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math_func.cpp
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1 /* $Id: math_func.cpp 26482 2014-04-23 20:13:33Z rubidium $ */
2
3 /*
4 * This file is part of OpenTTD.
5 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
6 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
7 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
8 */
9
12 #include "../stdafx.h"
13 #include "math_func.hpp"
14
15 #include "../safeguards.h"
16
26 int LeastCommonMultiple(int a, int b)
27 {
28 if (a == 0 || b == 0) return 0; // By definition.
29 if (a == 1 || a == b) return b;
30 if (b == 1) return a;
31
32 return a * b / GreatestCommonDivisor(a, b);
33 }
34
41 int GreatestCommonDivisor(int a, int b)
42 {
43 while (b != 0) {
44 int t = b;
45 b = a % b;
46 a = t;
47 }
48 return a;
49
50 }
51
59 int DivideApprox(int a, int b)
60 {
61 int random_like = ((a + b) * (a - b)) % b;
62
63 int remainder = a % b;
64
65 int ret = a / b;
66 if (abs(random_like) < abs(remainder)) {
67 ret += ((a < 0) ^ (b < 0)) ? -1 : 1;
68 }
69
70 return ret;
71 }
72
79 uint32 IntSqrt(uint32 num)
80 {
81 uint32 res = 0;
82 uint32 bit = 1UL << 30; // Second to top bit number.
83
84 /* 'bit' starts at the highest power of four <= the argument. */
85 while (bit > num) bit >>= 2;
86
87 while (bit != 0) {
88 if (num >= res + bit) {
89 num -= res + bit;
90 res = (res >> 1) + bit;
91 } else {
92 res >>= 1;
93 }
94 bit >>= 2;
95 }
96
97 /* Arithmetic rounding to nearest integer. */
98 if (num > res) res++;
99
100 return res;
101 }