NAME
isnan() — floating-point test for NaN
SYNOPSIS
#include <math.h>
int isnan(
floating-type
x);
DESCRIPTION
The
isnan()
macro determines whether its argument value is a NaN. The macro can
be used with either
double
or
float
arguments.
The ISO/ANSI C committee has approved the
isnan()
macro for inclusion in the forthcoming C9X draft standard. The
isnan()
macro implements the
isnan()
function recommended by the IEEE-754 standard for
floating-point arithmetic.
To use this macro, compile either with the default
-Ae
option or with the
-Aa
and
-D_HPUX_SOURCE
options. Make sure your program includes
<math.h>.
Link in the math library by specifying
-lm
on the compiler or linker command line.
The
isnan()
macro replaces the
isnan()
and
isnanf()
functions, which are obsolete and are no longer supported.
RETURN VALUE
The
isnan()
macro returns a nonzero value if and only if its argument has a NaN value.
ERRORS
No errors are defined.
EXAMPLE
Take certain actions if
x
is not a NaN:
#include <math.h>
/*...*/
double x;
/*...*/
if (!isnan(x))
/*...*/
STANDARDS CONFORMANCE
isnan(): SVID3, XPG4.2
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