The followingversionof i nteracti ve-i nterpreter adds twonewfeatures. First, it uses the macro handl er-case1 to handle errors. This macro evaluates its first argument, and normally just returns that value. However, if an error occurs, the subsequent arguments are checked for an error condition that matches the error that occurred. In this use, the case error matches all errors, and the action taken is to print the error condition and continue.