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; or cc -std=c99 isnan(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE; or cc -std=c99 isinf(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; 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 non-zero value if (fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE) |
| isnormal(x) | returns a non-zero value if (fpclassify(x) == FP_NORMAL) |
| isnan(x) | returns a non-zero 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.
For isinf(), the standards merely say that the return value is non-zero if and only if the argument has an infinite value.
NOTES
In glibc 2.01 and earlier, isinf() returns a non-zero 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 3.23 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/.
