Comment by dhfhduk | Hacker News Reader

Comment by dhfhduk | Hacker News Reader

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I have nothing against Kotlin. It seems to be coming out of nowhere to surpass more "tested" languages for lack of a better way of putting it, but as I'm reading about it I can truly see the appeal.

The one thing I'm having trouble figuring out, though, is how much it diverges from Java in terms of inheritance, traits, etc. The verbosity of Java is one thing, but its inheritance system is what made me want to pull my hair out.

Languages like Scala, Haskell, Rust, etc. are preferable to me in that way. Kotlin seems nice and clean--from what I've seen so far, with this "Android bump", Kotlin native, etc., I could even see it replacing Python--but I worry there's something lurking deeper.

This is the clearest thing I've found so far, but it's very old at this point:

http://codeofrob.com/entries/looking-at-kotlin---kicking-the...

It includes this quote that stokes my fears: "It feels as if the language designers haven't really designed at this point, they've just thrown a load of stuff at the wall because inheritance is something that all Java developers want and given us a few bad ways of doing something as well as something that has the potential to make us write better Java."

I don't have any attachment to Scala. However, I do think Scala, Rust, etc. have moved language design forward in significant, fundamental ways, and it would be nice to see those advancements recognized in the Android platform.

Take this all with a grain of salt, though, because I know next to nothing about Kotlin.

It's weird you'd accuse Kotlin of throwing stuff at the wall while simultaneously speaking kind of Scala. Scala has so many competing ideas & approaches just all mashed up into a blob.

Scala isn't so much a mishmash as it is fertile ground for people to do all kinds of weird stuff that looks like part of the language. Very much like C++, with the same potential for committing atrocities. And like C++ was, it's great from a programmer perspective (long lever, you get what you want/deserve) but bad from a corporate perspective. (Somehow C++ acquired an aura of corporate respectability, but in retrospect it's surprising, considering it has the same problems as Scala: a difficult and sometimes esoteric language, hard to hire for, amplifies programmers instead of smoothing them out, easy to misuse with tragic results, might walk by a developer's desk and see them consulting a book instead of pounding out LOC, etc.)

I'm thrilled that Google is supporting Kotlin, though. Official support for Scala was never going to happen, and Kotlin sounds like a huge step up. I regret sinking so much time into struggling with Scala on Android.

This is wrong. It might look like that from afar, but what seems like complex features in Scala are almost always actually combinations of simple, powerful features, and the combination works exactly the way you'd expect once you understand the simple features. (Almost all of the concrete examples people give of "Scala complexity" are actually library features implemented in plain Scala, and if you get confused you can always click through to the source and read how they're implemented, because they're just plain old code). Whereas in Kotlin they really do just implement every use case as a separate language-level feature.

JetBrians is possibly the best company on the planet to implement syntax improvements to Java, which is basically what Kotlin is.

They have deep experience with the syntax of a bunch of different languages. They know what Java is missing because they've seen a ton of different things in diverse languages.

Looking at Kotlin myself, they got rid of almost all of the painful syntactical blunders in Java. I'm seriously considering picking it up for my next project just looking at their main page. It looks fantastic.

Kotlin didn't change, the only difference is `trait` keyword replaced with `interface` keyword. But I'm not really getting this article. Inheritance is key principle of Object-Oriented Programming, throwing it away would be very stupid move. It could be abused, but everything could. Kotlin solves this in pragmatic way: if you need inheritance, you must declare it explicitly. If you want delegation, Kotlin got you covered with awesome delegate syntax. The choice is up to you.

Also remember that good compatibility with Java is a big priority for Kotlin, so inheritance works very similar to Java and compiles to the same obvious JVM structures.

Thanks. This is helpful. I guess part of what I'm wondering is how much Kotlin interfaces compare to Scala traits in the sense explained here:

https://en.wikibooks.org/wiki/Scala/Traits

Or, in another example, how does use of Rust impl map onto Kotlin?

http://www.jonathanturner.org/2016/02/down-the-rabbit-hole-w...

I really don't mean this as a criticism of Kotlin, I'm just trying to map this all out. Kotlin seems nice and like something I could use, but I'm sure it has its boundaries also.

No , inhertiance is not a key part of oop. Look at Rust and Go. https://lwn.net/Articles/548560/

I tend to agree. Sure, Kotlin is much more terse than Java. But looking at it I can't help much miss language features I've gotten used to in Rust, Haskell et al. I'm sure it's a wonderful language and an improvement over Java but there's nothing that excites me about it.

Hey, at least they've got nullable types? That's a big win over Java right there.

> Hey, at least they've got nullable types? That's a big win over Java right there.

Can you elaborate what you mean by nullable types?

You can set Object variables to null and with primitives you can do the same with their boxed alternatives (Integer) but I assume you mean something different?

Like the lack of types which can't be null? I can see how that's useful

I think they meant to say that Kotlin has non-nullable types.

The Kotlin page does a good job of explaining it if you aren't familiar. It's the single most important feature that makes Kotlin worth using over Java in my opinion: https://kotlinlang.org/docs/reference/null-safety.html

non-nullable*, Swift calls them optional types I believe. They use the same syntax for it, if you want your type to include "bottom" you add a ?

In Kotlin/Swift by default all types do not include "bottom" or "null". You add a ? to the type to indicate you may use that value, then the compiler will validate you're checking for the existence of null before you use the type.

It's one approach... I prefer the Haskell approach with a simple Maybe/Option type.

I have starting learning kotlin 2 years ago for Android but I have not yet touched Scala, so I am also biased.

After 2 hours with the kotlin koans (short exercises allowing you to learn the language), it was already clear that Kotlin solves most of java's limitations when writing android apps.

higher order functions : so powerful .. at the cost of dex (and I don't really care about dex size), I can get very flexible calls.

nullability backed in the compiler

100 % java interop

data classes

default parameters values ..

etc

IIRC, the larger runtime was what prevented Scala from being interesting on Android. I know that Scaloid has been working on making it more svelte though.

I think the case for Kotlin over Scala is that the runtime you have to link into your app is substantially smaller, which is important for mobile.

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