Type Classes for Lightweight Substructural Types

Edward Gan, Jesse A. Tov, and Greg Morrisett

In Proc. Third International Workshop on Linearity (LINEARITY 2014), July 2014.

Linear and substructural types are powerful tools, but adding them to standard functional programming languages often means introducing extra annotations and typing machinery. We propose a lightweight substructural type system design that recasts the structural rules of weakening and contraction as type classes; we demonstrate this design in a prototype language, Clamp.

Clamp supports polymorphic substructural types as well as an expressive system of mutable references. At the same time, it adds little additional overhead to a standard Damas–Hindley–Milner type system enriched with type classes. We have established type safety for the core model and implemented a type checker for Clamp in Haskell.


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