Reimplementing Mizar in Rust

Author Mario Carneiro

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Mario Carneiro
  • Carnegie Mellon University, Pittsburgh, PA, USA


I would like to thank Josef Urban and Jeremy Avigad for their support and encouragement, and Adam Naumowicz and SUM for taking the courage to finally open-source Mizar, without which it would not have been possible to publish this paper and accompanying code.

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Mario Carneiro. Reimplementing Mizar in Rust. In 14th International Conference on Interactive Theorem Proving (ITP 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 268, pp. 10:1-10:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)


This paper describes a new open-source proof processing tool, mizar-rs, a wholesale reimplementation of core parts of the Mizar proof system, written in Rust. In particular, the "checker" and "analyzer" of Mizar are implemented, which together form the trusted core of Mizar. This is to our knowledge the first and only external implementation of these components. Thanks to the loose coupling of Mizar’s passes, it is possible to use the checker as a drop-in replacement for the original, and we have used this to verify the entire MML in 11.8 minutes on 8 cores, a 4.8× speedup over the original Pascal implementation. Since Mizar is not designed to have a small trusted core, checking Mizar proofs entails following Mizar closely, so our ability to detect bugs is limited. Nevertheless, we were able to find multiple memory errors, four soundness bugs in the original (which were not being exploited in MML), in addition to one non-critical bug which was being exploited in 46 different MML articles. We hope to use this checker as a base for proof export tooling, as well as revitalizing development of the language.

Subject Classification

ACM Subject Classification
  • Mathematics of computing → Mathematical software performance
  • Software and its engineering → Formal methods
  • Social and professional topics → Systems analysis and design
  • Mizar
  • proof checker
  • software
  • Rust


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