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

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

SYNOPSIS
       #include 

       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 featuretestmacros(7)):

       fpclassify(), isfinite(), isnormal():
           XOPENSOURCE >= 600 || ISOC99SOURCE ||
           POSIXCSOURCE >= 200112L;
           or cc -std=c99
       isnan():
           BSDSOURCE || SVIDSOURCE || XOPENSOURCE || ISOC99SOURCE ||
           POSIXCSOURCE >= 200112L;
           or cc -std=c99
       isinf():
           BSDSOURCE || SVIDSOURCE || XOPENSOURCE >= 600 ||
           ISOC99SOURCE || POSIXCSOURCE >= 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:

       FPNAN        x is "Not a Number".

       FPINFINITE   x is either positive infinity or negative infinity.

       FPZERO       x is zero.

       FPSUBNORMAL  x is too small to be represented in normalized format.

       FPNORMAL     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) != FPNAN && fpclassify(x) != FPINFINITE)

       isnormal(x)   returns a nonzero value if (fpclassify(x) == FPNORMAL)

       isnan(x)      returns a nonzero value if (fpclassify(x) == FPNAN)

       isinf(x)      returns 1 if x is positive infinity, and -1 if x is nega‐
                     tive 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
       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 3.53 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.



                                  2010-09-20                     FPCLASSIFY(3)