content: /**
   * Copyright (c) 2020, the Alpha Team.
   * All rights reserved.
   *
   * 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.grounder.instantiation;
  
  import at.ac.tuwien.kr.alpha.core.grounder.Grounder;
  import at.ac.tuwien.kr.alpha.core.solver.ThriceTruth;
  
  /**
   * Helper type to represent truth values as understood by a {@link Grounder} and {@link LiteralInstantiator}.
   * 
   * Note that this enum is not related in any way to {@link ThriceTruth} and mainly serves to have a clear mechanism to indicate that the
   * truth value of an atom is not known at a given point in time (UNASSIGNED)
   * 
   * Copyright (c) 2020, the Alpha Team.
   */
  public enum AssignmentStatus {
  
  	/**
  	 * True
  	 */
  	TRUE,
  
  	/**
  	 * False
  	 */
  	FALSE,
  
  	/**
  	 * Unassigned - indicates that at a given point in time, a {@link LiteralInstantiationStrategy} can not determine whether a literal is true
  	 * or false. This is needed because some grounding strategies consider UNASSIGNED atoms to be valid ground instances in order to be able to
  	 * ground larger parts of a program earlier on in the ground/solve cycle
  	 */
  	UNASSIGNED;
  }
  