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 || _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 expres‐
       sion 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 3.74 of the Linux man-pages project.  A  description  of  the
       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at http://www.kernel.org/doc/man-pages/.



                                            2013-08-06                              FPCLASSIFY(3)