std::numeric_limits<T>::is_iec559

 

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static const bool is_iec559;		(until C++11)
static constexpr bool is_iec559;			(since C++11)

The value of std::numeric_limits<T>::is_iec559 is true for all floating-point types T which fulfill the requirements of IEC 559 (IEEE 754) standard. If std::numeric_limits<T>::is_iec559 is true, then std::numeric_limits<T>::has_infinity, std::numeric_limits<T>::has_quiet_NaN, and std::numeric_limits<T>::has_signaling_NaN are also true.

Standard specializations

T	value of std::numeric_limits<T>::is_iec559
/* 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>

template <typename... Types>
constexpr bool iec559 = (std::numeric_limits<Types>::is_iec559 or ...);

static_assert(not iec559<
    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
>);

template <typename T>
constexpr bool validate = []
{
    if constexpr (std::numeric_limits<T>::is_iec559)
        return
            std::numeric_limits<T>::has_infinity and
            std::numeric_limits<T>::has_quiet_NaN and
            std::numeric_limits<T>::has_signaling_NaN;
    return true;
}();
static_assert(validate<float> and validate<double> and validate<long double>);

int main()
{
    std::println("{}", std::numeric_limits<float>::is_iec559);
}

Possible output:

true

See also

has_infinity [static]	identifies floating-point types that can represent the special value “positive infinity” (public static member constant)
has_quiet_NaN [static]	identifies floating-point types that can represent the special value “quiet not-a-number” (NaN) (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)