NAN (3)

Leading comments

Copyright 2004 Andries Brouwer <aeb@cwi.nl>.

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(The comments found at the beginning of the groff file "man3/NAN.3".)

NAME

INFINITY, NAN, HUGE_VAL, HUGE_VALF, HUGE_VALL - floating-point constants

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.

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), math_error(7)

COLOPHON

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