RegeXeX: an interactive system providing regular expression exercises

This paper presents RegeXeX (Regular expression exercises), an interactive system for teaching students to write regular expressions. The system poses problems (prose descriptions of languages), students enter solutions (regular expressions defining these languages), and the system provides feedback. What is novel in this system is the type of feedback: students are not merely told that a submitted regular expression is wrong, they are given examples of strings that the expression either matches and shouldn't or does not match and should, and asked to try again. Additionally, student responses need only be equivalent to the solution, not identical. Results of classroom experience with this system are also reported, and demonstrate its effectiveness in teaching students to write regular expressions with little or no instructor interaction.RegeXeX is a freely available, portable system, written in C++ and using the Qt library for its GUI. It is distributed with several exercise sets, but is designed so instructors can easily write their own. The system logs student work and offers facilities for submitting log-files to instructors as well, allowing for automatic grading, or in-depth analysis of student performance and evolution of responses throughout the exercise set.