It's amazing how hard it is to get code to compile in Rust. This is the result of an hour-long struggle. It demonstrates one usage of `extra::json`. Hope it helps someone.

json_example.rs

// Compile with rustc 0.9-pre (727b70d 2013-11-17 21:11:24 -0800)

#[feature(managed_boxes)];

extern mod extra;

use extra::json;
use std::io::stdio;
use extra::serialize::Encodable;

#[deriving(Encodable, Decodable)]
struct Person {
    name: ~str,
    height: f64,
    age: int,
}

fn main() {
    let out = @mut stdio::stdout();
    let encoder = &mut json::Encoder((out as @mut std::io::Writer));
    let p = &Person{
        name: ~"Derek",
        height: 173.5,
        age: 20,
    };
    p.encode(encoder);
}