1 | #region License Information
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2 | /* HeuristicLab
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3 | * Copyright (C) 2002-2016 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
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4 | *
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5 | * This file is part of HeuristicLab.
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6 | *
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7 | * HeuristicLab is free software: you can redistribute it and/or modify
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8 | * it under the terms of the GNU General Public License as published by
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9 | * the Free Software Foundation, either version 3 of the License, or
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10 | * (at your option) any later version.
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11 | *
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12 | * HeuristicLab is distributed in the hope that it will be useful,
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13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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15 | * GNU General Public License for more details.
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16 | *
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17 | * You should have received a copy of the GNU General Public License
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18 | * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
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19 | */
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20 | #endregion
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21 |
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22 | using System;
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23 | using System.Collections.Generic;
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24 | using System.Linq;
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25 | using System.Runtime.InteropServices;
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26 | using HeuristicLab.Common;
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27 | using HeuristicLab.Core;
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28 | using HeuristicLab.Random;
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29 |
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30 | namespace HeuristicLab.ExpressionGenerator {
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31 | public static class ExpressionGenerator {
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32 | public static IEnumerable<Expression> GenerateRandomDistributedVariables(int numberOfVariables, string variablePrefix, IRandom randomDistribution) {
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33 | return Enumerable.Range(1, numberOfVariables).Select(x => Expression.RandomVariable(string.Format("{0}{1}", variablePrefix, x), randomDistribution));
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34 | }
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35 |
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36 | public static Expression NonlinearExpression(IRandom uniformRandom, Expression[] variables, bool useLog, bool useExp) {
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37 | var scalingTemplate = ScaledExpression(uniformRandom, variables, varianceRandom: new UniformDistributedRandom(uniformRandom, 1, 10));
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38 | var scaledVars = Instantiate(scalingTemplate, uniformRandom, 100, "scaledVar");
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39 |
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40 | var sumTemplate = new RandomArityTemplate(Sum, new UniformDistributedRandom(uniformRandom, 1, 3)) { Label = "+" };
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41 | sumTemplate.AddArguments(scaledVars);
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42 | var prodTemplate = new RandomArityTemplate(Product, new UniformDistributedRandom(uniformRandom, 1, 3)) { Label = "*" };
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43 | prodTemplate.AddArguments(variables);
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44 |
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45 | var logTemplate = LogOfScaledExpression(uniformRandom, Instantiate(sumTemplate, uniformRandom, 100, "sumOfScaledVars"),
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46 | minValue: new UniformDistributedRandom(uniformRandom, 0.1, 2),
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47 | valueRange: new UniformDistributedRandom(uniformRandom, 1, 10));
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48 |
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49 | var expTemplate = ExpOfScaledExpression(uniformRandom, Instantiate(prodTemplate, uniformRandom, 100, "prodOfVars"),
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50 | valueRange: new UniformDistributedRandom(uniformRandom, 1, 4)); // TODO should also specify an offset
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51 |
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52 | var scaledExprTemplate = new ScalingTemplate(new UniformDistributedRandom(uniformRandom, 1, 10)) { Label = "*" };
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53 | if (useLog) scaledExprTemplate.AddArguments(Instantiate(logTemplate, uniformRandom, 100, "log"));
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54 | if (useExp) scaledExprTemplate.AddArguments(Instantiate(expTemplate, uniformRandom, 100, "exp"));
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55 |
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56 | var mainTemplate = new RandomArityTemplate(Sum, new UniformDistributedRandom(uniformRandom, 3, 5));
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57 | mainTemplate.AddArguments(scaledVars);
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58 | if (useLog || useExp) {
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59 | mainTemplate.AddArguments(Instantiate(scaledExprTemplate, uniformRandom, 100, "scaledExpr"));
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60 | }
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61 | mainTemplate.Label = "+";
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62 |
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63 | return mainTemplate.Instantiate("main", uniformRandom, false);
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64 | }
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65 |
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66 | public static Expression Polynomial(IRandom uniformRandom, Expression[] variables, bool useLog, bool useExp) {
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67 | const int count = 10; // how many instances of each template should be produce?
