std::experimental:: nullopt
From cppreference.net
<
cpp
|
experimental
|
optional
C++
Experimental
| Technical Specification | ||||
| Filesystem library (filesystem TS) | ||||
| Library fundamentals (library fundamentals TS) | ||||
| Library fundamentals 2 (library fundamentals TS v2) | ||||
| Library fundamentals 3 (library fundamentals TS v3) | ||||
| Extensions for parallelism (parallelism TS) | ||||
| Extensions for parallelism 2 (parallelism TS v2) | ||||
| Extensions for concurrency (concurrency TS) | ||||
| Extensions for concurrency 2 (concurrency TS v2) | ||||
| Concepts (concepts TS) | ||||
| Ranges (ranges TS) | ||||
| Reflection (reflection TS) | ||||
| Mathematical special functions (special functions TR) | ||||
| Experimental Non-TS | ||||
| Pattern Matching | ||||
| Linear Algebra | ||||
| std::execution | ||||
| Contracts | ||||
| 2D Graphics |
std::experimental::optional
| Member functions | ||||
| Observers | ||||
| Modifiers | ||||
| Non-member functions | ||||
| Helper classes | ||||
| Helper objects | ||||
|
nullopt
|
||||
|
定义于头文件
<experimental/optional>
|
||
|
constexpr
nullopt_t nullopt
{
/*未指定*/
}
;
|
(库基础TS) | |
std::experimental::nullopt
是一个类型为
std::experimental::nullopt_t
的常量，用于表示处于未初始化状态的
optional
类型。
参见
|
(library fundamentals TS)
|
表示未初始化状态的可选类型指示符
(类) |