Characterising REGEX Languages by Regular Languages Equipped with Factor-Referencing

  • Markus L. Schmid
Part of the Lecture Notes in Computer Science book series (LNCS, volume 8633)


A (factor-)reference in a word is a special symbol that refers to another factor in the same word; a reference is dereferenced by substituting it with the referenced factor. We introduce and investigate the class ref-REG of all languages that can be obtained by taking a regular language R and then dereferencing all possible references in the words of R. We show that ref-REG coincides with the class of languages defined by regular expressions as they exist in modern programming languages like Perl, Python, Java, etc. (often called REGEX languages).


REGEX languages regular languages memory automata 


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Copyright information

© Springer International Publishing Switzerland 2014

Authors and Affiliations

  • Markus L. Schmid
    • 1
  1. 1.FB IV–Abteilung InformatikwissenschaftenUniversität TrierTrierGermany

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