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68 | int i = 1;
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69 | // the main template
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70 | var template = new RandomArityTemplate(Sum, new UniformDistributedRandom(uniformRandom, 2, count)) { Label = "+" };
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71 | template.AddArguments(variables);
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72 |
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73 | var sumTemplate = new RandomArityTemplate(Sum, new UniformDistributedRandom(uniformRandom, 1, variables.Length)) { Label = "+" };
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74 | sumTemplate.AddArguments(variables);
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75 |
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76 | var productTemplate = new RandomArityTemplate(Product, new UniformDistributedRandom(uniformRandom, 1, variables.Length)) { Label = "*" };
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77 | productTemplate.AddArguments(variables);
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78 |
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79 | var inverseTemplate = new FixedArityTemplate(Division, 1) { Label = "/" };
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80 | inverseTemplate.AddArguments(variables);
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81 | inverseTemplate.AddArguments(Enumerable.Range(1, count).Select(x => sumTemplate.Instantiate(string.Format("sum{0}", i++), uniformRandom)));
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82 | inverseTemplate.AddArguments(Enumerable.Range(1, count).Select(x => productTemplate.Instantiate(string.Format("prod{0}", i++), uniformRandom)));
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83 |
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84 | if (useLog) {
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85 | var logTemplate = new FixedArityTemplate(Log, 1) { Label = "log" };
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86 | logTemplate.AddArguments(variables);
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87 | logTemplate.AddArguments(Enumerable.Range(1, count).Select(x => sumTemplate.Instantiate(string.Format("sum{0}", i++), uniformRandom)));
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88 | template.AddArguments(Enumerable.Range(1, count).Select(x => logTemplate.Instantiate(string.Format("log{0}", i++), uniformRandom)));
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89 | inverseTemplate.AddArguments(Enumerable.Range(1, count).Select(x => logTemplate.Instantiate(string.Format("log{0}", i++), uniformRandom)));
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90 | }
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91 |
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92 | if (useExp) {
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93 | var expTemplate = new FixedArityTemplate(Exp, 1) { Label = "exp" };
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94 | expTemplate.AddArguments(variables);
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95 | expTemplate.AddArguments(Enumerable.Range(1, count).Select(x => productTemplate.Instantiate(string.Format("prod{0}", i++), uniformRandom)));
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96 | template.AddArguments(Enumerable.Range(1, count).Select(x => expTemplate.Instantiate(string.Format("exp{0}", i++), uniformRandom)));
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97 | inverseTemplate.AddArguments(Enumerable.Range(1, count).Select(x => expTemplate.Instantiate(string.Format("exp{0}", i++), uniformRandom)));
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98 | }
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99 |
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100 | template.AddArguments(Enumerable.Range(1, count).Select(x => inverseTemplate.Instantiate(string.Format("inv{0}", i++), uniformRandom)));
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101 | return template.Instantiate("polynomial", uniformRandom);
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102 | }
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103 |
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104 | // variance random must have support only positive numbers
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105 | private static ExpressionTemplate ScaledExpression(IRandom uniformRandom, IEnumerable<Expression> arguments, IRandom varianceRandom) {
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106 | var scalingTemplate = new ScalingTemplate(scaledVariance: varianceRandom);
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107 | scalingTemplate.AddArguments(arguments);
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108 | scalingTemplate.Label = "*";
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109 | return scalingTemplate;
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110 | }
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111 |
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112 | /// template scales and translates the argument expression first to guarantee positive values
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113 | private static ExpressionTemplate LogOfScaledExpression(IRandom uniformRandom, IEnumerable<Expression> arguments,
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114 | IRandom minValue = null, IRandom valueRange = null) {
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115 | var limitToRangeTemplate = new RangeTemplate(minValue, valueRange);
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116 | limitToRangeTemplate.AddArguments(arguments);
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117 |
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118 | var logTemplate = new FixedArityTemplate(Log, 1) { Label = "log" };
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119 | logTemplate.AddArguments(Enumerable.Range(1, 100).Select(i => limitToRangeTemplate.Instantiate(string.Format("log{0}", i), uniformRandom, false)));
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120 | return logTemplate;
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121 | }
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122 |
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123 | /// template scales the argument expression first to guarantee reasonable values
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124 | private static ExpressionTemplate ExpOfScaledExpression(IRandom uniformRandom, IEnumerable<Expression> arguments,
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125 | IRandom valueRange = null) {
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126 | var limitToRangeTemplate = new RangeTemplate(null, valueRange);
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127 | limitToRangeTemplate.AddArguments(arguments);
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128 |
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129 | var expTemplate = new FixedArityTemplate(Exp, 1) { Label = "exp" };
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130 | expTemplate.AddArguments(Enumerable.Range(1, 100).Select(i => limitToRangeTemplate.Instantiate(string.Format("exp{0}", i), uniformRandom, false)));
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131 | return expTemplate;
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132 | }
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133 |
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134 | public static IEnumerable<Expression> Instantiate(ExpressionTemplate template, IRandom random, int count, string name) {
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135 | return Enumerable.Range(1, count).Select(i => template.Instantiate(name + i, random, false));
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136 | }
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137 |
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138 | #region static functions
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139 | public static double Sum(IEnumerable<double> args) {
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140 | return args.Sum();
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141 | }
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142 |
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143 | public static double Product(IEnumerable<double> args) {
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144 | return args.Aggregate((x, y) => x * y);
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145 | }
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146 |
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147 | public static double Division(IEnumerable<double> args) {
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148 | if (args.Count() == 1)
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149 | return 1 / args.First();
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150 |
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151 | return args.Aggregate((x, y) => x / y);
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152 | }
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153 |
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154 | public static double Subtraction(IEnumerable<double> args) {
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155 | if (args.Count() == 1)
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156 | return -args.First();
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157 |
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158 | return args.Aggregate((x, y) => x - y);
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159 | }
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160 |
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161 | public static double Exp(IEnumerable<double> args) {
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162 | return Math.Exp(args.Single());
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163 | }
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164 |
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165 | public static double Log(IEnumerable<double> args) {
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166 | return Math.Log(args.Single());
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167 | }
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168 |
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169 | public static double Square(IEnumerable<double> args) {
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170 | var v = args.Single();
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171 | return v * v;
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172 | }
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173 | #endregion
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174 | }
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175 | }
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