commonMain.org.gciatto.kt.math.SignedMutableBigInteger.kt Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of kt-math Show documentation
Kotlin multi-platform porting of Java's BigIntegers and BigDecimals
There is a newer version: 0.10.0
/*
 * Copyright (c) 1999, 2007, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package org.gciatto.kt.math

/**
 * A class used to represent multiprecision integers that makes efficient
 * use of allocated space by allowing a number to occupy only part of
 * an array so that the arrays do not have to be reallocated as often.
 * When performing an operation with many iterations the array used to
 * hold a number is only increased when necessary and does not have to
 * be the same size as the number it represents. A mutable number allows
 * calculations to occur on the same number without having to create
 * a new number for every step of the calculation as occurs with
 * BigIntegers.
 *
 * Note that SignedMutableBigIntegers only support signed addition and
 * subtraction. All other operations occur as with MutableBigIntegers.
 *
 * @see CommonBigInteger
 *
 * @author Michael McCloskey
 * @since 1.3
 */

internal class SignedMutableBigInteger : MutableBigInteger {

    /**
     * The sign of this MutableBigInteger.
     */
    var sign = 1

    // Constructors

    /**
     * The default constructor. An empty MutableBigInteger is created with
     * a one word capacity.
     */
    constructor() : super() {}

    /**
     * Construct a new MutableBigInteger with a magnitude specified by
     * the int val.
     */
    constructor(`val`: Int) : super(`val`) {}

    /**
     * Construct a new MutableBigInteger with a magnitude equal to the
     * specified MutableBigInteger.
     */
    constructor(`val`: MutableBigInteger) : super(`val`) {}

    // Arithmetic Operations

    /**
     * Signed addition built upon unsigned plus and minus.
     */
    fun signedAdd(addend: SignedMutableBigInteger) {
        if (sign == addend.sign) {
            add(addend)
        } else {
            sign = sign * subtract(addend)
        }
    }

    /**
     * Signed addition built upon unsigned plus and minus.
     */
    fun signedAdd(addend: MutableBigInteger) {
        if (sign == 1) {
            add(addend)
        } else {
            sign = sign * subtract(addend)
        }
    }

    /**
     * Signed subtraction built upon unsigned plus and minus.
     */
    fun signedSubtract(addend: SignedMutableBigInteger) {
        if (sign == addend.sign) {
            sign = sign * subtract(addend)
        } else {
            add(addend)
        }
    }

    /**
     * Signed subtraction built upon unsigned plus and minus.
     */
    fun signedSubtract(addend: MutableBigInteger) {
        if (sign == 1) {
            sign = sign * subtract(addend)
        } else {
            add(addend)
        }
        if (intLen == 0) {
            sign = 1
        }
    }

    /**
     * Print out the first intLen ints of this MutableBigInteger's value
     * array starting at offset.
     */
    override fun toString(): String {
        return this.toBigInteger(sign).toString()
    }
}