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std::numeri...::quiet_NaN(3) C++ Standard Libary std::numeri...::quiet_NaN(3) NAME std::numeric_limits::quiet_NaN - std::numeric_limits::quiet_NaN Synopsis static T quiet_NaN() throw(); (until C++11) static constexpr T quiet_NaN() noexcept; (since C++11) Returns the special value "quiet not-a-number", as represented by the floating-point type T. Only meaningful if std::numeric_limits<T>::has_quiet_NaN == true. In IEEE 754, the most common binary representation of floating-point num- bers, any value with all bits of the exponent set and at least one bit of the fraction set represents a NaN. It is implementation-defined which values of the fraction rep- resent quiet or signaling NaNs, and whether the sign bit is meaningful. Return value T std::numeric_limits<T>::quiet_NaN() /* non-specialized */ T() bool false char 0 signed char 0 unsigned char 0 wchar_t 0 char8_t (C++20) 0 char16_t (C++11) 0 char32_t (C++11) 0 short 0 unsigned short 0 int 0 unsigned int 0 long 0 unsigned long 0 long long (C++11) 0 unsigned long long (C++11) 0 float implementation-defined (may be NAN) double implementation-defined long double implementation-defined Notes A NaN never compares equal to itself. Copying a NaN may not preserve its bit representation. Example Several ways to generate a NaN (the output string is compiler-spe- cific) // Run this code #include <iostream> #include <limits> #include <cmath> int main() { std::cout << std::numeric_limits<double>::quiet_NaN() << ' ' // nan << std::numeric_limits<double>::signaling_NaN() << ' ' // nan << std::acos(2) << ' ' // nan << std::tgamma(-1) << ' ' // nan << std::log(-1) << ' ' // nan << std::sqrt(-1) << ' ' // -nan << 0 / 0.0 << '\n'; // -nan std::cout << "NaN == NaN? " << std::boolalpha << ( std::numeric_limits<double>::quiet_NaN() == std::numeric_limits<double>::quiet_NaN() ) << '\n'; } Possible output: nan nan nan nan nan -nan -nan NaN == NaN? false See also has_quiet_NaN identifies floating-point types that can represent the special value [static] "quiet not-a-number" (NaN) (public static member constant) signaling_NaN returns a signaling NaN value of the given floating- point type [static] (public static member function) nan nanf nanl not-a-number (NaN) (C++11) (function) (C++11) (C++11) isnan checks if the given number is NaN (C++11) (function) http://cppreference.com 2022.07.31 std::numeri...::quiet_NaN(3)
NAME | Synopsis | Return value | Notes | Example | Possible output: | See also
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