INFINITY(3) Linux Programmers Manual INFINITY(3)
INFINITY, NAN, HUGE_VAL, HUGE_VALF, HUGE_VALL - floating-point con
The macro INFINITY expands to a float constant representing positive
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 plus infinity.
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 if
_ISOC99_SOURCE or _GNU_SOURCE is defined, or __STDC_VERSION__ is
defined and has a value not less than 199901L.
fpclassify(3), feature_test_macros(7), math_error(7)
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