clockwerk-opensim-stable – Blame information for rev 1
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1 | vero | 1 | /* |
2 | * Copyright (C) 2007-2008, Jeff Thompson |
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3 | * |
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4 | * All rights reserved. |
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5 | * |
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6 | * Redistribution and use in source and binary forms, with or without |
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7 | * modification, are permitted provided that the following conditions are met: |
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8 | * |
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9 | * * Redistributions of source code must retain the above copyright |
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10 | * notice, this list of conditions and the following disclaimer. |
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11 | * * Redistributions in binary form must reproduce the above copyright |
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12 | * notice, this list of conditions and the following disclaimer in the |
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13 | * documentation and/or other materials provided with the distribution. |
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14 | * * Neither the name of the copyright holder nor the names of its contributors |
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15 | * may be used to endorse or promote products derived from this software |
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16 | * without specific prior written permission. |
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17 | * |
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18 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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19 | * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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20 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
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21 | * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR |
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22 | * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, |
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23 | * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
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24 | * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR |
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25 | * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF |
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26 | * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING |
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27 | * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
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28 | * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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29 | */ |
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30 | |||
31 | using System; |
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32 | using System.Collections; |
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33 | using System.Collections.Generic; |
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34 | |||
35 | namespace OpenSim.Region.ScriptEngine.Shared.YieldProlog |
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36 | { |
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37 | public interface IUnifiable |
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38 | { |
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39 | IEnumerable<bool> unify(object arg); |
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40 | void addUniqueVariables(List<Variable> variableSet); |
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41 | object makeCopy(Variable.CopyStore copyStore); |
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42 | bool termEqual(object term); |
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43 | bool ground(); |
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44 | } |
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45 | |||
46 | /// <summary> |
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47 | /// A Variable is passed to a function so that it can be unified with |
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48 | /// value or another Variable. See getValue and unify for details. |
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49 | /// </summary> |
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50 | public class Variable : IUnifiable |
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51 | { |
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52 | // Use _isBound separate from _value so that it can be bound to any value, |
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53 | // including null. |
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54 | private bool _isBound = false; |
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55 | private object _value; |
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56 | |||
57 | /// <summary> |
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58 | /// If this Variable is unbound, then just return this Variable. |
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59 | /// Otherwise, if this has been bound to a value with unify, return the value. |
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60 | /// If the bound value is another Variable, this follows the "variable chain" |
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61 | /// to the end and returns the final value, or the final Variable if it is unbound. |
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62 | /// For more details, see http://yieldprolog.sourceforge.net/tutorial1.html |
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63 | /// </summary> |
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64 | /// <returns></returns> |
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65 | public object getValue() |
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66 | { |
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67 | if (!_isBound) |
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68 | return this; |
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69 | |||
70 | object result = _value; |
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71 | while (result is Variable) |
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72 | { |
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73 | if (!((Variable)result)._isBound) |
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74 | return result; |
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75 | |||
76 | // Keep following the Variable chain. |
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77 | result = ((Variable)result)._value; |
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78 | } |
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79 | |||
80 | return result; |
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81 | } |
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82 | |||
83 | /// <summary> |
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84 | /// If this Variable is bound, then just call YP.unify to unify this with arg. |
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85 | /// (Note that if arg is an unbound Variable, then YP.unify will bind it to |
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86 | /// this Variable's value.) |
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87 | /// Otherwise, bind this Variable to YP.getValue(arg) and yield once. After the |
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88 | /// yield, return this Variable to the unbound state. |
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89 | /// For more details, see http://yieldprolog.sourceforge.net/tutorial1.html |
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90 | /// </summary> |
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91 | /// <param name="arg"></param> |
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92 | /// <returns></returns> |
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93 | public IEnumerable<bool> unify(object arg) |
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94 | { |
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95 | if (!_isBound) |
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96 | { |
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97 | _value = YP.getValue(arg); |
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98 | if (_value == this) |
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99 | // We are unifying this unbound variable with itself, so leave it unbound. |
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100 | yield return false; |
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101 | else |
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102 | { |
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103 | _isBound = true; |
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104 | try |
