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

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

std::is_compound is a UnaryTypeTrait.

If T is a compound type (that is, array, function, object pointer, function pointer, member object pointer, member function pointer, reference, class, union, or enumeration, including any cv-qualified variants), provides the member constant value equal true. For any other type, value is false.

If the program adds specializations for std::is_compound or std::is_compound_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 Possible implementation
  • 3.6 Example
  • 3.7 See also

[edit] Template parameters

[edit] Helper variable template

| template< class T > constexpr bool is_compound_v = is_compound<T>::value; | | (since C++17) | | ------------------------------------------------------------------------------- | | ------------- |

Inherited from std::integral_constant

Member constants

| | true if T is a compound 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

Compound types are the types that are constructed from fundamental types. Any C++ type is either fundamental or compound.

[edit] Possible implementation

[edit] Example

#include #include   static_assert(not std::is_compound_v); static_assert(std::is_compound_v<int*>); static_assert(std::is_compound_v<int&>);   void f(); static_assert(std::is_compound_v<decltype(f)>); static_assert(std::is_compound_v<decltype(&f)>);   static_assert(std::is_compound_v<char[100]>);   class C {}; static_assert(std::is_compound_v);   union U {}; static_assert(std::is_compound_v);   enum struct E { e }; static_assert(std::is_compound_v); static_assert(std::is_compound_v<decltype(E::e)>);   struct S { int i : 8; int j; void foo(); }; static_assert(not std::is_compound_v<decltype(S::i)>); static_assert(not std::is_compound_v<decltype(S::j)>); static_assert(std::is_compound_v<decltype(&S::j)>); static_assert(std::is_compound_v<decltype(&S::foo)>);   int main() { std::cout << "All checks have passed\n"; }

[edit] See also