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  1. Coding of real‐valued continuous functions under WKL$\mathsf {WKL}$.Tatsuji Kawai - 2023 - Mathematical Logic Quarterly 69 (3):370-391.
    In the context of constructive reverse mathematics, we show that weak Kőnig's lemma () implies that every pointwise continuous function is induced by a code in the sense of reverse mathematics. This, combined with the fact that implies the Fan theorem, shows that implies the uniform continuity theorem: every pointwise continuous function has a modulus of uniform continuity. Our results are obtained in Heyting arithmetic in all finite types with quantifier‐free axiom of choice.
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  • Decidable fan theorem and uniform continuity theorem with continuous moduli.Makoto Fujiwara & Tatsuji Kawai - 2021 - Mathematical Logic Quarterly 67 (1):116-130.
    The uniform continuity theorem states that every pointwise continuous real‐valued function on the unit interval is uniformly continuous. In constructive mathematics, is strictly stronger than the decidable fan theorem, but Loeb [17] has shown that the two principles become equivalent by encoding continuous real‐valued functions as type‐one functions. However, the precise relation between such type‐one functions and continuous real‐valued functions (usually described as type‐two objects) has been unknown. In this paper, we introduce an appropriate notion of continuity for a modulus (...)
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