# INFINITY - Man Page

floating-point constants

## 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 *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.

## Standards

C11.

## History

C99.

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

## Referenced By

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