Reversible Session-Based Concurrency in Haskell

A reversible semantics enables to undo computation steps. Reversing message-passing, concurrent programs is a challenging and delicate task; one typically aims at causally consistent reversible semantics. Prior work has addressed this challenge in the context of a process model of multiparty protocols (or choreographies). In this paper, we describe a Haskell implementation of this reversible operational seman- tics. We exploit algebraic data types to faithfully represent three core ingredients: a process calculus, multiparty session types, and forward and backward reduction semantics. Our implementation bears witness to the convenience of pure functional programming for implementing reversible languages