OCaml Users in PariS (OUPS)

Le prochain OUPS aura lieu le mercredi 29 avril 2026. Le rendez-vous est fixé à 18h30 au 45 rue d'Ulm, amphithéâtre Rataud (2ème sous-sol). Il existe un plan des bâtiments.

L'inscription est obligatoire pour pouvoir accéder au meetup !
Les exposés seront également retransmis en ligne sur le galène du OUPS.
Toutes les informations sont disponibles sur le site du OUPS.

Programme :

When Turing machines meet GADTs -- Florian Angeletti

Have you ever wondered why one needs to write down explicit
unreachable clauses in a GADT-pattern matching? Or how much
computation one can sneak inside an OCaml type?

This talk proposes to answers those questions and more with a deep dive
into GADTs, the OCaml compiler implementation of the exhaustiveness
checking for pattern match, and how to best trick the typechecker into
finding the BB(3) champion by itself.

Extending OCaml's pattern matching -- Yanni Lefki

Pattern matching has been studied for decades and has been the subject of extensive research and numerous extensions. Nevertheless, recent language features—such as Rust’s if-let construct, and recent work such as Cheng and Parreaux (OOPSLA 2024), suggest that there is still room for improvement. We propose a streamlined approach that unifies pattern matching with extended forms of conditionals.

In particular, our prototype introduces binding-boolean-expressions, which allow variables to be bound within pattern guards, within if-conditions (and subsequently used in the then branch), and within while-conditions (and used in the loop body). Our system also incorporates Haskell-style views, enabling the definition of smart deconstructors, the dual of smart constructors.

In this talk, we present an ML-like language equipped with evaluation rules, typing rules, and a simple compilation scheme. We conclude with a demonstration of our implementation: an OCaml PPX prototype that parses an extended ML syntax exposing these constructs, type-checks programs according to our (highly intuitive!) rules, and translates them into a correct OCaml AST via our (non-optimizing) transformation.

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Les présentations seront suivies par des discussions libres. Les pizzas seront offertes par la fondation OCaml !