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(): _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 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.

CONFORMING TO
       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.

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 3.25 of the Linux man-pages project.  A description of the project, and information about
       reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



                                                           2008-08-07                                              FPCLASSIFY(3)