Session-ocaml: a Session-based Library with Polarities and Lenses
Keigo Imai
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Abstract
We propose session-ocaml, a novel library for session-typed concurrent/distributed programming in OCaml. Our technique solely relies on parametric polymorphism, which can encode core session type structures with strong static guarantees. Our key ideas are: () polarised session types, which give an alternative formulation of duality enabling OCaml to automatically infer an appropriate session type in a session with a reasonable notational overhead; and () a parameterised monad with a data structure called 'slots' manipulated with lenses, which can statically enforce session linearity and delegations. We show applications of session-ocaml including a travel agency usecase and an SMTP protocol.
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