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1   /*******************************************************************************
2   * SAT4J: a SATisfiability library for Java Copyright (C) 2004-2008 Daniel Le Berre
3   *
4   * All rights reserved. This program and the accompanying materials
5   * are made available under the terms of the Eclipse Public License v1.0
6   * which accompanies this distribution, and is available at
7   * http://www.eclipse.org/legal/epl-v10.html
8   *
9   * Alternatively, the contents of this file may be used under the terms of
10  * either the GNU Lesser General Public License Version 2.1 or later (the
11  * "LGPL"), in which case the provisions of the LGPL are applicable instead
12  * of those above. If you wish to allow use of your version of this file only
13  * under the terms of the LGPL, and not to allow others to use your version of
14  * this file under the terms of the EPL, indicate your decision by deleting
15  * the provisions above and replace them with the notice and other provisions
16  * required by the LGPL. If you do not delete the provisions above, a recipient
17  * may use your version of this file under the terms of the EPL or the LGPL.
18  *******************************************************************************/
19  package org.sat4j.csp;
20  
21  import java.io.FileNotFoundException;
22  import java.io.IOException;
23  import java.io.InputStreamReader;
24  import java.net.URL;
25  import java.util.HashMap;
26  import java.util.Map;
27  
28  import org.mozilla.javascript.Context;
29  import org.mozilla.javascript.Script;
30  import org.mozilla.javascript.Scriptable;
31  import org.sat4j.core.Vec;
32  import org.sat4j.csp.encodings.BinarySupportEncoding;
33  import org.sat4j.csp.encodings.DirectEncoding;
34  import org.sat4j.specs.ContradictionException;
35  import org.sat4j.specs.ISolver;
36  import org.sat4j.specs.IVec;
37  
38  /**
39   * A predicate is a formula given in intension.
40   * 
41   * @author daniel
42   */
43  public class Predicate implements Clausifiable {
44  
45      private String expr;
46  
47      private Encoding encoding;
48  
49      private final IVec<String> variables = new Vec<String>();
50  
51      private static Context cx;
52  
53      private static Scriptable scope;
54  
55      static {
56          cx = Context.enter(); 
57          scope = cx.initStandardObjects();
58          try {
59              URL url = Predicate.class.getResource("predefinedfunctions.js");
60              cx.evaluateReader(scope, new InputStreamReader(url.openStream()),
61                      "predefinedfunctions.js", 1, null);
62  
63          } catch (FileNotFoundException e) {
64              e.printStackTrace();
65          } catch (IOException e) {
66              e.printStackTrace();
67          }
68      }
69  
70      public Predicate() {
71      }
72  
73      public void setExpression(String expr) {
74          this.expr = expr.replaceAll("if\\(", "ite(");
75      }
76  
77      public void addVariable(String name) {
78          variables.push(name);
79      }
80  
81      private boolean evaluate(int[] values) {
82          assert values.length == variables.size();
83          for (int i = 0; i < variables.size(); i++) {
84              scope.put(variables.get(i), scope, values[i]);
85          }
86          Object result = myscript.exec(cx, scope);
87          return Context.toBoolean(result);
88      }
89  
90      public void toClause(ISolver solver, IVec<Var> vscope, IVec<Evaluable> vars)
91              throws ContradictionException {
92          if (myscript == null) {
93              myscript = cx.compileString(expr, "rhino.log", 1, null);
94          }
95          if (vscope.size() == 2) {
96              encoding = BinarySupportEncoding.instance();
97          } else {
98              encoding = DirectEncoding.instance();
99          }
100         encoding.onInit(solver, vscope);
101         int[] tuple = new int[vars.size()];
102         valuemapping.clear();
103         find(tuple, 0, vscope, vars, solver);
104         encoding.onFinish(solver, vscope);
105     }
106 
107     private final Map<Evaluable, Integer> valuemapping = new HashMap<Evaluable, Integer>();
108 
109     private Script myscript;
110 
111     private void find(int[] tuple, int n, IVec<Var> theScope,
112             IVec<Evaluable> vars, ISolver solver) throws ContradictionException {
113         if (valuemapping.size() == theScope.size()) {
114             for (int i = 0; i < tuple.length; i++) {
115                 Evaluable ev = vars.get(i);
116                 Integer value = valuemapping.get(ev);
117                 if (value == null) {
118                     tuple[i] = ev.domain().get(0);
119                 } else {
120                     tuple[i] = value;
121                 }
122             }
123             if (evaluate(tuple)) {
124                 encoding.onSupport(solver, theScope, valuemapping);
125             } else {
126                 encoding.onNogood(solver, theScope, valuemapping);
127             }
128         } else {
129             Var var = theScope.get(n);
130             Domain domain = var.domain();
131             for (int i = 0; i < domain.size(); i++) {
132                 valuemapping.put(var, domain.get(i));
133                 find(tuple, n + 1, theScope, vars, solver);
134             }
135             valuemapping.remove(var);
136         }
137     }
138 }