From Two-Way Transducers to Regular Function Expressions

  • Nicolas BaudruEmail author
  • Pierre-Alain Reynier
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 11088)


Transducers constitute a fundamental extension of automata. The class of regular word functions has recently emerged as an important class of word-to-word functions, characterized by means of (functional, or unambiguous, or deterministic) two-way transducers, copyless streaming string transducers, and MSO-definable graph transformations. A fundamental result in language theory is Kleene’s Theorem, relating finite state automata and regular expressions. In [3], the authors introduced a set of regular function expressions and proved a similar result for regular word functions, by showing the equivalence with copyless streaming string transducers. In this paper, we propose a direct, simplified and effective translation from unambiguous two-way transducers to regular function expressions extending the Brzozowski and McCluskey algorithm. In addition, we identify a subset of regular function expressions characterizing the (strict) subclass of functional sweeping transducers.


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© Springer Nature Switzerland AG 2018

Authors and Affiliations

  1. 1.Aix Marseille Univ, Université de Toulon, CNRS, LISMarseilleFrance

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