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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(): _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

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 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.

CONFORMING TO

       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.

NOTES

       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.)

SEE ALSO

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

COLOPHON

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                                  2008-08-07                     FPCLASSIFY(3)