RustyScheme

A toy Scheme interpreter written in Rust, loosely based on the R5RS Specification with a bit of Racket thrown in as well.

It supports a small number of standard library functions, as well as:

• Function and variable definition
• Quote, Quasiquote/unquote
• Apply & Eval
• Macros (not hygenic yet)
• Let expressions
• Tail-call optimization
• Continuations, Call-with-current-continuation
• Unicode
• REPL, with history

There are two versions of the interpreter:

• A straight-forward AST-walking interpreter, which uses the Rust stack and heap, and uses vectors to represent Scheme lists.
• A continuation-passing style interpreter, which supports tail-call optimization and continuations, uses the Rust stack and heap, and uses a linked list to represent Scheme lists.

In the future, I may develop an interpreter that manages its own stack and/or heap, and possibly a bytecode VM & compiler as well for comparison.

Requirements

• Rust 1.0-beta or later

Usage

Download and install Rust 1.0 from http://www.rust-lang.org/install.html.

To start a REPL using the default CPS interpreter:

cargo run

To execute a Scheme file using the default CPS interpreter:

cargo run examples/printing.scm

To start a REPL using the AST-walking interpreter:

cargo run -- -t ast_walk

To execute a Scheme file using the AST-walking interpreter:

cargo run -- -t ast_walk examples/printing.scm

To run the test suite:

cargo test

To watch for changes and auto-rebuild (on OS X):

gem install kicker -s http://gemcutter.org
./watch