001/*
002 * Units of Measurement Reference Implementation
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.units.ri.function;
031
032import tec.units.ri.AbstractConverter;
033import tec.units.ri.internal.MathUtil;
034import tec.uom.lib.common.function.ValueSupplier;
035
036/**
037 * <p>
038 * This class represents a logarithmic converter of limited precision. Such converter is typically used to create logarithmic unit. For example:[code]
039 * Unit&lt;Dimensionless&gt; BEL = Units.ONE.transform(new LogConverter(10).inverse()); [/code]
040 * </p>
041 *
042 * @author <a href="mailto:jean-marie@dautelle.com">Jean-Marie Dautelle</a>
043 * @author <a href="mailto:units@catmedia.us">Werner Keil</a>
044 * @version 1.0, October 6, 2016
045 * @since 1.0
046 */
047public final class LogConverter extends AbstractConverter implements ValueSupplier<String> { // implements Immutable<String> {
048
049  /**
050         * 
051         */
052  // private static final long serialVersionUID = -7584688290961460870L;
053
054  /**
055   * Holds the logarithmic base.
056   */
057  private double base;
058  /**
059   * Holds the natural logarithm of the base.
060   */
061  private double logOfBase;
062
063  /**
064   * Returns a logarithmic converter having the specified base.
065   *
066   * @param base
067   *          the logarithmic base (e.g. <code>Math.E</code> for the Natural Logarithm).
068   */
069  public LogConverter(double base) {
070    this.base = base;
071    this.logOfBase = MathUtil.log(base);
072  }
073
074  /**
075   * Returns the logarithmic base of this converter.
076   *
077   * @return the logarithmic base (e.g. <code>Math.E</code> for the Natural Logarithm).
078   */
079  public double getBase() {
080    return base;
081  }
082
083  @Override
084  public AbstractConverter inverse() {
085    return new ExpConverter(base);
086  }
087
088  @Override
089  public final String toString() {
090    if (base == Math.E) {
091      return "ln";
092    } else {
093      return "Log(" + base + ")";
094    }
095  }
096
097  @Override
098  public boolean equals(Object obj) {
099    if (!(obj instanceof LogConverter))
100      return false;
101    LogConverter that = (LogConverter) obj;
102    return this.base == that.base;
103  }
104
105  @Override
106  public int hashCode() {
107    long bits = Double.doubleToLongBits(base);
108    return (int) (bits ^ (bits >>> 32));
109  }
110
111  @Override
112  public double convert(double amount) {
113    return MathUtil.log(amount) / logOfBase;
114  }
115
116  // @Override
117  // public BigDecimal convert(BigDecimal value, MathContext ctx) throws
118  // ArithmeticException {
119  // return BigDecimal.valueOf(convert(value.doubleValue())); // Reverts to
120  // double conversion.
121  // }
122
123  public boolean isLinear() {
124    return false;
125  }
126
127  public String getValue() {
128    return toString();
129  }
130}