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FPCLASSIFY(3)		   Linux Programmer's Manual		 FPCLASSIFY(3)

       fpclassify, isfinite, isnormal, isnan, isinf - floating-point classifi‐
       cation macros

       #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 ||
	   _POSIX_C_SOURCE >= 200112L;
	   or cc -std=c99
	   _POSIX_C_SOURCE >= 200112L;
	   or cc -std=c99
	   _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
	   or cc -std=c99

       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 nor‐
		     mal 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 nega‐
		     tive infinity.

   Multithreading (see pthreads(7))
       The fpclassify(), isfinite(), isnormal(), isnan(), and  isinf()	macros
       are thread-safe.

       C99, POSIX.1.

       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.)

       finite(3), INFINITY(3), isgreater(3), signbit(3)

       This page is part of release 3.54 of the Linux  man-pages  project.   A
       description  of	the project, and information about reporting bugs, can
       be found at

				  2013-08-06			 FPCLASSIFY(3)

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