NAME¶

std::is_integral - std::is_integral

Synopsis¶

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

std::is_integral is a UnaryTypeTrait.

Checks whether T is an integral type. Provides the member constant value which is
equal to true, if T is the type bool, char
, char8_t
(since C++20), char16_t, char32_t, wchar_t, short, int, long, long long, or any
implementation-defined extended integer types, including any signed, unsigned, and
cv-qualified variants. Otherwise, value is equal to false.

If the program adds specializations for std::is_integral or std::is_integral_v, the
behavior is undefined.

Template parameters¶

T - a type to check

Helper variable template

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

Inherited from std::integral_constant

Member constants¶

value true if T is an integral type, false otherwise
[static] (public static member constant)

Member functions¶

operator bool converts the object to bool, returns value
(public member function)
operator() returns value
(C++14) (public member function)

Member types¶

Type Definition
value_type bool
type std::integral_constant<bool, value>

Possible implementation¶

// Note: this implementation uses C++20 facilities
template<class T>
struct is_integral : std::bool_constant<
requires (T t, T* p, void (*f)(T)) // T* parameter excludes reference types
{
reinterpret_cast<T>(t); // Exclude class types
f(0); // Exclude enumeration types
p + t; // Exclude everything not yet excluded but integral types
}> {};

Example¶

// Run this code

#include <type_traits>

static_assert
(
std::is_integral_v<float> == false &&
std::is_integral_v<int*> == false &&
std::is_integral_v<int> == true &&
std::is_integral_v<const int> == true &&
std::is_integral_v<bool> == true &&
std::is_integral_v<char> == true
);

class A {};
static_assert(std::is_integral_v<A> == false);

struct B { int x:4; };
static_assert(std::is_integral_v<B> == false);
using BF = decltype(B::x); // bit-field's type
static_assert(std::is_integral_v<BF> == true);

enum E : int {};
static_assert(std::is_integral_v<E> == false);

template <class T>
constexpr T same(T i)
{
static_assert(std::is_integral<T>::value, "Integral required.");
return i;
}
static_assert(same('"') == 042);

int main() {}

See also¶

integral specifies that a type is an integral type
(C++20) (concept)
is_integer identifies integer types
[static] (public static member constant of std::numeric_limits<T>)
is_floating_point checks if a type is a floating-point type
(C++11) (class template)
is_arithmetic checks if a type is an arithmetic type
(C++11) (class template)
is_enum checks if a type is an enumeration type
(C++11) (class template)