Why you might want to choose Ceylon
ceylon-lang.org
ceylon-lang.org
I want to like Ceylon because it's the language Scala should be (assuming that higher-kinded types made it in - I could never work without them). It's Scala with all the ugly parts polished away, Scala with ten years' progress in language design.
But it does nothing that Scala can't. Scala might need a pile of bodges to offer these things - Shapeless implicit macros to use tuples generically, type-level libraries abusing the implicit resolution rules to implement unions, a retrofitted JavaScript backend. But that stuff has been written now, and as a developer it works - maybe with a couple of ugly extra lines here and there, but that's all.
I'm glad it exists, but I just can't see people choosing the more polished language over the one with ten years worth of library and tool support when there's no USP beyond that polish.
One feature of Ceylon that caught my attention however is that Ceylon modules are implicitly OSGi modules. If you are building a microservices-type JVM application based on OSGi, Ceylon could make this a lot easier.
I dabble with whatever new languages come out as any other language geek, but at work it only matters the languages validated by the IT department or requested by the customer.
So, like many, I only work with languages blessed as first class languages in vendor SDKs.
With Scala and Clojure barely being adopted by most Java shops (in perpetual terms), I don't see where Ceylon might fit in without a story to sell.
Doing so ought to be trivial if they haven't. Java has a mode where it uses doubles everywhere. JavaScript has Math.fround() for single-precision arithmetic.
OTOH, Kotlin took whatever it could from Ceylon (the nullability types, flow-sensitive typing) while keeping 100% seamless interoperability with Java as the top priority, so it may not be a revolution, but its adoption costs are virtually zero. It doesn't even have much of a runtime library; it was designed in such a way that all cool features could be applied to Java's standard library. The idea was that abstractions are great as long as they don't come at the expense of more important features, such as availability of libraries, tools etc (Kotlin even supports Java's annotation processors, so popular libraries that rely on compile-time verification/code-generation such as Dagger can work on Kotlin code).
Of course, I take this much further than you and believe, unlike you, that the contribution of advanced language-level abstractions is not so pronounced at all (or, at least, it hasn't been shown to be significant), and obviously I have a very different perspective on Scala than you, but at least we can agree on something :)
[1]: Paper: http://lmeyerov.github.io/projects/socioplt/papers/oopsla201... Accompanying talk: https://www.youtube.com/watch?v=v2ITaI4y7_0
[2]: https://youtu.be/Dq2WQuWVrgQ?t=14m12s about why Java was designed the way it was
[3]: Sun had experimented with a JIT for Self long before it was introduced to Java, and the plan was to make Java exploit JITs almost from the get-go.
I do wish Kotlin had more pattern matching semantics but that's just me being picky, it's a really nice language.
To be fair, Kotlin has the advantage of being created by the company that makes IntelliJ, so it's got a big head start IDE-wise.
The other advantage of Kotlin is that it builds on top of the existing Java code base. Java has had decades to build up an ecosystem of frameworks and libraries. Kotlin builds on these with excellent interop.
From what I can see, Ceylon has a blend of strengths that should make it appeal to a certain segment of the market. On one hand, it's a fresh start and has a lot of the cleanness and terseness that I like from Kotlin. On the other, Gavin is clearly very much into type systems and type theory, and Ceylon has a more complex/powerful type system than Kotlin does.
I'll admit that I'm not totally sure whether the additional complexity is worth it, but I'm very open to being persuaded.
So it seems to me like Ceylon should appeal to people who currently like Scala or Haskell and push the type systems to the limit, but really want something without historical baggage like XML literals and other oddities. And I'm sure there are plenty of programmers like that.
The real question will be interop costs. Kotlin doesn't have any and that's the main reason people can consider it in existing projects, or introduction inside large corporations. Ceylon takes a more Scala-like approach where it has its own standard library, its own collections, etc.
