std::numeric_limits<T>:: is_specialized

From cppreference.com
C++
Utilities library
General utilities
Relational operators (deprecated in C++20)
Type support
std::numeric_limits
Static constants
numeric_limits::is_specialized
(C++11)
Static member functions
(C++11)
Helper types
static const bool is_specialized ;
(until C++11)
static constexpr bool is_specialized ;
(since C++11)

The value of std:: numeric_limits < T > :: is_specialized is true for all T for which there exists a specialization of std::numeric_limits .

Standard specializations

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

Example

Run this code 
#include <iostream>
#include <limits>
#include <type_traits>
 
int main()
{
    enum E{};
 
    std::cout << std::boolalpha
              << std::numeric_limits<bool>::is_specialized << '\n'
              << std::numeric_limits<long long>::is_specialized << '\n'
              << std::numeric_limits<std::true_type>::is_specialized << '\n'
              << std::numeric_limits<E>::is_specialized << '\n';
}

Possible output: 

true
true
false
false

See also

[static]
identifies integer types
(public static member constant)
[static]
identifies the IEC 559/IEEE 754 floating-point types
(public static member constant)
[static]
identifies exact types
(public static member constant)
[static]
identifies types that represent a finite set of values
(public static member constant)
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