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FPCLASSIFY(3) | Linux Programmer's Manual | FPCLASSIFY(3) |
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():
_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 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¶
This page is part of release 4.10 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 https://www.kernel.org/doc/man-pages/.2016-03-15 |