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Random number generators, probability distributions, combinatorics and statistics for Java.
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// ============================================================================
// Copyright 2006-2012 Daniel W. Dyer
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ============================================================================
package org.uncommons.maths.number;
import java.math.BigDecimal;
import java.math.BigInteger;
import org.uncommons.maths.Maths;
/**
* Immutable value object for representing a rational number (or vulgar fraction).
* Instances of this class provide a way to perform arithmetic on fractional values
* without loss of precision.
* This implementation automatically simplifies fractions (3/6 is stored as 1/2).
* The implementation also requires that the denominator is positive. The numerator
* may be negative.
* @author Daniel Dyer
* @since 1.2
*/
public final class Rational extends Number implements Comparable
{
/**
* Convenient constant representing a value of zero (0/1 as a rational).
*/
public static final Rational ZERO = new Rational(0);
/**
* Convenient constant representing a value of a quarter (1/4 as a rational).
*/
public static final Rational QUARTER = new Rational(1, 4);
/**
* Convenient constant representing a value of a third (1/3 as a rational).
*/
public static final Rational THIRD = new Rational(1, 3);
/**
* Convenient constant representing a value of a half (1/2 as a rational).
*/
public static final Rational HALF = new Rational(1, 2);
/**
* Convenient constant representing a value of two thirds (2/3 as a rational).
*/
public static final Rational TWO_THIRDS = new Rational(2, 3);
/**
* Convenient constant representing a value of three quarters (3/4 as a rational).
*/
public static final Rational THREE_QUARTERS = new Rational(3, 4);
/**
* Convenient constant representing a value of one (1/1 as a rational).
*/
public static final Rational ONE = new Rational(1);
private final long numerator;
private final long denominator;
/**
* Creates a vulgar fraction with the specified numerator and denominator.
* @param numerator The fraction's numerator (may be negative).
* @param denominator The fraction's denominator (must be greater than or
* equal to 1).
*/
public Rational(long numerator, long denominator)
{
if (denominator < 1)
{
throw new IllegalArgumentException("Denominator must be non-zero and positive.");
}
long gcd = Maths.greatestCommonDivisor(numerator, denominator);
this.numerator = numerator / gcd;
this.denominator = denominator / gcd;
}
/**
* Creates a rational value equivalent to the specified integer value.
* @param value The value of this rational as an integer.
*/
public Rational(long value)
{
this(value, 1);
}
/**
* Creates a rational value equivalent to the specified decimal value.
* @param value The value of this rational as a fractional decimal.
* @throws ArithmeticException If the BigDecimal value is too large to be
* represented as a Rational.
*/
public Rational(BigDecimal value)
{
BigDecimal trimmedValue = value.stripTrailingZeros();
BigInteger denominator = BigInteger.TEN.pow(trimmedValue.scale());
BigInteger numerator = trimmedValue.unscaledValue();
BigInteger gcd = numerator.gcd(denominator);
this.numerator = numerator.divide(gcd).longValue();
this.denominator = denominator.divide(gcd).longValue();
}
/**
* Returns the numerator of the fraction.
* @return The numerator.
*/
public long getNumerator()
{
return numerator;
}
/**
* Returns the denominator (divisor) of the fraction.
* @return The denominator.
*/
public long getDenominator()
{
return denominator;
}
/**
* Add the specified value to this value and return the result as a new object
* (also a rational). If the two values have different denominators, they will
* first be converted so that they have common denominators.
* @param value The value to add to this rational.
* @return A new rational value that is the sum of this value and the specified
* value.
*/
public Rational add(Rational value)
{
if (denominator == value.getDenominator())
{
return new Rational(numerator + value.getNumerator(), denominator);
}
else
{
return new Rational(numerator * value.getDenominator() + value.getNumerator() * denominator,
denominator * value.getDenominator());
}
}
/**
* Subtract the specified value from this value and return the result as a new object
* (also a rational). If the two values have different denominators, they will
* first be converted so that they have common denominators.
* @param value The value to subtract from this rational.
* @return A new rational value that is the result of subtracting the specified value
* from this value.
