London Scala Talks: Zainab Ali and Fabio Cognigni


LSUG goes on a road trip at's offices! For March's talks we are delighted to be joined by Zainab Ali who will be talking about typelevel programming using Scala and using Idris, and Fabio Cognigni, who will introduce us to ApiBuilder as an alternative to Swagger. Here are their abstracts:

Zainab Ali: The ascent to Idris

Type level programming greatly increases the robustness of our code, but is difficult to express in Scala. Idris, a language where types are first class, is much better at expressing such concepts. But Scala has come a long way in the past few years. This talk takes a closer look at type level programming in Idris and Scala. We start with a basic problem defined using values, and slowly add types to it in both languages. By using singleton and refined types, as well as typelevel induction, we'll rise to the challenge of Idris.

Fabio Cognigni: API spec driven development with ApiBuilder (and Swagger)

In this talk I'll share my experience in the last couple of years implementing and maintaining REST services written in Scala, in the microservice architecture we have in HBC Tech (Hudson's Bay Company). I'll go over the struggles I've experienced, the tools I've been using and the reasons why I moved from using Swagger to a tool called ApiBuilder. ApiBuilder has been built internally in Gilt (acquired by HBC) and recently open sourced ( It offers a great developer experience enforcing best practices like spec first design, versioning, backward and forward compatibility, code generation. ApiBuilder currently provides Scala generators for Play (up to 2.6) and http4s (up to 0.18).


Thanks to for providing the venue and eSynergySolutions for providing refreshments.

We're always on the lookout for new speakers with new ideas. If you'd like to give an LSUG Talk, get in touch using this Google Form. We'll work with you to develop your idea and prepare for your talk. It's the perfect way to try out public tech speaking: