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 || _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99
       isnan():
           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99
       isinf():
           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
           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.

ATTRIBUTES

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

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 3.54 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/.

                                                   2013-08-06                                      FPCLASSIFY(3)