1.\" Copyright (c) 1985, 1991 Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" from: @(#)rint.3 5.1 (Berkeley) 5/2/91 33.\" $Id: rint.3,v 1.3 1993/08/14 13:43:02 mycroft Exp $ 34.\" 35.Dd May 2, 1991 36.Dt RINT 3 37.Os 38.Sh NAME 39.Nm rint 40.Nd and round-to-closest integer functions 41.Sh SYNOPSIS 42.Fd #include <math.h> 43.Ft double 44.Fn rint "double x" 45.Sh DESCRIPTION 46The 47.Fn rint 48function finds the integer (represented as a double precision number) 49nearest to 50.Fa x 51in the direction of the prevailing rounding mode. 52.Sh NOTES 53On a 54.Tn VAX , 55.Fn rint x 56is equivalent to adding half to the magnitude 57and then rounding towards zero. 58.Pp 59In the default rounding mode, to nearest, 60on a machine that conforms to 61.Tn IEEE 62754, 63.Fn rint x 64is the integer nearest 65.Fa x 66with the additional stipulation 67that if 68.Li |rint(x)\-x|=1/2 69then 70.Fn rint x 71is even. 72Other rounding modes can make 73.Fn rint 74act like 75.Fn floor , 76or like 77.Fn ceil , 78or round towards zero. 79.Pp 80Another way to obtain an integer near 81.Fa x 82is to declare (in C) 83.Bd -literal -offset indent 84double x;\0\0\0\0 int k;\0\0\0\0k\0=\0x; 85.Ed 86.Pp 87Most C compilers round 88.Fa x 89towards 0 to get the integer 90.Fa k , 91but 92some do otherwise. 93If in doubt, use 94.Fn floor , 95.Fn ceil , 96or 97.Fn rint 98first, whichever you intend. 99Also note that, if x is larger than 100.Fa k 101can accommodate, the value of 102.Fa k 103and the presence or absence of an integer overflow are hard to 104predict. 105.Sh SEE ALSO 106.Xr abs 3 , 107.Xr fabs 3 , 108.Xr ceil 3 , 109.Xr floor 3 , 110.Xr ieee 3 , 111.Xr math 3 112.Sh HISTORY 113A 114.Fn rint 115function appeared in 116.At v6 . 117