Experiences with Effects in OCaml

The multicore branch of OCaml adds support for effect handlers. In this talk, we report our experiences with effects, both from converting existing code, and from writing new code. Converting the Angstrom parser from a callback style to effects greatly simplified the code, while also improving performance and reducing allocations. Our experimental Eio library uses effects to allow writing concurrent code in direct style, without the need for monads (as found in Lwt or Async). Thomas Leonard OCaml Labs Craig Ferguson Tarides Patrick Ferris OCaml Labs Sadiq Jaffer Opsian and OCaml Labs Tom Kelly OCaml Labs KC Sivaramakrishnan IIT Madras India Anil Madhavapeddy University of Cambridge, UK