JUCS - Journal of Universal Computer Science 27(4): 324-340, doi: 10.3897/jucs.66330
Regular Expressions with Lookahead
expand article infoMartin Berglund, Brink van der Merwe, Steyn van Litsenborgh
‡ Stellenbosch University, Stellenbosch, South Africa
Open Access

This paper investigates regular expressions which in addition to the standard operators of union, concatenation, and Kleene star, have lookaheads. We show how to translate regular expressions with lookaheads (REwLA) to equivalent Boolean automata having at most 3 states more than the length of the REwLA. We also investigate the state complexity when translating REwLA to equivalent deterministic finite automata (DFA).

Regular expressions, Lookahead expressions, Boolean automata