INFINITY(3) Library Functions Manual INFINITY(3)
NAME
INFINITY, NAN, HUGE_VAL, HUGE_VALF, HUGE_VALL - floating-point con-
stants
LIBRARY
Math library (libm)
SYNOPSIS
#define _ISOC99_SOURCE /* See feature_test_macros(7) */
#include <math.h>
INFINITY
NAN
HUGE_VAL
HUGE_VALF
HUGE_VALL
DESCRIPTION
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 sig-
naling 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 positive infinity.
STANDARDS
C11.
HISTORY
C99.
On a glibc system, the macro HUGE_VAL is always available. Availabil-
ity 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 de-
fined and has a value not less than 199901L.
SEE ALSO
fpclassify(3), math_error(7)
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