Third Func Prog Sweden 2025 – Online

Welcome to the third Func Prog Sweden MeetUp 2025 – Online

This MeetUp will be streamed live online on the Func Prog Sweden YouTube channel: https://www.youtube.com/c/FuncProgSweden

The program starts at 18:00 / 6 PM:

• Intro by Magnus Sedlacek
• Boost your command-line applications with potions! by Eric Torreborre
• Dependent types are everywhere! by Elisabeth Stenholm
• Post-show chat

Boost your command-line applications with potions!
How hard can it be to parse command-line arguments for an application?
My initial, and foolish, answer was “not too hard”. Thanks to this misplaced over-confidence this talk presents potions,
a command-line arguments parsing library written in Unison (https://unison-lang.org).

We will start with a tour of the library features: various type of options, support for environment variables, styled help, and more.
We will then dive into the implementation of the library, where the main workhorse is (drum roll) Unison's effect system called "abilities".

We’ll see what can be checked at compile-time, what can’t, how abilities are layered to provide different DSLs (domain-specific languages),
how they can be used to enclose state for mutually recursive functions, etc…

Finally, I will talk about some of the issues that slowed me down during the development, and why I feel that a full-fledge
Unison IDE will be indispensable for any medium to large scale project.

Eric Torreborre
I am a Rust/Elixir developer working at Ockam where we enable private systems to communicate without exposing their network to the Internet (ask me more if you're interested!). I am also a functional programmer at heart, having professional experience with both Scala and Haskell which I enjoyed very much!

Blog: https://etorreborre.blog
X.com: https://x.com/etorreborre
Bluesky: https://bsky.app/profile/etorreborre.blog

Dependent types are everywhere!
Have you ever heard of dependent types? Even if you have not, chances are you have most likely encountered some data structure that is actually dependently typed, without knowing it. In this talk I will explain what dependent types are and why they are everywhere, we just don’t notice them as we are so used to living without them. With dependent types we can express our structures more correctly, giving us more guarantees compile time. As a concrete example I will share my recent experience with writing a small questionnaire with a web frontend, all the parts of this construction that are actually dependently typed, and the differences between writing it with and without dependent types.

Elisabeth Stenholm
Elisabeth is 32 years old, born in Uppsala and raised in Stockholm. She has a PhD in dependent type theory from the University of Bergen, and is currently working as a fullstack developer at Frende Forsikring — a Norwegian insurance company based in Bergen. In her workday, Elisabeth writes primarily in the functional languages F# and Elm. She is passionate about type theory and functional programming, and enjoys sharing her knowledge on these topics with others.

LinkedIn: https://www.linkedin.com/in/elisabethstenholm/

Post-show chat
Once the live stream is over we will do a post show chat on the FPS Discord Server, where you can join and ask questions and meet more community members (this will no be recorded).

Invite for the FPS Discord Server: https://discord.gg/rMT6xRPwgZ

Video sponsor – Ada Beat
https://adabeat.com

Merch
If you want to spread functional programming and support the channel, buy something from the shop:
https://funcprogsweden.myspreadshop.net/

#funcprogsweden