import java.util.EmptyStackException;

public class CalculatorModel
{
    private Stack stack = new ArrayStack();
    
    public void push( double d )
    {
        stack.push( new Double( d ) );
    }
    
    public double pop()
        throws EmptyStackException
    {
        return (( Double ) stack.pop()).doubleValue();
    }
    
    public double div()
        throws EmptyStackException
    {
        double bot = pop();
        double top = pop();
        return top / bot;
    }
    
    public double mul()
        throws EmptyStackException
    {
        double r = pop();
        double l = pop();
        return l * r;
    }
    
    public double sub()
        throws EmptyStackException
    {
        double r = pop();
        double l = pop();
        return l - r;
    }
    
    public double add()
        throws EmptyStackException
    {
        double r = pop();
        double l = pop();
        return l + r;
    }
    
    public void clear()
    {
        stack.clear();
    }
    
    public boolean isEmpty()
    {
        return stack.isEmpty();
    }
}