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 * reserved comment block

 * DO NOT REMOVE OR ALTER!

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/*

 * 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.

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package com.sun.org.apache.xpath.internal.functions;

import com.sun.org.apache.xalan.internal.res.XSLMessages;

import com.sun.org.apache.xpath.internal.Expression;

import com.sun.org.apache.xpath.internal.ExpressionOwner;

import com.sun.org.apache.xpath.internal.XPathContext;

import com.sun.org.apache.xpath.internal.XPathVisitor;

import com.sun.org.apache.xpath.internal.compiler.Compiler;

import com.sun.org.apache.xpath.internal.objects.XObject;

/**

 * This is a superclass of all XPath functions.  This allows two

 * ways for the class to be called. One method is that the

 * super class processes the arguments and hands the results to

 * the derived class, the other method is that the derived

 * class may process it's own arguments, which is faster since

 * the arguments don't have to be added to an array, but causes

 * a larger code footprint.

 * @xsl.usage advanced

 */

public abstract class Function extends Expression

{

    static final long serialVersionUID = 6927661240854599768L;

  /**

   * Set an argument expression for a function.  This method is called by the

   * XPath compiler.

   *

   * @param arg non-null expression that represents the argument.

   * @param argNum The argument number index.

   *

   * @throws WrongNumberArgsException If the argNum parameter is beyond what

   * is specified for this function.

   */

  public void setArg(Expression arg, int argNum)

          throws WrongNumberArgsException

  {

                        // throw new WrongNumberArgsException(XSLMessages.createXPATHMessage("zero", null));

      reportWrongNumberArgs();

  }

  /**

   * Check that the number of arguments passed to this function is correct.

   * This method is meant to be overloaded by derived classes, to check for

   * the number of arguments for a specific function type.  This method is

   * called by the compiler for static number of arguments checking.

   *

   * @param argNum The number of arguments that is being passed to the function.

   *

   * @throws WrongNumberArgsException

   */

  public void checkNumberArgs(int argNum) throws WrongNumberArgsException

  {

    if (argNum != 0)

      reportWrongNumberArgs();

  }

  /**

   * Constructs and throws a WrongNumberArgException with the appropriate

   * message for this function object.  This method is meant to be overloaded

   * by derived classes so that the message will be as specific as possible.

   *

   * @throws WrongNumberArgsException

   */

  protected void reportWrongNumberArgs() throws WrongNumberArgsException {

      throw new WrongNumberArgsException(XSLMessages.createXPATHMessage("zero", null));

  }

  /**

   * Execute an XPath function object.  The function must return

   * a valid object.

   * @param xctxt The execution current context.

   * @return A valid XObject.

   *

   * @throws javax.xml.transform.TransformerException

   */

  public XObject execute(XPathContext xctxt) throws javax.xml.transform.TransformerException

  {

    // Programmer's assert.  (And, no, I don't want the method to be abstract).

    System.out.println("Error! Function.execute should not be called!");

    return null;

  }

  /**

   * Call the visitors for the function arguments.

   */

  public void callArgVisitors(XPathVisitor visitor)

  {

  }

  /**

   * @see com.sun.org.apache.xpath.internal.XPathVisitable#callVisitors(ExpressionOwner, XPathVisitor)

   */

  public void callVisitors(ExpressionOwner owner, XPathVisitor visitor)

  {

        if(visitor.visitFunction(owner, this))

        {

                callArgVisitors(visitor);

        }

  }

  /**

   * @see Expression#deepEquals(Expression)

   */

  public boolean deepEquals(Expression expr)

  {

        if(!isSameClass(expr))

                return false;

        return true;

  }

  /**

   * This function is currently only being used by Position()

   * and Last(). See respective functions for more detail.

   */

  public void postCompileStep(Compiler compiler)

  {

    // no default action

  }

}