public ProgState execute(ProgState prog)
        {
            MyIList <int> list = prog.getList();
            MyIDictionary <string, int> dict = prog.getDict();

            try {
                list.add(ex.eval(dict));
                return(prog);
            }
            catch (StmtExceptions e)
            {
                throw new ControllerException(e);
            }
        }