Thread by @Aaronontheweb

Adding key / entityId interfaces to discriminated unions in F# for use with @AkkaDotNET routing constructs like Cluster.Sharding is such a succinct way to implement a protocol docs.microsoft.com/en-us/dotnet/f…

@AkkaDotNET I'm almost done with my first set of domain state machines with my F# prototype and it's just a breeze compared to the same one I implemented in C# - I'm | | close to recommending it to some customers who have greenfield projects

Benefits of this approach, once I forced myself to learn it over the course of 4-5 2hr Twitch stream sessions:

1. Not having to worry about mutability - cuts out 80% of boilerplate code alone
2. Can make it nearly impossible to express illegal states via the type system

3. Very little third party library dependencies - validation et al is handled pretty concisely via "wrapped types" for primitives (i.e. @ScottWlaschin 's String50 and so on)
4. Decoupling functions from type declarations actually makes both more modular and re-usable

There's a lot more subtleties and nuances to learn still (i.e. active patterns) but it's amazing how easy it is to express something so robustly

Here's my implementation of that protocol in F# - I actually can't express this idea in C# very easily: "here's all of the possible commands you can receive in this protocol and by the way here's an identifier for the unique identity they should be sent to"

I could go a step further with this and try to define what possible _responses_ you can receive but I haven't gotten that far with my implementation or F# experience yet