Kotlin 1.1 Released with JavaScript Support, Coroutines and more
blog.jetbrains.com
blog.jetbrains.com
The only significant sources of variance were the following:
a) Groovy's support for functional programming is starting to show its age. It worked with everything, though.
b) The Scala 2.12 compiler has at least one bug that appears to affect its interaction with Java 8 lambdas (in particular, in at least one case expr.method() and (expr).method() will not pass the compiler's typecheck, but { val x = expr; x.method() } does. (All three pass IntelliJ's typechecker for Scala.) Outside of this (aggravating) issue and slower build times, it did work.
c) Java works well with everything but ends up being quite verbose, especially in regards to a functional programming style (no surprise there).
d) Kotlin (1.0) works well with everything and is relatively succinct except for Mockito due to everything defaulting to 'final' - but it appears that Kotlin 1.1 fixes this with a compiler plugin.
Based on my experience with all four languages, I would definitely try adding Kotlin to projects. It seems to be surprisingly mature and stable given how much less time it has spent in development (relative to the other three languages.)
I've never been comfortable doing big projects - multiple files, more than a few hundred lines of code - in a dynamically typed language. It's the same reason were seeing the big uptake of typescript. Statically typed languages give us so many superpowers when we need to do refactoring or any changes at all to an existing codebase. Just changing a function name in a dynamically typed language can be hell. Rearranging the parameter order is even worse, cause you have such trouble finding all of the function uses and where you need to update. With statically typed languages you get editor support for simple stuff like this and it becomes automatic and a push of a button almost.
Functional style in my opinion is about creating functions that operate on standardized data structures. Class based type systems actively discourage functional style, even when the language gives you a functional veneer over your OO code.
Haskell avoids this problem by using algebraic data types instead of class style types. Clojure avoids this problem by using dynamic typing.
I definitely do not associate 'functional' with static typing.
btw: is the source code available somwhere? Would be interesting to see a comparison between the languages.
It's worth pointing out that since Mockito 2.0, you've been able to opt into mocking final classes, making testing Kotlin pretty painless.
https://github.com/mockito/mockito/wiki/What's-new-in-Mockit...
There are many many things that should be valid Scala but are not, due to type check limitation. All kinds of times you should be able to infer the type, but the compiler cannot and you have to start naming types. Not sure this is really a "bug" but more of a wart. Sure is annoying when they happen, but not a "unique" thing to Java8 lambdas by any measure.
Given that Gradle was originally designed with Apache Groovy as its only language for writing its build config files, I'd say you should try again with the build system relevant to each language, such as SBT for Scala, Leiningen for Clojure, etc.
But it seems that Jetbrains has its own vision for Kotlin being a completely independent language. So while it works for me right now, I'm not sure if it will work in the future. They are going native and it'll bring a lot of changes, for sure. Honestly I would prefer it to stay as Java enhancer, as I'm not interested in Native and I need very little JavaScript interoperability, if any (probably just translating some common code between backend and frontend).
But we will see, I don't want to sound too pessimistic. Kotlin is the best language I've used so far.
1) It's hard for a new language to get traction. Lower odds that a new startup! They see so many ruby and python shops adding Go to their stack and want to compete in that space. Kotlin's biggest market seems to be android devs and competing with Go puts them in the datacenter.
2) IDEA's IDEs have a better value proposition to devs working with statically typed languages. Appealing to current Java devs builds the Kotlin ecosystem, but appealing to dynamic language devs expands IDEA's customer base more.
Also (just dreaming here) if Kotlin Native were to use some kind of Swift-like reference counting rather than a traditional GC, it could be really nice for interfacing with COM on Windows, where you need to be able to release references to COM objects immediately and possibly in a specific order. In a language with GC, your objects might not be collected soon enough, which leaves the references alive and the process hosting the COM object unable to shut down.
Application.Database.Classes.Item("MyClass").Refresh()
Python works much better with COM, in my experience, because of its more primitive but more predictable reference counting.
Unless you are talking about manually loading them.
Also, are you aware that UWP and .NET Native are built on COM?
