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Experimental library header <experimental/optional>

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Experimental library headers
Execution P2300
<experimental/execution>
Filesystem TS
<experimental/filesystem>
Parallelism TS (v1, v2)
experimental/algorithm
experimental/execution_policy
experimental/exception_list
experimental/numeric
<experimental/simd>
experimental/task_block
Library Fundamentals TS (v1, v2, v3)
experimental/algorithm
<experimental/any>
experimental/array
experimental/chrono
experimental/deque
experimental/forward_list
<experimental/functional>
experimental/future
experimental/iterator
experimental/list
experimental/map
experimental/memory
<experimental/memory_resource>
experimental/numeric
<experimental/optional>
experimental/propagate_const
experimental/random
experimental/ratio
experimental/regex
experimental/scope
experimental/set
experimental/source_location
experimental/string
<experimental/string_view>
experimental/system_error
experimental/tuple
experimental/type_traits
experimental/unordered_map
experimental/unordered_set
experimental/utility
experimental/vector

Concurrency TS
experimental/atomic
experimental/barrier
experimental/future
experimental/latch
Ranges TS
Coroutines TS
experimental/coroutine
Networking TS
experimental/buffer
experimental/executor
experimental/internet
experimental/io_context
<experimental/net>
experimental/netfwd
experimental/socket
experimental/timer
Reflection TS
<experimental/reflect>

此头文件是库基础技术规范 ( v1 , v2 ) 的组成部分。

目录

类

名称 描述
(library fundamentals TS)
可能持有或未持有对象的包装器
(类模板)
(library fundamentals TS)
指示对不包含值的 optional 进行受检访问时抛出的异常
(类)
(library fundamentals TS)
用于 optional 类型原位构造的消歧标签类型
(类)
特化 std::hash 算法
(类模板特化)
(library fundamentals TS)
表示未初始化状态的可选类型指示器
(类)

函数

比较操作
比较 optional 对象
(函数模板)
特化算法
特化 std::swap 算法
(函数)
创建 optional 对象
(函数模板)
哈希支持

概要 

namespace std {
  namespace experimental {
  inline namespace fundamentals_v1 {
    // 5.4, optional for object types
    template <class T> class optional;
    // 5.5, 原位构造
    struct in_place_t{};
    constexpr in_place_t in_place{};
    // 5.6, Disengaged state indicator
    struct nullopt_t{see below};
    constexpr nullopt_t nullopt(unspecified);
    // 5.7, Class bad_optional_access
    class bad_optional_access;
    // 5.8, 关系运算符
    template <class T>
      constexpr bool operator==(const optional<T>&, const optional<T>&);
    template <class T>
      constexpr bool operator!=(const optional<T>&, const optional<T>&);
    template <class T>
      constexpr bool operator<(const optional<T>&, const optional<T>&);
    template <class T>
      constexpr bool operator>(const optional<T>&, const optional<T>&);
    template <class T>
      constexpr bool operator<=(const optional<T>&, const optional<T>&);
    template <class T>
      constexpr bool operator>=(const optional<T>&, const optional<T>&);
    // 5.9, Comparison with nullopt
    template <class T> constexpr bool operator==(const optional<T>&, nullopt_t) noexcept;
    template <class T> constexpr bool operator==(nullopt_t, const optional<T>&) noexcept;
    template <class T> constexpr bool operator!=(const optional<T>&, nullopt_t) noexcept;
    template <class T> constexpr bool operator!=(nullopt_t, const optional<T>&) noexcept;
    template <class T> constexpr bool operator<(const optional<T>&, nullopt_t) noexcept;
    template <class T> constexpr bool operator<(nullopt_t, const optional<T>&) noexcept;
    template <class T> constexpr bool operator<=(const optional<T>&, nullopt_t) noexcept;
    template <class T> constexpr bool operator<=(nullopt_t, const optional<T>&) noexcept;
    template <class T> constexpr bool operator>(const optional<T>&, nullopt_t) noexcept;
    template <class T> constexpr bool operator>(nullopt_t, const optional<T>&) noexcept;
    template <class T> constexpr bool operator>=(const optional<T>&, nullopt_t) noexcept;
    template <class T> constexpr bool operator>=(nullopt_t, const optional<T>&) noexcept;
    // 5.10, Comparison with T
    template <class T> constexpr bool operator==(const optional<T>&, const T&);
    template <class T> constexpr bool operator==(const T&, const optional<T>&);
    template <class T> constexpr bool operator!=(const optional<T>&, const T&);
    template <class T> constexpr bool operator!=(const T&, const optional<T>&);
    template <class T> constexpr bool operator<(const optional<T>&, const T&);
    template <class T> constexpr bool operator<(const T&, const optional<T>&);
    template <class T> constexpr bool operator<=(const optional<T>&, const T&);
    template <class T> constexpr bool operator<=(const T&, const optional<T>&);
    template <class T> constexpr bool operator>(const optional<T>&, const T&);
    template <class T> constexpr bool operator>(const T&, const optional<T>&);
    template <class T> constexpr bool operator>=(const optional<T>&, const T&);
    template <class T> constexpr bool operator>=(const T&, const optional<T>&);
    // 5.11, 专用算法
    template <class T> void swap(optional<T>&, optional<T>&) noexcept(see below);
    template <class T> constexpr optional<see below> make_optional(T&&);
  } // namespace fundamentals_v1
  } // namespace experimental
  // 5.12, Hash support
  template <class T> struct hash;
  template <class T> struct hash<experimental::optional<T>>;
} // namespace std