A functional language built around algebraic effects, inferred types and native compilation. Write your application logic once; handlers connect it to storage, platform services and deterministic tests.
Osprey is alpha software. It compiles through LLVM to native binaries, WebAssembly and C ABI libraries for iOS and Android.
An editor needs the same save logic to work with real storage and a simulated failure:
effect Drafts { save: fn(string, string) -> Result<int, Error> }
fn saveDraft() = match perform Drafts.save("draft.txt", "Ship it.") {
Success _ => "Saved"
Error { message } => "Retry: ${message}"
}
let disk = handler Drafts {
save path text => writeFile(path, text)
}
let offline = handler Drafts {
save _ _ => Error { message: "offline" }
}
print("${disk(saveDraft)} / ${offline(saveDraft)}")
Saved / Retry: offline
disk really writes the file. offline simulates unavailable storage without touching the file system. saveDraft handles the outcome while its handler supplies the storage capability. UI and validation helpers can call it without passing storage objects through each layer. The compiler rejects calls with no matching handler.
Read the effects guide, including the ML version, or try Osprey online.
Install LLVM/clang, then install Osprey:
# macOS or Linux, with Homebrew
brew install nimblesite/tap/osprey
# Windows, with Scoop
scoop bucket add nimblesite https://github.com/Nimblesite/scoop-bucket
scoop install ospreyosprey program.osp --run
osprey program.osp --check
osprey program.osp --target=wasm32 --compile -o program.wasmSee the installation guide for LLVM setup, supported platforms and verification.
| Start here | What you will find |
|---|---|
| examples/ | Runnable programs, Talon Bank, Issue Inbox and GPT-2 |
| crates/ | Rust compiler, type checker, code generation, formatter, language server and debugger |
| compiler/runtime/ | C runtime and GPU adapters |
| tree-sitter-osprey/ | Default-flavor grammar |
| tests/ | Default and ML language suites with shared golden output |
| docs/ | Specifications, delivery plans and contributor architecture |
| website/ | Language guides, reference pages and public website |
| vscode-extension/, webcompiler/ | Editor integration and online compiler |
| scripts/ | Build rules, validation, platform tooling and packaging support |
| Book/, benchmarks/ | The Osprey book and measured comparisons |
The repository map explains the compilation pipeline, build entry points and where a change belongs. The contributing guide covers setup and coordination.
make setup
make build
make test
make ciRun these from the repository root. The compiler is written to target/release/osprey. Build rules live in scripts/make/; the root Makefile is their entry point.
- Effects: typed requests, reusable value handlers, native single-shot control operations and static interpretation. Guide.
- Types: inference, algebraic data types, exhaustive matching and explicit
Resultfailures. - Any syntax, one language: every flavor's concrete syntax tree lowers into one canonical AST, so types, effects and project modules are shared. Default braces (
.osp), ML layout (.ospml) and the Python flavor (.py, Osprey that looks like Python) ship today and mix in one project. - Arithmetic: integer faults require an explicit
Arithpolicy. Contract. - Native concurrency and memory: isolated fibers; default non-reclaiming allocation, tracing GC or reference counting.
Talon Bank shares web and mobile application logic; Issue Inbox shares iOS and Android state, UI descriptions and platform commands. Native hosts execute mobile SQL and HTTP commands and return completion events. GPT-2 uses two static tensor handlers for host lists and the GPU surface.
Dynamic control effects require native execution. WebAssembly and mobile support value handlers and static discharge; unsupported capabilities are rejected. Full scoped effect rows and reusable continuations remain unfinished. See feature status, specifications and active plans for the precise limits.
MIT licensed. See LICENSE and the release process.