First, we reconstruct Wim Veldman's result that Open Induction on Cantor space can be derived from Double-negation Shift and Markov's Principle. In doing this, we notice that one has to use a countable choice axiom in the proof and that Markov's Principle is replaceable by slightly strengthening the Double-negation Shift schema. We show that this strengthened version of Double-negation Shift can nonetheless be derived in a constructive intermediate logic based on delimited control operators, extended with axioms for higher-type Heyting Arithmetic. We formalize the argument and thus obtain a proof term that directly derives Open Induction on Cantor space by the shift and reset delimited control operators of Danvy and Filinski.
@InProceedings{ilik_et_al:LIPIcs.TYPES.2013.188, author = {Ilik, Danko and Nakata, Keiko}, title = {{A Direct Version of Veldman's Proof of Open Induction on Cantor Space via Delimited Control Operators}}, booktitle = {19th International Conference on Types for Proofs and Programs (TYPES 2013)}, pages = {188--201}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-939897-72-9}, ISSN = {1868-8969}, year = {2014}, volume = {26}, editor = {Matthes, Ralph and Schubert, Aleksy}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TYPES.2013.188}, URN = {urn:nbn:de:0030-drops-46320}, doi = {10.4230/LIPIcs.TYPES.2013.188}, annote = {Keywords: Open Induction, Axiom of Choice, Double Negation Shift, Markov's Principle, delimited control operators} }
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