std::is_literal_type - cppreference.com (original) (raw)

| | | | | ---------------------------------------------- | | ------------------------------------------------------ | | template< class T > struct is_literal_type; | | (since C++11) (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.

Contents

• 1 Template parameters
• 2 Helper variable template
• 3 Inherited from std::integral_constant
  • 3.1 Member constants
  • 3.2 Member functions
  • 3.3 Member types
  • 3.4 Notes
  • 3.5 Example
  • 3.6 Defect reports
  • 3.7 External links

[edit] Template parameters

[edit] Helper variable template

| template< class T > 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

| | true if T is a literal type, false otherwise (public static member constant) | | ------------------------------------------------------------------------------- |

Member functions

| | converts the object to bool, returns value (public member function) | | ---------------------------------------------------------------------- | | | returns value (public member function) |

Member types

[edit] Notes

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

[edit] Example

#include   struct A { int m; }; static_assert(std::is_literal_type_v == true);   struct B { virtual ~B(); }; static_assert(std::is_literal_type_v == false);   int main() {}

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit] 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."