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std::is_compound - cppreference.com

From cppreference.com

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.

Template parameters

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

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>
#include <iostream>

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[100]>);

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()
{
    std::cout << "All checks have passed\n";
}

See also