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 exponential converter of limited precision. Such converter is used to create inverse of logarithmic unit.
039 *
040 * <p>
041 * This class is package private, instances are created using the {@link LogConverter#inverse()} method.
042 * </p>
043 *
044 * @author <a href="mailto:jean-marie@dautelle.com">Jean-Marie Dautelle</a>
045 * @author <a href="mailto:units@catmedia.us">Werner Keil</a>
046 * @version 1.0, October 6, 2016
047 * @since 1.0
048 */
049public final class ExpConverter extends AbstractConverter implements ValueSupplier<String> {
050
051  /**
052         * 
053         */
054  // private static final long serialVersionUID = -8851436813812059827L;
055
056  /**
057   * Holds the logarithmic base.
058   */
059  private double base;
060
061  /**
062   * Holds the natural logarithm of the base.
063   */
064  private double logOfBase;
065
066  /**
067   * Creates 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 ExpConverter(double base) {
073    this.base = base;
074    this.logOfBase = MathUtil.log(base);
075  }
076
077  /**
078   * Returns the exponential base of this converter.
079   *
080   * @return the exponential base (e.g. <code>Math.E</code> for the Natural Exponential).
081   */
082  public double getBase() {
083    return base;
084  }
085
086  @Override
087  public AbstractConverter inverse() {
088    return new LogConverter(base);
089  }
090
091  @Override
092  public final String toString() {
093    if (base == Math.E) {
094      return "e";
095    } else {
096      return "Exp(" + base + ")";
097    }
098  }
099
100  @Override
101  public boolean equals(Object obj) {
102    if (!(obj instanceof ExpConverter))
103      return false;
104    ExpConverter that = (ExpConverter) obj;
105    return this.base == that.base;
106  }
107
108  @Override
109  public int hashCode() {
110    long bits = Double.doubleToLongBits(base);
111    return (int) (bits ^ (bits >>> 32));
112  }
113
114  @Override
115  public double convert(double amount) {
116    return MathUtil.exp(logOfBase * amount);
117  }
118
119  // @Override
120  // public BigDecimal convert(BigDecimal value, MathContext ctx) throws
121  // ArithmeticException {
122  // return BigDecimal.valueOf(convert(value.doubleValue())); // Reverts to
123  // double conversion.
124  // }
125
126  public boolean isLinear() {
127    return false;
128  }
129
130  public String getValue() {
131    return toString();
132  }
133}