Over 4000 free audio and video lectures, seminars and teaching resources from Oxford University.
Skip to Content Skip to Navigation

Thank you for visiting! Please consider filling out our questionnaire. This will help us improve our service providing free educational media recorded from the University of Oxford. Many thanks!

Click here to access the survey (3 minutes to complete).

On the Expressive Power of User-Defined Effects: Effect Handlers, Monadic Reflection, Delimited Control

Loading Video...
Duration: 0:18:19 | Added: 13 Dec 2017
Ohad Kammar, University of Oxford, UK, gives the second presentation in the fourth panel, Effects, in the ICFP 2017 conference.

Co-written by Yannick Forster (Saarland University, Germany and University of Cambridge, UK), Sam Lindley (University of Edinburgh).

We compare the expressive power of three programming abstractions for user-defined computational effects: Bauer and Pretnar's effect handlers, Filinski's monadic reflection, and delimited control without answer-type-modification. This comparison allows a precise discussion about the relative expressiveness of each programming abstraction. It also demonstrates the sensitivity of the relative expressiveness of user-defined effects to seemingly orthogonal language features.

We present three calculi, one per abstraction, extending Levy's call-by-push-value. For each calculus, we present syntax, operational semantics, a natural type-and-effect system, and, for effect handlers and monadic reflection, a set-theoretic denotational semantics. We establish their basic meta-theoretic properties: safety, termination, and, where applicable, soundness and adequacy. Using Felleisen's notion of a macro translation, we show that these abstractions can macro-express each other, and show which translations preserve typeability. We use the adequate finitary set-theoretic denotational semantics for the monadic calculus to show that effect handlers cannot be macro-expressed while preserving typeability either by monadic reflection or by delimited control. We supplement our development with a mechanised Abella formalisation.

Copy and paste this HTML snippet to embed the audio or video on your site: