Re-examining regular expressions with backreferences
Most modern regular expression matching libraries (one of the rare exceptions being Google's RE2) allow backreferences, operations which bind a substring to a variable, allowing it to be matched again verbatim. However, both real-world implementations and definitions in the literature use diffe...
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| Vydané v: | Theoretical computer science Ročník 940; s. 66 - 80 |
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| Hlavní autori: | , |
| Médium: | Journal Article |
| Jazyk: | English |
| Vydavateľské údaje: |
Elsevier B.V
09.01.2023
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| Predmet: | |
| ISSN: | 0304-3975, 1879-2294, 1879-2294 |
| On-line prístup: | Získať plný text |
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| Shrnutí: | Most modern regular expression matching libraries (one of the rare exceptions being Google's RE2) allow backreferences, operations which bind a substring to a variable, allowing it to be matched again verbatim. However, both real-world implementations and definitions in the literature use different syntactic restrictions and have differences in the semantics of the matching of backreferences. Our aim is to compare these various flavors by considering the classes of formal languages that each can describe, establishing, as a result, a hierarchy of language classes. Beyond the hierarchy itself, some complexity results are given, and as part of the effort on comparing language classes new pumping lemmas are established, old classes are extended to new ones, and several incidental results on the nature of these language classes are given. |
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| ISSN: | 0304-3975 1879-2294 1879-2294 |
| DOI: | 10.1016/j.tcs.2022.10.041 |