1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
|
/* $OpenBSD: div.c,v 1.6 2015/09/13 08:31:47 guenther Exp $ */
/*
* 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. 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 <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.
*
* 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 && r.rem < 0) {
r.quot++;
r.rem -= denom;
}
return (r);
}
DEF_STRONG(div);
|
