v7 man page for fpclassify

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():
	   _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(),    | Thread safety | MT-Safe |
       |isnormal(), isnan(), isinf() |		     |	       |
       +-----------------------------+---------------+---------+
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 4.15 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/.

								    2017-09-15							     FPCLASSIFY(3)