VLex: Visualizing a Lexical Analyzer Generator

Lexical analyzer generators such as lex and its many successors are based on well-understood concepts. Yet, students often have problems to intuitively grasp and visualize these concepts, especially in compiler engineering courses that emphasize the use of tools over fundamental algorithms. VLex is designed to close the gap left by existing visualization tools, and to help students to understand the approach taken and the algorithms used in lexical analyzer generators. It has the “look and feel” of a lexical analyzer generator, rather than that of a theory animation tool. It can handle multiple lexical states and accepting states can return different tokens. VLex visualizes the algorithms typically implemented in a lexical analyzer generator in the lex tradition, i.e., converting regular expressions via non-deterministic into a deterministic finite automata and then minimizing these automata. The visualization works incrementally, and the user can choose any location to control how the algorithms continue. VLex can also animate the different automata during