std::is_invocable, std::is_invocable_r, std::is_nothrow_invocable, std::is_nothrow_invocable_r

From cppreference.com
< cpp‎ | types
 
 
 
Type support
Basic types
Fundamental types
Fixed width integer types (C++11)
Numeric limits
C numeric limits interface
Runtime type information
Type traits
Type categories
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
Type properties
(C++11)
(C++11)
(C++11)
(C++14)
(C++11)
(C++11)(deprecated in C++17)
(C++11)
Type trait constants
Metafunctions
(C++17)
Supported operations
Relationships and property queries
(C++11)
(C++11)
(C++11)
(C++11)
is_invocableis_invocable_ris_nothrow_invocableis_nothrow_invocable_r
(C++17)(C++17)(C++17)(C++17)
Type modifications
(C++11)(C++11)(C++11)
Type transformations
(C++11)
(C++11)
(C++17)
(C++11)(deprecated in C++17)(C++17)
 
Defined in header <type_traits>
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) Determines whether Fn can be invoked with the arguments ArgTypes.... Formally, determines whether INVOKE(declval<Fn>(), declval<ArgTypes>()...) is well formed when treated as an unevaluated operand, where INVOKE is the operation defined in Callable.
2) Determines whether Fn can be invoked with the arguments ArgTypes... to yield a result that is convertible to R. Formally, determines whether INVOKE<R>(declval<Fn>(), declval<ArgTypes>()...) is well formed when treated as an unevaluated operand, where INVOKE is the operation defined in Callable
3) Determines whether Fn is callable with the arguments ArgTypes... (same as (1)), and that such call is known not to throw any exceptions.
4) Determines whether Fn can be invoked with the arguments ArgTypes... to yield a result that is convertible to R (same as (2)), and that such call is known not to throw any exceptions.

Fn, R and all types in the parameter pack ArgTypes shall each be a complete type, (possibly cv-qualified) void, or an array of unknown bound. Otherwise, the behavior is undefined.

Helper variable templates

Defined in header <type_traits>
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)

Inherited from std::integral_constant

Member constants

value
[static]
true if INVOKE<R>(declval<Fn>(), declval<ArgTypes>()...) is well formed when treated as an unevaluated operand , false otherwise
(public static member constant)

Member functions

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

Member types

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

Examples

See also

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