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arXiv · 2204.11235

Continuous rational functions are deterministic regular

Olivier Carton·Gaëtan Douéneau-Tabot
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Abstract

A word-to-word function is rational if it can be realized by a non-deterministic one-way transducer. Over finite words, it is a classical result that any rational function is regular, i.e. it can be computed by a deterministic two-way transducer, or equivalently, by a deterministic streaming string transducer (a one-way automaton which manipulates string registers). This result no longer holds for infinite words, since a non-deterministic one-way transducer can guess, and check along its run, properties such as infinitely many occurrences of some pattern, which is impossible for a deterministic machine. In this paper, we identify the class of rational functions over infinite words which are also computable by a deterministic two-way transducer. It coincides with the class of rational functions which are continuous, and this property can thus be decided. This solves an open question raised in a previous paper of Dave et al.

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Olivier Carton, Gaëtan Douéneau-Tabot. 2022-11-03. Continuous rational functions are deterministic regular. https://arxiv.org/abs/2204.11235

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