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}