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- Title
Extended Regular Expressions: Succinctness and Decidability.
- Authors
Freydenberger, Dominik
- Abstract
Most modern implementations of regular expression engines allow the use of variables (also called backreferences). The resulting extended regular expressions (which, in the literature, are also called practical regular expressions, rewbr, or regex) are able to express non-regular languages. The present paper demonstrates that extended regular-expressions cannot be minimized effectively (neither with respect to length, nor number of variables), and that the tradeoff in size between extended and 'classical' regular expressions is not bounded by any recursive function. In addition to this, we prove the undecidability of several decision problems (universality, regularity, and cofiniteness) for extended regular expressions. Furthermore, we show that all these results hold even if the extended regular expressions contain only a single variable.
- Subjects
DECIDABILITY (Mathematical logic); RECURSIVE functions; CONJOINT analysis; MATHEMATICAL variables; STATISTICAL decision making; MATHEMATICAL literature
- Publication
Theory of Computing Systems, 2013, Vol 53, Issue 2, p159
- ISSN
1432-4350
- Publication type
Article
- DOI
10.1007/s00224-012-9389-0