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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   * Based on the original MiniSat specification from:
20   * 
21   * An extensible SAT solver. Niklas Een and Niklas Sorensson. Proceedings of the
22   * Sixth International Conference on Theory and Applications of Satisfiability
23   * Testing, LNCS 2919, pp 502-518, 2003.
24   *
25   * See www.minisat.se for the original solver in C++.
26   * 
27   *******************************************************************************/
28  package org.sat4j.specs;
29  
30  /**
31   * The most general abstraction for handling a constraint.
32   * 
33   * @author leberre
34   * 
35   */
36  public interface IConstr {
37  
38  	/**
39  	 * @return true iff the clause was learnt during the search
40  	 */
41  	boolean learnt();
42  
43  	/**
44  	 * @return the number of literals in the constraint.
45  	 */
46  	int size();
47  
48  	/**
49  	 * returns the ith literal in the constraint
50  	 * 
51  	 * @param i
52  	 *            the index of the literal
53  	 * @return a literal
54  	 */
55  	int get(int i);
56  
57  	/**
58  	 * To obtain the activity of the constraint.
59  	 * 
60  	 * @return the activity of the clause.
61  	 * @since 2.1
62  	 */
63  	double getActivity();
64  
65  	/**
66  	 * Partition constraints into the ones that can only be found once on the
67  	 * trail (e.g. clauses) and the ones that can be found several times (e.g.
68  	 * cardinality constraints and pseudo-boolean constraints).
69  	 * 
70  	 * @return true if the constraint can be used several times as a reason to
71  	 *         propagate a literal.
72  	 * @since 2.3.1
73  	 */
74  	boolean canBePropagatedMultipleTimes();
75  }