A Functional Programming Language with Versions

TL;DR

This paper introduces Lambda VL, a core calculus for a programming language that natively supports multiple versions of packages, enhancing software safety and update flexibility.

Contribution

It presents a novel language design with versioned values and a type system extending coeffect calculus to ensure safe multi-version programming.

Findings

Lambda VL supports multiple package versions within a program.

The type system guarantees valid version combinations.

Framework enables future language features like module systems.

Abstract

While modern software development heavily uses versioned packages, programming languages rarely support the concept of versions in their semantics, which makes software updates more bulky and unsafe. This paper proposes a programming language that intrinsically supports versions. The main goals are to design core language features to support multiple versions in one program and establish a proper notion of type safety with those features. The proposed core calculus, called Lambda VL, has versioned values, each containing different values under different versions. We show the construction of the type system as an extension of coeffect calculus by mapping versions to computational resources. The type system guarantees the existence of a valid combination of versions for a program. The calculus enables programming languages to use multiple versions of a package within a program. It will serve as a basis for designing advanced language features like module systems and semantic versioning.