std::numeric_limits::is_integer(3)

NAME
std::numeric_limits::is_integer - std::numeric_limits::is_integer

Synopsis
   static const bool is_integer; (until C++11)
   static constexpr bool is_integer; (since C++11)
   The value of std::numeric_limits<T>::is_integer is true for all integer arithmetic
   types T and false otherwise. This constant is meaningful for all specializations.

Standard specializations
   T value of std::numeric_limits<T>::is_integer
   /* non-specialized */ false
   bool true
   char true
   signed char true
   unsigned char true
   wchar_t true
   char8_t (C++20) true
   char16_t (C++11) true
   char32_t (C++11) true
   short true
   unsigned short true
   int true
   unsigned int true
   long true
   unsigned long true
   long long (C++11) true
   unsigned long long (C++11) true
   float false
   double false
   long double false

Example
// Run this code
 #include <cstddef>
 #include <cstdint>
 #include <numeric>
 int main()
 {
     static_assert(
             std::numeric_limits<bool>::is_integer
         && std::numeric_limits<std::size_t>::is_integer
         && std::numeric_limits<std::int32_t>::is_integer
         && std::numeric_limits<std::int64_t>::is_integer
         && std::numeric_limits<decltype(42)>::is_integer
         && !std::numeric_limits<float>::is_integer
         && !std::numeric_limits<double>::is_integer
         && !std::numeric_limits<long double>::is_integer
         && !std::numeric_limits<decltype([](){})>::is_integer // P0315R4
     );
 }

See also
   is_integral checks if a type is an integral type
   (C++11) (class template)
   is_signed identifies signed types
   [static] (public static member constant)
   is_exact identifies exact types
   [static] (public static member constant)
   is_bounded identifies types that represent a finite set of values
   [static] (public static member constant)