What I meant is, Kotlin raised the bar in the interop department to new heights: it uses the same collection types, so there's no conversion between Java and some other SDK, but still manages to enhance them via compiler magic and extensions. It has an auto-converter tool so nobody has to waste time rewriting code that already works in order to use the new features. It can use annotation processors, etc.
Of course it also pays a fairly steep price to get that.
The thing is that Scala tried to do that for years, and after years of battling subtle, leaky abstractions, they picked a different design.
It feels like Kotlin designers are completely unaware of what other languages tried and keep repeating all the mistakes ...
In my experience it works well. I've yet to encounter anything surprising or leaky. Actually the abstractions it provides are fairly thin: you can normally look at Kotlin code and understand quickly what it compiles down to.
It may be that in the end, Kotlin succeeds where Scala struggled, simply because the Kotlin designers do a better job.
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.
- 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
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).
Android could use a better language than Java 7 (or even 8) and Kotlin seems to be the only one that can easily replace it.
The biggest downsides I've encountered are around the deeper-magic Java interop, with stuff like Dropwizard's HK2 dependency injection system getting a little messy--especially around non-nullable parameters--but that stuff is, all things considered, a small part of the application.
The study sounds interesting, though there are obvious risks to trusting self-reports, but I think you're taking a broader meaning of "familiarity" than they're using - I read the result as "programmers are likely to use a language that they know when starting a project" and I don't think you can generalize to "programmers are more likely to use a new language that's similar to a language they know" (apologies if there's something in the video that's not in the text, can't watch videos here). Certainly past a certain point the library ecosystem and pool of familiar programmers become self-sustaining, and I can well believe that such things would be the biggest factors in any given project's choice - but that can't possibly explain how a language gets to that point in the first place.
For many of us the distinguishing characteristic of Java was that it was heavily marketed, often to managers; in the early days it felt like a lot of Java users were doing so under orders. (With 1.5 and the introduction of generics the language became a lot more programmer-friendly and I think at that point it developed a lot more grassroots popularity). Being less cynical I think Java did offer something unique in the form of crossplatform multithreading with a well-defined memory model - it's easy to forget how valuable that seemed, particularly as the world moves away from conventional threading. Possibly the combination of memory-safety and claims of C-like performance was new as well? I'm speculating here as I'm not so familiar with the less popular alternatives, but I think it's not simply a case of Java being less weird or more blue-collar than Self or Modula. The popularity of Python (with weird syntax and modula-like modules) and Javascript (with a Self-like inheritance model) show that that level of weirdness is no barrier if a language has a compelling advantage.
(Likewise Go, I think - it's taking programmers largely from Python/Ruby land where it can claim a USP in the form of performance (while retaining good async support and some level of conciseness). And again, marketing seems to be somewhat involved - so often when I ask "Why did you choose Go over OCaml?" the answer is "What's OCaml?".)
I think the clearest strike against the blue-collar approach is Perl. Perl took an extremely "pragmatic" attitude to language design, adopting many "most bang-for-the-buck features" (deemphasising consistency or underlying coherence), and put a lot of emphasis on tooling and libraries with CPAN, PerlUnit and the like. And for a time it was very successful - but ultimately it became a language that was very hard to evolve, whereas other languages (in particular Python and Ruby) were able to catch up on the tooling side and their coherence gave them an advantage in the long-term. I think Kotlin is making the same... mistake would be too strong a word, Perl is a success story by many measures, but I think Kotlin is taking a very short-term strategy; it feels like every time someone figures out a clever thing you can do with implicits in Scala it gets added to Kotlin as a language feature. Everything about it feels very ad-hoc, particularly in comparison to Ceylon. So I think that while Kotlin may be a very effective language for the short term it's going to be a very brittle one that will struggle to adapt in the future.
I guess that's the closest thing to a counterexample to my original claim - a lot of people did move from Perl to Python with no USP beyond being clearer and smoother. FWIW I think the issues with Perl were deeper than those with Scala; there is some ad-hoc junk in the language (structural types should never have been added, nor should Dynamic, async/await aren't worth it...) but it feels quite peripheral, I think the core still fits together nicely. But hey, if those issues do end up forming enough of a toehold for Ceylon to take over, I'm fine with that too.
