std::is_integral

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

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, longlong, 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

a type to check

Helper variable template

template< class T >
constexpr bool is_integral_v = is_integral<T>::value;

(since C++17)

Inherited from std::integral_constant

Member constants

value

[static]

true if T is an integral 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>

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

#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() {}

integral (C++20)	specifies that a type is an integral type (concept)
is_integer [static]	identifies integer types (public static member constant of `std::numeric_limits<T>`)
is_floating_point (C++11)	checks if a type is a floating-point type (class template)
is_arithmetic (C++11)	checks if a type is an arithmetic type (class template)
is_enum (C++11)	checks if a type is an enumeration type (class template)
is_integral_type (C++26)	checks if reflected type is an integral type (function)

© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
https://en.cppreference.com/cpp/types/is_integral