J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1999-2007 Sun Microsystems, Inc. All Rights Reserved. |
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 4 | * |
| 5 | * This code is free software; you can redistribute it and/or modify it |
| 6 | * under the terms of the GNU General Public License version 2 only, as |
| 7 | * published by the Free Software Foundation. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun in the LICENSE file that accompanied this code. |
| 10 | * |
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 14 | * version 2 for more details (a copy is included in the LICENSE file that |
| 15 | * accompanied this code). |
| 16 | * |
| 17 | * You should have received a copy of the GNU General Public License version |
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, |
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 20 | * |
| 21 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package java.math; |
| 27 | |
| 28 | /** |
| 29 | * A class used to represent multiprecision integers that makes efficient |
| 30 | * use of allocated space by allowing a number to occupy only part of |
| 31 | * an array so that the arrays do not have to be reallocated as often. |
| 32 | * When performing an operation with many iterations the array used to |
| 33 | * hold a number is only increased when necessary and does not have to |
| 34 | * be the same size as the number it represents. A mutable number allows |
| 35 | * calculations to occur on the same number without having to create |
| 36 | * a new number for every step of the calculation as occurs with |
| 37 | * BigIntegers. |
| 38 | * |
| 39 | * Note that SignedMutableBigIntegers only support signed addition and |
| 40 | * subtraction. All other operations occur as with MutableBigIntegers. |
| 41 | * |
| 42 | * @see BigInteger |
| 43 | * @author Michael McCloskey |
| 44 | * @since 1.3 |
| 45 | */ |
| 46 | |
| 47 | class SignedMutableBigInteger extends MutableBigInteger { |
| 48 | |
| 49 | /** |
| 50 | * The sign of this MutableBigInteger. |
| 51 | */ |
| 52 | int sign = 1; |
| 53 | |
| 54 | // Constructors |
| 55 | |
| 56 | /** |
| 57 | * The default constructor. An empty MutableBigInteger is created with |
| 58 | * a one word capacity. |
| 59 | */ |
| 60 | SignedMutableBigInteger() { |
| 61 | super(); |
| 62 | } |
| 63 | |
| 64 | /** |
| 65 | * Construct a new MutableBigInteger with a magnitude specified by |
| 66 | * the int val. |
| 67 | */ |
| 68 | SignedMutableBigInteger(int val) { |
| 69 | super(val); |
| 70 | } |
| 71 | |
| 72 | /** |
| 73 | * Construct a new MutableBigInteger with a magnitude equal to the |
| 74 | * specified MutableBigInteger. |
| 75 | */ |
| 76 | SignedMutableBigInteger(MutableBigInteger val) { |
| 77 | super(val); |
| 78 | } |
| 79 | |
| 80 | // Arithmetic Operations |
| 81 | |
| 82 | /** |
| 83 | * Signed addition built upon unsigned add and subtract. |
| 84 | */ |
| 85 | void signedAdd(SignedMutableBigInteger addend) { |
| 86 | if (sign == addend.sign) |
| 87 | add(addend); |
| 88 | else |
| 89 | sign = sign * subtract(addend); |
| 90 | |
| 91 | } |
| 92 | |
| 93 | /** |
| 94 | * Signed addition built upon unsigned add and subtract. |
| 95 | */ |
| 96 | void signedAdd(MutableBigInteger addend) { |
| 97 | if (sign == 1) |
| 98 | add(addend); |
| 99 | else |
| 100 | sign = sign * subtract(addend); |
| 101 | |
| 102 | } |
| 103 | |
| 104 | /** |
| 105 | * Signed subtraction built upon unsigned add and subtract. |
| 106 | */ |
| 107 | void signedSubtract(SignedMutableBigInteger addend) { |
| 108 | if (sign == addend.sign) |
| 109 | sign = sign * subtract(addend); |
| 110 | else |
| 111 | add(addend); |
| 112 | |
| 113 | } |
| 114 | |
| 115 | /** |
| 116 | * Signed subtraction built upon unsigned add and subtract. |
| 117 | */ |
| 118 | void signedSubtract(MutableBigInteger addend) { |
| 119 | if (sign == 1) |
| 120 | sign = sign * subtract(addend); |
| 121 | else |
| 122 | add(addend); |
| 123 | if (intLen == 0) |
| 124 | sign = 1; |
| 125 | } |
| 126 | |
| 127 | /** |
| 128 | * Print out the first intLen ints of this MutableBigInteger's value |
| 129 | * array starting at offset. |
| 130 | */ |
| 131 | public String toString() { |
| 132 | BigInteger b = new BigInteger(this, sign); |
| 133 | return |
| 134 | b.toString(); |
| 135 | } |
| 136 | |
| 137 | } |