Having said that, as you correctly note there are other paths to adoption, such as being the only language on a popular platform (JavaScript, Objective-C, Swift), or being a scripting language. Those seem to have their own rules.
[1] Although Java wasn't more marketed than other heavily-marketed alternatives at the time, and Python and JavaScript both have their own peculiar adoption stories, with JavaScript still trying to look similar to its "sister-language" Java, and then being the only choice on a popular platform, and Python taking a long time for decent adoption that even today is far from C/Java/C# levels of popularity, and either case being, or at least starting out as scripting languages for small programs -- not as languages for "serious" systems.
Certainly there were problems I faced in day-to-day Java programming that were visibly due to a crude type system - NPEs, the awkwardness of working with checked exceptions (I do think Ceylon has missed a trick by not using union types to interoperate with Java checked exceptions), SQL injection vulnerabilities caused by not having a taint checker. Other problems I recognised as being due to crude typing in retrospect - the fact that missing transaction annotations could failed silently in confusing ways ( http://thecodelesscode.com/case/211 ), the ease of forgetting to close files, the way all the ways of doing async were either invisible or painfully verbose. Ultimately, everything that we resorted to (inherently non refactor-safe) annotations for. (For what it's worth, I originally picked up Scala based on my experience with the JSR308 checkers framework - the functionality was valuable but too many tools didn't interoperate with it properly, so I looked for a language that had the same thing built-in).
Any individual problem from that list you can solve at the language level - some of them have been solved in Java already, and more in the likes of Kotlin. But a powerful type system is a tool that, once it's built into the language, lets you solve them all even if you didn't think of them first. (Macros have the same kind of power, but maintainability of macros is a real problem). I don't think we'll find an example of a powerful type system being better at a specific feature any more than we'd find an example of a generic data structure being better than a specific one; the value comes in being able to do many things the same way.
Making a language that can be evolved effectively is certainly a real problem - again Perl is the clearest example, but I've also heard complaints about how long it's taken Java to implement features that have been agreed on for years (lambdas, modularization). I don't know whether it's the problem King was intending to solve with Ceylon (though I do think Rust represents a very deliberate effort at the same thing) and I don't think it's easy to prove that you have solved it short of waiting a few decades - I certainly don't have any hard evidence about what factors make a language able to evolve in the long run. Nor would it be a compelling marketing story even if you could prove it. But I think it's still worth working on.
Another question is, how bad those problems you mentioned really are. Concurrency bugs are terrible, and simple data typing bugs are usually a non-issue, but tainting/resource-use (i.e. solvable with intersection/linear types respectively) may be bad enough. I really wish someone would conduct an empirical research comprising a taxonomy of bugs, their frequency, and their cost. Such data would be infinitely more useful for language design in the industry than, say, all research going into session types (not trying to pick on session types research, but I hope you catch my meaning when I speak of actual applied utility).
BTW, I think any interesting idea is worth working on. The problem is that a language is a very expensive tool -- and a risky one -- so when it comes to industrial, rather than academic, use a lot of care should be taken when picking one, so it's better to err on the side of caution.
[1]: See Scala's collections as an extreme example. Is it really necessary to go through all that trouble of unreadable code just to save us a cast here and there that has never really bothered anyone?
I do think implicit conversions allow too much; IMO we need typeclasses and extension methods. So my ideal design for a language would include implicit parameters but not implicit conversions, and instead have dedicated support for extension methods. That said we do need to be able to use typeclasses without disrupting method application syntax (i.e. support the use case that means Spray prefers the implicit-conversion-based "magnet pattern" rather than a typeclass).
More generally I think there will be languages that allow too much and languages that ban too much, and we need languages on both sides of the line to allow us to converge on something better. Most places I've worked have had a strong code review/pull request culture which may have coloured my experience - I just haven't seen the Scala maintainability problems you talk about.
