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;
  import java.util.Iterator;
  
  import jltl2ba.APElement;
  import jltl2ba.APSet;
  import jltl2ba.MyBitSet;
  
  /**
   * Class representing a subset of 2^AP where AP is the set of 
   * atomic propositions (APSet). It stores two bits per AP: 
   * One bit to determine if the value of this AP is set, 
   * the second bit to store the value.<br>
   * Additionally, the APMonom can have the special values
   * TRUE or FALSE.<br>
   */
  public class APMonom {
  
  	private MyBitSet bits_set;
  	private MyBitSet bits_value;
  	private boolean booleanValue;
  
  	public APMonom()
  	{
  		bits_set = new MyBitSet();
  		bits_value = new MyBitSet();
  		booleanValue = true;
  	}
  
  	public APMonom(boolean b) {
  		bits_set = new MyBitSet();
  		bits_value = new MyBitSet();
  		booleanValue = b;
  	}
  
  	public APMonom(MyBitSet set, MyBitSet value)
  	{
  		bits_set = set;
  		bits_value = value;
  	}
  
  	/**
  	 * Is the AP set?
  	 * @param index index of AP
  	 * @return <b>true</b> if AP is set
  	 */
  	public boolean isSet(int index) throws PrismException {
  		if (!isNormal()) {
  			// TRUE / FALSE -> the bit is not set
  			return false;
  		}
  		return bits_set.get(index);
  	}
  
  	/**
  	 * Gets the value for this AP. You can't get the value if the AP is not set.
  	 * @param index index of AP
  	 * @return <b>true</b> if AP is true
  	 */
  	public boolean getValue(int index) throws PrismException {
  		if (!isNormal()) {
  			throw new PrismException("Can't get AP, is either TRUE/FALSE!");
  		}
  
  		if (!bits_set.get(index)) {
  			throw new PrismException("Can't get value: AP not set!");
  		}
  
  		return bits_value.get(index);
  	}
  
  	/**
  	 * Sets the value for this AP. Implicitly, it also sets the AP to 'set'.
  	 * @param index index of AP
  	 * @param value value of AP
  	 */
  	public void setValue(int index, boolean value) {
  		bits_set.set(index, true);
  		bits_value.set(index, value);
  	}
  
  
  	/**
  	 * Perform a logical AND operation of this APMonom with a single AP.
  	 * @param index index index of AP
  	 * @param value value of AP
  	 */
  	public void andAP(int index, boolean value) {
  		if (isFalse()) {return;}
  
  		if (!isTrue()) {
  			if (bits_set.get(index) && bits_value.get(index) != value) {
  				// contradiction
  				booleanValue = false;
  				bits_set.clear();
  				bits_value.clear();
  				return;
  			}
  		}
  		setValue(index, value);
  	}
  
  
  	/**
  	 * Unsets this AP.
  	 * @param index index of AP
  	 */
  	public void unset(int index) {
  		bits_value.set(index,false);
  		bits_set.set(index, false);
  	}
  
  
  	/**
  	 * Checks if this APMonom is equivalent to TRUE.
  	 * @return <b>true</b> if this APMonom is TRUE
  	 */
  	public boolean isTrue() {
  		return (!isNormal() && booleanValue);
  	}
  
  	/**
  	 * Checks if this APMonom is equivalent to FALSE.
  	 * @return <b>true</b> if this APMonom is FALSE
  	 */
  	public boolean isFalse() {
  		return (!isNormal() && !booleanValue);
  	}
  
  	/**
  	 * Checks if this APMonom is a normal APMonon (not equivalent to TRUE or FALSE).
  	 * @return <b>true</b> if this APMonom is normal (not TRUE/FALSE).
  	 */
  	public boolean isNormal() {
  		return !bits_set.isEmpty();
  	}
  
  	/**
  	 * Provides access to the underlying MyBitSet representing the
  	 * value (AP occurs in positive or negative form).
  	 * @return the SimpleBitSet of the values
  	 */
  	public MyBitSet getValueBits() {
  		return bits_value;
  	}
  
  	/**
  	 * Provides access to the underlying MyBitSet representing the
  	 * bits that are set (AP occurs).
  	 * @return the SimpleBitSet of the occuring APs
  	 */
  	public MyBitSet getSetBits() {
  		return bits_set;
  	}
  
  	/** Checks to see if the MyBitSet representation is normalized. */
  	public boolean isNormalized() {
  		if (isTrue() || isFalse()) {
  			return true;
  		}
  		MyBitSet tmp = getValueBits();
  		tmp.andNot(bits_set);
  		return tmp.isEmpty();
  	}
  
  	/**
  	 * Output APMonom
  	 */
  	public String toString()
  	{
  		String rv = "";
  		if (isTrue()) {
  			return "true";
  		} else if (isFalse()) {
  			return "false";
  		} else {
  			for (int i = 0; i < bits_set.size(); i++) {
  				if (bits_set.get(i)) {
  					if (bits_value.get(i)) {
  						rv = rv + "+" + i;
  					} else {
  						rv = rv + "-" + i;
  					}
  				}
  			}
  		}
  		return rv;
  	}
  
