content: /*
   * Copyright (c) 2018-2020, 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.common;
  
  import at.ac.tuwien.kr.alpha.core.solver.Antecedent;
  
  public interface NoGoodInterface extends Iterable<Integer> {
  
  	/**
  	 * Returns the literal at the given index.
  	 * @param index the index position within the NoGood.
  	 * @return the literal at the index.
  	 */
  	int getLiteral(int index);
  
  	/**
  	 * Returns whether the NoGood has a head.
  	 * @return true if the NoGood has a head.
  	 */
  	boolean hasHead();
  
  	/**
  	 * Returns the head literal of the NoGood, if present.
  	 * @return the head literal if the NoGood has a head, otherwise an arbitrary integer.
  	 */
  	int getHead();
  
  	/**
  	 * Returns the size, i.e., number of literals, in the NoGood.
  	 * @return the size of the NoGood.
  	 */
  	int size();
  
  	default boolean isUnary() {
  		return size() == 1;
  	}
  
  	default boolean isBinary() {
  		return size() == 2;
  	}
  
  	Antecedent asAntecedent();
  
  	Type getType();
  
  	/**
  	 * The possible nogood types
  	 */
  	enum Type {
  		/**
  		 * Unremovable nogood from the input program
  		 */
  		STATIC,
  
  		/**
  		 * Removable support nogood from the input program
  		 */
  		SUPPORT,
  
  		/**
  		 * Removable nogood learnt from a conflict
  		 */
  		LEARNT,
  
  		/**
  		 * Nogood containing solver-internal atoms
  		 */
  		INTERNAL,
  	}
  }
  