1. When writing a COM add-in for a host application. When the application wants to shut down, the add-in must release all references to the objects of the host application, otherwise the process doesn't shut down. (At least with the application I'm currently writing an add-in for!)
2. When using out-of-process COM servers such as Excel from another application. This tends to leave lots of "excel.exe" processes running unless you explicitly release everything.
See for example: https://www.add-in-express.com/creating-addins-blog/2013/11/...
Here is Microsoft describing how they ran into this problem when mixing COM and .NET in Visual Studio, how they solved it using Marshal.ReleaseComObject, how that itself caused other problems later when they combined it with CCW, and ... I'm not sure what their ultimate correct solution was:
https://blogs.msdn.microsoft.com/vcblog/2006/09/19/mixing-de...
https://blogs.msdn.microsoft.com/visualstudio/2010/03/01/mar...
I am aware of UWP bringing COM back into fashion again, which is why I'm interested in potentially using Kotlin Native with it. :)
I guess the reason for never bumping into it was that all use cases I encountered so far, the controls were in-process and died when the application terminated.
But I think that for really smooth interop with the host platform, it won't be good enough to have just one generic Kotlin Native, that compiles to native code with a cross-platform compiler infrastructure like LLVM. It would be much better to have multiple Kotlin native implementations that integrate well with various host platforms. For example:
* Kotlin for Apple platforms: Every Kotlin object is an ObjC object, and ObjC APIs can be used with minimal glue code in optimized builds. All Kotlin strings are NSStrings and vice versa. Same with collections (NSArray, NSDictionary, and their mutable counterparts); Kotlin's separation of read-only and mutable interfaces is a good match for this platform.
* Kotlin for Universal Windows Platform: UWP, being COM-based, doesn't have a root object type like the Apple platforms. Still, we'll want to be able to call UWP APIs and implement UWP interfaces with minimal runtime glue. And UWP has a reference-counted immutable string type (HSTRING), so all HSTRINGs should be Kotlin strings and vice versa. I don't recall how collections work on UWP.
* Kotlin for classic Win32 + COM: Similar to UWP, but the situation with strings is more complicated. BSTR isn't reference counted, so on this platform, Kotlin would probably need to have its own string implementation, with bridging to and from BSTR for COM interfaces.
We've seen 1/10 the memory usage on golang vs java with similar performance, so properly executed there is a big opportunity in the native space.
Kotlin is close to the ideal language for me because it is just Java done right. If they want to go native and can do it without impairing any of the JVM usability, I guess go for it. But I don't see the point behind it. I don't develop native apps so maybe I just don't know enough, but it seems like Go and Rust have already satisfied the desire for modern natively compiled languages.
I feel the same way about the Kotlin compiling to Javascript ability. I write both the frontend and backend of web apps so I theoretically should be the exact target market for Kotlin to Javascript but I have no interest in it. ES6 and/or Typescript work better there and have an entire ecosystem around them. And even if they didn't work for me I'd prefer Dart which targets the frontend first instead of being an extra like Kotlin Javascript.
My advice to Kotlin: Stick with what you do best. Kotlin is on the exact right track on the JVM but I think all these different modes are going to make people more cautious about adopting it in any of them because they'll worry it's a jack of all trades but master of none.
I find it's a fundamentally better language than both and so being able to write CLI tools and other smaller stuff in it would be nice while still being able to leverage Kotlin + JVM on the backend would also be nice.
Just wanted to point that out in case you didn't know that already.
>[...] but it seems like Go and Rust have already satisfied the desire for modern natively compiled languages
Not for me. Go's type system is too primitive, and Rust is maybe too low level if you don't need the advantages compared to languages with a GC. So a language like Kotlin with a better type system (than go) fits nicely in between the two (that might change if Rust get's a GC type). Especially since it will probably have (or has already?) better tooling considering that Jetbreains is behind it.
Funny enough, all commercial JDKs do support AOT compilation to native code, and Oracle is slowly adding support for it as well.
