FPCLASSIFY(3) Linux Programmers Manual FPCLASSIFY(3)
NAME
fpclassify, isfinite, isnormal, isnan, isinf  floatingpoint classifi
cation macros
SYNOPSIS
#include
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; or cc std=c99
isnan(): _BSD_SOURCE  _SVID_SOURCE  _XOPEN_SOURCE 
_ISOC99_SOURCE; or cc std=c99
isinf(): _BSD_SOURCE  _SVID_SOURCE  _XOPEN_SOURCE >= 600 
_ISOC99_SOURCE; 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 floatingpoint expression as argument. The result
is one of the following values:
FP_NAN x is "Not a Number".
FP_INFINITE
x is either plus or minus 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 normal
floatingpoint 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)
isnan(x)
returns a nonzero value if (fpclassify(x) == FP_NAN)
isinf(x)
returns 1 if x is positive infinity, and 1 if x is negative
infinity.
CONFORMING TO
C99.
NOTES
In glibc 2.01 and earlier, isinf() returns a nonzero value (actually:
1) if x is an infinity (positive or negative). (This is all that C99
requires.)
SEE ALSO
finite(3), INFINITY(3), isgreater(3)
COLOPHON
This page is part of release 3.05 of the Linux manpages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/manpages/.
20070726 FPCLASSIFY(3)
