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.TH INFINITY 3  2017-09-15 "" "Linux Programmer's Manual"

.SH NAME

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

.SH SYNOPSIS

.nf

.BR "#define _ISOC99_SOURCE" "      /* See feature_test_macros(7) */"

.B #include <math.h>

.PP

.B INFINITY

.PP

.B NAN

.PP

.B HUGE_VAL

.B HUGE_VALF

.B HUGE_VALL

.fi

.SH DESCRIPTION

The macro

.B INFINITY

expands to a

.I float

constant representing positive infinity.

.PP

The macro

.B NAN

expands to a

.I float

constant representing a quiet NaN

(when supported).

A

.I quiet

NaN is a NaN ("not-a-number") that does not raise exceptions

when it is used in arithmetic.

The opposite is a

.I signaling

NaN.

See IEC 60559:1989.

.PP

The macros

.BR HUGE_VAL ,

.BR HUGE_VALF ,

.B HUGE_VALL

expand to constants of types

.IR double ,

.I float

and

.IR "long double" ,

respectively,

that represent a large positive value, possibly positive infinity.

.SH CONFORMING TO

C99.

.SH AVAILABILITY

On a glibc system, the macro

.B HUGE_VAL

is always available.

Availability of the

.B NAN

macro can be tested using

.BR "#ifdef NAN" ,

and similarly for

.BR INFINITY ,

.BR HUGE_VALF ,

.BR HUGE_VALL .

They will be defined by

.I <math.h>

if

.B _ISOC99_SOURCE

or

.B _GNU_SOURCE

is defined, or

.B __STDC_VERSION__

is defined

and has a value not less than 199901L.

.SH SEE ALSO

.BR fpclassify (3),

.BR math_error (7)

.SH COLOPHON

This page is part of release 4.15 of the Linux

.I man-pages

project.

A description of the project,

information about reporting bugs,

and the latest version of this page,

can be found at

\%https://www.kernel.org/doc/man\-pages/.