[Pl-seminar] 3rd October : Ohad Kammar - On the expressive power of user-defined effects

[Aviral Goel]

NUPRL Seminar presents

*Ohad Kammar*
University of Oxford (https://www.cs.ox.ac.uk/people/ohad.kammar/main.html)

10:00 AM
Wednesday, October 3rd, 2018
Room 366 WVH (http://www.ccs.neu.edu/home/wand/directions.html)


*On the expressive power of user-defined effects*

*Abstract*

Computational effects, such as mutable state, memory allocation,
non-determinism, and I/O interaction, allow programs to implicitly
exhibit complex behaviour. I will discuss three abstractions that
allow programmers to extend a language with user-defined effects:

+ Control operators (call-cc, shift/reset, etc.)  are a
well-established abstraction for user-defined effects, and I will
consider the specific shift/dollar without answer-type-modification.

+ Since the 90s, functional languages have used monads for
user-defined effects, and I will consider Filinski's monadic
reflection.

+ In the last decade, the community started looking into Plotkin and
Pretnar's handlers for algebraic effects (extensible effects in
Haskell, OCaml multicore, the Eff, Frank, Koka, and Links programming
languages) as a programming abstraction, and I will consider deep
handlers without forwarding.

I will compare the relative expressive power of these three
abstractions using Felleisen's notion of macro-translations.  This
comparison demonstrates the sensitivity of relative expressiveness of
user-defined effects to seemingly orthogonal language features.

This talk is based on the paper:

On the expressive power of user-defined effects: effect handlers,
monadic reflection, delimited control.
Yannick Forster, Ohad Kammar, Sam Lindley, and Matija
Pretnar. Proceedings of the 22nd ACM SIGPLAN International Conference
on Functional Programming, PACMPL 1(ICFP): 13:1-13:29 (2017),
arXiv:1610.09161, DOI: 10.1145/3110257.

*Bio*

Ohad Kammar is a postdoctoral research associate at the
University of Oxford  Department of Computer Science, a
Career Development Fellow at Balliol College Oxford,
and an incoming Royal Society University Research Fellow at the
University of Edinburgh School of Informatics.
His fields of interests include programming language modelling and
design, logic, and the foundations of computer science.
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