001/*
002 * Units of Measurement Implementation for Java SE
003 * Copyright (c) 2005-2017, Jean-Marie Dautelle, Werner Keil, V2COM.
004 *
005 * All rights reserved.
006 *
007 * Redistribution and use in source and binary forms, with or without modification,
008 * are permitted provided that the following conditions are met:
009 *
010 * 1. Redistributions of source code must retain the above copyright notice,
011 *    this list of conditions and the following disclaimer.
012 *
013 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions
014 *    and the following disclaimer in the documentation and/or other materials provided with the distribution.
015 *
016 * 3. Neither the name of JSR-363 nor the names of its contributors may be used to endorse or promote products
017 *    derived from this software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
020 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
021 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
022 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
023 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
026 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
028 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package tec.uom.se.function;
031
032import java.io.Serializable;
033import java.math.BigDecimal;
034import java.math.MathContext;
035import java.util.Objects;
036
037import tec.uom.lib.common.function.ValueSupplier;
038import tec.uom.se.AbstractConverter;
039
040/**
041 * <p>
042 * This class represents a logarithmic converter of limited precision. Such converter is typically used to create logarithmic unit. For example:[code]
043 * Unit<Dimensionless> BEL = Unit.ONE.transform(new LogConverter(10).inverse()); [/code]
044 * </p>
045 *
046 * @author <a href="mailto:jean-marie@dautelle.com">Jean-Marie Dautelle</a>
047 * @author <a href="mailto:units@catmedia.us">Werner Keil</a>
048 * @version 1.0, October 10, 2016
049 */
050public final class LogConverter extends AbstractConverter implements ValueSupplier<String> { // implements Immutable<String> {
051
052  /**
053         * 
054         */
055  private static final long serialVersionUID = -7584688290961460870L;
056
057  /**
058   * Holds the logarithmic base.
059   */
060  private final double base;
061  /**
062   * Holds the natural logarithm of the base.
063   */
064  private final double logOfBase;
065
066  /**
067   * Returns a logarithmic converter having the specified base.
068   *
069   * @param base
070   *          the logarithmic base (e.g. <code>Math.E</code> for the Natural Logarithm).
071   */
072  public LogConverter(double base) {
073    this.base = base;
074    this.logOfBase = Math.log(base);
075  }
076
077  /**
078   * Returns the logarithmic base of this converter.
079   *
080   * @return the logarithmic base (e.g. <code>Math.E</code> for the Natural Logarithm).
081   */
082  public double getBase() {
083    return base;
084  }
085
086  @Override
087  public AbstractConverter inverse() {
088    return new ExpConverter(base);
089  }
090
091  @Override
092  public final String toString() {
093    if (base == Math.E) {
094      return "ln";
095    } else {
096      return "Log(" + base + ")";
097    }
098  }
099
100  @Override
101  public boolean equals(Object obj) {
102    if (this == obj) {
103      return true;
104    }
105    if (obj instanceof LogConverter) {
106      LogConverter that = (LogConverter) obj;
107      return Objects.equals(base, that.base);
108    }
109    return false;
110  }
111
112  @Override
113  public int hashCode() {
114    return Objects.hash(base);
115  }
116
117  @Override
118  public double convert(double amount) {
119    return Math.log(amount) / logOfBase;
120  }
121
122  @Override
123  public BigDecimal convert(BigDecimal value, MathContext ctx) throws ArithmeticException {
124    return BigDecimal.valueOf(convert(value.doubleValue())); // Reverts to
125    // double
126    // conversion.
127  }
128
129  @Override
130  public boolean isLinear() {
131    return false;
132  }
133
134  @Override
135  public String getValue() {
136    return toString();
137  }
138}