/*
 * Copyright (c) 2008, Manuel Mausz <manuel at mausz.at>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the copyright holders nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
 * TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */
 
import java.util.Stack;
 
/**
 * Implements mathematical addition
 *
 * @version 1.0
 * @author  Manuel Mausz (manuel at mausz.at)
 * @author  http://manuel.mausz.at/
 */
class AddOperation implements UPNOperation
{
  /**
   * constructor
   */
  public AddOperation()
  {
  }
 
  /**
   * returns operations symbol
   *
   * @return operation symbol
   */
  public String getOperationSymbol()
  {
    return "+";
  }
 
  /**
   * performs the actual execution
   *
   * @param op stack to retrieve the values from
   */
  public void execute (Stack<Double> op)
    throws InvalidParameterException
  {
    double v1, v2, res;
 
    if (op.empty())
      throw new InvalidParameterException("Insuifficent operands on stack");
    v1 = op.pop();
    if (Math.abs(v1) < EPSILON)
      v1 = 0;
 
    if (op.empty())
      throw new InvalidParameterException("Insuifficent operands on stack");
    v2 = op.pop();
    if (Math.abs(v2) < EPSILON)
      v2 = 0;
 
    res = v1 + v2;
    if (Math.abs(res) < EPSILON)
      res = 0;
    op.push(res);
  }
}