NAME
isnan
- test for not-a-number
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
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)
STANDARDS
The
isnan(
)
macro conforms to
ISO/IEC 9899:1999 (``ISO C99'') .