fpclassify(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

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

NAME         top

       fpclassify, isfinite, isnormal, isnan, isinf - floating-point
       classification macros

SYNOPSIS         top

       #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 <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

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

DESCRIPTION         top

       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         top

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

       ┌──────────────────────────────────────┬───────────────┬─────────┐
       │Interface                             Attribute     Value   │
       ├──────────────────────────────────────┼───────────────┼─────────┤
       │fpclassify(), isfinite(), isnormal(), │ Thread safety │ MT-Safe │
       │isnan(), isinf()                      │               │         │
       └──────────────────────────────────────┴───────────────┴─────────┘

CONFORMING TO         top

       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         top

       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         top

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

COLOPHON         top

       This page is part of release 5.13 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
       https://www.kernel.org/doc/man-pages/.

                               2021-03-22                  FPCLASSIFY(3)

Pages that refer to this page: finite(3)INFINITY(3)isgreater(3)nan(3)math_error(7)