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Kotlin is much nicer than Java, that's for sure. It strives to be compatible both ways (calling Java from Kotlin and vice versa), which I think has helped with

Kotlin is much nicer than Java, that's for sure. It strives to be compatible both ways (calling Java from Kotlin and vice versa), which I think has helped with its adoption. It also means that it cannot have very wild features that can't be mapped nicely to the world of Java, which I think has its downsides. My main gripe with Kotlin is some of its design choices for syntax. I really really really don't like its syntax for lambdas, specifically. A code block in curly braces could be both a lambda with an implicit argument, or a list of statements. You have to inspect the context to see which one it is, or rely on intelliJ to make the former type slightly bolder. That is so bad for comprehension, and I think the only reason it was done like that was to allow for some cute hacks where control flow constructs such as map, fold etc. could be implemented using lambdas and still look like regular imperative code. Another thing is that you can create lambdas with an implicit binder that you can refer to as "it" inside the body. It may save you one or two keystrokes, but it also encourages the programmer to be lazy about naming things. Combined with the fact that curly braces are overloaded, whenever I see "it" in code, my eyes scan frantically for the first opening curly brace, and I then have to determine whether it is a lambda with an explicit binder (then it isn't my binder, and I have to continue searching), a statement block (then it also isn't my binder), or a lambda with an implicit binder. Don't get me started on nested lambdas with implicit "it" binders that shadow each other.

thu2111 7y ago
Well, they see it more as a core language feature than a cute hack. Kotlin 1.0 was big into DSLs as a competitive advantage, though I don't think it got adopted in the way they hoped and I don't see much talk about it anymore. But the idea was you can make libraries where you can write code like this: val page = html { head { title = "Title" } body { etc } } It looks like it's a part of the language and naturally integrates with features like code folding, but it's actually all just functions and objects anyone can create. DSLs have taken off in one area: UI construction. There's TornadoFX for JavaFX, SwiftUI on Apple and JetPack Compose for Android. I've tried both new and old approaches extensively and to be honest I'm not sure this is actually better than using a proper GUI builder, but for small fragments of UI it's pretty neat. Sort of like what JSX does in React but more principled and type safe.
- ulrikrasmussen 7y ago
  I don't see why you can't create DSLs with an equally compact syntax which doesn't overload the curly braces. Yes, it would look different, but it would be more readable. Curly brace lambdas give a first impression of readability, but they really are not when you consider how they affect the binding structure.

thu2111 7y ago

Well, they see it more as a core language feature than a cute hack. Kotlin 1.0 was big into DSLs as a competitive advantage, though I don't think it got adopted in the way they hoped and I don't see much talk about it anymore. But the idea was you can make libraries where you can write code like this: val page = html { head { title = "Title" } body { etc } } It looks like it's a part of the language and naturally integrates with features like code folding, but it's actually all just functions and objects anyone can create. DSLs have taken off in one area: UI construction. There's TornadoFX for JavaFX, SwiftUI on Apple and JetPack Compose for Android. I've tried both new and old approaches extensively and to be honest I'm not sure this is actually better than using a proper GUI builder, but for small fragments of UI it's pretty neat. Sort of like what JSX does in React but more principled and type safe.

ulrikrasmussen 7y ago
I don't see why you can't create DSLs with an equally compact syntax which doesn't overload the curly braces. Yes, it would look different, but it would be more readable. Curly brace lambdas give a first impression of readability, but they really are not when you consider how they affect the binding structure.