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       fpclassify,   isfinite,   isnormal,   isnan,   isinf  -  floating-point
       classification 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
           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
           _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
                     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.


       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)


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       description of the project, and information about reporting  bugs,  can
       be found at

                                  2010-09-20                     FPCLASSIFY(3)