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Comment by throwawaymaths | Hacker News Reader

Did they really implement the type system in scala!!?

(If someone knows better I'd love to know! The readme is awful short on details)

Yeah that’s interesting. Flow uses OCaml, ditto for their Python type checker. Hack is C++, and Relay uses Rust. (Although I think some of the other type checkers are migrating from OCaml to Rust).

Curious about the perf implications with using a JVM language for a compiler vs native.

Forget about perf. Who wants to import a separate stack to get a sidecar tool. Separately, if you're an elixir user this would mean you can't easily hook it into say compiler callbacks (though if I'm reading this code directly it reads Erlang ast -- I tried doing a typechecker for elixir ast, and decided that reading bytecode was a better choice since it's simpler)

Starting with bytecode seems harder because you no longer know what the expression terms are. So they are harder (impossible?) to typecheck.

You type the registers as data flows through them. It's easier, trust me. Both Erlang and especially elixir puts a whole lot of sugar on top of the low level instructions which can make reasoning about data structures harder. And as a bonus it works with all beam languages.

Hmm ok, I'll take your word for it. There is another issue too though, which is that the BEAM itself is being replaced with a native-code VM. I don't know if the compiler for that starts with bytecode.

I think you're confused. Not architecture (x86, arm) bytecode, BEAM bytecode. Erlang compiles down to An intermediate bytecode like java does.

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