Elsevier

Information Processing Letters

Volume 65, Issue 4, 27 February 1998, Pages 169-172
Information Processing Letters

Regular expressions with nested levels of back referencing form a hierarchy

https://doi.org/10.1016/S0020-0190(98)00007-6Get rights and content

Abstract

For many years, regular expressions with back referencing have been used in a variety of software products in common use, including operating systems, editors, and programming languages. In these products, regular expressions have been extended with a naming construct. If a subexpression is named by some variable, whenever this subexpression matches some string, that string is assigned to the variable. Later occurrences of the same variable will then match the string assigned to it. This construction greatly increases the power of regular expressions and is useful in text searching as well as in text substitution in large documents. We study the nested usage of this operator, and prove that the power of the expressions increase with the number of nested levels that are allowed.

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There are more references available in the full text version of this article.

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    2023, Leibniz International Proceedings in Informatics, LIPIcs
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Supported in part by the esprit Long Term Research Programme of the EU under project number 20244 (alcom-it). Odense University.

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