com.sri.ai.util.math.MixedRadixNumber Maven / Gradle / Ivy
/*
* Copyright (c) 2013, SRI International
* All rights reserved.
* Licensed under the The BSD 3-Clause License;
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://opensource.org/licenses/BSD-3-Clause
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 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.
*
* Neither the name of the aic-util 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 COPYRIGHT HOLDERS AND CONTRIBUTORS
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*/
package com.sri.ai.util.math;
import java.math.BigInteger;
import java.util.List;
import com.google.common.annotations.Beta;
/**
* For details on Mixed Radix Number Representations.
*
* Will proceed from right to left in sequence based on the radix values provided.
*
* @author Ciaran O'Reilly
*/
@Beta
public class MixedRadixNumber extends Number {
//
private static final long serialVersionUID = 1L;
//
private BigInteger value = BigInteger.ZERO;
private BigInteger maxValue = BigInteger.ZERO;
private int[] radices = null;
private int[] currentNumeralValue = null;
private BigInteger[] cachedRadixValues = null;
private boolean recalculateValue = false;
/**
* Constructs a mixed radix number with a specified value and a specified
* array of radices.
*
* @param value
* the value of the mixed radix number
* @param radices
* the radices used to represent the value of the mixed radix
* number
*/
public MixedRadixNumber(BigInteger value, int[] radices) {
this.value = value;
this.radices = new int[radices.length];
System.arraycopy(radices, 0, this.radices, 0, radices.length);
initialize();
}
/**
* Constructs a mixed radix number with a specified value and a specified
* list of radices.
*
* @param value
* the value of the mixed radix number
* @param radices
* the radices used to represent the value of the mixed radix
* number
*/
public MixedRadixNumber(BigInteger value, List radices) {
this.value = value;
this.radices = new int[radices.size()];
for (int i = 0; i < radices.size(); i++) {
this.radices[i] = radices.get(i);
}
initialize();
}
/**
* Constructs a mixed radix number with a specified array of numerals and a
* specified array of radices.
*
* @param radixValues
* the numerals of the mixed radix number
* @param radices
* the radices of the mixed radix number
*/
public MixedRadixNumber(List radixValues, List radices) {
this.radices = new int[radices.size()];
for (int i = 0; i < radices.size(); i++) {
this.radices[i] = radices.get(i);
}
initialize();
int[] radValues = new int[radixValues.size()];
for (int i = 0; i < radValues.length; i++) {
radValues[i] = radixValues.get(i);
}
setCurrentValueFor(radValues);
}
/**
* Constructs a mixed radix number with a specified array of numerals and a
* specified array of radices.
*
* @param radixValues
* the numerals of the mixed radix number
* @param radices
* the radices of the mixed radix number
*/
public MixedRadixNumber(int[] radixValues, int[] radices) {
this(BigInteger.ZERO, radices);
setCurrentValueFor(radixValues);
}
/**
*
* @return return the current value of the mixed radix number as a
* BigInteger.
*/
public BigInteger getValue() {
if (recalculateValue) {
value = getValueFor(currentNumeralValue);
recalculateValue = false;
}
return value;
}
/**
* Returns the maximum value which can be represented by the current array
* of radices.
*
* @return the maximum value which can be represented by the current array
* of radices.
*/
public BigInteger getMaxAllowedValue() {
return maxValue;
}
/**
* Returns the value of the mixed radix number with the specified array of
* numerals and the current array of radices.
*
* @param radixValues
* the current radix values.
*
* @return the value of the mixed radix number
*
* @throws IllegalArgumentException
* if any of the specified numerals is less than zero, or if any
* of the specified numerals is greater than it's corresponding
* radix.
*/
public BigInteger getValueFor(int[] radixValues) {
if (radixValues.length != radices.length) {
throw new IllegalArgumentException(
"Radix values not same size as Radices.");
}
BigInteger cvalue = BigInteger.ZERO;
BigInteger mvalue = BigInteger.ONE;
for (int i = radixValues.length-1; i >= 0; i--) {
if (radixValues[i] < 0 || radixValues[i] >= radices[i]) {
throw new IllegalArgumentException("Radix numeral value " + i
+ " is out of range for radix at this position");
}
if (i != radixValues.length-1) {
mvalue = mvalue.multiply(cachedRadixValues[radices[i + 1]]);
}
cvalue = cvalue.add(mvalue
.multiply(cachedRadixValues[radixValues[i]]));
}
return cvalue;
}
/**
* Sets the value of the mixed radix number with the specified array of
* numerals and the current array of radices.
*
* @param radixValues
* the numerals of the mixed radix number
*/
public void setCurrentValueFor(int[] radixValues) {
this.value = getValueFor(radixValues);
System.arraycopy(radixValues, 0, this.currentNumeralValue, 0,
radixValues.length);
}
/**
*
* @return true if you can increment by 1 the current value, false
* otherwise.
