116 lines
3.2 KiB
Groff
116 lines
3.2 KiB
Groff
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.\" Copyright (c) 1985, 1991 Regents of the University of California.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)rint.3 5.1 (Berkeley) 5/2/91
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.\"
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.Dd May 2, 1991
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.Dt RINT 3
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.Os
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.Sh NAME
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.Nm rint
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.Nd and round-to-closest integer functions
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.Sh SYNOPSIS
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.Fd #include <math.h>
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.Ft double
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.Fn rint "double x"
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.Sh DESCRIPTION
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The
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.Fn rint
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function finds the integer (represented as a double precision number)
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nearest to
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.Fa x
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in the direction of the prevailing rounding mode.
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.Sh NOTES
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On a
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.Tn VAX ,
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.Fn rint x
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is equivalent to adding half to the magnitude
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and then rounding towards zero.
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.Pp
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In the default rounding mode, to nearest,
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on a machine that conforms to
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.Tn IEEE
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754,
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.Fn rint x
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is the integer nearest
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.Fa x
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with the additional stipulation
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that if
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.Li |rint(x)\-x|=1/2
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then
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.Fn rint x
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is even.
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Other rounding modes can make
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.Fn rint
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act like
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.Fn floor ,
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or like
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.Fn ceil ,
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or round towards zero.
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.Pp
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Another way to obtain an integer near
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.Fa x
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is to declare (in C)
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.Bd -literal -offset indent
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double x;\0\0\0\0 int k;\0\0\0\0k\0=\0x;
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.Ed
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.Pp
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Most C compilers round
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.Fa x
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towards 0 to get the integer
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.Fa k ,
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but
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some do otherwise.
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If in doubt, use
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.Fn floor ,
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.Fn ceil ,
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or
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.Fn rint
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first, whichever you intend.
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Also note that, if x is larger than
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.Fa k
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can accommodate, the value of
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.Fa k
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and the presence or absence of an integer overflow are hard to
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predict.
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.Sh SEE ALSO
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.Xr abs 3 ,
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.Xr fabs 3 ,
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.Xr ceil 3 ,
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.Xr floor 3 ,
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.Xr ieee 3 ,
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.Xr math 3
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.Sh HISTORY
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A
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.Fn rint
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function appeared in
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.At v6 .
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