std::is_literal_type

< cpp‎ | types
Defined in header <type_traits>
template< class T >
struct is_literal_type;
 (since C++11)
(deprecated in C++17)
(removed in C++20)

(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 true. For any other type, value is false.

The behavior is undefined if std::remove_all_extents_t<T> is an incomplete type and not (possibly cv-qualified) void.

The behavior of a program that adds specializations for is_literal_type or is_literal_type_v (since C++17) is undefined.

Template parameters

T - a type to check

Helper variable template

template< class T >
inline constexpr bool is_literal_type_v = is_literal_type<T>::value;
 (since C++17)
(deprecated)
(removed in C++20)

Inherited from std::integral_constant

Member constants

value
[static]
 true if T is a literal 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>

Notes

Only literal types may be used as parameters to or returned from constexpr functions. Only literal classes may have constexpr member functions.

Example

#include <iostream>
#include <type_traits>
 
struct A {
    int m;
};
 
struct B {
    virtual ~B();
};
 
int main()
{
    std::cout << std::boolalpha;
    std::cout << std::is_literal_type<A>::value << '\n';
    std::cout << std::is_literal_type<B>::value << '\n';
}

Output:

true
false

References

  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."