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Comment by palata | Hacker News Reader

> I had some Scala 3 feelings when reading the vision, I hope Rust doesn't gets too pushy with type systems ideas.

I don't know if it is true or not, but my feeling is that Scala brought a lot of new ideas. But as I read somewhere, "Scala was written by compiler people, to write compilers", and I can understand that feeling.

Kotlin came after Scala (I think?) and seems to have gotten a lot of inspiration from Scala. But somehow Kotlin managed to stay "not too complex", unlike Scala.

All that to say, Rust has been innovating in the zero-cost abstraction memory safe field. If it went the way of Scala, I wonder if another language could be "the Kotlin of Rust"? Or is that Zig already? (I have no idea about Zig)

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> But somehow Kotlin managed to stay "not too complex", unlike Scala.

It's not really true anymore, Kotlin has slowly absorbed most of the same features and ideas even though they're sometimes pretty half-baked, and it's even less principled than the current Scala ecosystem. JetBrains also wants to make Kotlin target every platform under the sun.

At this point, the only notable difference are HKTs and Scala's metaprogramming abilities. Kotlin stuck to a compiler plugin exposing a standard interface (kotlinx.serialization) for compile-time codegen. Scala can do things like deriving an HTTP client from an OpenAPI specification on the fly, by the LSP backend.

> JetBrains also wants to make Kotlin target every platform under the sun

So did Scala long before. It's just that Kotlin got a lot more traction for different reasons.

Not to the same extent. Scala.JS and Kotlin.JS are somewhat comparable, other targets not so much. There was no serious attempt at making Scala target mobile devices, even during the window of opportunity with Scala on Android.

> even during the window of opportunity with Scala on Android.

I don't understand this. You can run any pure Java jar on Android, pretty sure you can do that with Scala too? It's not exactly a "different platform" in terms of programming language. Sure it needs tooling and specific libraries, but that's higher level than the programming language.

Jetbrains is doing interop with Swift (Kotlin -> ObjC -> Swift and more recently Kotlin -> C -> Swift), which Scala never did. But I don't really see how this is relevant in this conversation.

You can run Scala on Android and it's been done but it never worked well nor was given priority. Which is understandable as the commercial entities behind Scala already struggle to build the ecosystem and tooling in spaces where the language shines.

For instance the Android runtime has chronically lagged behind mainline JVM bytecode versions, iirc once Scala started to emit Java 8 bytecode, Android was stuck on Java 6.

Kotlin had other obvious advantages on Android like its thin standard library or the inlining of higher-order functions.

> I wonder if another language could be "the Kotlin of Rust"?

Some people would say that Swift is that language since it's potentially memory safe like Rust and is described as friendlier to novices. There's some room for disagreement wrt. the latter point.

Well many languages are memory safe. Java has been memory safe forever. Rust is the one that is memory-safe with zero-cost abstractions, right?

Rust is also data race safe to boot.

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