2003 | OriginalPaper | Buchkapitel
Regex and Extended Regex
verfasst von : Cezar Câmpeanu, Kai Salomaa, Sheng Yu
Erschienen in: Implementation and Application of Automata
Verlag: Springer Berlin Heidelberg
Enthalten in: Professional Book Archive
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Regex are used in many programs such as Perl, Awk, Python, egrep, vi, emacs etc. It is known that regex are different from regular expressions. In this paper, we give regex a formal treatment. We make a distinction between regex and extended regex; while regex present regular languages, extended regex present a family of languages larger than regular languages. We prove a pumping lemma for the languages expressed by extended regex. We show that the languages represented by extended regex are incomparable with context-free languages and a proper subset of context-sensitive languages.