Live Coding on Elm Open Source Series

Hello everyone! I’m starting a new live coding series where I work on Elm Open Source projects and learn from people in the community!We’re kicking off our first session tomorrow morning. We’ll be streaming at

The Phantom Builder Pattern with @jfmengels

The builder pattern lets you conveniently configure data in a pipeline. In this session, Jeroen will show us a powerful technique to use phantom types to allow us to ensure constraints in that pipeline.
We’ll apply this pattern to make some improvements to the elm-pages API.

Tomorrow (Monday) at 9:30 AM Pacific

You can add the event to your calendar, and see more events as I schedule them here:

I’ve got a few more sessions that I’m working on scheduling. Mostly, I’ll be pairing with community members on some of my Elm Open Source projects, like elm-graphql, elm-pages, and dillonkearns/elm-markdown. I’m thinking it could also be fun to do some Q and A sessions about these libraries. I’m hoping to make it a regular thing. If you have suggestions or feedback, I’d love to hear from you!

Hope you enjoy!


Yesterday’s session was really fun! The recording is up, and I’ve posted a new event for Monday, March 16 @ 11am Pacific. We’re going to implement a Github-Flavored Markdown table parser from scratch :sunglasses:

Find the recording and the new session details at


Hey Dillon and Jeroen!

This is such a great use case of phantom types! Thank you for sharing! Looking forward to the 16th of march!

I wrote a simple example of the phantom builder pattern:


This topic was automatically closed 10 days after the last reply. New replies are no longer allowed.