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std::is_compound

From cppreference.com
< cpp‎ | types
 
 
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is_compound
(C++11)
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Defined in header <type_traits>
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

[edit] Template parameters

T - a type to check

[edit] 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>

[edit] Notes

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

[edit] Possible implementation

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

[edit] 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";
}

[edit] See also

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