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/*
* 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 factor
*
* @version 1.0
* @author Manuel Mausz (manuel at mausz.at)
* @author http://manuel.mausz.at/
*/
class FacOperation implements UPNOperation
{
/**
* constructor
*/
public FacOperation()
{
}
/**
* 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, res = 1;
if (op.empty())
throw new InvalidParameterException("Insuifficent operands on stack");
v1 = op.pop();
if (Math.abs(v1) < EPSILON)
v1 = 0;
int x = (int)Math.abs(v1);
if (v1 < 0 || v1 - x != 0)
throw new InvalidParameterException("Factorial is only defined for natural Numbers");
for(int i = 1; i <= x; i++)
res *= i;
op.push(res);
}
}