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1 eva 1 /*
2 * Copyright (C) 2007-2008, Jeff Thompson
3 *
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions are met:
8 *
9 * * Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * * Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * * Neither the name of the copyright holder nor the names of its contributors
15 * may be used to endorse or promote products derived from this software
16 * without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
22 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
23 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
24 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
25 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
26 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
27 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
28 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30  
31 using System;
32 using System.Collections.Generic;
33  
34 namespace OpenSim.Region.ScriptEngine.Shared.YieldProlog
35 {
36 public class Functor : IUnifiable
37 {
38 public readonly Atom _name;
39 public readonly object[] _args;
40  
41 public Functor(Atom name, object[] args)
42 {
43 if (args.Length <= 3)
44 {
45 if (args.Length == 0)
46 throw new Exception("For arity 0 functor, just use name as an Atom");
47 else if (args.Length == 1)
48 throw new Exception("For arity 1 functor, use Functor1");
49 else if (args.Length == 2)
50 throw new Exception("For arity 2 functor, use Functor2");
51 else if (args.Length == 3)
52 throw new Exception("For arity 3 functor, use Functor3");
53 else
54 // (This shouldn't happen, but include it for completeness.
55 throw new Exception("Cannot create a Functor of arity " + args.Length);
56 }
57  
58 _name = name;
59 _args = args;
60 }
61  
62 public Functor(string name, object[] args)
63 : this(Atom.a(name), args)
64 {
65 }
66  
67 /// <summary>
68 /// Return an Atom, Functor1, Functor2, Functor3 or Functor depending on the
69 /// length of args.
70 /// Note that this is different than the Functor constructor which requires
71 /// the length of args to be greater than 3.
72 /// </summary>
73 /// <param name="name"></param>
74 /// <param name="args"></param>
75 /// <returns></returns>
76 public static object make(Atom name, object[] args)
77 {
78 if (args.Length <= 0)
79 return name;
80 else if (args.Length == 1)
81 return new Functor1(name, args[0]);
82 else if (args.Length == 2)
83 return new Functor2(name, args[0], args[1]);
84 else if (args.Length == 3)
85 return new Functor3(name, args[0], args[1], args[2]);
86 else
87 return new Functor(name, args);
88 }
89  
90 /// <summary>
91 /// Call the main make, first converting name to an Atom.
92 /// </summary>
93 /// <param name="name"></param>
94 /// <param name="args"></param>
95 /// <returns></returns>
96 public static object make(string name, object[] args)
97 {
98 return make(Atom.a(name), args);
99 }
100  
101 /// <summary>
102 /// If arg is another Functor, then succeed (yield once) if this and arg have the
103 /// same name and all functor args unify, otherwise fail (don't yield).
104 /// If arg is a Variable, then call its unify to unify with this.
105 /// Otherwise fail (don't yield).
106 /// </summary>
107 /// <param name="arg"></param>
108 /// <returns></returns>
109 public IEnumerable<bool> unify(object arg)
110 {
111 arg = YP.getValue(arg);
112 if (arg is Functor)
113 {
114 Functor argFunctor = (Functor)arg;
115 if (_name.Equals(argFunctor._name))
116 return YP.unifyArrays(_args, argFunctor._args);
117 else
118 return YP.fail();
119 }
120 else if (arg is Variable)
121 return ((Variable)arg).unify(this);
122 else
123 return YP.fail();
124 }
125  
126 public override string ToString()
127 {
128 string result = _name + "(" + YP.getValue(_args[0]);
129 for (int i = 1; i < _args.Length; ++i)
130 result += ", " + YP.getValue(_args[i]);
131 result += ")";
132 return result;
133 }
134  
135 public bool termEqual(object term)
136 {
137 term = YP.getValue(term);
138 if (term is Functor)
139 {
140 Functor termFunctor = (Functor)term;
141 if (_name.Equals(termFunctor._name) && _args.Length == termFunctor._args.Length)
142 {
143 for (int i = 0; i < _args.Length; ++i)
144 {
145 if (!YP.termEqual(_args[i], termFunctor._args[i]))
146 return false;
147 }
148 return true;
149 }
150 }
151 return false;
152 }
153  
154 public bool lessThan(Functor functor)
155 {
156 // Do the equal check first since it is faster.
157 if (!_name.Equals(functor._name))
158 return _name.lessThan(functor._name);
159  
160 if (_args.Length != functor._args.Length)
161 return _args.Length < functor._args.Length;
162  
163 for (int i = 0; i < _args.Length; ++i)
164 {
165 if (!YP.termEqual(_args[i], functor._args[i]))
166 return YP.termLessThan(_args[i], functor._args[i]);
167 }
168  
169 return false;
170 }
171  
172 public bool ground()
173 {
174 for (int i = 0; i < _args.Length; ++i)
175 {
176 if (!YP.ground(_args[i]))
177 return false;
178 }
179 return true;
180 }
181  
182 public void addUniqueVariables(List<Variable> variableSet)
183 {
184 for (int i = 0; i < _args.Length; ++i)
185 YP.addUniqueVariables(_args[i], variableSet);
186 }
187  
188 public object makeCopy(Variable.CopyStore copyStore)
189 {
190 object[] argsCopy = new object[_args.Length];
191 for (int i = 0; i < _args.Length; ++i)
192 argsCopy[i] = YP.makeCopy(_args[i], copyStore);
193 return new Functor(_name, argsCopy);
194 }
195 }
196 }