isnan(3m) [sunos man page]

isnan(3M)						  Mathematical Library Functions						 isnan(3M)

NAME

       isnan - test for NaN

SYNOPSIS

   C90 Mode
       cc [ flag... ] file... -lm [ library... ]
       #include <math.h>

       int isnan(double x);

   C99 Mode
       #include <math.h>

       int isnan(real--floating x);

DESCRIPTION

       In C90 mode, the isnan() function tests whether x is NaN.

       In  C99	mode,  the  isnan()  macro determines whether its argument value is NaN. First, an argument represented in a format wider than its
       semantic type is converted to its semantic type. The determination is then based on the type of the argument.

RETURN VALUES

       Both the isnan() function and macro return non-zero if and only if x is NaN.

ERRORS

       No errors are defined.

WARNINGS

       In C99 mode, the practice of explicitly supplying a prototype for isnan() after the line

       #include <math.h>

       is obsolete and will no longer work.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       fpclassify(3M), isfinite(3M), isinf(3M), isnormal(3M), math.h(3HEAD), signbit(3M), attributes(5), standards(5)

SunOS 5.10							    1 Dec 2003								 isnan(3M)

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)