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FPCLASSIFY
Linux Programmer's Manual (3)
20130806
NAME
fpclassify, isfinite, isnormal, isnan, isinf  floatingpoint
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 floatingpoint 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 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.
ATTRIBUTES
Multithreading (see pthreads(7))
The
fpclassify(),
isfinite(),
isnormal(),
isnan(),
and
isinf()
macros are threadsafe.
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
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project.
A description of the project,
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Index
 NAME

 SYNOPSIS

 DESCRIPTION

 ATTRIBUTES

 Multithreading (see pthreads(7))

 CONFORMING TO

 NOTES

 SEE ALSO

 COLOPHON

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