_isnan
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.