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std::is_literal_type(3) | C++ Standard Libary | std::is_literal_type(3) |
NAME¶
std::is_literal_type - std::is_literal_type
Synopsis¶
Defined in header <type_traits>
template< class T > (since C++11)
struct is_literal_type; (deprecated in C++17)
(removed in C++20)
std::is_literal_type is a UnaryTypeTrait.
(This type trait has been deprecated^[1] and removed^[2] as offering
negligible
value to generic code.)
If T satisfies all requirements of LiteralType, provides the member constant
value
equal to true. For any other type, value is false.
If std::remove_all_extents_t<T> is an incomplete type and not (possibly
cv-qualified) void, the behavior is undefined.
If the program adds specializations for std::is_literal_type or
std::is_literal_type_v, the behavior is undefined.
Template parameters¶
T - a type to check
Helper variable template
template< class T > (since C++17)
inline constexpr bool is_literal_type_v = (deprecated)
is_literal_type<T>::value; (removed in C++20)
Inherited from std::integral_constant
Member constants¶
value true if T is a literal type, false otherwise
[static] (public static member constant)
Member functions¶
operator bool converts the object to bool, returns value
(public member function)
operator() returns value
(C++14) (public member function)
Member types¶
Type Definition
value_type bool
type std::integral_constant<bool, value>
Notes¶
Only literal types may be used as parameters to or returned from
constexpr
functions. Only literal classes may have constexpr member functions.
Example¶
// Run this code
#include <type_traits>
struct A { int m; };
static_assert(std::is_literal_type_v<A> == true);
struct B { virtual ~B(); };
static_assert(std::is_literal_type_v<B> == false);
int main() {}
Defect reports
The following behavior-changing defect reports were applied retroactively to
previously published C++ standards.
DR Applied to Behavior as published Correct behavior
LWG 2015 C++11 T could be an array of incomplete the behavior is
class type with unknown bound undefined in this case
External links¶
1. ↑ Alisdair Meredith. "Deprecate the is_literal
Trait". Deprecating Vestigial
Library Parts in C++17. "The is_literal type trait offers negligible
value to
generic code, as what is really needed is the ability to know that a specific
construction would produce constant initialization."
2. ↑ Alisdair Meredith, Stephan T. Lavavej, Tomasz Kamiński.
"Deprecated type
traits". Reviewing Deprecated Facilities of C++17 for C++20.
"Strong
recommendation: Remove the traits that can live on as zombies. [...] Toronto
Review: Accept strong recommendation, strike from C++20."
2024.06.10 | http://cppreference.com |