FPCLASSIFY
Section: Linux Programmer's Manual (3)
Updated: 2010-09-20
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);
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
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.
CONFORMING TO
C99, POSIX.1.
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 3.27 of the Linux
man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- CONFORMING TO
-
- NOTES
-
- SEE ALSO
-
- COLOPHON
-
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Time: 07:35:13 GMT, March 26, 2013