NAME
isnan —
test for not-a-number
LIBRARY
library “libc”
SYNOPSIS
#include
<math.h>
int
isnan(real-floating
x);
DESCRIPTION
Theisnan()
macro determines whether its argument x is not-a-number
(“NaN”). An argument represented in a format wider than its
semantic type is converted to its semantic type first. The determination is
then based on the type of the argument.
IEEE 754
It is determined whether the value of x is a NaN.
VAX
NaNs are not supported.
RETURN VALUES
The isnan() macro returns a non-zero value
if the value of x is a NaN. Otherwise 0 is
returned.
SEE ALSO
fpclassify(3), isfinite(3), isinf(3), isinff(3), isnanf(3), isnormal(3), math(3), signbit(3)
IEEE Standard for Binary Floating-Point Arithmetic, Std 754-1985, ANSI.
STANDARDS
The isnan() macro conforms to
ISO/IEC 9899:1999
(“ISO C99”).