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172
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1 using Implab;
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2 using System;
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3 using System.Collections.Generic;
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4 using System.Diagnostics;
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5 using System.Linq;
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6
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7 namespace Implab.Automaton.RegularExpressions {
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8 /// <summary>
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9 /// Используется для построения ДКА по регулярному выражению, сначала обходит
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10 /// регулярное выражение и вычисляет followpos, затем используется метод
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11 /// <see cref="BuildDFA(IDFADefinition)"/> для построения автомата.
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12 /// </summary>
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178
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13 public class RegularExpressionVisitor : IVisitor {
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172
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14 int m_idx;
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177
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15 Token m_root;
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172
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16 HashSet<int> m_firstpos;
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17 HashSet<int> m_lastpos;
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18
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19 readonly Dictionary<int, HashSet<int>> m_followpos = new Dictionary<int, HashSet<int>>();
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20 readonly Dictionary<int, int> m_indexes = new Dictionary<int, int>();
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177
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21 readonly HashSet<int> m_ends = new HashSet<int>();
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172
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22
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178
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23 readonly IDFATableBuilder m_builder;
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24 readonly IAlphabetBuilder<HashSet<int>> m_states = new MapAlphabet<HashSet<int>>(
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25 false,
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26 new CustomEqualityComparer<HashSet<int>>(
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27 (x, y) => x.SetEquals(y),
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28 x => x.Sum(n => n.GetHashCode())
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29 )
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30 );
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31
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32 public RegularExpressionVisitor(IDFATableBuilder builder) {
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33 Safe.ArgumentNotNull(builder, "builder");
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34
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35 m_builder = builder;
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172
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36 }
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37
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178
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38 HashSet<int> Followpos(int pos) {
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172
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39 HashSet<int> set;
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40 return m_followpos.TryGetValue(pos, out set) ? set : m_followpos[pos] = new HashSet<int>();
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41 }
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42
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43 bool Nullable(object n) {
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177
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44 if (n is EmptyToken || n is StarToken)
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172
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45 return true;
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177
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46 var altToken = n as AltToken;
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172
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47 if (altToken != null)
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48 return Nullable(altToken.Left) || Nullable(altToken.Right);
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177
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49 var catToken = n as CatToken;
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172
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50 if (catToken != null)
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51 return Nullable(catToken.Left) && Nullable(catToken.Right);
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52 return false;
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53 }
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54
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178
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55 protected int Index {
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56 get { return m_idx; }
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57 }
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172
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58
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177
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59 public void Visit(AltToken token) {
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172
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60 if (m_root == null)
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61 m_root = token;
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62 var firtspos = new HashSet<int>();
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63 var lastpos = new HashSet<int>();
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64
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65 token.Left.Accept(this);
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66 firtspos.UnionWith(m_firstpos);
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67 lastpos.UnionWith(m_lastpos);
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68
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69 token.Right.Accept(this);
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70 firtspos.UnionWith(m_firstpos);
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71 lastpos.UnionWith(m_lastpos);
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72
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73 m_firstpos = firtspos;
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74 m_lastpos = lastpos;
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75 }
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76
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177
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77 public void Visit(StarToken token) {
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172
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78 if (m_root == null)
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79 m_root = token;
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80 token.Token.Accept(this);
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81
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82 foreach (var i in m_lastpos)
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83 Followpos(i).UnionWith(m_firstpos);
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84 }
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85
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177
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86 public void Visit(CatToken token) {
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172
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87 if (m_root == null)
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88 m_root = token;
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89
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90 var firtspos = new HashSet<int>();
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91 var lastpos = new HashSet<int>();
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92 token.Left.Accept(this);
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93 firtspos.UnionWith(m_firstpos);
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94 var leftLastpos = m_lastpos;
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95
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96 token.Right.Accept(this);
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97 lastpos.UnionWith(m_lastpos);
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98 var rightFirstpos = m_firstpos;
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99
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100 if (Nullable(token.Left))
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101 firtspos.UnionWith(rightFirstpos);
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102
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103 if (Nullable(token.Right))
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104 lastpos.UnionWith(leftLastpos);
