code: /*
   * This file is part of a Java port of the program ltl2dstar
   * (http://www.ltl2dstar.de/) for PRISM (http://www.prismmodelchecker.org/)
   * Copyright (C) 2005-2007 Joachim Klein <j.klein@ltl2dstar.de>
   * Copyright (c) 2007 Carlos Bederian
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as 
   *  published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  package jltl2dstar;
  
  import prism.PrismException;
  
  /**
   * Specialized UnionAcceptanceCalculator for RabinAcceptance, for calculating the acceptance in the union automaton.
   * This approach merges the acceptance signatures of the two states in the union tuple, the union is provided by
   * the semantics of the Rabin acceptance condition (There <i>exists</i> an acceptance pair ....)
   */
  public class UnionAcceptanceCalculator {
  
  	/** The acceptance condition of the first automaton. */
  	private RabinAcceptance _acc_1;
  	/** The acceptance condition of the second automaton. */
  	private RabinAcceptance _acc_2;
  
  	/** The size of the acceptance condition in the original automaton. */
  	private int _acc_size_1, _acc_size_2;
  
  	/**
  	 * Constructor. 
  	 * @param acc_1 The RabinAcceptance condition from automaton 1
  	 * @param acc_2 The RabinAcceptance condition from automaton 2
  	 */
  	public UnionAcceptanceCalculator(RabinAcceptance acc_1,	RabinAcceptance acc_2) throws PrismException {
  		_acc_1 = acc_1;
  		_acc_2  = acc_2;
  		_acc_size_1 = _acc_1.size();
  		_acc_size_2 = _acc_2.size();
  	}
  
  	/**
  	 * Prepares the acceptance condition in the result union automaton. If the two automata have k1 and k2 
  	 * acceptance pairs, this function allocates k1+k2 acceptance pairs in the result automaton.
  	 * @param acceptance_result The acceptance condition in the result automaton.
  	 */
  	public void prepareAcceptance(RabinAcceptance acceptance_result) {
  		acceptance_result.newAcceptancePairs(_acc_size_1+_acc_size_2);
  	}
  
  
  	/**
  	 * Calculate the acceptance signature for the union of two states.
  	 * @param da_state_1 index of the state in the first automaton
  	 * @param da_state_2 index of the state in the second automaton
  	 * @return A Rabin acceptance signature
  	 */
  	RabinSignature calculateAcceptance(int da_state_1, int da_state_2) {
  		RabinSignature signature = new RabinSignature(_acc_size_1 + _acc_size_2);
  
  		for (int i = 0; i < _acc_size_1; i++) {
  			if (_acc_1.isStateInAcceptance_L(i, da_state_1)) {
  				signature.setL(i, true);
  			}
  			if (_acc_1.isStateInAcceptance_U(i, da_state_1)) {
  				signature.setU(i, true);
  			}
  		}
  
  		for (int j=0; j < _acc_size_2; j++) {
  			if (_acc_2.isStateInAcceptance_L(j, da_state_2)) {
  				signature.setL(j + _acc_size_1, true);
  			}
  			if (_acc_2.isStateInAcceptance_U(j, da_state_2)) {
  				signature.setU(j + _acc_size_1, true);
  			}
  		}
  		return signature;
  	}
  }
  