Yeah, it's one of Rust's strongest features, as it allows progressive migration of native code, and also allows Rust to serve as a fast/low-overhead extension language for Ruby and Python (etc.).

More details:

- http://doc.rust-lang.org/book/ffi.html#calling-rust-code-fro... - http://doc.rust-lang.org/1.6.0/book/rust-inside-other-langua...