/*

  * Licensed to the Apache Software Foundation (ASF) under one or more

  * contributor license agreements.  See the NOTICE file distributed with

  * this work for additional information regarding copyright ownership.

  * The ASF licenses this file to You 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 org.apache.commons.el;

 import javax.servlet.jsp.el.ELException;

 import javax.servlet.jsp.el.FunctionMapper;

 import javax.servlet.jsp.el.VariableResolver;

 /**

  *

  * <p>The abstract class from which all expression types

  * derive.

  * 

  * @author Nathan Abramson - Art Technology Group

  * @author Shawn Bayern

  * @version $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: bayard $

  **/

 public abstract class Expression

 {

   //-------------------------------------

   // Member variables

   //-------------------------------------

   //-------------------------------------

   /**

    *

    * Returns the expression in the expression language syntax

    **/

   public abstract String getExpressionString ();

   //-------------------------------------

   /**

    *

    * Evaluates the expression in the given context

    **/

   public abstract Object evaluate (VariableResolver pResolver, FunctionMapper functions)

     throws ELException;

   //-------------------------------------

   /**

    * Returns an expression with all <code>FunctionInvocation</code>s replaced by

    * <code>BoundFunctionInvocation</code>s.

    * @param functions the functions to use in this transformation

    * @return an Expression identical to this expression except with all

    *    <code>FunctionInvocation</code>s replaced by

    *    <code>BoundFunctionInvocation</code>s.

    * @throws ELException if any of the functions in this <code>Expression</code> are

    *    not present in <code>functions</code>

    */

   public abstract Expression bindFunctions(FunctionMapper functions)

       throws ELException;

 }