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Coding of real-valued continuous functions under WKL$\mathsf {WKL}$
Authors:Tatsuji Kawai
Institution:Department of Information Science, Kochi University, Kochi, Japan
Abstract:In the context of constructive reverse mathematics, we show that weak K?nig's lemma ( WKL $\mathsf {WKL}$ ) implies that every pointwise continuous function f : 0 , 1 ] R $f : 0,1]\rightarrow \mathbb {R}$ is induced by a code in the sense of reverse mathematics. This, combined with the fact that WKL $\mathsf {WKL}$ implies the Fan theorem, shows that WKL $\mathsf {WKL}$ implies the uniform continuity theorem: every pointwise continuous function f : 0 , 1 ] R $f : 0,1]\rightarrow \mathbb {R}$ 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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