tec.units.ri.function.LogConverter Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of unit-ri Show documentation
Unit Standard (JSR 363) Reference Implementation.
There is a newer version: 1.0.3
/**
 *  Unit-API - Units of Measurement API for Java
 *  Copyright (c) 2005-2014, Jean-Marie Dautelle, Werner Keil, V2COM.
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
 *
 * 2. 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.
 *
 * 3. Neither the name of JSR-363 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 "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package tec.units.ri.function;

import tec.units.ri.AbstractConverter;


/**
 *  This class represents a logarithmic converter of limited precision.
 *     Such converter  is typically used to create logarithmic unit.
 *     For example:[code]
 *     Unit BEL = Units.ONE.transform(new LogConverter(10).inverse());
 *     [/code]
 *
 * @author  Jean-Marie Dautelle
 * @author  Werner Keil
 * @version 0.3, August 3, 2014
 */
public final class LogConverter extends AbstractConverter 
	implements ValueSupplier { //implements Immutable {

    /**
	 * 
	 */
//	private static final long serialVersionUID = -7584688290961460870L;
	
	/**
     * Holds the logarithmic base.
     */
    private double base;
    /**
     * Holds the natural logarithm of the base.
     */
    private double logOfBase;

    /**
     * Returns a logarithmic converter having the specified base.
     *
     * @param  base the logarithmic base (e.g. Math.E for
     *         the Natural Logarithm).
     */
    public LogConverter(double base) {
        this.base = base;
        this.logOfBase = Math.log(base);
    }

    /**
     * Returns the logarithmic base of this converter.
     *
     * @return the logarithmic base (e.g. Math.E for
     *         the Natural Logarithm).
     */
    public double getBase() {
        return base;
    }

    @Override
    public AbstractConverter inverse() {
        return new ExpConverter(base);
    }

    @Override
    public final String toString() {
        if (base == Math.E) {
            return "ln";
        } else {
            return "Log(" + base + ")";
        }
    }

    @Override
    public boolean equals(Object obj) {
        if (!(obj instanceof LogConverter))
            return false;
        LogConverter that = (LogConverter) obj;
        return this.base == that.base;
    }

    @Override
    public int hashCode() {
        long bits = Double.doubleToLongBits(base);
        return (int) (bits ^ (bits >>> 32));
    }

    @Override
    public double convert(double amount) {
        return Math.log(amount) / logOfBase;
    }

//    @Override
//    public BigDecimal convert(BigDecimal value, MathContext ctx) throws ArithmeticException {
//        return BigDecimal.valueOf(convert(value.doubleValue())); // Reverts to double conversion.
//    }

    @Override
    public boolean isLinear() {
        return false;
    }

    @Override
	public String getValue() {
		return toString();
	}
}