std::array::empty

constexpr bool empty() noexcept;

测试array是否为空。

Returns a bool value indicating whether the array container is empty, i.e. whether its size is 0.

返回一个bool值标记array大小是否为0，即size是否为0.

This function does not modify the content of the array in any way. To clear the content of an array object, use array::fill.

该方法不会以任何方式修改array的内容，如果要清空内容，可以使用fill.

Parameters

none

Return Value

true if the array size is 0, false otherwise.

如果array的size为0,返回true,否则返回false

This is a constexpr.

Example

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// array::empty
#include <iostream>
#include <array>

int main ()
{
  std::array<int,0> first;
  std::array<int,5> second;
  std::cout << "first " << (first.empty() ? "is empty" : "is not empty") << '\n';
  std::cout << "second " << (second.empty() ? "is empty" : "is not empty") << '\n';
  return 0;
}

Output:

first is empty
second is not empty

Complexity

Constant.

Iterator validity

No changes.

Data races

No contained elements are accessed: concurrently accessing or modifying them is safe.

没有容器元素被访问，同时访问以及修改他们都是安全的。

Exception safety

No-throw guarantee: this member function never throws exceptions.

该成员方法不会抛出异常。