content: /**
   * Copyright (c) 2017-2020, the Alpha Team.
   * All rights reserved.
   * <p>
   * Additional changes made by Siemens.
   * <p>
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   * <p>
   * 1) Redistributions of source code must retain the above copyright notice, this
   * list of conditions and the following disclaimer.
   * <p>
   * 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.
   * <p>
   * 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.commons.programs.literals;
  
  import java.util.List;
  import java.util.Set;
  
  import org.apache.commons.collections4.SetUtils;
  
  import at.ac.tuwien.kr.alpha.api.grounder.Substitution;
  import at.ac.tuwien.kr.alpha.api.programs.Predicate;
  import at.ac.tuwien.kr.alpha.api.programs.atoms.Atom;
  import at.ac.tuwien.kr.alpha.api.programs.literals.Literal;
  import at.ac.tuwien.kr.alpha.api.programs.terms.Term;
  import at.ac.tuwien.kr.alpha.api.programs.terms.VariableTerm;
  
  /**
   * A potentially negated {@link AbstractAtom}
   *
   * Copyright (c) 2017-2018, the Alpha Team.
   */
  public abstract class AbstractLiteral implements Literal {
  
  	protected final Atom atom;
  	protected final boolean positive;
  
  	public AbstractLiteral(Atom atom, boolean positive) {
  		this.atom = atom;
  		this.positive = positive;
  	}
  
  	@Override
  	public Atom getAtom() {
  		return atom;
  	}
  
  	@Override
  	public boolean isNegated() {
  		return !positive;
  	}
  
  	@Override
  	public abstract Literal negate();
  
  	@Override
  	public abstract Literal substitute(Substitution substitution);
  
  	@Override
  	public abstract Set<VariableTerm> getBindingVariables();
  
  	@Override
  	public abstract Set<VariableTerm> getNonBindingVariables();
  
  	/**
  	 * Union of {@link #getBindingVariables()} and {@link #getNonBindingVariables()}
  	 */
  	@Override
  	public Set<VariableTerm> getOccurringVariables() {
  		return SetUtils.union(getBindingVariables(), getNonBindingVariables());
  	}
  
  	/**
  	 * @see AbstractAtom#getPredicate()
  	 */
  	@Override
  	public Predicate getPredicate() {
  		return atom.getPredicate();
  	}
  
  	/**
  	 * @see AbstractAtom#getTerms()
  	 */
  	@Override
  	public List<Term> getTerms() {
  		return atom.getTerms();
  	}
  
  	/**
  	 * @see AbstractAtom#isGround()
  	 */
  	@Override
  	public boolean isGround() {
  		return atom.isGround();
  	}
  
  	@Override
  	public String toString() {
  		return (positive ? "" : "not ") + atom.toString();
  	}
  
  	@Override
  	public boolean equals(Object o) {
  		if (this == o) {
  			return true;
  		}
  		if (o == null || getClass() != o.getClass()) {
  			return false;
  		}
  
  		Literal that = (Literal) o;
  
  		return atom.equals(that.getAtom()) && positive == !that.isNegated();
  	}
  
  	@Override
  	public int hashCode() {
  		return 12 * atom.hashCode() + (positive ? 1 : 0);
  	}
  
  }
  