001/*
002 * Units of Measurement Reference Implementation
003 * Copyright (c) 2005-2016, 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 0.5, December 28, 2015
047 */
048public final class ExpConverter extends AbstractConverter implements ValueSupplier<String> {
049
050  /**
051         * 
052         */
053  // private static final long serialVersionUID = -8851436813812059827L;
054
055  /**
056   * Holds the logarithmic base.
057   */
058  private double base;
059
060  /**
061   * Holds the natural logarithm of the base.
062   */
063  private double logOfBase;
064
065  /**
066   * Creates a logarithmic converter having the specified base.
067   *
068   * @param base
069   *          the logarithmic base (e.g. <code>Math.E</code> for the Natural Logarithm).
070   */
071  public ExpConverter(double base) {
072    this.base = base;
073    this.logOfBase = MathUtil.log(base);
074  }
075
076  /**
077   * Returns the exponential base of this converter.
078   *
079   * @return the exponential base (e.g. <code>Math.E</code> for the Natural Exponential).
080   */
081  public double getBase() {
082    return base;
083  }
084
085  @Override
086  public AbstractConverter inverse() {
087    return new LogConverter(base);
088  }
089
090  @Override
091  public final String toString() {
092    if (base == Math.E) {
093      return "e";
094    } else {
095      return "Exp(" + base + ")";
096    }
097  }
098
099  @Override
100  public boolean equals(Object obj) {
101    if (!(obj instanceof ExpConverter))
102      return false;
103    ExpConverter that = (ExpConverter) obj;
104    return this.base == that.base;
105  }
106
107  @Override
108  public int hashCode() {
109    long bits = Double.doubleToLongBits(base);
110    return (int) (bits ^ (bits >>> 32));
111  }
112
113  @Override
114  public double convert(double amount) {
115    return MathUtil.exp(logOfBase * amount);
116  }
117
118  // @Override
119  // public BigDecimal convert(BigDecimal value, MathContext ctx) throws
120  // ArithmeticException {
121  // return BigDecimal.valueOf(convert(value.doubleValue())); // Reverts to
122  // double conversion.
123  // }
124
125  public boolean isLinear() {
126    return false;
127  }
128
129  public String getValue() {
130    return toString();
131  }
132}