  	/**
  	 * Performs an intersection check.
  	 * @param m1 the first APMonom
  	 * @param m2 the second APMonom
  	 * @return <b>true</b> if the intersection of <i>m1</i> and <i>m2</i> is empty.
  	 * 
  	 * FIXME: I'm not sure if this does what it says it does, but ltl2dstar does it this way.
  	 */
  	public boolean isIntersectionEmpty(APMonom m2) {
  		// check if there are contradicting values 
  		MyBitSet set_in_both = getSetBits();
  		set_in_both.and(m2.getSetBits());
  
  		MyBitSet maskedm1 = getValueBits();
  		maskedm1.and(set_in_both);
  
  		MyBitSet maskedm2 = m2.getValueBits();
  		maskedm2.and(set_in_both);
  
  		return ! maskedm1.equals(maskedm2);
  	}
  
  	/**
  	 * Perform logical conjunction with other APMonom.
  	 * @param other the other APMonom
  	 */
  	public APMonom and(APMonom other) {
  		if (this.isFalse() || other.isFalse()) {
  			return new APMonom(false);
  		}
  
  		if (this.isTrue()) {return other;}
  		if (other.isTrue()) {return this;}
  
  		// both are not TRUE/FALSE:
  
  		if (this.isIntersectionEmpty(other)) {
  			//  return APMonom equivalent to false
  			return new APMonom(false);
  		}
  
  		// both Monoms are not contradicting...
  		MyBitSet result_set = this.getSetBits();
  		result_set.or(other.getSetBits());
  
  		MyBitSet result_value = this.getValueBits();
  		result_value.or(other.getValueBits());
  
  		return new APMonom(result_set, result_value);
  	}
  
  	/**
  	 * Perform 'minus' operation (equal to *this & !other).
  	 * @param other the other APMonom
  	 */
  	APMonom andNot(APMonom other) {
  		if (this.isFalse()) {
  			// false & anything == false
  			return new APMonom(false);
  		}
  
  		if (other.isFalse()) {
  			// *this & !(false) == *this & true == *this
  			return this;
  		}
  
  		if (other.isTrue()) {
  			// *this & !(true) == *this & false == false
  			return new APMonom(false);
  		}
  
  		// the result will be false, if there are two set bits
  		// with equal value
  		MyBitSet set_in_both= getSetBits();
  		set_in_both.and(other.getSetBits());
  
  		MyBitSet maskedm1 = getValueBits();
  		maskedm1.and(set_in_both);
  
  		MyBitSet maskedm2 = other.getValueBits();
  		maskedm2.and(set_in_both);
  		maskedm2.flip(0,maskedm2.size());
  
  		if (!maskedm1.equals(maskedm2)) {
  			// return false;
  			return new APMonom(false);
  		}
  		MyBitSet result_set = getSetBits();
  		result_set.or(other.getSetBits());
  
  		MyBitSet result_value = getValueBits();
  		result_value.andNot(other.getValueBits());
  
  		return new APMonom(result_set, result_value);
  	}
  
  
  	/**
  	 * Checks for equality.
  	 * @param other the other APMonom
  	 * @return <b>true</b> if this and the other APMonom are equal
  	 */
  	public boolean equals(APMonom other) {
  		return (isNormal() && other.isNormal() &&
  				getValueBits().equals(other.getValueBits()) && 
  				getSetBits().equals(other.getSetBits()) ||
  				isTrue() && other.isTrue() ||
  				isFalse() && other.isFalse());
  	}
  
  	public boolean equals(Object other) {
  		return ((other instanceof APMonom) && this.equals((APMonom) other));
  	}
  
  	public Iterator<APElement> APElementIterator(APSet s)
  	{
  		return (Iterator<APElement>) new APMonom2APElements(s, this);  
  	}
  
  	public void setFromPosNeg(MyBitSet pos, MyBitSet neg) throws PrismException
  	{
  		int sz = pos.size() > neg.size() ? pos.size() : neg.size();
  
  		if (pos.intersects(neg)) {
  			throw new PrismException("MyBitSet contradiction");
  		}
  		if ((pos.cardinality() == sz)
  				|| (pos.cardinality() == 0 && neg.cardinality() == 0)) {
  			bits_set = new MyBitSet(sz);
  			bits_value = new MyBitSet(sz);
  			booleanValue = true;
  		}
  		else if (neg.cardinality() == sz) {
  			bits_set = new MyBitSet(sz);
  			bits_value = new MyBitSet(sz);
  			booleanValue = false;
  		}
  		else {
  			if (pos.size() == sz) {
  				bits_set = (MyBitSet) pos.clone();
  				bits_set.or(neg);  
  				bits_value = (MyBitSet) pos.clone();
  			}
  			else {
  				bits_set = (MyBitSet) neg.clone();
  				bits_set.or(pos);  
  				bits_value = new MyBitSet(sz); 
  				bits_value.or(pos);
  			}
  		}
  	}
  }
  