faylang/fay

Health v2 · maintenance only

Flags: no_releases

Adoption not part of the score

1286 stars · 86 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-30, confidence not recorded

Fay is a statically typed, lazy, purely functional proper subset of Haskell that compiles to JavaScript. It offers a trivial JavaScript FFI, automatic JSON transcoding, a Fay monad for side effects, and cabal-installable packages.

Use cases

• compile haskell code to javascript
• write frontend logic in a haskell subset
• get static typing for code that runs in the browser
• transcode values between haskell and json automatically
• call javascript functions from a purely functional language
• produce small minifier-friendly javascript output

When to choose

• you know Haskell and want to target the browser with familiar syntax and types
• you need a small, simple compiler with a trivial JavaScript FFI rather than full GHC
• you want cabal-installable language packages and server-side transcoding support

When to avoid

• you need full Haskell/GHC features - Fay is deliberately a proper subset
• you need an actively maintained toolchain - the last release was 2021 and documentation has been stale since 2017
• you want deep integration with the modern JavaScript ecosystem or large production apps - PureScript or GHCJS are safer choices

Facets

cli-tool · maturity abandoned

compiler programming-language programming-languages compilers web-development frontend browser cli cross-platform haskell javascript altjs functional-programming statically-typed transpiler ffi json cabal

Member repositories

For agents

markdown · JSON · MCP: product_card(name="faylang/fay")