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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
     allbox; lbw28 lb lb l l l.  Interface Attribute Value T{ fpclassify(),
     isfinite(), isnormal(), isnan(), isinf() T}   Thread safety  MT-Safe


     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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