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https://github.com/maplant/scheme-rs
Embedded Scheme for the Async Rust Ecosystem
https://github.com/maplant/scheme-rs
Last synced: 7 days ago
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Embedded Scheme for the Async Rust Ecosystem
- Host: GitHub
- URL: https://github.com/maplant/scheme-rs
- Owner: maplant
- License: mpl-2.0
- Created: 2023-08-12T22:18:39.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2024-12-26T01:08:53.000Z (15 days ago)
- Last Synced: 2024-12-26T02:21:45.150Z (15 days ago)
- Language: Rust
- Homepage:
- Size: 322 KB
- Stars: 40
- Watchers: 2
- Forks: 2
- Open Issues: 13
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# 
Scheme-rs: Embedded Scheme for the Async Rust Ecosystem
Scheme-rs is a work-in-progress implementation of the [R6RS](https://www.r6rs.org/final/r6rs.pdf) specification
of the scheme programming language that is designed to work with async Rust runtimes like [tokio](https://tokio.rs/).
In essence, it is a embedded scripting language for the async Rust ecosystem.
Scheme-rs is intended to be fully compliant with R6RS, and R7RS large when it is eventually released. To that end
the bones are mostly there but some key issues remain.
Eventually, I would like scheme-rs to be more opinionated in the extras it provides, and include a package manager.
That is obviously a long way away.
## Features currently supported by scheme-rs:
- Tail-call optimizations are fully supported
- Garbage Collected via [Bacon-Rajan Concurrent Cycle Collection](https://pages.cs.wisc.edu/~cymen/misc/interests/Bacon01Concurrent.pdf)
- Most key forms (let/let*/letrec/lambda/define etc)
- Call by current continuation
- Transformers (define-syntax, syntax-case, make-variable-transformer)
- Spawning tasks and awaiting futures
## Features currently unsupported by scheme-rs:
- Exceptions and error handling
- Ports and IO operations
- Most API functions are not implemented
- A large portion of lexical structures are missing; there's no way to specify recursive data structures
- And many more that I cannot think of off the top of my head
## Usage:
### Running a REPL:
A REPL is the default entry point for scheme-rs at the current moment. You can access it by running `cargo run`
in the repo's root directory (examples taken from wikipedia):
```
~/scheme-rs> cargo run
Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.03s
Running `target/debug/scheme-rs`
> (let loop ((n 1))
(if (> n 10)
'()
(cons n
(loop (+ n 1)))))
$1 = (1 2 3 4 5 6 7 8 9 10)
>>> (let* ((yin
((lambda (cc) (display "@") cc) (call-with-current-continuation (lambda (c) c))))
(yang
((lambda (cc) (display "*") cc) (call-with-current-continuation (lambda (c) c)))))
(yin yang))
@*@**@***@****@*****@******@*******@********@*********@**********@***********@**********...^C
```
### Creating Builtin Functions:
Scheme-rs provides a `builtin` function attribute macro to allow you to easily define builtins. For example,
here is the definition of the `number?` builtin in the source code:
```rust
#[builtin("number?")]
pub async fn is_number(
_cont: &Option>,
arg: &Gc,
) -> Result, RuntimeError> {
let arg = arg.read().await;
Ok(Gc::new(Value::Boolean(matches!(&*arg, Value::Number(_)))))
}
```