std::numeric_limits<T>::has_quiet_NaN

 

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static const bool has_quiet_NaN;		(until C++11)
static constexpr bool has_quiet_NaN;			(since C++11)

See More

The value of std::numeric_limits<T>::has_quiet_NaN is true for all types T capable of representing the special value “Quiet Not-A-Number”. This constant is meaningful for all floating-point types and is guaranteed to be true if std::numeric_limits<T>::is_iec559 == true.

Standard specializations

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

Example

Run this code

#include <limits>
#include <print>
#include <ratio>

template <typename... Types>
constexpr bool not_quiet = ((not std::numeric_limits<Types>::has_quiet_NaN) and ...);

static_assert(not_quiet<
    bool, char, signed char, unsigned char, wchar_t, char8_t, char16_t, char32_t, short,
    unsigned short, int, unsigned int, long, unsigned long, long long, unsigned long long
>);

static_assert(not std::numeric_limits<std::nano>::has_quiet_NaN);

int main()
{
    std::println("{}", std::numeric_limits<float>::has_quiet_NaN);
}

Possible output:

true

See also

quiet_NaN [static]	returns a quiet NaN value of the given floating-point type (public static member function)
has_infinity [static]	identifies floating-point types that can represent the special value “positive infinity” (public static member constant)
has_signaling_NaN [static]	identifies floating-point types that can represent the special value “signaling not-a-number” (NaN) (public static member constant)