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

       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; or cc -std=c99
       isnan(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE; or cc -std=c99
       isinf(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; 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 non-zero value if
                     (fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE)

       isnormal(x)   returns a non-zero value if (fpclassify(x) == FP_NORMAL)

       isnan(x)      returns a non-zero 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 non-zero if and only if the argument has an
       infinite value.

       In glibc 2.01 and earlier, isinf() returns a non-zero 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 3.22 of the Linux man-pages project.  A description of the project, and informa-
       tion about reporting bugs, can be found at

                                  2008-08-07                     FPCLASSIFY(3)