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FPCLASSIFY(3) Linux Programmer's Manual FPCLASSIFY(3)


     fpclassify, isfinite, isnormal, isnan, isinf - floating-point classifi-
     cation macros


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


     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)
     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 nega-
                   tive infinity.


     For  an  explanation  of  the  terms  used   in   this   section,   see
     |Interface                    | Attribute     | Value   |
     |fpclassify(), isfinite(),    | Thread safety | MT-Safe |
     |isnormal(), isnan(), isinf() |               |         |


     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.


     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.)


     finite(3), INFINITY(3), isgreater(3), signbit(3)


     This page is part of release 4.16 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
                                2017-09-15                     FPCLASSIFY(3)
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