Contributing: Building from the source code

If you are a developer and want to help us build better tools for open and transparent data-driven story-telling, this is the place to start! The Gamma is written using the awesome F# language and compiled to JavaScript using Fable, so this is fun project if you want to play with some nice technology!

The Gamma project structure

All project source code is available under the the-gamma organization on GitHub. If you want to run everything locally, you’ll need to clone and run the following three projects:

  • thegamma-script is the most important one. It implements the parser, compiler, analyzer and live editor for the simple programming language that powers The Gamma. The project is written using F# and compiled to JavaScript via Fable.

  • thegamma-sample-web is a minimal web site that you can use for testing your changes. This is a pure Node.js web page using the Express framework. Live version is running on Azure, but it’s a plain Node.js web site and will run anywhere.

  • thegamma-services implements the REST service that provides data for the sample visualizations. This is built using F# and Suave and there are a number of scripts. The data source for Olympic medals is implemented here.

Getting started with F#  

If you are new to Fable and F#, you’ll need to install F# first. There is a good documentation on how to do this on for all platforms.

  • On Mac and Linux, the best option is to use mono (which is the runtime that F# uses). F# works with many popular editors including Emacs and Atom. If you have no preferences, many people use Visual Studio Code with the Ionide plugin.

  • On Windows, most F# developers use the latest version of Visual Studio, which comes with F# support (but make sure to choose it during the installation), although you can also use more lightweight Visual Studio Code with Ionide plugin. The .NET runtime is already included with Windows.

  • No special installation is needed for Fable. Fable is available on npm and it will get downloaded for you when you build The Gamma. However, the Fable web site contains plenty of useful resources if you want to learn more about it!

Cloning and running locally

To run The Gamma locally, you first need to clone thegamma-script repository. This is the source code for thegamma-script npm package, which implements the compiler etc.:

git clone
cd thegamma-script
npm install
npm link
npm run watch

The npm run watch command will run the Fable compiler in background and watch for changes in the source code. When you make any change and save the file, the compiled output (in the dist folder) will be updated. Before running npm run watch, it is a good idea to run npm link see docs, which lets you reference the local version of the package from the sample web site (and see your changes instantly).

Next, we clone and run thegamma-sample-web, which is a minimal web site that uses thegamma-script package:

git clone
cd thegamma-sample-web
npm install
npm link thegamma-script
npm start

If you run npm link thegamma-script, your local build of the package thegamma-script will be used instead of the one from the npm. When you save a file in thegamma-script project, you will see the changes (almost) immediately in the sample web site! Running npm start should also open browser window with the locally hosted demo.

Finally, if you also want to run a local version of the REST service that provides data for the olympics (and other data sources), you need to clone thegamma-services too:

git clone
cd thegamma-services

The script will download dependencies and start the services in background at localhost:10042. It will watch for file changes and when you make a change, it will automatically reload the modified services. To use the local version of services in the sample web, modify the line that defines the services variable in index.html.