Section (3) fpclassify
Name
fpclassify, isfinite, isnormal, isnan, isinf — floating-point classification macros
Synopsis
#include <math.h>
int
fpclassify( |
x) ; |
int
isfinite( |
x) ; |
int
isnormal( |
x) ; |
int
isnan( |
x) ; |
int
isinf( |
x) ; |
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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 normal 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)
isnan
(x
)-
returns a nonzero value if (fpclassify(x) == FP_NAN)
isinf
(x
)-
returns 1 if
x
is positive infinity, and −1 ifx
is negative infinity.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
Interface | Attribute | Value |
fpclassify (), isfinite (), isnormal (), isnan (), isinf () |
Thread safety | MT-Safe |
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.)
COLOPHON
This page is part of release 4.16 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
https://www.kernel.org/doc/man−pages/.
Copyright 2002 Walter Harms (walter.harmsinformatik.uni-oldenburg.de) %%%LICENSE_START(GPL_NOVERSION_ONELINE) Distributed under GPL %%%LICENSE_END This was done with the help of the glibc manual. 2004-10-31, aeb, corrected |