Comment by jorgemf | Hacker News Reader

Comment by jorgemf | Hacker News Reader

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pattern matching: swift has switf and kotlin has when, both are very similar

recursive data structures: I don't get this one, kotlin has all the java api available and all the third party libraries. As java has been here for much longer than swift I guess that swift is lacking more here than kotlin.

Tail call optimization: kotlin has the special word tailrec for this

Yes, kotlin has a lot of things. It also has co-routines like in go, it also compiles to java script and much more.

The reason Google is supporting kotlin and not swift or scaala is because they have to do nothing to support it. Kotlin compiles to bytecode, so it doesnt matter your code is written in java or kotlin because when you compile it it is bytecode at the end. Scala needs to add a runtime when compiling to bytecode, it takes much longer to compile than kotlin and it is not fully compatible with java as kotlin. And Swift it is just something completely different, they should change the virtual machine in order to support it.

Pattern matching: Kotlin has a `when` that desugars into if when statements, but it's pretty far from pattern matching like you see in Scala, Swift, and more traditional functional languages.

Recursive data structures: Yeah, for some reason I wrote recursive data structure when I was thinking of algebraic data types, like Scala can encode with case classes. I often use them in Scala or OCaml to make recursive data structures which is why I mistakenly used that term instead of ADTs.

TCO: glad to see I was wrong. Kotlin added support for this in the past year.

Android: I realize that to support Swift on Android, Google would need to do significant work, but they wouldn't have to change the VM since Swift could also be compiled to Dalvik bytecode. But obviously that would be a lot of work. I only mention Swift since there were rumors in the past that Google was considering fully supporting Swift on Android.

Plus, to be clear, you can run Swift on Android now using the native SDK, just not on Dalvik for making GUI apps.

> Kotlin has a `when` that desugars into if when statements

Actually not. Not now, probably it was the case at the begining of the language.

> algebraic data types

they removed some restriction of sealed classes in 1.1. So I am not sure this is true anymore.

The memory management in Swift is completely different than in Java. That is the main reason you need to make changes in the virtual machine. JVM uses the garbage collector while swift uses reference counter.

> Scala needs to add a runtime when compiling to bytecode

This is nonsense? It doesn't need any more "runtime" than Kotlin does.

> it is not fully compatible with java as kotlin.

This is a lie. (I don't say this lightly, but I've seen it too often from too many kotlin advocates for it to be an innocent mistake)

> Scala needs to add a runtime when compiling to bytecode

Last time I checked you needed like 500kb of libraries for any scala program compiled to Android. Kotlin is a few kb. Kotlin is a small addition to the java API, Scala needs much more things.

> it is not fully compatible with java as kotlin.

As far as I know, the way scala treats types and functions make it that sometimes you cannot call scala code from java. Well, you can most times but requieres a lot of wrappers. This doesn't happen in kotlin.

I learn scala few years ago, my memory is weak and things may change. But I wanted to use it for android and give up quite quickly because of lot of issues. For kotlin was like love at first sight. No problems at all.

> Last time I checked you needed like 500kb of libraries for any scala program compiled to Android. Kotlin is a few kb.

30kb for Scala is the figure elsewhere in this thread and that sounds a lot more in line with my experience. Note that you never have to use e.g. Scala collections if you don't want to (and thanks to typeclasses you can write elegant code that works with both Scala collections and Java ones, so you can reuse libraries across both).

> As far as I know, the way scala treats types and functions make it that sometimes you cannot call scala code from java. Well, you can most times but requieres a lot of wrappers. This doesn't happen in kotlin.

Nope. There's no difference, just kotlin propaganda.

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