code: /**
   * <copyright>
   * Copyright (c) 2010-2014 Henshin developers. All rights reserved. 
   * This program and the accompanying materials are made available 
   * under the terms of the Eclipse Public License v1.0 which 
   * accompanies this distribution, and is available at
   * http://www.eclipse.org/legal/epl-v10.html
   * </copyright>
   */
  package org.eclipse.emf.henshin.interpreter.matching.conditions;
  
  public interface IFormula {
  	
  	/**
  	 * Formula which always evaluates to <code>true</code>.
  	 */
  	public final IFormula TRUE = new IFormula() {
  		public boolean eval() {
  			return true;
  		}
  	};
  
  	/**
  	 * Formula which always evaluates to <code>false</code>.
  	 */
  	public final IFormula FALSE = new IFormula() {
  		public boolean eval() {
  			return false;
  		}
  	};
  
  	/**
  	 * Evaluate this formula.
  	 * @return Result of the evaluation.
  	 */
  	boolean eval();
  	
  }
  