Kotlin is getting first class support on next generation Spring web framework with functional programming support - https://speakerdeck.com/sdeleuze/functional-web-applications...
it's almost done with first class support for vert.x which is a high-performance reactive webframework https://github.com/vert-x3/vertx-kotlin-common
The reactor project (erlang for the jvm?) is building first class support for kotlin https://github.com/reactor
I think its going to be a great year for building backend systems on jvm.
There are many languages for backends and tons of libraries. But there is hardly any substitute of Java in Android(if you don't consider JS solving every problem in this planet). If JetBrains only concentrate on building an ecosystem for android, it can become "the real Swift for android".
I built a dummy app for android in Kotlin. It was great. The same thing I tried in Scala(it didn't go very well).
Is Kotlin really faster than Scala?
In any case they aren't as bad as C++ (at least until modules arrive).
Speaking as a fan of Scala, I find that scalac takes a noticeable amount of time even to compile trivial Hello World-type programs. Huge C++ codebases like Chromium or Boost take ages to compile, but I seriously doubt a comparable Scala codebase would be faster.
Do Scala compilation times get measured in hours?
Just the other day I gave up compiling Cocos2D-X, after it crossed the one hour threshold on my humble dual core, 8GB.
But no not hours bad.. but say a 3 minute partial compile for a 1 line change is enough to kill your dev cycle. (Not sure it is 3 minutes bad for most projects these days, but its very hard to have a 2 second Scala compile)
As for C++ compile times, the major culprit are templates. Changing a single line of the implementation of a template requires to recompile all code using that template. Scala does not have this problem, because it has generics for most of the things that C++ templates are used, and generics support separate compilation.
Gradle definitely has a daemon: https://docs.gradle.org/current/userguide/gradle_daemon.html
I think in Scala you can do similar "must recompile all" if you do things like change a global implicit.
> I often get 1-5s incremental compile times on a 20 kLOC codebase
20k is still toy project size though. Try incremental compile with 100k or 200k LOC. It gets bad.
As for compiling 200k LOC - just split it into modules with sane dependencies and then you don't have that problem.
> I think in Scala you can do similar "must recompile all" if you do things like change a global implicit.
But there is a world of a difference between changing a signature of an implicit than changing an implementation of a template. If you change the implementation of an implicit, the only thing that needs recompiling is the class defining the implicit, nothing more.
I think any design for generics that provides the same guarantees as C++ templates (type-safe, resolved at compile-time, value types aren't boxed) is necessarily going to cause long compilation times. The only other implementation I know of that checks all three boxes is Rust's, and so far generic Rust is even slower to compile than templated C++.
It very much depends on which features of Scala you use. If you restrict yourself to the features available in Kotlin or other "better Java" languages, Scala compiler isn't much slower. Where Scala compiler gets really slow are implicits - so if you try to write Scala as if it were Haskell then you are probably in trouble.
This isn't true of Ada, Modula-3 or Eiffel generics.
As for Rust, yes their compilation story still needs some improvements, but they still need to enable incremental compilation and cargo is yet to be able to handle binary dependencies across projects.
Where I suffered more in C++ compilation times was building the latest versions from either Swift or Rust, LLVM just takes ages to compile.
Thankfully I mostly use C++ as helping hand for Java/.NET.
I'm not familiar with those languages, but it appears that Eiffel and Modula-3 generics only work with boxed (implemented as pass-by-reference) types, and Eiffel doesn't have pass-by-value types at all.
It does look like Ada generics fulfil those three conditions.
Modula-3 supports value types just like any Algol language, you just need to provide the types you want when instatiating a generic module interface. Modula-3 generics work at module level.
Here is an example for numeric types, with a generic module for all numeric operations:
https://github.com/modula3/cm3/blob/d31f6ca184c66755317ba990...
Specialized to LONGINT.
https://github.com/modula3/cm3/blob/d31f6ca184c66755317ba990...
https://github.com/modula3/cm3/blob/d31f6ca184c66755317ba990...
It is a bit convoluted, but it isn't easy to track down a simple example.
