content: /**
   * Copyright (c) 2016-2019, 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.programs.atoms;
  
  /**
   * Provides methods to convert atoms to literals and vice versa,
   * and to obtain and change information on the polarity of a literal.
   * A literal is represented by an integer whose least significant bit is
   * 1 if the literal is negated and 0 otherwise, and whose other bits
   * encode the atom.
   */
  public final class Literals {
  	/**
  	 * Given a literal, returns the corresponding atom.
  	 * @param literal the literal to translate.
  	 * @return the corresponding atom.
  	 */
  	public static int atomOf(int literal) {
  		return literal >> 1;
  	}
  
  	/**
  	 * A utility to check if a given literal is negated.
  	 * @param literal the literal to check.
  	 * @return {@code true} iff the literal is negated, {@code false} otherwise.
  	 */
  	public static boolean isNegated(int literal) {
  		return (literal & 0x1) == 1;
  	}
  
  	public static boolean isPositive(int literal) {
  		return (literal & 0x1) == 0;
  	}
  
  	public static int negateLiteral(int literal) {
  		return literal ^ 0x1;
  	}
  
  	public static int atomToLiteral(int atom, boolean truth) {
  		return truth ? atomToLiteral(atom) : atomToNegatedLiteral(atom);
  	}
  
  	public static int atomToLiteral(int atom) {
  		return atom << 1;
  	}
  
  	public static int atomToNegatedLiteral(int atom) {
  		return negateLiteral(atomToLiteral(atom));
  	}
  
  	public static int positiveLiteral(int literal) {
  		return literal & ~0x1;
  	}
  
  	public static String literalToString(int literal) {
  		return (isPositive(literal) ? "+" : "-") + atomOf(literal);
  	}
  }
  