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std::is_callable, std::is_nothrow_callable

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Type support
Type properties
(C++11)
(C++11)
(C++11)
(C++14)
Type trait constants
Metafunctions
(C++17)
Supported operations
Relationships and property queries
(C++11)
(C++11)
(C++11)
(C++11)
is_callableis_nothrow_callable
(C++17)(C++17)
Type modifications
(C++11)(C++11)(C++11)
Type transformations
(C++11)
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(C++17)
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Defined in header <type_traits>
template <class, class R = void> struct is_callable; // not defined


template <class Fn, class... ArgTypes, class R>

struct is_callable<Fn(ArgTypes...), R>;
(1) (since C++17)
template <class, class R = void> struct is_nothrow_callable; // not defined


template <class Fn, class... ArgTypes, class R>

struct is_nothrow_callable<Fn(ArgTypes...), R>;
(2) (since C++17)
1) Determines whether Fn is callable with the arguments ArgTypes... and the result would be convertible to R. Formally, determines whether INVOKE(declval<Fn>(), declval<ArgTypes>()..., R) is well formed when treated as an unevaluated operand, where INVOKE is the operation defined in Callable.
2) Determines whether Fn is callable with the arguments ArgTypes... and the result would be convertible to R (same as (1)), and that such call is known not to throw any exceptions.

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

Contents

[edit] Helper variable templates

Defined in header <type_traits>
template <class T, class R = void>
constexpr bool is_callable_v  = std::is_callable<T, R>::value;
(1) (since C++17)
template <class T, class R = void>
constexpr bool is_nothrow_callable_v = std::is_nothrow_callable<T, R>::value;
(2) (since C++17)

Inherited from std::integral_constant

Member constants

value
[static]
true if INVOKE(declval<Fn>(), declval<ArgTypes>()..., R) 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>

[edit] Notes

Version (1) of this trait may be implemented in terms of std::is_convertible and std::result_of.

[edit] Examples

[edit] See also

(C++17)
invokes any Callable object with given arguments
(function template) [edit]
(C++11)
deduces the return type of a function call expression
(class template) [edit]
(C++11)
obtains a reference to its argument for use in unevaluated context
(function template) [edit]