INFINITY man page

INFINITY, NAN, HUGE_VAL, HUGE_VALF, HUGE_VALL ā€” floating-point constants


#define _ISOC99_SOURCE      /* See feature_test_macros(7) */
#include <math.h>





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 positive infinity.

Conforming to



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), math_error(7)


This page is part of release 4.13 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at

Referenced By

fpclassify(3), math_error(7).

The man pages HUGE_VAL(3), HUGE_VALF(3), HUGE_VALL(3) and NAN(3) are aliases of INFINITY(3).

2017-09-15 Linux Programmer's Manual