FPCLASSIFY
Updated: 2015-08-08
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NAME
fpclassify, isfinite, isnormal, isnan, isinf - floating-point classification macrosSYNOPSIS
#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
-
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99
-
_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.
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.)SEE ALSO
finite(3), INFINITY(3), isgreater(3), signbit(3)COLOPHON
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Index
- NAME
- SYNOPSIS
- DESCRIPTION
- ATTRIBUTES
- CONFORMING TO
- NOTES
- SEE ALSO
- COLOPHON