Homomorphisms Preserving Deterministic Context-Free Languages

  • Tommi Lehtinen
  • Alexander Okhotin
Part of the Lecture Notes in Computer Science book series (LNCS, volume 7410)

Abstract

The paper characterizes the family of homomorphisms, under which the deterministic context-free languages, the LL context-free languages and the unambiguous context-free languages are closed. The family of deterministic context-free languages is closed under a homomorphism h if and only if h is either a code of bounded deciphering delay, or the images of all symbols under h are powers of the same string. The same characterization holds for LL context-free languages. The unambiguous context-free languages are closed under h if and only if either h is a code, or the images of all symbols under h are powers of the same string.

Keywords

Regular Language Closure Property Nonterminal Symbol Free Language Synchronization Delay 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • Tommi Lehtinen
    • 1
    • 2
  • Alexander Okhotin
    • 1
  1. 1.Department of MathematicsUniversity of TurkuTurkuFinland
  2. 2.Turku Centre for Computer ScienceFinland

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