2)非成员any_cast函数提供对所含对象的类型安全访问。 鼓励实现避免小对象的动态分配,但这种优化仅可以应用于std::is_nothrow_move_constructible对其返回true的类型。 通常,实现会对std::is_nothrow_move_constructible为true的类型进行小对象优化(避免动态分配)。
std::any::any C++ Utilities library std::any constexprany()noexcept; (1)(since C++17) any(constany&other); (2)(since C++17) any(any&&other)noexcept; (3)(since C++17) template<classValueType> any(ValueType&&value); (4)(since C++17) ...
4,5)The program is ill-formed ifstd::is_void_v<T>istrue. Parameters operand-targetanyobject Return value 1,2)Returnsstatic_cast<T>(*std::any_cast<U>(&operand)). 3)Returnsstatic_cast<T>(std::move(*std::any_cast<U>(&operand))). ...
类std::bad_any_castnamespace std { class bad_any_cast : public bad_cast { public: // 特殊成员函数的规范见 [exception] const char* what() const noexcept override; }; }类std::anynamespace std { class any { public: // 构造与析构 constexpr any() noexcept; any(const any& other);...
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All member functions ofstd::vectorareconstexpr: it is possible to create and usestd::vectorobjects in the evaluation of a constant expression. However,std::vectorobjects generally cannot beconstexpr, because any dynamically allocated storage must be released in the same evaluation of constant expres...
Address of an lvalue may be taken: &++i[1] and &std::endl are valid expressions. (重点来了,左值是可以取地址的,这也是区分左值和右值的唯一正确的标志) A modifiable lvalue may be used as the left-hand operand of the built-in assignment and + compound assignment operators. ...
optional(C++17)−any(C++17) variant(C++17)−format(C++20) 文字列ライブラリ basic_string basic_string_view(C++17) ヌル終端文字列: バイト−マルチバイト−ワイド コンテナライブラリ array(C++11)−vector map−unordered_map(C++11) ...
Create account Planned Maintenance The site will be in a temporary read-only mode in the next few weeks to facilitate some long-overdue software updates. We apologize for any inconvenience this may cause! C++ reference C++11,C++14,C++17,C++20,C++23,C++26│Compiler supportC++11,C++14,C++17,...
std::any:: std::any::type From cppreference.com conststd::type_info&type()constnoexcept; (since C++17) Queries the contained type. Parameters (none) Return value Thetypeidof the contained value if instance is non-empty, otherwisetypeid(void)....