(If I thought the complexity of collections was necessary to avoid casts then I would defend it - casts can fail and so it's very nice to have a codebase where they're banned entirely (enforced with wartremover). But I don't think it is - FWIW Odersky's asked for proposals for scala collections in version 3, and I think there's a substantial push towards at least some simplification - perhaps replacing CanBuildFrom with a 1-parameter typeclass that would retain most of the power and simplify the code. The showing-off cases like BitSet#map would require one more method call, but no casts)
Maybe, or maybe not all language designers have the goal of making their language as popular as possible. A language can be popular enough, such that it has a good community and good set of libraries, without trying to get everyone to switch.
In fact, depending on what you're looking for, a language can become too popular. In this case, you start getting people in the community that detract from it, rather than contribute to it.
> but I just can't see people choosing the more polished language over the one with ten years worth of library and tool support when there's no USP beyond that polish
It seems all a matter of time. What would Ceylon look like to you after some years of library and tool support?
I think the assertion is that it is not obvious why it would be superceded by Ceylon. So, if there's no obvious reason to move to Ceylon, who is going to get the ecosystem to a level that it will compete with Scala's?
Now, I personally wouldn't be so bold as to suggest that it will always be 10 years behind Scala. I have no idea. But it isn't clear why the language itself is offering sufficient advantage.
More likely, at least to me, is that some of the ideas that Ceylon's shown are practical e.g. union and intersection types, will find their way into more languages because of it.
Of course, someone could produce the next big thing in it tomorrow and do for Ceylon what Rails did for Ruby. Then I'd go find a hat to eat.
The question is: why would you use Ceylon over the competition?
There are a number of reason I can think of. You want to target node.js too; you're a Haskeller in your spare time. That sort of thing.
But the question still stands. Is there enough to prefer it to Scala, Kotlin or, gasp, Java?
Honestly, I don't know. But equally there's nothing that stands out for me. If anything this has actually made me think I should probably look at Kotlin again.
http://ceylon-lang.org/blog/2015/06/03/generic-function-refs... http://ceylon-lang.org/blog/2015/06/12/more-type-functions/
> Shapeless implicit macros to use tuples generically
What can you do in Ceylon about this? Or are we talking about a dream?
> a retrofitted JavaScript backend
Not sure what you mean. Scala.js is reusing the Scala compiler in what happens to be the cleanest transition I've seen to such a different platform. And compared to other Javascript compilers, like ones for Ocaml or Haskell, this one actually works well and stays up to date. Care to explain?
I mentioned higher-kinded types; last I knew they were an experimental feature. I thought Ceylon offered some way to do "open interfaces" (the vital part of typeclasses IMO)? If not then that's definitely an issue.
> And what can you do in Ceylon about this? Or our we talking about a dream?
In Ceylon you have arity abstraction over tuples built in, so you can do HList-style operations by default. Scala will supposedly add this in Don Giovanni but in the meantime you have to use Shapeless with its implicit macros and it's slightly less nice (e.g. the error messages are less clear).
>Scala.js is reusing the Scala compiler in what happens to be the cleanest transition I've seen. Care to explain?
I think it's fair to call Scala.js "retrofitted", and I think the article is right that a language that was designed from the ground up to be JVM-independent will inevitably be better at it.
My whole point was that these are minor rough edges to Scala that aren't really that important, so I'm not sure why you're being so defensive.
Thanks for the clarifications.
javax.time is considered by some to be one of the best, most well-designed general and versatile libraries for date and time related matters out there, regardless in any language.
How would things be improved by throwing that away, and inventing something different? I think keeping the API and providing an implementation for Scala.js is a much more reasonable approach.
Designing a date/time requires very rare skills and knowledge that most people lack. A re-implementation of javax.time means all the documentation, tests and existing code can be re-used and allow correctness checks against the existing implementation.
It's not. There just is no shim for java.time currently! Even worse, there could be licensing issues[1].
EDIT: That, and some of us are unfortunately still on JDK7 until the next Ubuntu LTS. Not that that's scala.js's fault, but it's a practical issue.
