Example of using a code generator,
which is [CoffeeScript](https://coffeescript.org/) in this example.

```
npm install
./build.js -watch -run
```

Now try editing the `.coffee` files and see your program being rebuilt and run in response.

The generated program is a single JavaScript file at `out/main.js`.
Source mapping is also generated at `out/main.js.map` which correctly maps to your coffee files
(rather than the intermediate JS files generated by the CoffeeScript compiler.)