ExpressionEvaluator.java

/*
 * Copyright (C) 2012 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package interactivespaces.evaluation;

/**
 * An evaluator for some expressions.
 *
 * @author Keith M. Hughes
 */
public interface ExpressionEvaluator {

  /**
   * Set the evaluation environment
   *
   * @param environment
   *          the evaluation environment for the evaluator
   */
  void setEvaluationEnvironment(EvaluationEnvironment environment);

  /**
   * Evaluate a string expression.
   *
   * @param initial
   *          the initial string expression to evaluate. It will contain
   *          {@code code $ expr} at various places.
   *
   * @return The string with all expressions evaluated.
   *
   * @throws EvaluationInteractiveSpacesException
   *           An evaluation error of some sort occurred.
   */
  String evaluateStringExpression(String initial) throws EvaluationInteractiveSpacesException;

  /**
   * Evaluate an expression.
   *
   * @param expression
   *          the expression to evaluate in whatever expression language is
   *          being supported.
   *
   * @return The value of the expression.
   *
   * @throws EvaluationInteractiveSpacesException
   *           An evaluation error of some sort occurred.
   */
  Object evaluateExpression(String expression) throws EvaluationInteractiveSpacesException;
}