Chapter

Language and Automata Theory and Applications

Volume 5457 of the series Lecture Notes in Computer Science pp 279-289

On Extended Regular Expressions

  • Benjamin CarleAffiliated withDept. of Computer Science, University at Albany–SUNY
  • , Paliath NarendranAffiliated withDept. of Computer Science, University at Albany–SUNY

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Abstract

In this paper we extend the work of Campeanu, Salomaa and Yu [1] 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 [2].