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

翻译：多正则函数的字符串到字符串等价性（f = g）是否可判定仍是未解决问题。我们考虑基于Bojańczyk(2018)中λ-演算定义的多正则函数的高阶扩展。在此设定下，通过从铺砌问题归约可证明等价性是不可判定的。