isfinite

       cation 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 nor-
                     mal 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)


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 3.35 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://man7.org/linux/man-pages/.



                                  2010-09-20                     FPCLASSIFY(3)
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