Checks given double-precision floating-point value for not a number (NaN).
int _isnan( double x );
| Routine | Required Header | Compatibility |
| _isnan | <float.h> | Win 95, Win NT |
For additional compatibility information, see Compatibility in the Introduction.
Libraries
| LIBC.LIB | Single thread static library, retail version |
| LIBCMT.LIB | Multithread static library, retail version |
| MSVCRT.LIB | Import library for MSVCRT.DLL, retail version |
Return Value
_isnan returns a nonzero value (TRUE) if the argument x is a NaN; otherwise it returns 0 (FALSE).
Parameter
x
Double-precision floating-point value
Remarks
The _isnan function tests a given double-precision floating-point value x, returning a nonzero value if x is a NaN. A NaN is generated when the result of a floating-point operation cannot be represented in Institute of Electrical and Electronics Engineers (IEEE) format. For information about how a NaN is represented for output, see printf.