Standard Template Library (STL) - std::queue::pop

Standard Template Library (STL) - std::queue::pop

public member function - 公開成員函數

1. std::queue::pop

void pop();

removes the first element - 刪除隊列的第一個元素。

Remove next element
刪除 queue 中前端的元素。

Removes the next element in the queue, effectively reducing its size by one.
刪除 queue 中前端的元素，有效地將其大小減小一個。

The element removed is the oldest element in the queue whose value can be retrieved by calling member queue::front.
刪除的元素是 queue 中插入最早的元素，可以通過調用成員 queue::front 來檢索其值。

This calls the removed element’s destructor.
這將調用已刪除元素的析構函數。

This member function effectively calls the member function pop_front of the underlying container object.
這個成員函數有效地調用底層容器對象的成員函數 pop_front。

2. Parameters

none

3. Return value

none

4. Examples

4.1 std::queue::pop

//============================================================================
// Name        : std::queue::push/pop
// Author      : Yongqiang Cheng
// Version     : Version 1.0.0
// Copyright   : Copyright (c) 2019 Yongqiang Cheng
// Description : Hello World in C++, Ansi-style
//============================================================================

#include <iostream>       // std::cin, std::cout
#include <queue>          // std::queue

int main()
{
	std::queue<int> queue_data;
	int int_data;

	std::cout << "Please enter some integers (enter 0 to end):\n";

	do
	{
		std::cin >> int_data;
		queue_data.push(int_data);
	} while (int_data);

	std::cout << "queue_data contains: ";
	while (!queue_data.empty())
	{
		std::cout << ' ' << queue_data.front();
		queue_data.pop();
	}
	std::cout << '\n';

	return 0;
}

The example uses push to add a new elements to the queue, which are then popped out in the same order.
該示例使用 push 將新元素添加到隊列中，然後以相同順序彈出。

Please enter some integers (enter 0 to end):
3
6
8
0
queue_data contains:  3 6 8 0

5. Complexity - 複雜度

Constant (calling pop_front on the underlying container).
常量 (在底層容器上調用 pop_front)。

6. Data races - 數據競爭

The container and up to all its contained elements are modified.
容器及其所有包含的元素均已修改。

7. Exception safety - 異常安全性

Provides the same level of guarantees as the operation performed on the underlying container object.
提供與對底層容器對象執行的操作相同級別的保證。

assignment [ə'saɪnmənt]：n. 任務，佈置，賦值

References

http://www.cplusplus.com/reference/queue/queue/pop/
https://en.cppreference.com/w/cpp/container/queue/pop