Context-freeness of the power of context-free languages is undecidable

  • Authors:
  • Henning Bordihn

  • Affiliations:
  • Institut für Informatik, Universität Potsdam, August-Bebel-Straße 89, Haus 4, D-14482 Potsdam, Germany

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2004

Quantified Score

Hi-index 5.23

Visualization

Abstract

The power of a language L is the set of all powers of the words in L. In this paper, the following decision problem is investigated. Given a context-free language L, is the power of L context-free? We show that this problem is decidable for languages over unary alphabets, but it is undecidable whenever languages over alphabets with at least two letters are considered.