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arXiv · 2604.11935

Polyregular equivalence is undecidable in higher-order types

Mikołaj Bojańczyk·Grzegorz Fabiański·Rafał Stefański
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Abstract

It is open whether equivalence ( f = g ) is decidable for string-to-string polyregular functions. We consider their higher-order extension based on the {\lambda}-calculus definition of polyregular functions from Boja\'nczyk (2018). In this setting, equivalence is undecidable by reduction from the tiling problem.

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Mikołaj Bojańczyk, Grzegorz Fabiański, Rafał Stefański. 2026-04-13. Polyregular equivalence is undecidable in higher-order types. https://arxiv.org/abs/2604.11935

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