public abstract class StackNumberQuestion extends edu.cmu.cs.stage3.alice.core.question.NumberQuestion {
public final StackProperty stack = new StackProperty( this, "stack", null );
//protected abstract double getValue( Stack stack );
protected abstract int getValue( Stack stack );
public Object getValue() {
Stack stackValue = stack.getStackValue();
if( stackValue!=null ) {
return new Integer( getValue( stackValue ) );
} else {
return null;
}