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105
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106 m_firstpos = firtspos;
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107 m_lastpos = lastpos;
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108
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109 foreach (var i in leftLastpos)
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110 Followpos(i).UnionWith(rightFirstpos);
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111
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112 }
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113
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177
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114 public void Visit(EmptyToken token) {
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172
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115 if (m_root == null)
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116 m_root = token;
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117 }
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118
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177
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119 public void Visit(SymbolToken token) {
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172
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120 if (m_root == null)
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121 m_root = token;
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122 m_idx++;
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123 m_indexes[m_idx] = token.Value;
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124 m_firstpos = new HashSet<int>(new[] { m_idx });
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125 m_lastpos = new HashSet<int>(new[] { m_idx });
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126 }
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127
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178
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128 public virtual void Visit(EndToken token) {
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172
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129 if (m_root == null)
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130 m_root = token;
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131 m_idx++;
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178
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132 m_indexes[m_idx] = AutomatonConst.UNCLASSIFIED_INPUT;
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177
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133 m_firstpos = new HashSet<int>(new[] { m_idx });
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134 m_lastpos = new HashSet<int>(new[] { m_idx });
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135 Followpos(m_idx);
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136 m_ends.Add(m_idx);
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172
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137 }
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138
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178
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139 public void BuildDFA() {
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140 AddState(m_firstpos);
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141 SetInitialState(m_firstpos);
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172
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142
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178
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143 if(IsFinal(m_firstpos))
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144 MarkFinalState(m_firstpos);
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172
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145
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146 var inputMax = m_indexes.Values.Max();
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147 var queue = new Queue<HashSet<int>>();
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148
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149 queue.Enqueue(m_firstpos);
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150
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151 while (queue.Count > 0) {
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178
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152 var s1 = queue.Dequeue();
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172
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153
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154 for (int a = 0; a <= inputMax; a++) {
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178
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155 var s2 = new HashSet<int>();
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156 foreach (var p in s1) {
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172
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157 if (m_indexes[p] == a) {
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178
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158 s2.UnionWith(Followpos(p));
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172
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159 }
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160 }
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178
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161 if (s2.Count > 0) {
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162 if (!HasState(s2)) {
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163 AddState(s2);
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164 if (IsFinal(s2))
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165 MarkFinalState(s2);
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166
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167 queue.Enqueue(s2);
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168 }
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172
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169
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178
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170 DefineTransition(s1, s2, a);
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172
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171 }
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178
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172
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172
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173 }
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174 }
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175 }
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176
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178
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177 protected bool HasState(HashSet<int> state) {
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178 return m_states.Contains(state);
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179 }
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180
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181 protected void AddState(HashSet<int> state) {
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182 Debug.Assert(!HasState(state));
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183
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184 m_states.DefineSymbol(state);
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185 }
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186
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187 protected int Translate(HashSet<int> state) {
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188 Debug.Assert(HasState(state));
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189
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190 return m_states.Translate(state);
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191 }
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192
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193 protected virtual void SetInitialState(HashSet<int> state) {
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194 m_builder.SetInitialState(Translate(state));
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195 }
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196
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197 protected virtual void MarkFinalState(HashSet<int> state) {
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198 m_builder.MarkFinalState(Translate(state));
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199 }
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200
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201 protected virtual void DefineTransition(HashSet<int> s1, HashSet<int> s2, int ch) {
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202
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203 m_builder.Add(new AutomatonTransition(Translate(s1), Translate(s2), ch));
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204 }
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205
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177
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206 bool IsFinal(IEnumerable<int> state) {
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207 Debug.Assert(state != null);
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208 return state.Any(m_ends.Contains);
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209 }
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210
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172
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211 }
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212 }
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