content: /**
   * Copyright (c) 2019, 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.depgraph;
  
  import at.ac.tuwien.kr.alpha.api.programs.analysis.DependencyGraph;
  
  /**
   * An edge in a dependency graph to be used in adjacency lists (i.e., only the target of the edge is recorded). Edges
   * are labelled with a boolean sign indicating the polarity of the edge.
   * 
   * Copyright (c) 2019-2020, the Alpha Team.
   */
  public class EdgeImpl implements DependencyGraph.Edge {
  
  	private final DependencyGraph.Node target;
  	private final boolean              sign;
  
  	/**
  	 * Creates a new edge for a dependency graph. Read as "target depends on source". The sign indicates whether the
  	 * dependency is positive or negative (target node depends on default negated atom).
  	 * Note: working assumption is that strong negation is treated like a positive dependency.
  	 * 
  	 * @param target the target node.
  	 * @param sign the polarity of the edge.
  	 */
  	public EdgeImpl(DependencyGraph.Node target, boolean sign) {
  		this.target = target;
  		this.sign = sign;
  	}
  
  	@Override
  	public boolean equals(Object o) {
  		if (!(o instanceof DependencyGraph.Edge)) {
  			return false;
  		}
  		EdgeImpl other = (EdgeImpl) o;
  		return this.target.equals(other.target) && this.sign == other.sign;
  	}
  
  	@Override
  	public int hashCode() {
  		return ("" + target.getPredicate().toString() + sign).hashCode();
  	}
  
  	@Override
  	public String toString() {
  		return "(" + (sign ? "+" : "-") + ") ---> " + target.toString();
  	}
  	
  	@Override
  	public DependencyGraph.Node getTarget() {
  		return target;
  	}
  
  	@Override
  	public boolean getSign() {
  		return sign;
  	}
  
  }
  