,
Graham Hutton
Creative Commons Attribution 4.0 International license
Internalising classes of datatypes has been a longstanding pursuit in type theory. For example, containers capture strictly positive types, while combinatorial species capture finitely labelled structures. To date, however, there has been no similar attempt to internalise classes of operations on datatypes. In this paper we show how the theory of operads, which extend species with a well-behaved notion of composition, provides a natural approach to internalising finitary operations. We present an internalisation of a generalised notion of operad in homotopy type theory, which provides a generic framework for capturing and reasoning about operations with particular algebraic properties. All our results are formalised in Cubical Agda.
@InProceedings{hewer_et_al:LIPIcs.TYPES.2025.4,
author = {Hewer, Brandon and Hutton, Graham},
title = {{HoTT Operads}},
booktitle = {31st International Conference on Types for Proofs and Programs (TYPES 2025)},
pages = {4:1--4:24},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-441-3},
ISSN = {1868-8969},
year = {2026},
volume = {384},
editor = {Nordvall Forsberg, Fredrik and McKinna, James},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TYPES.2025.4},
URN = {urn:nbn:de:0030-drops-270228},
doi = {10.4230/LIPIcs.TYPES.2025.4},
annote = {Keywords: operads, homotopy type theory, proof assistants}
}