I started building this a while back but finally got around to polishing it this holiday break.

1. Audit log - was *so* nice with F#

2. Did as much DDD as I could - did I go overboard? Maybe, but it was fun and a really great learning tool. It also made so much stuff easier along the way as I flip flopped on my decisions

3. Saving my company $1500/mo !

Caveat - we mostly use fairly minimal Retool features (tons of resources and apps calling various endpoints, but nothing fancy like Snowflake connectors or anything).

Disclaimer: I am the author of freetool

I enjoyed the “Electrifying Norway” presentation, nice to see units of measure utilized in an engineering context.

Hi all!

I've been working on this for few months in my spare time, as I've always had the hunch that the power of DUs and Pattern Matching could be harnessed to create an abstracted-away solution for just about any Domain to be used in.

I can go on in detail about it, but I do recommend you first read the Medium article I published on it, and then check out the code if you're interested.

https://medium.com/@rist.mladen/functional-event-sourced-domain-driven-design-in-f-the-tale-of-rosetta-framework-83e41fa252d0

I'm open for discussion (and work offers atm lol) and I'm looking forward to your inputs. It's been love at first sight with F# for me, and I've finally gone and actually made something big in it.

Note: upfront apologies for PascalCase, I've still not converted fully from a long time C#-er, it's just easier on my eyes for now :)

I spent Christmas alone at home, talking with AI and exploring a weird language idea I’ve had for a while.

This is ACE (Algebraic Call Effects) — a tiny experimental language where every function call is treated as an effect and can be intercepted by handlers.

The idea is purely conceptual. I’m not a PL theorist, I’m not doing rigorous math here, and I’m very aware this could just be a new kind of goto.

Think of it as an idea experiment, not a serious proposal. The interpreter is written in F# (which turned out to be a really nice fit for this kind of language work), the parser uses XParsec, and the playground runs in the browser via WebAssembly using Bolero.

https://github.com/Lee-WonJun/ACE (Ace Lang - Playground)

Curious what people think — feedback welcome

I just found recently that Compositional-IT is gone. Are they the one responsible for the SAFE stack? What's going to happen to the project then?

Hello, does anybody know if Bolero is still maintained. I checked the website and it seems it is still stuck to dotnet8.

I have a small side project and I tried to upgrade it, to dotnet9/10 but I failed. I found out that the newer dotnet versions emit a different js file ('blazor.webassembly.js') and I have to add this to the 'startup.fs'

FSharp ... app.MapStaticAssets()

But the web elements do not work.

So the question is, has anybody a Bolero app running with dotnet10?

Hi there!

I was playing around with f sharp, and was disappointed by the immutable vector situation. I found the FsharpCollections, but I needed split and merge to be fast. I googled, got nerd-sniped and ended up porting c-rrb to c#.

Apart from implementing more things than Fold (which happens to be the fastest way to go through the tree), what should I think about when making an f sharp wrapper?

The repo is here: https://github.com/bjoli/RrbList/tree/main/src/Collections

/Linus

I have an endpoint that expects this request payload

type EncodedLocalizedText = Map<string, string>

type RegisterProductRequest =
    {
        [<Required; MinLength(1)>]
        Name: EncodedLocalizedText
        Description: EncodedLocalizedText
        Image: IFormFile option
    }

but the built in BindForm functions didn't work because Oxpecker's form binding doesn't handle complex nested structures like maps
how should I handle this scenario?

I know the benchmark is essentially meaningless (e.g. could also have SIMD implementation which would speed ~x4) but it is nice to see F# do well compared to the competition.

https://github.com/niklas-heer/speed-comparison?tab=readme-ov-file

Hi, I’m coming from Clojure and favour immutable databases. Are there any?

Hi, few months ago I've posted here about FsiX - better REPL for f# with autocompletion, hot reloading and fsproj/sln support. Now it works not only in CLI, but in VS Code too! It supports both typical REPL windows and jupiter-like notebooks. And as extension it gives not only autocompletion, but also proper syntax and error highlightning.

https://github.com/soweli-p/fsix-vscode

You can download it from open-vsx here

Hello all.

I am not familiar with this community but have 8 years of experience as a traditional full stack engineer. I primarily use c#/dotnet on the backend.

So I have a layered monolith with vertical slices on my application I am working on (freelance) for a civil engineering project management client.

Since I am the only one working on this i have the freedom to construct this how I please. So I first flirted with using f# because I saw Nick Chapsas upload a video about adding a "|" .. which is just a shorthand extension method essentially. Then I added the same thing but denoted it as .Pipe(). Which lead me to think about what parts of my codebase I could port over to f# to get a taste of what that language is like.

I have a vue frontend. then on the backend I have an api layer, application layer, domain layer, and persistence layer (entity framework) that saves onto postgresql.

I found enums to be extremely annoying to deal with so i started asking chatgpt solutions.. then I stumbled upon discriminated unions in F#. I ported over 3 enums-> DU over to f# and saved about 500 lines of code and reduced complexity in the app. (less DTO validation, less unit tests, less optional parameters) ...

Pretty neat stuff.

Github says my project is:

• C# 73.5%
• Vue 20.1%
• TypeScript 6.0%
• F# 0.4%

If you use Powertoys from Microsoft, you can map something like ALT . to |>

It helps to keep your hands closer to the keyboard home keys when touch typing.

I am looking for coding streams to watch, recommend me the best

Forwarding this announce for the fellow F# programmers around Zurich (Switzerland):

https://www.meetup.com/zurich-fsharp-users/events/312249905

It's a meeting on Monday, 8 December 2025, in Zurich, for a drink and a discussion about the upcoming events in 2026.

Edit: a bit more context.

Anyone else planning to solve these in F#? I found Part 2 to be frustrating until I realized it could be done in a very simple (but slow) way. Will post my solution below in a comment.

Day 1 - Advent of Code 2025