**isnan**

SYNOPSIS
#include <math.h>
int fpclassify(x);
int isfinite(x);
int isnormal(x);
int isnan(x);
int isinf(x);
Link with -lm.
Feature Test Macro Requirements for glibc (see **feature_test_macros(7)**):
fpclassify(), isfinite(), isnormal():
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99
isnan():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99
isinf():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99
DESCRIPTION
Floating point numbers can have special values, such as infinite or
NaN. With the macro fpclassify(x) you can find out what type x is.
The macro takes any floating-point expression as argument. The result
is one of the following values:
FP_NAN x is "Not a Number".
FP_INFINITE x is either positive infinity or negative infinity.
FP_ZERO x is zero.
FP_SUBNORMAL x is too small to be represented in normalized format.
FP_NORMAL if nothing of the above is correct then it must be a nor-
mal floating-point number.
The other macros provide a short answer to some standard questions.
isfinite(x) returns a nonzero value if
(fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE)
isnormal(x) returns a nonzero value if (fpclassify(x) == FP_NORMAL)
|fpclassify(), isfinite(), | Thread safety | MT-Safe |
|isnormal(), isnan(), isinf() | | |
+-----------------------------+---------------+---------+
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, C99.
For isinf(), the standards merely say that the return value is nonzero
if and only if the argument has an infinite value.
NOTES
In glibc 2.01 and earlier, isinf() returns a nonzero value (actually:
1) if x is positive infinity or negative infinity. (This is all that
C99 requires.)
SEE ALSO
**finite(3)**, **INFINITY(3)**, **isgreater(3)**, **signbit(3)**
COLOPHON
This page is part of release 4.04 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
http://www.kernel.org/doc/man-pages/.
2015-08-08 **FPCLASSIFY(3)**

###### Man Pages Copyright Respective Owners. Site Copyright (C) 1994 - 2019
Hurricane Electric.
All Rights Reserved.