I built a Game Boy emulator in F#

cermicelli

Finally someone putting in actual human effort to learn something, and not a LLM helped me build X in Y minutes. There is some hope for humanity after all I suppose.

hmokiguess

F# is super fun, awesome work!

z500

That's so cool! I love F#, but I wrote a little Smalltalk interpreter in it and I can confirm it isn't exactly a speed demon for that kind of thing if you use it as intended lol

__loam

I'm actually starting a new project to create a gba emulator in zig, and also starting with chip8. I'm going to skip nand to tetris because I played Turing complete. Cool to see I'm on the right track!

MattCruikshank

Sorry for the tangent - does anyone have some really zoomed in views of GB, GBColor, GBA screens in operation? I'd love for retro shaders to be able to more faithfully reproduce. I mean, ideally, we'd run different color test patterns through, in different lighting conditions, to build a really detailed model, right?

yoyohello13

I always find emulators written in functional languages impressive. It tends to be much easier to map hardware to an imperative language. I enjoy seeing the functional abstractions people come up with.

debugnik

Cool to see F# here! Emulators are a great way to learn a language. On first sight you chose well between more or less idiomatic F# for each job. Some low hanging fruit to reduce allocations: the discriminated unions in Instructions.fs could be [<Struct>], reusing field names to reuse internal fields. Also, minor nitpick but I'm confused about some of the registers. They are already of type byte, the setters with `a &&& 0xFFuy` don't add anything over `member val A = 0uy with get, set`. I'm guessing this changed over time.

Ginop

I misread Fem-Boy and I was not understanding the context anymore lol

CSMastermind

Insanely cool. I've had it in the back of my mind to write a Rust compiler for the game boy for a long time and everytime I see something like this I think about brushing off that project.

thrownawaysz

mildy related but wasn't there an emulator (maybe not GB but NES or SNES?) which had a visual panel showing each CPU cycle step by step? afaik it was very slow but the 1000% accuracy was the goal not playability.

mkw5053

Very cool. Makes me want to build something with F*

dmitrygr

> No code is free from the influence of AI these days, even learning projects Speak for yourself

deadbabe

Building emulators is cool but everyone does it, and the end result is more or less the same. Is there some things that could be done during the process to perhaps make an emulator a little more unique instead of a perfect replica?

BadBadJellyBean

When I read F# I always have to think of the song with the same name by Tim Minchin and it starts playing in my head.

redrobein

F# is a good language, but I feel like it's forever stuck in C#'s shadow. A lot of the library code is C# and .NET handmedowns. Not interfaces or libraries crafted with F# in mind, often having no explicit documentation for use with F# either.

sirjaz

This is awesome. Love seeing projects like this.

DeathArrow

Now I would like to see the other way around, F# running on Game Boy.

tehnub

Interesting, enjoyable post. Like the bit about data modeling. I've been dabbling in some OCaml and that kind of modeling is the best part. Also interesting to learn of CAMLBOY. Feedback to the author: Skip the AI edit step. I'd have preferred grammar errors or inelegance to what we have here, which is a bit stale.