Modular implicits

TL;DR

Modular implicits extend OCaml with type-directed implicit module parameters, enabling ad-hoc polymorphism similar to Scala implicits and modular type classes, supporting features like inheritance and associated types.

Contribution

This paper introduces modular implicits, a novel extension to OCaml that simplifies ad-hoc polymorphism using type-directed implicit modules based on OCaml's first-class functors.

Findings

Supports systematic ad-hoc overloading features

Naturally integrates with OCaml's module system

Enables inheritance and associated types

Abstract

We present modular implicits, an extension to the OCaml language for ad-hoc polymorphism inspired by Scala implicits and modular type classes. Modular implicits are based on type-directed implicit module parameters, and elaborate straightforwardly into OCaml's first-class functors. Basing the design on OCaml's modules leads to a system that naturally supports many features from other languages with systematic ad-hoc overloading, including inheritance, instance constraints, constructor classes and associated types.