protected void EncapsulateNoValue(LogicalExpression expression)
        {
            if (expression is ValueExpression)
            {
                expression.Accept(this);
            }
            else
            {
                Result.Append("(");
                expression.Accept(this);

                // trim spaces before adding a closing paren
                while (Result[Result.Length - 1] == ' ')
                    Result.Remove(Result.Length - 1, 1);

                Result.Append(") ");
            }
        }