std::numeric_limits::signaling_NaN - cppreference.com (original) (raw)
| static T signaling_NaN() throw(); | | (until C++11) | | --------------------------------------------- | | ------------- | | static constexpr T signaling_NaN() noexcept; | | (since C++11) |
Returns the special value "signaling not-a-number", as represented by the floating-point type T. Only meaningful if std::numeric_limits<T>::has_signaling_NaN == true. In IEEE 754, the most common binary representation of floating-point numbers, 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 represent quiet or signaling NaNs, and whether the sign bit is meaningful.
[edit] Return value
| T | std::numeric_limits<T>::signaling_NaN() |
|---|---|
| /* non-specialized */ | T() |
| bool | false |
| char | 0 |
| signed char | 0 |
| unsigned char | 0 |
| wchar_t | 0 |
| char8_t (since C++20) | 0 |
| char16_t (since C++11) | 0 |
| char32_t (since C++11) | 0 |
| short | 0 |
| unsigned short | 0 |
| int | 0 |
| unsigned int | 0 |
| long | 0 |
| unsigned long | 0 |
| long long (since C++11) | 0 |
| unsigned long long (since C++11) | 0 |
| float | implementation-defined (may be FLT_SNAN) |
| double | implementation-defined (may be DBL_SNAN) |
| long double | implementation-defined (may be LDBL_SNAN) |
[edit] Notes
A NaN never compares equal to itself. Copying a NaN is not required, by IEEE-754, to preserve its bit representation (sign and payload), though most implementation do.
When a signaling NaN is used as an argument to an arithmetic expression, the appropriate floating-point exception may be raised and the NaN is "quieted", that is, the expression returns a quiet NaN.
[edit] Example
Demonstrates the use of a signaling NaN to raise a floating-point exception:
Output:
After sNaN was obtained, no exceptions are raised After sNaN was multiplied by 2, FE_INVALID is raised After the quieted NaN was multiplied by 2, no exceptions are raised The result is nan
[edit] See also
| | identifies floating-point types that can represent the special value "signaling not-a-number" (NaN) (public static member constant) [edit] | | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | returns a quiet NaN value of the given floating-point type (public static member function) [edit] | | | checks if the given number is NaN (function) [edit] |