NAME
isnan —
test for not-a-number
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <math.h>
int
isnan(
real-floating
x);
DESCRIPTION
The
isnan() 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”).