fpclassify, isfinite, isnormal, isnan, isinf — floating-point classification macros
#include <math.h>
int
fpclassify( |
x); |
int
isfinite( |
x); |
int
isnormal( |
x); |
int
isnan( |
x); |
int
isinf( |
x); |
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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_NANx is "Not a
Number".
FP_INFINITEx is either
positive infinity or negative infinity.
FP_ZEROx is
zero.
FP_SUBNORMALx is too
small to be represented in normalized format.
FP_NORMALif 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 if x is negative
infinity.
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 |
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.
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.)
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/.
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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 |