*/
public Rational subtract(Rational value)
{
if (denominator == value.getDenominator())
{
return new Rational(numerator - value.getNumerator(), denominator);
}
else
{
return new Rational(numerator * value.getDenominator() - value.getNumerator() * denominator,
denominator * value.getDenominator());
}
}
/**
* Multiply this rational by the specified value and return the result as a new
* object (also a Rational).
* @param value The amount to multiply by.
* @return A new rational value that is the result of multiplying this value by
* the specified value.
*/
public Rational multiply(Rational value)
{
return new Rational(numerator * value.getNumerator(),
denominator * value.getDenominator());
}
/**
* Divide this rational by the specified value and return the result as a new
* object (also a Rational).
* @param value The amount to divide by.
* @return A new rational value that is the result of dividing this value by
* the specified value.
*/
public Rational divide(Rational value)
{
return new Rational(numerator * value.getDenominator(),
denominator * value.getNumerator());
}
/**
* Returns the integer equivalent of this rational number. If
* there is no exact integer representation, it returns the closest
* integer that is lower than the rational value (effectively the
* truncated version of calling {@link #doubleValue()}).
* @return The (truncated) integer value of this rational.
*/
public int intValue()
{
return (int) longValue();
}
/**
* Returns the integer equivalent of this rational number as a long.
* If there is no exact integer representation, it returns the closest
* long that is lower than the rational value (effectively the
* truncated version of calling {@link #doubleValue()}).
* @return The (truncated) long value of this rational.
*/
public long longValue()
{
return (long) doubleValue();
}
/**
* Returns the result of dividing the numerator by the denominator.
* Will result in a loss of precision for fractions that have no
* exact float representation.
* @return The closest double-precision floating point equivalent of
* the fraction represented by this object.
*/
public float floatValue()
{
return (float) doubleValue();
}
/**
* Returns the result of dividing the numerator by the denominator.
* Will result in a loss of precision for fractions that have no
* exact double representation.
* @return The closest double-precision floating point equivalent of
* the fraction represented by this object.
*/
public double doubleValue()
{
return (double) numerator / denominator;
}
/**
* Determines whether this rational value is equal to some other object.
* To be considered equal the other object must also be a Rational object
* with an indentical numerator and denominator.
* @param other The object to compare against.
* @return True if the objects are equal, false otherwise.
*/
@Override
public boolean equals(Object other)
{
if (this == other)
{
return true;
}
if (other == null || getClass() != other.getClass())
{
return false;
}
Rational rational = (Rational) other;
return denominator == rational.getDenominator()
&& numerator == rational.getNumerator();
}
/**
* Over-ridden to be consistent with {@link #equals(Object)}.
* @return The hash code value.
*/
@Override
public int hashCode()
{
int result = (int) (numerator ^ (numerator >>> 32));
result = 31 * result + (int) (denominator ^ (denominator >>> 32));
return result;
}
/**
* Returns a String representation of the rational number, expressed as
* a vulgar fraction (i.e. 1 and 1/3 is shown as 4/3). If the rational
* is equal to an integer, the value is simply displayed as that integer
* with no fractional part (i.e. 2/1 is shown as 2).
* @return A string representation of this rational value.
*/
@Override
public String toString()
{
StringBuilder buffer = new StringBuilder();
buffer.append(numerator);
if (denominator != 1)
{
buffer.append('/');
buffer.append(denominator);
}
return buffer.toString();
}
/**
* Compares this value with the specified object for order. Returns a negative
* integer, zero, or a positive integer as this value is less than, equal to, or
* greater than the specified value.
* @param other Another Rational value.
* @return A negative integer, zero, or a positive integer as this value is less
* than, equal to, or greater than the specified value.
*/
public int compareTo(Rational other)
{
if (denominator == other.getDenominator())
{
return ((Long) numerator).compareTo(other.getNumerator());
}
else
{
Long adjustedNumerator = numerator * other.getDenominator();
Long otherAdjustedNumerator = other.getNumerator() * denominator;
return adjustedNumerator.compareTo(otherAdjustedNumerator);
}
}
}
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