| isnormal(3) - phpMan
FPCLASSIFY(3) Linux Programmer's Manual FPCLASSIFY(3)
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 expresâ
sion 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
Multithreading (see pthreads(7))
The fpclassify(), isfinite(), isnormal(), isnan(), and isinf() macros are thread-safe.
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 3.74 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 http://www.kernel.org/doc/man-pages/.
2013-08-06 FPCLASSIFY(3)
|