A nominal exploration of intuitionism

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Colleges, School and Institutes


This papers extends the Nuprl proof assistant (a system representative of the class of extensional type theories `a la Martin-Löf) with named exceptions and handlers, as well as a nominal fresh operator. Using these new features, we prove a version of Brouwer’s Continuity Principle for numbers. We also provide a simpler proof of a weaker version of this principle that only uses diverging terms. We prove these two principles in Nuprl’s meta-theory using our formalization of Nuprl in Coq and show how we can reflect these metatheoretical results in the Nuprl theory as derivation rules. We also show that these additions preserve Nuprl’s key meta-theoretical properties, in particular consistency and the congruence of Howe’s
computational equivalence relation. Using continuity and the fan theorem we prove important results of Intuitionistic Mathematics: Brouwer’s continuity theorem and bar induction on monotone bars.


Original languageEnglish
Title of host publicationProceedings of the 5th ACM SIGPLAN Conference on Certified Programs and Proofs, CPP 2016
Publication statusPublished - 18 Jan 2016
Event5th ACM SIGPLAN Conference on Certified Programs and Proofs - St. Petersburg, FL, United States
Duration: 18 Jan 201619 Jan 2016


Conference5th ACM SIGPLAN Conference on Certified Programs and Proofs
CountryUnited States
CitySt. Petersburg, FL


  • Intuitionistic Type Theory, Nuprl, Coq, Continuity, Nominal Type Theory, Exceptions, Squashing, Truncation