*/
public boolean canIncrement() {
boolean canIncrement = false;
for (int i = 0; i < radices.length; i++) {
if (currentNumeralValue[i] != radices[i] - 1) {
canIncrement = true;
break;
}
}
return canIncrement;
}
/**
* Increments the value of the mixed radix number, if the value is less than
* the maximum value which can be represented by the current array of
* radices.
*
* @return true if the increment was successful.
*/
public boolean increment() {
boolean canIncrement = canIncrement();
if (canIncrement) {
for (int i = radices.length-1; i >= 0; i--) {
if (currentNumeralValue[i] < radices[i] - 1) {
currentNumeralValue[i] = currentNumeralValue[i] + 1;
for (int j = i + 1; j < radices.length; j++) {
currentNumeralValue[j] = 0;
}
break;
}
}
recalculateValue = true;
}
return canIncrement;
}
/**
*
* @return true if you can decrement by 1 the current value, false
* otherwise.
*/
public boolean canDecrement() {
boolean canDecrement = false;
for (int i = radices.length-1; i >= 0; i--) {
if (currentNumeralValue[i] != 0) {
canDecrement = true;
break;
}
}
return canDecrement;
}
/**
* Decrements the value of the mixed radix number, if the value is greater
* than zero.
*
* @return true if the decrement was successful.
*/
public boolean decrement() {
boolean canDecrement = canDecrement();
if (canDecrement) {
for (int i = radices.length-1; i >= 0; i--) {
if (currentNumeralValue[i] > 0) {
currentNumeralValue[i] = currentNumeralValue[i] - 1;
for (int j = i + 1; j < radices.length; j++) {
currentNumeralValue[j] = radices[j] - 1;
}
break;
}
}
recalculateValue = true;
}
return canDecrement;
}
/**
* Returns the numeral at the specified position.
*
* @param atPosition
* the position of the numeral to return
* @return the numeral at the specified position.
*/
public int getCurrentNumeralValue(int atPosition) {
if (atPosition >= 0 && atPosition < radices.length) {
return currentNumeralValue[atPosition];
}
throw new IllegalArgumentException(
"Argument atPosition must be >=0 and < " + radices.length);
}
//
// START-Number
@Override
public int intValue() {
return getValue().intValue();
}
@Override
public long longValue() {
return getValue().longValue();
}
@Override
public float floatValue() {
return getValue().floatValue();
}
@Override
public double doubleValue() {
return getValue().doubleValue();
}
// END-Number
//
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < radices.length; i++) {
sb.append("[");
sb.append(this.getCurrentNumeralValue(i));
sb.append("]");
}
return sb.toString();
}
//
// PRIVATE
//
/**
* Sets the maximum value which can be represented by the current array of
* radices and related working attributes.
*
* @throws IllegalArgumentException
* if no radices are defined, if any radix is less than one, or
* if the current value is greater than the maximum value which
* can be represented by the current array of radices.
*/
private void initialize() {
if (0 == radices.length) {
throw new IllegalArgumentException(
"At least 1 radix must be defined.");
}
for (int i = 0; i < radices.length; i++) {
if (radices[i] < 1) {
throw new IllegalArgumentException(
"Invalid radix, must be >= 1");
}
}
// Cache the possible radix values
// so we don't have to create BigIntegers
// for the same set of values multiple times
int maxRadixValue = 0;
for (int i = 0; i < radices.length; i++) {
if (radices[i] > maxRadixValue) {
maxRadixValue = radices[i];
}
}
cachedRadixValues = new BigInteger[maxRadixValue + 1];
for (int i = 0; i <= maxRadixValue; i++) {
cachedRadixValues[i] = BigInteger.valueOf(i);
}
// Calculate the maxValue allowed
maxValue = cachedRadixValues[radices[0]];
for (int i = 1; i < radices.length; i++) {
maxValue = maxValue.multiply(cachedRadixValues[radices[i]]);
}
maxValue = maxValue.subtract(BigInteger.ONE);
if (value.max(maxValue) != maxValue && !value.equals(maxValue)) {
throw new IllegalArgumentException(
"The value ["
+ value
+ "] cannot be represented with the radices provided, max value is "
+ maxValue);
}
currentNumeralValue = new int[radices.length];
// Now set the current numeral values based on
// the current value of the mixed radix number
BigInteger quotient = value;
for (int i = radices.length -1; i >= 0; i--) {
if (!quotient.equals(BigInteger.ZERO)) {
currentNumeralValue[i] = quotient.mod(
cachedRadixValues[radices[i]]).intValue();
quotient = quotient.divide(cachedRadixValues[radices[i]]);
}
else {
currentNumeralValue[i] = 0;
}
}
}
}
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