Runners in action

TL;DR

This paper introduces a new mathematical and programming model called runners, based on algebraic effects, enabling modular resource management and virtual machine definition, supported by formal semantics and practical implementations.

Contribution

It formalizes runners within an equational calculus and provides a sound denotational semantics, along with prototype implementations in OCaml and Haskell.

Findings

Formalization of runners in an equational calculus

Sound and coherent denotational semantics for resource management

Prototype language and library implementations in OCaml and Haskell

Abstract

Runners of algebraic effects, also known as comodels, provide a mathematical model of resource management. We show that they also give rise to a programming concept that models top-level external resources, as well as allows programmers to modularly define their own intermediate "virtual machines". We capture the core ideas of programming with runners in an equational calculus $\lambda_{\mathsf{coop}}$, which we equip with a sound and coherent denotational semantics that guarantees the linear use of resources and execution of finalisation code. We accompany $\lambda_{\mathsf{coop}}$ with examples of runners in action, provide a prototype language implementation in OCaml, as well as a Haskell library based on $\lambda_{\mathsf{coop}}$.