[justthistime_]

Well, I don't think what you say is based on reality if you look at all the broken, half-designed stuff they are trying to ship. (Not understanding (yet) why some design decisions are bad, doesn't mean they aren't bad.)

It feels like they are digging through Scala's graveyard of discarded ideas without even realizing it. Most of what they try to do differently has already been considered in the past and has been rejected by the Scala developers for good reasons – years ago.

Kotlin's struggles are a good example that knowing how to build IDE support for existing languages doesn't give you the skills to design a programming language from scratch.

    The Kotlin designers specifically call out Scala's
    mistakes when discussing why they do things differently.

Yes, I have to give them that. They (and their "fans") excel at PR, marketing and FUD.

[modersky]

Different languages have different design tradeoffs. I had many profitable exchanges with Andrey Breslav and other Kotlin designers. We can have a technical discussion about the design choices without getting into a fight about who is more competent.

[udalov]

Could you please give a few examples of "all the broken, half-designed stuff they are trying to ship"?

[justthistime_]

- extension methods

- property syntax + magic identifier

- reified

- immutable wrappers around mutable collections

- const

- multiple redundant ways of defining generic upper bounds

- companion objects + syntax

- operator/infix rules

- constantly changing nullability rules

[pron]

I think you are falling into the mistake of associating what you call design with features. How features are implemented and how consistent they are with some pure notion of their role is secondary to how they serve the high-level design goals. Once you understand Kotlin's design goals you see that the features and their implementation make a lot of sense. If you think the features aim to serve another goal, then the features might seem inconsistent. Outside of academic languages, language features exist to serve particular purpose, and so their "academic" form may be compromised to serve that purpose better. There is no point in isolating features from their purpose and then arguing over them without first understanding their goal in that particular language, as the same feature can serve different (or subtly different) purposes in different languages, or a feature must be twisted in order to allow the goal to be better achieved. There is no way to say whether a feature is good or "broken" without first analyzing the language's goals, and a feature that may be bad in one language may be great in another.

As Scala (or Ceylon) has such radically different goals from Kotlin, it doesn't make much sense to discuss which features were imported and how without first understanding the why. Kotlin's designers didn't say, "I like this Scala feature but not that one"; they said, "we have this goal and this Scala feature serves it but that one doesn't". A language is not measured by what features it has, but by how those features serve its goals, and whether those goals are appropriate to begin with (i.e. provide a good cost/benefit ratio).

[justthistime_]

Sorry, but I don't plan on reading your confused ramblings.

[pron]

Have I done something to offend you? Because you are being extremely rude. You are entitled to think whatever you want about my ramblings, confused or otherwise, and you are even entitled to not try to understand them or even read them at all. But your outbursts are inappropriate. Continue expressing yourself in this way and you will be banned from HN.

[monkeyfacebag]

What's broken about extension methods? I have zero experience Scala and about a week's worth of experience with Kotlin, but so far I'm finding extension methods to be pretty straightforward and useful. What am I missing?

[justthistime_]

Extremely poor cost/benefit ratio.

[pron]

Extremely poor cost/benefit ratio for what purpose? If your main goal is to adopt existing classes and libraries as your own (i.e. without any loss of functionality compared to language-native libraries), then extension methods obviously have an extremely high cost/benefit ratio. You can't analyze a feature in isolation of the language's goals. Features exist to serve a purpose, and are measured by how well they serve it.

[pron]

To give an analogy, a shoulder-fired missile might have a terrible cost/benefit ratio if you're trying to hunt an antelope, but if you're trying to disable a tank, then I'd say it's cost/benefit ratio is pretty good.