content: /* 
   * Kodkod -- Copyright (c) 2005-present, Emina Torlak
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   * THE SOFTWARE.
   */
  package kodkod.engine.bool;
  
  import java.util.Iterator;
  
  import kodkod.util.collections.Containers;
  import kodkod.util.ints.Ints;
  
  
  /**
   * Represents a boolean variable.  
   * 
   * @invariant op = Operator.VAR
   * @invariant no inputs && label in [1, ..., Integer.MAX_VALUE)
   * @author Emina Torlak
   */
  public final class BooleanVariable extends BooleanFormula {
  	final int label;
  	private final int hashcode;
  
  	/**
  	 * Constructs a new BooleanVariable with the given label.
  	 * @requires label != 0
  	 * @ensures this.label' = label
  	 */
  	BooleanVariable(int label) {
  		super(null);
  		assert label != 0;
  		this.label = label;
  		this.hashcode = Ints.superFastHash(label);
  	}
  		
  	/**
  	 * Returns a hash of this variable's label.
  	 * @return Ints.superFastHash(this.label)
  	 */
  	@Override
  	int hash(Operator op) {
  		return hashcode;
  	}
  	
  	/**
  	 * Returns the label for this value. 
  	 * @return this.label
  	 */
  	@Override
  	public int label() {	return label; }
  	
  	/**
  	 * Returns a string representation of this variable.
  	 * @return a string representation of this variable.
  	 */
  	public String toString() {
  		return Integer.toString(label);
  	}
  
  	/**
  	 * Passes this value and the given
  	 * argument value to the visitor, and returns the resulting value.
  	 * @return the value produced by the visitor when visiting this node
  	 * with the given argument.
  	 */
  	@Override
  	public <T, A> T accept(BooleanVisitor<T,A> visitor, A arg) {
  		return visitor.visit(this, arg);
  	}
  
  	/**
  	 * Returns the VAR operator.
  	 * @return Operator.VAR
  	 */
  	@Override
  	public Operator op() {
  		return Operator.VAR;
  	}
  
  	/**
  	 * Returns an empty iterator.
  	 * @return an empty iterator
  	 */
  	@Override
  	public Iterator<BooleanFormula> iterator() {
  		return Containers.emptyIterator();
  	}
  
  	/**
  	 * Returns 0.
  	 * @return 0
  	 */
  	@Override
  	public int size() {
  		return 0;
  	}
  
  	/**
  	 * Throws an IndexOutOfBoundsException.
  	 * @throws IndexOutOfBoundsException
  	 */
  	@Override
  	public BooleanFormula input(int i) {
  		throw new IndexOutOfBoundsException();
  	}
  
  	/**
  	 * Returns a hashcode for this variable.
  	 * @return a hashcode for this variable.
  	 */
  	public int hashCode() { 
  		return hashcode;
  	}
  }
  