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ICFP 2019
Sun 18 - Fri 23 August 2019 Berlin, Germany
Fri 23 Aug 2019 13:30 - 14:00 at Aurora Borealis - Paper Session 6: Effects Chair(s): Ki Yung Ahn

For over two decades, monad transformers have been the main modular approach for expressing purely functional side-effects in Haskell. Yet, in recent years algebraic effects have emerged as an alternative whose popularity is still growing.

While the two approaches have been well-studied, there is still confusion about their relative merits and expressiveness, especially when it comes to their comparative modularity. This paper clarifies the connection between the two approaches—some of which is folklore—and spells out consequences that we believe should be better known.

We characterise a class of algebraic effects that is modular, and show how these correspond to a specific class of monad transformers. In particular, we show that our modular algebraic effects gives rise to monad transformers. Moreover, every monad transformer for algebraic operations gives rise to a modular effect handler.

Fri 23 Aug

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13:30 - 15:00
Paper Session 6: EffectsHaskell at Aurora Borealis
Chair(s): Ki Yung Ahn Hannam University
Research paper
Monad Transformers and Modular Algebraic Effects: What Binds Them Together
Tom Schrijvers KU Leuven, Maciej Piróg University of Wrocław, Nicolas Wu Imperial College London, Mauro Jaskelioff CONICET, Argentina
Research paper
Scoping Monadic Relational Database Queries
Anton Ekblad Chalmers University of Technology