Manpage of FPCLASSIFY

FPCLASSIFY

Section: Linux Programmer's Manual (3)
Updated: 2016-03-15
Index
 

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():

_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
isnan():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
    || _XOPEN_SOURCE
    || /* Since glibc 2.19: */ _DEFAULT_SOURCE
    || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
isinf():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
    || /* Since glibc 2.19: */ _DEFAULT_SOURCE
    || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
 

DESCRIPTION

Floating point numbers can have special values, such as infinite or NaN. With the macro fpclassify(x)you can find out what type xis. The macro takes any floating-point expression as argument. The result is one of the following values:
FP_NAN
xis "Not a Number".
FP_INFINITE
xis either positive infinity or negative infinity.
FP_ZERO
xis zero.
FP_SUBNORMAL
xis 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 xis positive infinity, and -1 if xis negative infinity.
 

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).
InterfaceAttributeValue
fpclassify(), isfinite(), isnormal(), isnan(), isinf() Thread safetyMT-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 xis positive infinity or negative infinity. (This is all that C99 requires.)  

SEE ALSO

finite(3), INFINITY(3), isgreater(3), signbit(3)


 

Index

NAME
SYNOPSIS
DESCRIPTION
ATTRIBUTES
CONFORMING TO
NOTES
SEE ALSO

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Time: 22:27:50 GMT, June 20, 2016