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Linux 2.6 - man page for huge_vall (linux section 3)

INFINITY(3)						     Linux Programmer's Manual						       INFINITY(3)

NAME
INFINITY, NAN, HUGE_VAL, HUGE_VALF, HUGE_VALL - floating-point constants
SYNOPSIS
#define _ISOC99_SOURCE #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 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.
CONFORMING TO
C99.
AVAILABILITY
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.
SEE ALSO
fpclassify(3), feature_test_macros(7), math_error(7)
COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. 2007-07-26 INFINITY(3)