std::is_compound

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is_compound
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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

T - 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

Run this code
#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() {}

See also

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