mirror of
https://github.com/autc04/Retro68.git
synced 2024-12-11 03:52:59 +00:00
127 lines
3.9 KiB
C
127 lines
3.9 KiB
C
/*
|
|
FUNCTION
|
|
<<div>>---divide two integers
|
|
|
|
INDEX
|
|
div
|
|
|
|
SYNOPSIS
|
|
#include <stdlib.h>
|
|
div_t div(int <[n]>, int <[d]>);
|
|
|
|
DESCRIPTION
|
|
Divide
|
|
@tex
|
|
$n/d$,
|
|
@end tex
|
|
@ifnottex
|
|
<[n]>/<[d]>,
|
|
@end ifnottex
|
|
returning quotient and remainder as two integers in a structure <<div_t>>.
|
|
|
|
RETURNS
|
|
The result is represented with the structure
|
|
|
|
. typedef struct
|
|
. {
|
|
. int quot;
|
|
. int rem;
|
|
. } div_t;
|
|
|
|
where the <<quot>> field represents the quotient, and <<rem>> the
|
|
remainder. For nonzero <[d]>, if `<<<[r]> = div(<[n]>,<[d]>);>>' then
|
|
<[n]> equals `<<<[r]>.rem + <[d]>*<[r]>.quot>>'.
|
|
|
|
To divide <<long>> rather than <<int>> values, use the similar
|
|
function <<ldiv>>.
|
|
|
|
PORTABILITY
|
|
<<div>> is ANSI.
|
|
|
|
No supporting OS subroutines are required.
|
|
*/
|
|
|
|
/*
|
|
* Copyright (c) 1990 Regents of the University of California.
|
|
* All rights reserved.
|
|
*
|
|
* This code is derived from software contributed to Berkeley by
|
|
* Chris Torek.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
* 3. All advertising materials mentioning features or use of this software
|
|
* must display the following acknowledgement:
|
|
* This product includes software developed by the University of
|
|
* California, Berkeley and its contributors.
|
|
* 4. Neither the name of the University nor the names of its contributors
|
|
* may be used to endorse or promote products derived from this software
|
|
* without specific prior written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
* SUCH DAMAGE.
|
|
*/
|
|
|
|
#include <_ansi.h>
|
|
#include <stdlib.h> /* div_t */
|
|
|
|
div_t
|
|
div (int num,
|
|
int denom)
|
|
{
|
|
div_t r;
|
|
|
|
r.quot = num / denom;
|
|
r.rem = num % denom;
|
|
/*
|
|
* The ANSI standard says that |r.quot| <= |n/d|, where
|
|
* n/d is to be computed in infinite precision. In other
|
|
* words, we should always truncate the quotient towards
|
|
* 0, never -infinity or +infinity.
|
|
*
|
|
* Machine division and remainer may work either way when
|
|
* one or both of n or d is negative. If only one is
|
|
* negative and r.quot has been truncated towards -inf,
|
|
* r.rem will have the same sign as denom and the opposite
|
|
* sign of num; if both are negative and r.quot has been
|
|
* truncated towards -inf, r.rem will be positive (will
|
|
* have the opposite sign of num). These are considered
|
|
* `wrong'.
|
|
*
|
|
* If both are num and denom are positive, r will always
|
|
* be positive.
|
|
*
|
|
* This all boils down to:
|
|
* if num >= 0, but r.rem < 0, we got the wrong answer.
|
|
* In that case, to get the right answer, add 1 to r.quot and
|
|
* subtract denom from r.rem.
|
|
* if num < 0, but r.rem > 0, we also have the wrong answer.
|
|
* In this case, to get the right answer, subtract 1 from r.quot and
|
|
* add denom to r.rem.
|
|
*/
|
|
if (num >= 0 && r.rem < 0) {
|
|
++r.quot;
|
|
r.rem -= denom;
|
|
}
|
|
else if (num < 0 && r.rem > 0) {
|
|
--r.quot;
|
|
r.rem += denom;
|
|
}
|
|
return (r);
|
|
}
|