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 }