content: /**
   * Copyright (c) 2017-2018, the Alpha Team.
   * All rights reserved.
   *
   * Additional changes made by Siemens.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   * 1) Redistributions of source code must retain the above copyright notice, this
   *    list of conditions and the following disclaimer.
   *
   * 2) Redistributions in binary form must reproduce the above copyright notice,
   *    this list of conditions and the following disclaimer in the documentation
   *    and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  package at.ac.tuwien.kr.alpha.core.solver;
  
  import static at.ac.tuwien.kr.alpha.core.programs.atoms.Literals.atomOf;
  import static at.ac.tuwien.kr.alpha.core.programs.atoms.Literals.isPositive;
  
  class Choice {
  	private final int atom;
  	private final boolean truthValue;
  	private final boolean backtracked;
  
  	Choice(int atom, boolean truthValue, boolean backtracked) {
  		this.atom = atom;
  		this.truthValue = truthValue;
  		this.backtracked = backtracked;
  	}
  
  	Choice(int literal, boolean backtracked) {
  		this(atomOf(literal), isPositive(literal), backtracked);
  	}
  
  	/**
  	 * Returns the inverse choice to the given one.
  	 * @param choice the choice to invert.
  	 * @return a new Choice representing the inverse of the given one, or null if the given choice was already backtracked.
  	 */
  	public static Choice getInverted(Choice choice) {
  		if (choice.isBacktracked()) {
  			return null;
  		}
  		return new Choice(choice.getAtom(), !choice.getTruthValue(), true);
  	}
  
  	public int getAtom() {
  		return atom;
  	}
  
  	public boolean getTruthValue() {
  		return truthValue;
  	}
  
  	public boolean isBacktracked() {
  		return backtracked;
  	}
  
  	@Override
  	public String toString() {
  		return atom + "=" + (truthValue ? "TRUE" : "FALSE");
  	}
  }
  