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