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():
       _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
   isnan():
       _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
           || _XOPEN_SOURCE
           || /* Since glibc 2.19: */ _DEFAULT_SOURCE
           || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
   isinf():
       _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
           || /* Since glibc 2.19: */ _DEFAULT_SOURCE
           || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

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

   For   an   explanation   of   the  terms  used  in  this  section,  see
   attributes(7).

   
   Interface                     Attribute      Value   
   
   fpclassify(), isfinite(),     Thread safety  MT-Safe 
   isnormal(), isnan(), isinf()                         
   

CONFORMING TO

   POSIX.1-2001, POSIX.1-2008, C99.

   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

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                              2016-03-15                     FPCLASSIFY(3)

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