On Extended Regular Expressions
- Cite this paper as:
- Carle B., Narendran P. (2009) On Extended Regular Expressions. In: Dediu A.H., Ionescu A.M., Martín-Vide C. (eds) Language and Automata Theory and Applications. LATA 2009. Lecture Notes in Computer Science, vol 5457. Springer, Berlin, Heidelberg
In this paper we extend the work of Campeanu, Salomaa and Yu  on extended regular expressions featured in the Unix utility egrep and the popular scripting language Perl. We settle the open issue of closure under intersection and provide an improved pumping lemma that will show that a larger class of languages is not recognizable by extended regular expressions. We also investigate some questions regarding extended multi-pattern languages introduced by Nagy in .
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