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 );
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
_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 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
- 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.
CONFORMING TO
C99, POSIX.1.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 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.2010-09-20 |