The square of a language L is the set of all words pp where p β L. The square of a regular language may be regular too or context-free or none of both. We give characterizations for each of these cases and show that it is decidable whether a regular language has one of these properties.
Regular component decomposition of regular languages
β Scribed by Y.J. Liu
- Publisher
- Elsevier Science
- Year
- 2003
- Tongue
- English
- Weight
- 198 KB
- Volume
- 299
- Category
- Article
- ISSN
- 0304-3975
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β¦ Synopsis
A language is regular if it can be recognized by a ΓΏnite automaton. According to the pumping lemma, every inΓΏnite regular language contains a regular subset of the form uv + w, where u; v; w are words and v is not empty. It is known that every regular language can be expressed as ( iβI uiv + i wi) βͺ F, where I is an index set, ui; wi β A * ; vi β A + ; i β I and F is a ΓΏnite set of words over the alphabet A. This expression is called a regular component decomposition of the language. A language is called regular component splittable if it can be expressed as a disjoint union of regular components and a ΓΏnite set. A language which has a regular component decomposition with ΓΏnite index is called a ΓΏnite regular component representable language. It has been shown that every ΓΏnite regular component representable language is regular component splittable by Shyr and Yu in (Discrete Appl. Math. 82 (1998) 219). They conjectured that every regular language is regular component splittable in (Acta Math. Hung. 78(3) (1998) 251). The conjecture is proved in this paper.
π SIMILAR VOLUMES
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