code: //==============================================================================
  //
  //Copyright (c) 2016-
  //Authors:
  //	* Joachim Klein <klein@tcs.inf.tu-dresden.de> (TU Dresden)
  //	* Dave Parker <d.a.parker@cs.bham.ac.uk> (University of Birmingham/Oxford)
  //
  //------------------------------------------------------------------------------
  //
  //This file is part of PRISM.
  //
  //PRISM is free software; you can redistribute it and/or modify
  //it under the terms of the GNU General Public License as published by
  //the Free Software Foundation; either version 2 of the License, or
  //(at your option) any later version.
  //
  //PRISM 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 PRISM; if not, write to the Free Software Foundation,
  //Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  //
  //==============================================================================
  
  package acceptance;
  
  import common.IterableBitSet;
  import jdd.JDD;
  import jdd.JDDNode;
  import jdd.JDDVars;
  import prism.PrismNotSupportedException;
  
  /**
   * A Büchi acceptance condition (based on JDD state sets).
   * The acceptance is defined via a set of "accepting" states
   * (sometimes also called final states) and is accepting if
   *  "infinitely often an accepting state is visited"
   */
  public class AcceptanceBuchiDD implements AcceptanceOmegaDD
  {
  	/** The accepting states */
  	private JDDNode acceptingStates;
  
  	/**
  	 * Constructor, set acceptingStates.
  	 * Becomes owner of the references of acceptingStates.
  	 */
  	public AcceptanceBuchiDD(JDDNode acceptingStates)
  	{
  		this.acceptingStates = acceptingStates;
  	}
  	
  	/**
  	 * Constructor, from a BitSet-based AcceptanceBuchi.
  	 *
  	 * @param acceptance the BitSet-based acceptance condition
  	 * @param ddRowVars JDDVars of the row variables corresponding to the bits in the bit set
  	 */
  	public AcceptanceBuchiDD(AcceptanceBuchi acceptance, JDDVars ddRowVars)
  	{
  		acceptingStates = JDD.Constant(0);
  		// get BDD based on the acceptingState bit set
  		for (int i : IterableBitSet.getSetBits(acceptance.getAcceptingStates())) {
  			acceptingStates = JDD.SetVectorElement(acceptingStates, ddRowVars, i, 1.0);
  		}
  	}
  
  	/** Get a referenced copy of the state set of the accepting states.
  	 * <br>[ REFS: <i>result</i>, DEREFS: <i>none</i> ]
  	 */
  	public JDDNode getAcceptingStates()
  	{
  		JDD.Ref(acceptingStates);
  		return acceptingStates;
  	}
  
  	/**
  	 * Set the accepting states.
  	 * Becomes owner of the reference to acceptingStates.
  	 */
  	public void setAcceptingStates(JDDNode acceptingStates)
  	{
  		clear();
  		this.acceptingStates = acceptingStates;
  	}
  
  	@Override
  	public boolean isBSCCAccepting(JDDNode bscc_states)
  	{
  		return JDD.AreIntersecting(acceptingStates, bscc_states);
  	}
  
  	@Override
  	public AcceptanceBuchiDD clone()
  	{
  		return new AcceptanceBuchiDD(acceptingStates.copy());
  	}
  
  	@Override
  	public void intersect(JDDNode restrict)
  	{
  		acceptingStates = JDD.And(acceptingStates, restrict.copy());
  	}
  
  	@Override
  	public String getSizeStatistics()
  	{
  		return "one set of accepting states";
  	}
  
  	@Override
  	public AcceptanceType getType()
  	{
  		return AcceptanceType.BUCHI;
  	}
  
  	/**
  	 * Get the Streett acceptance condition that is the equivalent of this Buchi condition.
  	 */
  	public AcceptanceStreettDD toStreett()
  	{
  		AcceptanceStreettDD streett = new AcceptanceStreettDD();
  		streett.add(new AcceptanceStreettDD.StreettPairDD(JDD.Constant(1), acceptingStates.copy()));
  		return streett;
  	}
  
  	@Override
  	public AcceptanceOmegaDD complement(AcceptanceType... allowedAcceptance) throws PrismNotSupportedException
  	{
  		if (AcceptanceType.contains(allowedAcceptance, AcceptanceType.RABIN)) {
  			return complementToRabin();
  		} else if (AcceptanceType.contains(allowedAcceptance, AcceptanceType.STREETT)) {
  			return complementToStreett();
  		} else if (AcceptanceType.contains(allowedAcceptance, AcceptanceType.GENERIC)) {
  			return complementToGeneric();
  		}
  		throw new PrismNotSupportedException("Can not complement " + getType() + " acceptance to a supported acceptance type");
  	}
  
  	/**
  	 * Get a Rabin acceptance condition that is the complement of this condition, i.e.,
  	 * any word that is accepted by this condition is rejected by the returned Rabin condition.
  	 *
  	 * @return the complement Rabin acceptance condition
  	 */
  	public AcceptanceRabinDD complementToRabin()
  	{
  		AcceptanceRabinDD rabin = new AcceptanceRabinDD();
  		rabin.add(new AcceptanceRabinDD.RabinPairDD(acceptingStates.copy(), JDD.Constant(1)));
  		return rabin;
  	}
  
  	/**
  	 * Get a Streett acceptance condition that is the complement of this condition, i.e.,
  	 * any word that is accepted by this condition is rejected by the returned Streett condition.
  	 * <br>
  	 * Relies on the fact that once the goal states have been reached, all subsequent states
  	 * are goal states.
  	 *
  	 * @return the complement Streett acceptance condition
  	 */
  	public AcceptanceStreettDD complementToStreett()
  	{
  		AcceptanceStreettDD streett = new AcceptanceStreettDD();
  		streett.add(new AcceptanceStreettDD.StreettPairDD(acceptingStates.copy(), JDD.Constant(0)));
  		return streett;
  	}
  
  	@Override
  	public AcceptanceGenericDD toAcceptanceGeneric()
  	{
  		return new AcceptanceGenericDD(AcceptanceGeneric.ElementType.INF, acceptingStates.copy());
  	}
  
  	@Override
  	@Deprecated
  	public String getTypeAbbreviated()
  	{
  		return getType().getNameAbbreviated();
  	}
  
  	@Override
  	@Deprecated
  	public String getTypeName()
  	{
  		return getType().getName();
  	}
  
  	@Override
  	public void clear()
  	{
  		if (acceptingStates != null) {
  			JDD.Deref(acceptingStates);
  		}
  	}
  
  }
  