/*******************************************************************************
    * SAT4J: a SATisfiability library for Java Copyright (C) 2004-2008 Daniel Le Berre
    *
    * All rights reserved. This program and the accompanying materials
    * are made available under the terms of the Eclipse Public License v1.0
    * which accompanies this distribution, and is available at
    * http://www.eclipse.org/legal/epl-v10.html
    *
    * Alternatively, the contents of this file may be used under the terms of
   * either the GNU Lesser General Public License Version 2.1 or later (the
   * "LGPL"), in which case the provisions of the LGPL are applicable instead
   * of those above. If you wish to allow use of your version of this file only
   * under the terms of the LGPL, and not to allow others to use your version of
   * this file under the terms of the EPL, indicate your decision by deleting
   * the provisions above and replace them with the notice and other provisions
   * required by the LGPL. If you do not delete the provisions above, a recipient
   * may use your version of this file under the terms of the EPL or the LGPL.
   * 
   * Based on the original MiniSat specification from:
   * 
   * An extensible SAT solver. Niklas Een and Niklas Sorensson. Proceedings of the
   * Sixth International Conference on Theory and Applications of Satisfiability
   * Testing, LNCS 2919, pp 502-518, 2003.
   *
   * See www.minisat.se for the original solver in C++.
   * 
   *******************************************************************************/
  package org.sat4j.minisat.constraints.cnf;
  
  import org.sat4j.core.LiteralsUtils;
  import org.sat4j.minisat.core.Constr;
  import org.sat4j.minisat.core.ILits;
  import org.sat4j.minisat.core.UnitPropagationListener;
  import org.sat4j.specs.IVecInt;
  
  /**
   * 
   * @author daniel
   * @since 2.1
   */
  public class UnitClause implements Constr {
  
  	protected final int literal;
  
  	public UnitClause(int value) {
  		literal = value;
  	}
  
  	public void assertConstraint(UnitPropagationListener s) {
  		s.enqueue(literal, this);
  	}
  
  	public void calcReason(int p, IVecInt outReason) {
  		if (p == ILits.UNDEFINED)
  			outReason.push(LiteralsUtils.neg(p));
  	}
  
  	public double getActivity() {
  		throw new UnsupportedOperationException();
  	}
  
  	public void incActivity(double claInc) {
  		// silent to prevent problems with xplain trick.
  	}
  
  	public boolean locked() {
  		throw new UnsupportedOperationException();
  	}
  
  	public void register() {
  		throw new UnsupportedOperationException();
  	}
  
  	public void remove(UnitPropagationListener upl) {
  		upl.unset(literal);
  	}
  
  	public void rescaleBy(double d) {
  		throw new UnsupportedOperationException();
  	}
  
  	public void setLearnt() {
  		throw new UnsupportedOperationException();
  	}
  
  	public boolean simplify() {
  		return false;
  	}
  
  	public boolean propagate(UnitPropagationListener s, int p) {
  		throw new UnsupportedOperationException();
  	}
  
  	public int get(int i) {
  		if (i > 0)
  			throw new IllegalArgumentException();
  		return literal;
  	}
  
 	public boolean learnt() {
 		return false;
 	}
 
 	public int size() {
 		return 1;
 	}
 
 	public void forwardActivity(double claInc) {
 		// silent to prevent problems with xplain trick.
 	}
 
 	@Override
 	public String toString() {
 		return Lits.toString(literal);
 	}
 
 	public boolean canBePropagatedMultipleTimes() {
 		return false;
 	}
 }