Parallel Algebraic Effect Handlers

Abstract: Algebraic effects and handlers support composable and structured control-flow abstraction. However, existing designs of algebraic effects often require effects to be executed sequentially. This paper studies parallel algebraic effect handlers. In particular, we formalize {\lambda}p, an untyped lambda calculus which models two key features, effect handlers and parallelizable computations, the latter of which takes the form of a for expression as inspired by the Dex programming language. We present various interesting examples expressible in our calculus, and provide a Haskell implementation. We hope this paper provides a basis for future designs and implementations of parallel algebraic effect handlers.