1 | using System.Threading;
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2 |
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3 | namespace HeuristicLab.Algorithms.PushGP.Expressions {
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4 | using System;
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5 | using System.Collections.Generic;
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6 | using System.Diagnostics;
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7 | using System.Linq;
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8 | using System.Text;
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9 | using Interpreter;
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10 |
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11 | public class ExecExpandExpression : WrapperExpression<Expression[]> {
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12 | private const string Prefix = "( ";
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13 | private const string PrefixReduced = "[";
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14 | private const string Postfix = ")";
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15 | private const string PostfixReduced = "]";
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16 | private const string Delimiter = " ";
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17 |
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18 | public static readonly ExecExpandExpression Empty = new ExecExpandExpression();
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19 |
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20 | private readonly Lazy<string> _stringValue;
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21 | private readonly int[] _treeIndex;
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22 | public readonly int Depth;
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23 |
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24 | private readonly int _hashCode;
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25 |
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26 | public ExecExpandExpression(params Expression[] state) : base(state) {
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27 | IsEmpty = State.Length == 0;
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28 |
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29 | Depth = CalcDepth();
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30 | _treeIndex = BuildTreeIndex();
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31 | _hashCode = HashExpressions();
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32 |
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33 | _stringValue = new Lazy<string>(BuildString, LazyThreadSafetyMode.ExecutionAndPublication);
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34 | }
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35 |
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36 | public ExecExpandExpression(IEnumerable<Expression> state) : this(state.ToArray()) {
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37 | // TODO: lazy evaluation of ToArray()
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38 | }
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39 |
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40 | #if DEBUG
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41 |
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42 | private static void CheckIfNested(int level, ExecExpandExpression target, ExecExpandExpression current,
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43 | IList<ExecExpandExpression> visited) {
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44 | if (visited.Any(x => ReferenceEquals(x, current)))
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45 | Debugger.Break();
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46 |
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47 | visited.Add(current);
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48 | if (level <= 0) {
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49 | // hirarchy depth > level
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50 | Debugger.Break();
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51 | return;
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52 | }
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53 |
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54 | for (var i = 0; i < current.State.Length; i++) {
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55 | if (current.State[i].GetType() != typeof(ExecExpandExpression))
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56 | continue;
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57 |
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58 | var subExpression = current.State[i] as ExecExpandExpression;
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59 |
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60 | if (ReferenceEquals(target, subExpression)) {
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61 | // Endless recursion dedected
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62 | Debugger.Break();
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63 | }
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64 |
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65 | CheckIfNested(level - 1, target, subExpression, visited);
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66 | }
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67 |
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68 | visited.RemoveAt(visited.Count - 1);
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69 | }
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70 |
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71 | #endif
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72 |
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73 | public IReadOnlyList<Expression> Expressions
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74 | {
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75 | get { return State; }
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76 | }
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77 |
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78 | public bool IsEmpty { get; private set; }
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79 |
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80 | /// <summary>
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81 | /// Returns the amount of elements in the whole tree
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82 | /// </summary>
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83 | /// <returns></returns>
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84 | public int TotalCount
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85 | {
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86 | get
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87 | {
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88 | return IsEmpty
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89 | ? 1
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90 | // + 1 because this is also counted
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91 | : _treeIndex[0] + 1;
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92 | }
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93 | }
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94 |
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95 | public override string ToString() {
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96 | return _stringValue.Value;
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97 | }
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98 |
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99 | private int HashExpressions() {
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100 | var hash = 19 * 31 + this.GetType().GetHashCode();
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101 |
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102 | for (var i = 0; i < this.State.Length; i++) {
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103 | hash = hash * 31 + this.State[i].GetHashCode();
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104 | }
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105 |
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106 | return hash;
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107 | }
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108 |
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109 | protected override int CalcHashCode() {
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110 | return _hashCode;
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111 | }
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112 |
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113 | public ExecExpandExpression Copy() {
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114 | // as the empty list is a static stateless expression, no copy required
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115 | return this == Empty || IsEmpty ? Empty : new ExecExpandExpression(State);
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116 | }
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117 |
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118 | public Expression[] CopyExpressions() {
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119 | var copy = new Expression[State.Length];
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120 | Array.Copy(State, copy, State.Length);
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121 |
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122 | return copy;
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123 | }
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124 |
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125 | public override void Eval(IPushGpInterpreter interpreter) {
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126 | interpreter.ExecStack.Push(State);
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127 | }
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128 |
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129 | private int CalcDepth() {
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130 | var subExpressions = State.Where(e => e.GetType() == typeof(ExecExpandExpression));
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131 | var depth = subExpressions.Any()
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132 | ? subExpressions.Select(e => e as ExecExpandExpression).Max(e => e.Depth) + 1
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133 | : 1;
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134 |
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135 | return depth;
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136 | }
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137 |
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138 | private string BuildString() {
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139 | // prevent stack overflow
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140 | if (this.TotalCount > 50)
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141 | return PrefixReduced + this.State.Length + PostfixReduced;
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142 |
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143 | var sb = new StringBuilder();
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144 |
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145 | sb.Append(Prefix);
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146 | for (var i = this.State.Length - 1; i >= 0; i--) sb.Append(this.State[i] + Delimiter);
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147 | sb.Append(Postfix);
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148 | return sb.ToString();
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149 | }
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150 |
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151 | private int[] BuildTreeIndex() {
