Puffin

Puffin is a minimal functional programming language inspired by Scheme and ML. It features a self-hosting compiler, a gradual type system, modules, and a typed foreign function interface. The language was created by extending an earlier teaching-focused compiler using Claude Code under the direction of Kristopher Micinski.

Its development added several features to the base teaching language drawn from Jeremy Siek's compiler book. These include match patterns and quasiquoting, a gradual type system based on consistency, a simple standard library with sets and hashes along with other facilities, a module system inspired by SML, and a typed FFI. The implementation remains prototypical in areas such as gradual typing and modules. Ports of several Racket applications have been written in Puffin as part of its exploration.

It is positioned for use in language and compiler experimentation, with the stated goal of eventually replacing Racket for day-to-day brainstorming about compilers and interpreters. A browser-based version allows users to try the language directly in their browser. Source code is available on GitHub, and the project includes tutorial, standard library, documentation, and example materials.