Filtrations of Formal Languages by Arithmetic Progressions
نویسندگان
چکیده
A filtration of a formal language L by a sequence s maps L to the set of words formed by taking the letters of words of L indexed only by s. We consider the languages resulting from filtering by all arithmetic progressions. If L is regular, then we prove that only finitely many distinct languages result. By contrast, there exist CFL’s that give infinitely many distinct languages as a result. We use our technique to prove a similar result for the operation diag, which extracts the diagonal of words of square length.
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ورودعنوان ژورنال:
- Fundam. Inform.
دوره 123 شماره
صفحات -
تاریخ انتشار 2013