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.math.BigDecimal;
033import java.math.MathContext;
034import java.util.Objects;
035
036import tec.uom.lib.common.function.ValueSupplier;
037import tec.uom.se.AbstractConverter;
038
039/**
040 * <p>
041 * This class represents a exponential converter of limited precision. Such converter is used to create inverse of logarithmic unit.
042 *
043 * <p>
044 * This class is package private, instances are created using the {@link LogConverter#inverse()} method.
045 * </p>
046 *
047 * @author <a href="mailto:jean-marie@dautelle.com">Jean-Marie Dautelle</a>
048 * @author <a href="mailto:units@catmedia.us">Werner Keil</a>
049 * @version 1.0, Oct 10, 2016
050 * @since 1.0
051 */
052public final class ExpConverter extends AbstractConverter implements ValueSupplier<String> {
053
054  /**
055         * 
056         */
057  private static final long serialVersionUID = -8851436813812059827L;
058
059  /**
060   * Holds the logarithmic base.
061   */
062  private final double base;
063
064  /**
065   * Holds the natural logarithm of the base.
066   */
067  private final double logOfBase;
068
069  /**
070   * Creates a logarithmic converter having the specified base.
071   *
072   * @param base
073   *          the logarithmic base (e.g. <code>Math.E</code> for the Natural Logarithm).
074   */
075  public ExpConverter(double base) {
076    this.base = base;
077    this.logOfBase = Math.log(base);
078  }
079
080  /**
081   * Returns the exponential base of this converter.
082   *
083   * @return the exponential base (e.g. <code>Math.E</code> for the Natural Exponential).
084   */
085  public double getBase() {
086    return base;
087  }
088
089  @Override
090  public AbstractConverter inverse() {
091    return new LogConverter(base);
092  }
093
094  @Override
095  public final String toString() {
096    if (base == Math.E) {
097      return "e";
098    } else {
099      return "Exp(" + base + ")";
100    }
101  }
102
103  @Override
104  public boolean equals(Object obj) {
105    if (this == obj) {
106      return true;
107    }
108    if (obj instanceof ExpConverter) {
109      ExpConverter that = (ExpConverter) obj;
110      return Objects.equals(base, that.base);
111    }
112    return false;
113  }
114
115  @Override
116  public int hashCode() {
117    return Objects.hash(base);
118  }
119
120  @Override
121  public double convert(double amount) {
122    return Math.exp(logOfBase * amount);
123  }
124
125  @Override
126  public BigDecimal convert(BigDecimal value, MathContext ctx) throws ArithmeticException {
127    return BigDecimal.valueOf(convert(value.doubleValue())); // Reverts to
128    // double
129    // conversion.
130  }
131
132  @Override
133  public boolean isLinear() {
134    return false;
135  }
136
137  @Override
138  public String getValue() {
139    return toString();
140  }
141}