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Life & fun · August 12, 2025

Coalton Playground – Type-Safe Lisp in the Browser

I built a browser-based REPL for Coalton, a statically typed Lisp dialect that merges Haskell’s type system with Common Lisp. Coalton gives you: - Algebraic data types, pattern matching, static guarantees - Full interoperability with dynamic Lisp functions Demo & examples: https://coalton.app Under the hood: Prebuilt SBCL cores with Coalton preloaded, running on a droplet

Coalton Playground – Type-Safe Lisp in the Browser launched on August 12, 2025 with 19 votes, #675 of 8,530 launches that month and more than 90% of that year's launches. The site was still online in September 2026, 1 year on.

Visit coalton.app ↗Alternativestop 8% of August 2025

In plain words

Coalton Playground is a browser-based REPL for Coalton, a statically typed Lisp dialect combining Haskell's type system with Common Lisp's dynamic features. It lets developers write code with algebraic data types, pattern matching, and static guarantees while maintaining full interoperability with standard Lisp functions. The tool runs prebuilt SBCL cores with Coalton preloaded, allowing users to experiment with type-safe functional programming directly in a web browser.

written from the facts on this page · September 2026

From the sources

Statically-typed Lisp with Haskell-style features. Try it in your browser.

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