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.
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.