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():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

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

       allbox;  lbw27  lb  lb  l  l  l.  Interface Attribute Value T{ round(),
       roundf(), roundl() T}   Thread safety  MT-Safe

CONFORMING TO
       C99, POSIX.1-2001, POSIX.1-2008.

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 max-
       imum 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 num-
       ber 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 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
       https://www.kernel.org/doc/man-pages/.



                                  2017-09-15                          ROUND(3)