Steel

About

Steel is an embeddable scheme interpreter, with a standalone interpreter/REPL included as well. The language is implemented as a bytecode virtual machine. At the moment, it is mostly compliant with R5RS, only missing let-syntax support. Support for R7Rs is underway.

Warning The API is relatively stable, however it may change at any time while pre 1.0. Care will be taken to keep things backwards compatible where possible.

Features

• R5RS support
• Modules, using require and provide much like Racket.
• syntax-rules and syntax-case macros.
• Easy integration with native Rust functions and structs, either through embedding or via FFI.
• Higher order Contracts
• Built in immutable data structures, including:
  • lists
  • vectors
  • hashmaps
  • hashsets

For more details, see the book.

Getting Started

This github repository contains a CLI interpreter. To try it out on the online playground, go to the Steel playground. To get started using a REPL with the crates, make sure you first have Rust installed.

Then, clone the repo and run the following command:

cargo run

This will launch a REPL instance that looks something like this:

Full install

If you'd like to install everything, just run the following command:

cargo xtask install

This will install:

• The steel interpreter, steel
• The package manager, forge
• The dylib installer, cargo-steel-lib (also available via the interpreter)
• The steel language server
• The standard library, found under the cogs directory

Nix

Steel can also be installed with Nix. Add the following to your Home Manager config:

home.packages = [
  pkgs.steel
];

Packages

If you would like to customize the location of installed packages, please set the STEEL_HOME environment variable. Steel currently follows XDG if present, and otherwise assumes the default of $HOME/.steel if the STEEL_HOME environment variable is not already set.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

See CONTRIBUTING.md.