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152 | var treeIndex = new int[State.Length];
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153 |
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154 | var next = 1;
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155 |
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156 | for (var i = State.Length - 1; i >= 0; i--) {
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157 | var subExpression = State[i];
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158 |
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159 | treeIndex[i] = next;
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160 |
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161 | if (subExpression.GetType() == typeof(ExecExpandExpression)) {
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162 | next += (subExpression as ExecExpandExpression).TotalCount;
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163 | } else {
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164 | next++;
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165 | }
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166 | }
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167 |
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168 | return treeIndex;
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169 | }
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170 |
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171 | /// <summary>
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172 | /// Returns the element with the given index whereby the tree is indexed in depth first manner
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173 | /// </summary>
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174 | /// <param name="index">The index of the required element</param>
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175 | /// <returns>The required element</returns>
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176 | public Expression GetFromTree(int index) {
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177 | return GetFromTree(index, (root, parent, child, childIndex, parentIndex) => child);
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178 | }
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179 |
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180 | /// <returns>The required element</returns>
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181 | public T GetFromTree<T>(int index,
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182 | Func<ExecExpandExpression, ExecExpandExpression, Expression, int, int, T> resolver) {
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183 | return GetFromTree(index, 0, null, resolver);
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184 | }
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185 |
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186 | private T GetFromTree<T>(int index, int parentIndex, ExecExpandExpression parent,
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187 | Func<ExecExpandExpression, ExecExpandExpression, Expression, int, int, T> resolver) {
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188 | if (index == 0) return resolver(parent, parent, this, 0, parentIndex);
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189 |
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190 | var min = State.Length - 1;
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191 | var max = 0;
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192 | var mid = (min + max) / 2;
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193 |
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194 | while ((max <= min) && (_treeIndex[mid] != index)) {
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195 | if (_treeIndex[mid] > index) max = mid + 1;
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196 | else min = mid - 1;
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197 |
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198 | mid = (min + max) / 2;
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199 | }
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200 |
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201 | return _treeIndex[mid] == index
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202 | ? resolver(parent, this, State[mid], mid, parentIndex)
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203 | : (State[mid + 1] as ExecExpandExpression).GetFromTree(index - _treeIndex[mid + 1], mid + 1,
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204 | this, resolver);
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205 | }
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206 | }
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207 |
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208 | /// <summary>
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209 | /// If the top item of the BOOLEAN stack is TRUE then this removes the second item on the EXEC stack, leaving the first
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210 | /// item to be executed. If it is false then it removes the first item, leaving the second to be executed. This is similar to
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211 | /// CODE.IF except that it operates on the EXEC stack. This acts as a NOOP unless there are at least two items on the EXEC stack and
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212 | /// one item on the BOOLEAN stack.
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213 | /// </summary>
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214 | public class ExecIfExpression : StatelessExpression {
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215 | public ExecIfExpression() : base("EXEC.IF") {
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216 | }
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217 |
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218 | public override void Eval(IPushGpInterpreter interpreter) {
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219 | // not enough arguments on stack
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220 | if ((interpreter.BooleanStack.Count == 0) || (interpreter.ExecStack.Count < 2)) return;
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221 |
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222 | var condition = interpreter.BooleanStack.Pop();
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223 |
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224 | if (condition) interpreter.ExecStack.RemoveAt(interpreter.ExecStack.Count - 2);
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225 | else interpreter.ExecStack.RemoveTop();
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226 | }
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227 | }
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228 |
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229 | /// <summary>
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230 | /// Inserts beneath the top item of the EXEC stack a new item of the form
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231 | /// "( EXEC.Y <TopItem> )".
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232 | /// </summary>
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233 | public class ExecYExpression : StatelessExpression {
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234 | public ExecYExpression() : base("EXEC.Y") {
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235 | }
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236 |
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237 | public override void Eval(IPushGpInterpreter interpreter) {
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238 | // not enough arguments on stack
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239 | if ((interpreter.ExecStack.Count == 0) || (interpreter.Configuration.MaxPointsInProgram < 2)) return;
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240 |
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241 | var top = interpreter.ExecStack.Top;
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242 | var result = new ExecExpandExpression(top, new ExecYExpression());
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243 |
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244 | interpreter.ExecStack.Insert(interpreter.ExecStack.Count - 1, result);
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245 | }
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246 | }
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247 |
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248 | /// <summary>
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249 | /// Removes the second item on the EXEC stack.
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250 | /// </summary>
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251 | public class ExecKExpression : StatelessExpression {
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252 | public ExecKExpression() : base("EXEC.K") {
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253 | }
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254 |
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255 | public override void Eval(IPushGpInterpreter interpreter) {
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256 | if (interpreter.ExecStack.Count < 2) return;
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257 |
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258 | var top = interpreter.ExecStack.Pop();
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259 | interpreter.ExecStack.SetTop(top);
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260 | }
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261 | }
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262 |
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263 | /// <summary>
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264 | /// Pops 3 items from the EXEC stack, which we will call A, B, and C
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265 | /// (with A being the first one popped). Then pushes a list containing B and C back onto the EXEC stack, followed by
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266 | /// another instance of C, followed by another instance of A.
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267 | /// </summary>
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268 | public class ExecSExpression : StatelessExpression {
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269 | public ExecSExpression() : base("EXEC.S") {
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270 | }
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271 |
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272 | public override void Eval(IPushGpInterpreter interpreter) {
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273 | if (interpreter.ExecStack.Count < 3) return;
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274 |
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275 | var expression = interpreter.ExecStack.Pop(2);
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276 | var a = expression[1];
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277 | var b = expression[0];
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278 | var c = interpreter.ExecStack.Top;
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279 |
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280 | var newTop = new ExecExpandExpression(c, b);
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281 |
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282 | interpreter.ExecStack.SetTop(newTop);
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283 | interpreter.ExecStack.Push(c, a);
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284 | }
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285 | }
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286 | } |
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