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)