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std::is_implicit_lifetime

From cppreference.com
< cpp‎ | types
 
 
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is_implicit_lifetime
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Defined in header <type_traits>
template< class T >
struct is_implicit_lifetime;
(since C++23)

std::is_implicit_lifetime is a UnaryTypeTrait.

If T is an implicit-lifetime type, provides the member constant value equal to true. For any other type, value is false.

The behavior is undefined if T is an incomplete type other than an array type or (possibly cv-qualified) void.

If the program adds specializations for std::is_implicit_lifetime or std::is_implicit_lifetime_v, the behavior is undefined.

Contents

[edit] Template parameters

T - a type to check

[edit] Helper variable template

template< class T >
constexpr bool is_implicit_lifetime_v = is_implicit_lifetime<T>::value;
(since C++23)

Inherited from std::integral_constant

Member constants

value
[static]
true if T is an implicit-lifetime type, 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

Feature-test macro Value Std Feature
__cpp_lib_is_implicit_lifetime 202302L (C++23) std::is_implicit_lifetime

[edit] Example

// The following types are collectively called implicit-lifetime types:
// * scalar types:
//     * arithmetic types
//     * enumeration types
//     * pointer types
//     * pointer-to-member types
//     * std::nullptr_t
// * implicit-lifetime class types
//     * is an aggregate whose destructor is not user-provided
//     * has at least one trivial eligible constructor and a trivial,
//       non-deleted destructor
// * array types
// * cv-qualified versions of these types.
#include <type_traits>
 
static_assert(std::is_implicit_lifetime_v<int>); // arithmetic type is a scalar type
static_assert(std::is_implicit_lifetime_v<const int>); // cv-qualified a scalar type
 
enum E { e };
static_assert(std::is_implicit_lifetime_v<E>); // enumeration type is a scalar type
static_assert(std::is_implicit_lifetime_v<int*>); // pointer type is a scalar type
static_assert(std::is_implicit_lifetime_v<std::nullptr_t>); // scalar type
 
struct S { int x, y; };
// S is an implicit-lifetime class: an aggregate without user-provided destructor
static_assert(std::is_implicit_lifetime_v<S>);
 
static_assert(std::is_implicit_lifetime_v<int S::*>); // pointer-to-member
 
struct X { ~X() = delete; };
// X is not implicit-lifetime class due to deleted destructor
static_assert(!std::is_implicit_lifetime_v<X>);
 
static_assert(std::is_implicit_lifetime_v<int[8]>); // array type
static_assert(std::is_implicit_lifetime_v<volatile int[8]>); // cv-qualified array type
 
int main() {}

[edit] See also

(C++11)
checks if a type is a scalar type
(class template) [edit]
(C++11)
checks if a type is an array type
(class template) [edit]
checks if a type is an aggregate type
(class template) [edit]
implicitly creates objects in given storage with the object representation reused
(function template) [edit]