std::is_compound

< cpp‎ | types

Defined in header `<type_traits>`
template< class T > struct is_compound;		(since C++11)

std::is_compound is an 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.

The behavior of a program that adds specializations for std::is_compound or std::is_compound_v (since C++17) is undefined.

Template parameters

a type to check

Helper variable template

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

Inherited from std::integral_constant

Member constants

value

[static]

true if T is a compound 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

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

Possible implementation

template<class T>
struct is_compound : std::integral_constant<bool, !std::is_fundamental<T>::value> {};

Example

#include <type_traits>
 
static_assert(not std::is_compound_v<int>);
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['a']>);
 
class C {};
static_assert(std::is_compound_v<C>);
 
union U {};
static_assert(std::is_compound_v<U>);
 
enum struct E { e };
static_assert(std::is_compound_v<E>);
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() {}

is_fundamental (C++11)	checks if a type is a fundamental type (class template)
is_scalar (C++11)	checks if a type is a scalar type (class template)
is_object (C++11)	checks if a type is an object type (class template)
is_array (C++11)	checks if a type is an array type (class template)