aEnvironment.iCurrentOutput.Write("Function not yet implemented : TraceStack");
aEnvironment.iCurrentOutput.Write("Function not yet implemented : TraceStack"); throw new Yacasexception("Function not yet supported");
    public void Eval(LispEnvironment aEnvironment,int aStackTop) throws Exception    {      aEnvironment.iCurrentOutput.Write("Function not yet implemented : TraceStack");//TODO FIXME    }