We generalize to a rich dependent type theory a proof originally developed by Escardó that all System 𝚃 functionals are continuous. It relies on the definition of a syntactic model of Baclofen Type Theory, a type theory where dependent elimination must be strict, into the Calculus of Inductive Constructions. The model is given by three translations: the axiom translation, that adds an oracle to the context; the branching translation, based on the dialogue monad, turning every type into a tree; and finally, a layer of algebraic binary parametricity, binding together the two translations. In the resulting type theory, every function f : (ℕ → ℕ) → ℕ is externally continuous.
@InProceedings{baillon_et_al:LIPIcs.CSL.2022.5, author = {Baillon, Martin and Mahboubi, Assia and P\'{e}drot, Pierre-Marie}, title = {{Gardening with the Pythia A Model of Continuity in a Dependent Setting}}, booktitle = {30th EACSL Annual Conference on Computer Science Logic (CSL 2022)}, pages = {5:1--5:18}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-218-1}, ISSN = {1868-8969}, year = {2022}, volume = {216}, editor = {Manea, Florin and Simpson, Alex}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2022.5}, URN = {urn:nbn:de:0030-drops-157256}, doi = {10.4230/LIPIcs.CSL.2022.5}, annote = {Keywords: Type theory, continuity, syntactic model} }
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