For example, in Scala, nullable references are just another monad object implemented in plain Scala, while in Kotlin they have a special syntax around Java's null pointer.
http://www.lihaoyi.com/post/FromfirstprinciplesWhyIbetonScal...
I have a few concerns about Kotlin's JS backend:
How much can the complete JS bundle be optimized by an advanced whole-program optimizer like the Google Closure Compiler?
Kotlin for JS has no reflection, and I think JetBrains should not look into that as they said they are. But is there powerful compile-time code generation instead, e.g. through annotation processors?
Is there, or will there be, a healthy ecosystem of pure-Kotlin libraries that can be used with both the JVM and JS?
JavaScript backend generates code understandable by static analyzers so it can be optimized. Anyway, we going to continue works in this area in near future.
> Kotlin for JS has no reflection, and I think JetBrains should not look into that as they said they are. But is there powerful compile-time code generation instead, e.g. through annotation processors?
Why do you think that reflection is a bad idea? Honestly, we don't have a final decision about it, it requires investigations and discussions. Note it's very important for us to have an ability to provide good tools (e.g IDE support) for features.
> Is there, or will there be, a healthy ecosystem of pure-Kotlin libraries that can be used with both the JVM and JS?
We will work on it.
OK, reflection isn't necessarily a bad idea. Clearly development tools need it, including future tools that run in the browser (e.g. an in-browser IDE). But I think that applications that are not development tools should not use reflection, because it interferes with static optimization, as the article that I linked in my original comment explains. So most libraries should probably not use reflection either. That means we need an alternative to reflection. For example, chapter 10 of _Kotlin in Action_ uses reflection to implement a serialization library. I think it would be better to use build-time code generation for that, even outside the JS use case (e.g. reflection interfers with optimization of Android app packages with ProGuard).
Edit: By the way, thanks for taking the time to respond.
I think Kotlin is the statically-typed language I've been waiting for, especially with the team's interest in native and JS targets.
But Kotlin also has simplicity that, for example, Scala doesn't. I tried Clojure after spending a couple months with Scala and giving up, and then I used Clojure fulltime for 3+ years.
Eventually, I felt like I was hitting a ceiling with Clojure since it lacked good static analysis. I moved to Node because I felt like, if I'm going to use a dynamically-typed language, I might as well use the ubiquitous one. Also, Clojure was a hard sell to other developers I would meet.
What Clojure does have is an ecosystem of simplicity that I hope the Kotlin ecosystem will adopt.
For example, compare ztellman's http://aleph.io/ (Clojure) to Java's Netty or to the somewhat mind-numbing https://docs.oracle.com/javase/8/docs/api/java/util/concurre.... And compare Clojure's Ring to any Java web framework.
Even Spark, Java's simplest option afaict, doesn't have real middleware, just before/after "filters". That's why I went with the `(Request) -> Response` signature over the `(Request, Response) -> Unit` signature.
There's also ClojureScript's integration and tooling which are pretty impressive these days while Kotlin's JS support is still fledgling.
Though these are the impressions of someone who has only been using Kotlin for a few months without a Java background. And it's not like anyone should be using my lil framework in production, it's just a hobby.
Better type safety means less crashes.
Definitely excited. It's an awesome JVM language.
I follow /r/kotlin as well. Advanced idioms and stuff I've just picked up looking through GitHub repositories.
What I really like about Kotlin is just about everything "works" as it should or you can usually write a Google search that will reference Stack Overflow. I don't have to dig much to find answers and in the absolute worst case I can just drop back to Java and do it the classic way.
I think the only thing I find really annoying about Vert.x is the lack of built-in JSON -> object binding. I've written some cheap glue code to fix that though.
I think Gson is more common on the Android side of things where Kotlin has (I believe) a lot more popularity than on the backend.
Developing a modern frontend app is complex enough with Javascript or Typescript. It's pretty hard to ask people to figure it out from scratch in Kotlin by just saying that it's possible but not showing how.
Also, is it possible to set up kotlin source code in gradle to compile both to JS and the JVM at the same time? I'm specificially thinking that it'd be nice to "share" code between front and backend for some logic and data model definitions.... I think that'd be a killer feature.