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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 hang
by debugnik 5mo ago
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.
- ibejoeb 5mo agoThe Register source has this comment: // Registers can't be a record type because the values need to be truncated to 8 bits when writing, so setters are needed // This is for the web renderer as Fable transpiles uint8 to Number (more than 8 bits) in JS and doesn't apply any truncation // Known non-standard behaviour in Fable (https://fable.io/docs/javascript/compatibility.html#numeric-types) So, I think, it's just conservatively cleaning the data due to Fable's widening via js Number on the web target.
- debugnik 5mo agoOof, thanks for pointing that out, I hadn't noticed and I've only ever used F# on .NET. That's terrible on Fable's part, the least they could do is truncate. I wasn't aware Fable's translation is so naive.
- ibejoeb 5mo agoI haven't used Fable much, but apparently it maps .NET arrays to js TypedArray. Presumably you could keep the registers in 8-element array and fable will properly produce a Uint8Array. I'd like to benchmark that.
- rienbdj 5mo agoIt’s really hard to please everyone all of the time on this front. This kind of thing is why Roc compiles to WASM but not JS.
- omcnoe 5mo agoFable is great but it has a surprising number of these hidden behaviour changes that are really hard to detect when writing code against it.
- keithnz 5mo agoIt's actually discussed in the article in the part where he ports it to fable (he also tried blazor)
- debugnik 5mo agoI admit I skimmed from there on because I don't find web dev exciting, but you're right, it is. That's a terribly naive translation on Fable's part.