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105 | { |
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106 | yield return false; |
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107 | } |
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108 | finally |
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109 | { |
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110 | // Remove the binding. |
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111 | _isBound = false; |
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112 | } |
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113 | } |
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114 | } |
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115 | else |
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116 | { |
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117 | // disable warning on l1, don't see how we can |
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118 | // code this differently |
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119 | #pragma warning disable 0168, 0219 |
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120 | foreach (bool l1 in YP.unify(this, arg)) |
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121 | yield return false; |
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122 | #pragma warning restore 0168, 0219 |
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123 | } |
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124 | } |
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125 | |||
126 | public override string ToString() |
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127 | { |
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128 | object value = getValue(); |
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129 | if (value == this) |
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130 | return "_Variable"; |
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131 | else |
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132 | return getValue().ToString(); |
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133 | } |
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134 | |||
135 | /// <summary> |
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136 | /// If bound, call YP.addUniqueVariables on the value. Otherwise, if this unbound |
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137 | /// variable is not already in variableSet, add it. |
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138 | /// </summary> |
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139 | /// <param name="variableSet"></param> |
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140 | public void addUniqueVariables(List<Variable> variableSet) |
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141 | { |
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142 | if (_isBound) |
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143 | YP.addUniqueVariables(getValue(), variableSet); |
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144 | else |
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145 | { |
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146 | if (variableSet.IndexOf(this) < 0) |
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147 | variableSet.Add(this); |
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148 | } |
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149 | } |
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150 | |||
151 | /// <summary> |
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152 | /// If bound, return YP.makeCopy for the value, else return copyStore.getCopy(this). |
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153 | /// However, if copyStore is null, just return this. |
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154 | /// </summary> |
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155 | /// <param name="copyStore"></param> |
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156 | /// <returns></returns> |
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157 | public object makeCopy(Variable.CopyStore copyStore) |
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158 | { |
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159 | if (_isBound) |
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160 | return YP.makeCopy(getValue(), copyStore); |
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161 | else |
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162 | return copyStore == null ? this : copyStore.getCopy(this); |
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163 | } |
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164 | |||
165 | public bool termEqual(object term) |
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166 | { |
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167 | if (_isBound) |
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168 | return YP.termEqual(getValue(), term); |
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169 | else |
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170 | return this == YP.getValue(term); |
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171 | } |
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172 | |||
173 | public bool ground() |
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174 | { |
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175 | if (_isBound) |
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176 | // This is usually called by YP.ground which already did getValue, so this |
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177 | // should never be reached, but check anyway. |
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178 | return YP.ground(getValue()); |
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179 | else |
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180 | return false; |
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181 | } |
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182 | |||
183 | /// <summary> |
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184 | /// A CopyStore is used by makeCopy to track which Variable objects have |
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185 | /// been copied. |
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186 | /// </summary> |
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187 | public class CopyStore |
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188 | { |
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189 | private List<Variable> _inVariableSet = new List<Variable>(); |
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190 | private List<Variable> _outVariableSet = new List<Variable>(); |
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191 | |||
192 | /// <summary> |
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193 | /// If inVariable has already been copied, return its copy. Otherwise, |
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194 | /// return a fresh Variable associated with inVariable. |
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195 | /// </summary> |
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196 | /// <param name="inVariable"></param> |
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197 | /// <returns></returns> |
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198 | public Variable getCopy(Variable inVariable) |
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199 | { |
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200 | int index = _inVariableSet.IndexOf(inVariable); |
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201 | if (index >= 0) |
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202 | return _outVariableSet[index]; |
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203 | else |
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204 | { |
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205 | Variable outVariable = new Variable(); |
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206 | _inVariableSet.Add(inVariable); |
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207 | _outVariableSet.Add(outVariable); |
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208 | return outVariable; |
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209 | } |
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210 | } |
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211 | |||
212 | /// <summary> |
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213 | /// Return the number of unique variables that have been copied. |
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214 | /// </summary> |
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215 | /// <returns></returns> |
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216 | public int getNUniqueVariables() |
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217 | { |
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218 | return _inVariableSet.Count; |
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219 | } |
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220 | } |
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221 | } |
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222 | } |