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      std::is_literal_type

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      is_literal_type
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      Defined in header <type_traits>
      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

      [edit]Template parameters

      T - a type to check

      [edit]Helper variable template

      template<class T >
      constexprbool is_literal_type_v = is_literal_type<T>::value;
      		(since C++17)
      (deprecated)
      (removed in C++20)
      [edit]

      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_typebool
      typestd::integral_constant<bool, value>

      [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

      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(){}

      [edit]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 2015C++11 T could be an array of incomplete
      class type with unknown bound       		the behavior is
      undefined in this case

      [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."
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