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



NAME
       round, roundf, roundl - round to nearest integer, away from zero

SYNOPSIS
       #include <math.h>

       double round(double x);
       float roundf(float x);
       long double roundl(long double x);

       Link with -lm.

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       round(), roundf(), roundl():
           _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99

DESCRIPTION
       These  functions  round  x  to the nearest integer, but round halfway cases away from zero
       (regardless of the current rounding direction, see fenv(3)), instead  of  to  the  nearest
       even integer like rint(3).

       For example, round(0.5) is 1.0, and round(-0.5) is -1.0.

RETURN VALUE
       These functions return the rounded integer value.

       If x is integral, +0, -0, NaN,  or infinite, x itself is returned.

ERRORS
       No errors occur.  POSIX.1-2001 documents a range error for overflows, but see NOTES.

VERSIONS
       These functions first appeared in glibc in version 2.1.

ATTRIBUTES
   Multithreading (see pthreads(7))
       The round(), roundf(), and roundl() functions are thread-safe.

CONFORMING TO
       C99, POSIX.1-2001.

NOTES
       POSIX.1-2001  contains  text  about overflow (which might set errno to ERANGE, or raise an
       FE_OVERFLOW exception).  In practice, the result cannot overflow on any  current  machine,
       so  this error-handling stuff is just nonsense.  (More precisely, overflow can happen only
       when the maximum value of the exponent is smaller than the number of mantissa  bits.   For
       the  IEEE-754  standard  32-bit and 64-bit floating-point numbers the maximum value of the
       exponent is 128 (respectively, 1024), and the number of mantissa bits is 24 (respectively,
       53).)

       If you want to store the rounded value in an integer type, you probably want to use one of
       the functions described in lround(3) instead.

SEE ALSO
       ceil(3), floor(3), lround(3), nearbyint(3), rint(3), trunc(3)

COLOPHON
       This page is part of release 3.74 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 http://www.kernel.org/doc/man-pages/.



                                            2013-06-21                                   ROUND(3)