The miniature, embeddable R7RS Scheme implementation in Rust
Stak Scheme aims to be:
- An embeddable Scheme interpreter for Rust with very small memory footprint and reasonable performance
- The minimal implementation of the R7RS-small standard
- A subset of Chibi Scheme, Gauche, and Guile
- A portable scripting environment that supports even no-
stdand no-allocplatforms
For more information and usage, visit the full documentation.
To install Stak Scheme as a library in your Rust project, run:
cargo add stak
cargo add --build stak-build
cargo install stak-compileFor full examples, see the examples directory.
To install the Scheme interpreter as a command, run:
cargo install stakFirst, prepare a Scheme script at src/hello.scm.
(import (scheme base))
(write-string "Hello, world!\n")Then, add a build script at build.rs to build the Scheme source file into bytecodes.
use stak_build::{build_r7rs, BuildError};
fn main() -> Result<(), BuildError> {
build_r7rs()
}Now, you can include the Scheme script into a program in Rust using the stak::include_module macro.
use core::error::Error;
use stak::{
device::StdioDevice,
file::VoidFileSystem,
include_module,
process_context::VoidProcessContext,
module::{Module, UniversalModule},
r7rs::{SmallError, SmallPrimitiveSet},
time::VoidClock,
vm::Vm,
};
const HEAP_SIZE: usize = 1 << 16;
// Include a Scheme script in the bytecode format built by the build script above.
static MODULE: UniversalModule = include_module!("hello.scm");
fn main() -> Result<(), Box<dyn Error>> {
run(&MODULE.bytecode())?;
Ok(())
}
fn run(bytecodes: &[u8]) -> Result<(), SmallError> {
// Prepare a heap memory of a virtual machine.
let mut heap = [Default::default(); HEAP_SIZE];
// Create a virtual machine with its heap memory primitive procedures.
let mut vm = Vm::new(
&mut heap,
SmallPrimitiveSet::new(
// Attach standard input, output, and error of this process to a virtual machine.
StdioDevice::new(),
// Use void system interfaces for security because we don't need them for this example.
VoidFileSystem::new(),
VoidProcessContext::new(),
VoidClock::new(),
),
)?;
// Initialize a virtual machine with bytecodes.
vm.initialize(bytecodes.iter().copied())?;
// Run bytecodes on a virtual machine.
vm.run()
}Currently, in-memory standard input (stdin) and output (stdout) to Scheme scripts are the only way to communicate information between Rust programs and Scheme scripts.
use core::{error::Error, str::{self, FromStr}};
use stak::{
device::ReadWriteDevice,
file::VoidFileSystem,
include_module,
process_context::VoidProcessContext,
module::{Module, UniversalModule},
r7rs::{SmallError, SmallPrimitiveSet},
time::VoidClock,
vm::Vm,
};
const BUFFER_SIZE: usize = 1 << 8;
const HEAP_SIZE: usize = 1 << 16;
static MODULE: UniversalModule = include_module!("fibonacci.scm");
fn main() -> Result<(), Box<dyn Error>> {
let input = 15;
let mut output = vec![];
let mut error = vec![];
run(&MODULE.bytecode(), input.to_string().as_bytes(), &mut output, &mut error)?;
// If stderr is not empty, we assume that some error has occurred.
if !error.is_empty() {
return Err(str::from_utf8(&error)?.into());
}
// Decode and test the output.
assert_eq!(isize::from_str(&str::from_utf8(&output)?)?, 610);
Ok(())
}
fn run(
bytecodes: &[u8],
input: &[u8],
output: &mut Vec<u8>,
error: &mut Vec<u8>,
) -> Result<(), SmallError> {
let mut heap = [Default::default(); HEAP_SIZE];
let mut vm = Vm::new(
&mut heap,
SmallPrimitiveSet::new(
// Create and attach an in-memory I/O device.
ReadWriteDevice::new(input, output, error),
VoidFileSystem::new(),
VoidProcessContext::new(),
VoidClock::new(),
),
)?;
vm.initialize(bytecodes.iter().copied())?;
vm.run()
}- This project is based on Ribbit Scheme, the small and portable R4RS implementation.
- Scheme programming language
- The R7RS-small standard