Léonard's website

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Hello 👋

My name is Léonard Oest O’Leary.

I’m finishing my Master’s degree in computer languages and compilers, working on Ribbit.

I’m on the job market!

For the past five years, I have been building compilers and programming languages in both research and industry settings. I was hired at Meta (Facebook), developed my own compiler as part of my master’s degree, contributed to LLVM, and published at renowned conferences such as ISMM (co-located with PLDI).

For more details, please refer to my CV.

About

I started my academic journey before university, publishing papers during Cégep with Jihene Rezgui, Ph.D. Upon entering university, I worked with Prof. Marc Feeley who sparked my interest in functional languages and their implementations. I was fortunate enough to be surrounded by exceptional mentors such as Prof. Stefan Monnier and Prof. Ian Arawjo during my bachelor’s and now my master’s studies.

My recent work primarily revolves around implementations of functional programming languages. This originates from a deeper joy in understanding complex systems and extracting their essence. Reflections on this subject lead me to compact compilers, embeddable virtual machines, garbage collection algorithms, debugger interface design, and some hidden graph theory.

Apart from academic work, I love to tinker and learn new things. I have written some games, programmed a robot to drive and fixed a regression in LLVM. I also worked at Meta for less than a week as a Production Engineer.

If you find my work interesting, have questions or comments, contact me!

Contact

You can reach me by email at: leonard <at> oestoleary <dot> com, by replacing the <dot> with a . and the <at> with an @.

You can also find me on GitHub, LinkedIn, orcid and Google Scholar.

Academic Contributions

Does Back-stepping Help Programmers Debug?
Léonard Oest O'Leary, Jingyue Zhang, Olivier Melancon, Ian Arawjo and Marc Feeley.
In PLATEAU 2026 @ Carnegie Mellon University, March 2026.
(Preprint)(Slides)
Arborescent Garbage Collection: A Dynamic Graph Approach to Immediate Cycle Collection. *Best paper award*.
Frédéric Lahaie-Bertrand, Léonard Oest O'Leary, Olivier Melancon, Marc Feeley and Stefan Monnier.
In International Symposium on Memory Management (ISMM25), June 2025.
(PDF)(ACM website)(Recording)(Slides)
A R4RS Compliant REPL in 7 KB.
Léonard Oest O'Leary, Mathis Laroche, and Marc Feeley.
In Scheme and Functional Programming Workshop (SFPW'23), September 2023.
(PDF)(arXiv)(Recording)(Slides)(Code)
A Compact and Extensible Portable Scheme VM.
Léonard Oest O'Leary, and Marc Feeley.
In MoreVMs Workshop (MOREVMS@PROGRAMMING'23), March 2023.
(PDF)(ACM website)(Code)
A platform for Sharing Artificial Intelligence Algorithms in Autonomous Driving : An overview of Enhanced LAOP.
Jihene Rezgui, Clement Bisaillon, and Léonard Oest O'Leary.
In International Symposium on Networks, Computers and Communications (ISNCC20), June 2020.
(PDF)(IEEE website)
Finding better learning algorithms for self-driving cars: An overview of the LAOP platform.
Jihene Rezgui, Clement Bisaillon, and Léonard Oest O'Leary.
In International Symposium on Networks, Computers and Communications (ISNCC19), June 2019.
(PDF)(IEEE website)
Training Genetic Neural Networks Algorithms for Autonomous Cars with the LAOP Platform.
Jihene Rezgui, Léonard Oest O'Leary, Clement Bisaillon, Lamia Chaari Fourati.
In International Wireless Communications & Mobile Computing Conference (IWCMC19), August 2019.
(PDF)(IEEE Website)

Teaching and Engagement

I have been a teaching assistant for the following courses at the University of Montréal:

Programming Languages and Compiling (IFT3065-IFT6232) - Winter 2023, Winter 2025.
Introduction to programming (IFT1015) - Fall 2020, Fall 2021, Winter 2022.
Introduction to programming for Neuroscience (IFT1016) - Fall 2019, Fall 2020.

I have also been the president of AÉDIROUM, the student association of the Department of Computer Science and Operations Research (DIRO) at the University of Montréal. I was elected for the 2021–2022 term.

Awards and Scholarships

Best Paper Award @ ISMM25 (International Symposium on Memory Management). This was awarded for Arborescent Garbage Collection: A Dynamic Graph Approach to Immediate Cycle Collection.
Natural Sciences and Engineering Research Council (NSERC), Canada Graduate Scholarship, Master’s.
Fonds de recherche du Québec Nature et technologies(FRQNT), Bourses de formation à la maîtrise.
Natural Sciences and Engineering Research Council (NSERC), Undergraduate Student Research Awards. Awarded twice.
Fonds de recherche du Québec Nature et technologies(FRQNT), Suppléments aux bourses de 1er cycle. Awarded twice.
University of Montreal, Bachelor’s entry scholarship.