INFINITY, NAN, HUGE_VAL, HUGE_VALF, HUGE_VALL — floating-point constants
#define _ISOC99_SOURCE #include <math.h> INFINITY NAN HUGE_VAL HUGE_VALF HUGE_VALL
The macro INFINITY expands
to a float constant representing
positive infinity.
The macro NAN expands to a
float constant representing a quiet
NaN (when supported). A quiet NaN is a NaN
("not-a-number") that does not raise exceptions when it is
used in arithmetic. The opposite is a signaling NaN. See IEC
60559:1989.
The macros HUGE_VAL,
HUGE_VALF, HUGE_VALL expand to constants of types
double, float and long
double, respectively, that represent a large positive
value, possibly plus infinity.
On a glibc system, the macro HUGE_VAL is always available. Availability
of the NAN macro can be tested
using #ifdef NAN, and
similarly for INFINITY,
HUGE_VALF, HUGE_VALL. They will be defined by
<math.h> if
_ISOC99_SOURCE or _GNU_SOURCE is defined, or __STDC_VERSION__ is defined and has a value
not less than 199901L.