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std::is_integral

From cppreference.com
< cpp‎ | types
 
 
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(C++11)
is_integral
(C++11)
Type properties
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Compile-time rational arithmetic
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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, 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 is undefined.

Contents

[edit] Template parameters

T - a type to check

[edit] 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>

[edit] 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
    }> {};

[edit] 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() {}

[edit] See also

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