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std::optional::swap

可选：：交换

void swap( optional& other ) noexcept(/* see below */​(since C++17)

将内容与other...

  • 如果两者都没有*this也不other包含一个值，函数没有任何效果。

  • 如果只有一个*this和other包含值%28让%27调用此对象in另一个un%29，包含的值为un是直接初始化从std::move(*in)的包含值被销毁。in好像in->T::~T().打完这个电话后，in不包含值；un包含一个值。

  • 如果两者都是*this和other包含值，则通过调用usingstd::swap; swap(**this, *other)...T值必须满足Swappable...

参数

other-the optional object to exchange the contents with

返回值

%280%29

例外

noexcept规格：

noexcept(std::is_nothrow_move_constructible_v<T>&&

std::is_nothrow_swappable_v<T>)

在抛出异常的情况下，所包含的值的状态*this和other的例外安全保证swap类型T或T%27s移动构造函数，以调用的值为准。对两个人来说*this和other，如果对象包含一个值，则会留下一个值，而另一个则相反。

另见

std::swap(std::optional) (C++17)specializes the std::swap algorithm (function)

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