Linux.com

roundf.3

ROUND

Section: Linux Programmer's Manual (3)
Updated: 2008-08-11
Index Return to Main Contents
 

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; 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.  

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 3.21 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/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
VERSIONS
CONFORMING TO
NOTES
SEE ALSO
COLOPHON

 

Comments

Subscribe to Comments Feed

Upcoming Linux Foundation Courses

  1. LFD320 Linux Kernel Internals and Debugging
    04 Aug » 08 Aug - Virtual
    Details
  2. LFD405 Embedded Linux Development with Yocto Project
    04 Aug » 07 Aug - Santa Clara, CA
    Details
  3. LFD312 Developing Applications For Linux
    18 Aug » 22 Aug - Virtual
    Details

View All Upcoming Courses

Become an Individual Member
Check out the Friday Funnies

Sign Up For the Linux.com Newsletter


Who we are ?

The Linux Foundation is a non-profit consortium dedicated to the growth of Linux.

More About the foundation...

Frequent Questions

Join / Linux Training / Board