1 /*
2 * SAT4J: a SATisfiability library for Java Copyright (C) 2004-2006 Daniel Le Berre
3 *
4 * Based on the original minisat specification from:
5 *
6 * An extensible SAT solver. Niklas E?n and Niklas S?rensson. Proceedings of the
7 * Sixth International Conference on Theory and Applications of Satisfiability
8 * Testing, LNCS 2919, pp 502-518, 2003.
9 *
10 * This library is free software; you can redistribute it and/or modify it under
11 * the terms of the GNU Lesser General Public License as published by the Free
12 * Software Foundation; either version 2.1 of the License, or (at your option)
13 * any later version.
14 *
15 * This library is distributed in the hope that it will be useful, but WITHOUT
16 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
17 * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
18 * details.
19 *
20 * You should have received a copy of the GNU Lesser General Public License
21 * along with this library; if not, write to the Free Software Foundation, Inc.,
22 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
23 *
24 */
25
26 package org.sat4j.minisat.core;
27
28 import org.sat4j.specs.IVec;
29
30 /**
31 * That interface manages the solver's internal vocabulary. Everything related
32 * to variables and literals is available from here.
33 *
34 * For sake of efficiency, literals and variables are not object in SAT4J. They
35 * are represented by numbers. If the vocabulary contains n variables, then
36 * variables should be accessed by numbers from 1 to n and literals by numbers
37 * from 2 to 2*n+1.
38 *
39 * For a Dimacs variable v, the variable index in SAT4J is v, it's positive
40 * literal is 2*v (v << 1) and it's negative literal is 2*v+1 ((v<<1)^1).
41 * Note that one can easily access to the complementary literal of p by using
42 * bitwise operation ^.
43 *
44 * In SAT4J, literals are usualy denoted by p or q and variables by v or x.
45 *
46 * @author leberre
47 */
48 public interface ILits {
49
50 public static int UNDEFINED = -1;
51
52 public abstract void init(int nvar);
53
54 /**
55 * Translates a Dimacs literal into an internal representation literal.
56 *
57 * @param x
58 * the Dimacs literal (a non null integer).
59 * @return the literal in the internal representation.
60 */
61 public abstract int getFromPool(int x);
62
63 /**
64 * Returns true iff the variable is used in the set of constraints.
65 *
66 * @param x
67 * @return true iff the variable belongs to the formula.
68 */
69 boolean belongsToPool(int x);
70
71 public abstract void resetPool();
72
73 public abstract void ensurePool(int howmany);
74
75 public abstract void unassign(int lit);
76
77 public abstract void satisfies(int lit);
78
79 public abstract boolean isSatisfied(int lit);
80
81 public abstract boolean isFalsified(int lit);
82
83 public abstract boolean isUnassigned(int lit);
84
85 /**
86 * @param lit
87 * @return true iff the truth value of that literal is due to a unit
88 * propagation or a decision.
89 */
90 public abstract boolean isImplied(int lit);
91
92 /**
93 * to obtain the max id of the variable
94 *
95 * @return the maximum number of variables in the formula
96 */
97 public abstract int nVars();
98
99 /**
100 * to obtain the real number of variables appearing in the formula
101 *
102 * @return the number of variables used in the pool
103 */
104 int realnVars();
105
106 public abstract int not(int lit);
107
108 public abstract void reset(int lit);
109
110 public abstract int getLevel(int lit);
111
112 public abstract void setLevel(int lit, int l);
113
114 public abstract Constr getReason(int lit);
115
116 public abstract void setReason(int lit, Constr r);
117
118 public abstract IVec<Undoable> undos(int lit);
119
120 public abstract void watch(int lit, Propagatable c);
121
122 /**
123 * @param lit
124 * a literal
125 * @return the list of all the constraints that watch the negation of lit
126 */
127 public abstract IVec<Propagatable> watches(int lit);
128
129 public abstract String valueToString(int lit);
130 }