fpclassify(3) | Library Functions Manual | fpclassify(3) |
fpclassify, isfinite, isnormal, isnan, isinf - floating-point classification macros
Math library (libm, -lm)
#include <math.h>
int fpclassify(x); int isfinite(x); int isnormal(x); int isnan(x); int isinf(x);
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 <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
isinf():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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:
The other macros provide a short answer to some standard questions.
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 |
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.
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.)
2023-02-05 | Linux man-pages 6.03 |