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.
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”).
CAVEATS
On VAX the isnan() function always returns
0, as the architecture doesn't support NaN.