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.ast;
  
  
  import kodkod.ast.visitor.ReturnVisitor;
  import kodkod.ast.visitor.VoidVisitor;
  
  /** 
   * A constant {@link kodkod.ast.Formula formula}, true or false.
   *
   * @invariant no children
   * @author Emina Torlak 
   */
  public abstract class ConstantFormula extends Formula {
  	private final boolean value;
  	/**
  	 * Constructs a constant formula with the given value.
  	 */
  	ConstantFormula(boolean value) {
  		this.value = value;
  	}
      
  	/**
  	 * Returns the boolean value that corresponds to this 
  	 * constant formula.
  	 * @return this=TRUE => true, false
  	 */
  	public final boolean booleanValue() { return value; }
  	
  	 /**
  	    * {@inheritDoc}
  	    * @see kodkod.ast.Formula#accept(kodkod.ast.visitor.ReturnVisitor)
  	    */
  	    public <E, F, D, I> F accept(ReturnVisitor<E, F, D, I> visitor) {
  	        return visitor.visit(this);
  	    }
  	    
  	    /**
  	     * {@inheritDoc}
  	     * @see kodkod.ast.Node#accept(kodkod.ast.visitor.VoidVisitor)
  	     */
  	    public void accept(VoidVisitor visitor) {
  	        visitor.visit(this);
  	    }
  	    
  	    /**
  	     * {@inheritDoc}
  	     * @see kodkod.ast.Node#toString()
  	     */
  	public String toString() {
  		return String.valueOf(booleanValue());
  	}
  }
  
  