std::is_invocable_r

STD：：是[医]可调用，std：：is[医]可调用[医]R，STD：：[医]无抛[医]可调用，std：：is[医]无抛[医]可调用[医]r

Defined in header
template <class Fn, class... ArgTypes> struct is_invocable;	(1)	(since C++17)
template <class R, class Fn, class... ArgTypes> struct is_invocable_r;	(2)	(since C++17)
template <class Fn, class... ArgTypes> struct is_nothrow_invocable;	(3)	(since C++17)
template <class R, class Fn, class... ArgTypes> struct is_nothrow_invocable_r;	(4)	(since C++17)

1%29决定Fn可以用参数调用ArgTypes....正式决定是否INVOKE(declval<Fn>(), declval<ArgTypes>()...)如果将其视为未计算的操作数，则为格式良好的操作数，其中INVOKE中定义的操作吗？Callable...

2%29决定Fn可以用参数调用ArgTypes...产生可转换为R.正式决定是否INVOKE<R>(declval<Fn>(), declval<ArgTypes>()...)如果将其视为未计算的操作数，则为格式良好的操作数，其中INVOKE中定义的操作吗？Callable

3%29决定Fn是可以用参数调用的。ArgTypes...%28与%281%29%29相同，并且已知此调用不会引发任何异常。

4%29决定Fn可以用参数调用ArgTypes...产生可转换为R%28与%282%29%29相同，并且已知此调用不会引发任何异常。

Fn, R和参数包中的所有类型。ArgTypes每一个都是一个完整的类型，%28可能是cv-合格%29void，或者一系列未知的界限。否则，行为就没有定义。

Defined in header
template <class Fn, class... ArgTypes> inline constexpr bool is_invocable_v = std::is_invocable<Fn, ArgTypes...>::value;	(1)	(since C++17)
template <class R, class Fn, class... ArgTypes> inline constexpr bool is_invocable_r_v = std::is_invocable_r<R, Fn, ArgTypes...>::value;	(2)	(since C++17)
template <class Fn, class... ArgTypes> inline constexpr bool is_nothrow_invocable_v = std::is_nothrow_invocable<Fn, ArgTypes...>::value;	(3)	(since C++17)
template <class R, class Fn, class... ArgTypes> inline constexpr bool is_nothrow_invocable_r_v = std::is_nothrow_invocable_r<R, Fn, ArgTypes...>::value;	(4)	(since C++17)

value static	true if INVOKE(declval(), declval()...) is well formed when treated as an unevaluated operand , false otherwise (public static member constant)

operator bool	converts the object to bool, returns value (public member function)
operator() (C++14)	returns value (public member function)

Type	Definition
value_type	bool
type	std::integral_constant<bool, value>

invoke (C++17)	invokes any Callable object with given arguments (function template)
result_ofinvoke_result (C++11)(deprecated in C++17)(C++17)	deduces the result type of invoking a callable object with a set of arguments (class template)
declval (C++11)	obtains a reference to its argument for use in unevaluated context (function template)

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