream of numbers. I need to process a collected set of numbers only when some condition is satisfied. If condition is not satisfied i need to throw all the elements in the queue and then start storing new numbers in that. For emptying the queue, i couldn't find clear() method. So i am looping like below.

while(!q.empty())
    q.pop();

I got efficient algorithm for clearing queue at

http://stackoverflow.com/questions/709146/how-do-i-clear-the-stdqueue-efficiently

My question is: Why queue doesn't support clear() function ?

When deque and vector are supporting clear() method, what is the technical difficulty in supporting it for queue ?

Or is my above usecase very rare and hence not supported ? Thank you.

解决方案

According to http://www.cplusplus.com/reference/stl/queue/,

queues are implemented as containers adaptors, which are classes that use an encapsulated object of a specific container class as its underlying container, providing a specific set of member functions to access it elements.

which means that the queue uses an already existing container, and is just really is an interface to this container as a FIFO queue.

This means queues are not meant to be cleared. If you need to clear a queue, this means you actually need to use an object that is not a queue, and therefore you should instead use the actual underlying container type, being a deque by default.

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