# std::is_integral

From cppreference.com
< cpp‎ | types

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

`std::is_integral` is an 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.

The behavior of a program that adds specializations for `std::is_integral` or `std::is_integral_v` (since C++17) is undefined.

### Template parameters

T | - | a type to check

### Helper variable template

template< class T > inline 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

Run this code

    #include <iomanip>
    #include <iostream>
    #include <type_traits>

    class A {};

    struct B { int x:4{2}; };
    using BF = decltype(B::x); // bit-field's type

    enum E : int {};

    template <class T>
    T f(T i)
    {
        static_assert(std::is_integral<T>::value, "Integral required.");
        return i;
    }

    #define SHOW(...) \
        std::cout << std::setw(29) << #__VA_ARGS__ << " == " << __VA_ARGS__ << '\n'

    int main()
    {
        std::cout << std::boolalpha;

        SHOW(std::is_integral<A>::value);
        SHOW(std::is_integral_v<E>);
        SHOW(std::is_integral_v<float>);
        SHOW(std::is_integral_v<int*>);
        SHOW(std::is_integral_v<int>);
        SHOW(std::is_integral_v<const int>);
        SHOW(std::is_integral_v<bool>);
        SHOW(std::is_integral_v<char>);
        SHOW(std::is_integral_v<BF>);
        SHOW(f(123));
    }

Output:

       std::is_integral<A>::value == false
            std::is_integral_v<E> == false
        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
           std::is_integral_v<BF> == true
                           f(123) == 123

### See also

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)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/types/is_integral&oldid=152517"