EDIT: ... and of course having a duplicate implementation of java.time (JDK + the shim-which-is-basically-a-reimplementation-in-JS) could be considered "reinventing the wheel"! :) If you have to reinvent the wheel, then doing it such that it at least behaves completely consistently across all backend platforms is preferable, IMO.
Your last point is not the only thing that matters though. If the runtime already ships with packages X, there is no point in shipping your own implementation.
(Which is exactly what Scala/Scala.js does with math stuff: it reuses BigInteger from the runtime on the JVM, but ships its own implementation with Scala.js.)
That's why I'd rather have a single implementation for anything non-trivial and just retarget that to each backend using more low-level primitives. After all you're using a different language -- using a different date/time API shouldn't be much of a problem.
I'm not saying it'll be bug-free. My point is that it'll have exactly the same bugs on either platform. This may be preferable to having different bugs on different platforms.
Different bugs on different platforms are like an early Christmas present:
You don't even need to write tests which include your "expectations" of the result anymore.
Just call the code with randomized inputs for both platforms, and if there is a difference, you found a bug.
You don't really get to say what other people think Scala should be. You like higher kinds, so do I, I'm glad they are in Scala but most people have never even heard the term and to them, they would much rather have a language with fewer features than one with more.
That's the goal that Ceylon and Kotlin are trying to achieve.
Perhaps it's just a joke, but if it's not: sure you're entitled to dislike Hibernate and prefer other ways to talk to a DB, but it's still one of the most widely used ORM on the JVM so it may not be perfect but it is also a huge success.
:( This is something that would, in itself, direct me to Kotlin or something else. I know that Eclipse is a better fit for Ceylon (because both are intimately related to OSGi), but I really wouldn't want to go back.
Maybe others feel differently.
I think you'll decide your gut was wrong, but there's only one way to be sure.
"Note that not all Ceylon modules are available for both platforms. A module might be cross-platform, it might by JVM-only, or it might be JavaScript-only. Of course, ceylon.language is completely cross-platform."
Having some modules for JVM and some are for JavaScript-only would make things a little bit more confusing than if the language picked one. I haven't decided if this is a very significant thing or not.
I mean, examples of things that are cross-platform in Ceylon: collections, localization, promises, regexes, HTML construction, logging, testing, dates/times.
Examples of things that are platform specific: I/O, database access, filesystem access, distributed transactions, the HTTP server.
That's pretty reasonable and natural, isn't it?
Like the fact that on the main page, the link to the online editor is not under the "Try it out" section. The explore action from that section is also misleading.
Or a clean hello world, with a real project structure documented
Or the way collections are documented. Basically, you have section 6 from the tour of ceylon: Streams, sequences and tuples. But it's not obvious what is the big difference between streams and sequences and the fact that sequences borrow the array notation while being immutable doesn't help either. Even when you go to the List api, which is the interface any Java developer will look for,you can't find the mutable collections, because they live in another module.
https://github.com/ceylon/ceylon-lang.org/issues
Thanks.
Since moving to Kotlin for my projects, I really enjoy the power that these provide: https://kotlinlang.org/docs/reference/extensions.html
What does Ceylon give me over Kotlin?
- union and intersection types
- an elegant and powerful representation of tuple and function types
- reified generics
- the cleanest solution to the problem of null
- awesome modularity
- a language module [that] completely abstracts the underlying runtime, and offers a set of elegant APIs that vastly improve on those available natively
- a language specification
None of which is offered by Kotlin.
That's quite a lot, actually.
- an elegant and powerful representation of tuple and function types -- Okay, Kotlin could do with this
- reified generics -- This is apparently expensive on the JVM: http://blog.jetbrains.com/kotlin/2014/12/m10-is-out/
- the cleanest solution to the problem of null -- I think saying that `String? x = "abc"` is cleaner than `var b: String? = "abc"` is subjective. -- Does Ceylon have Safe Casts? https://kotlinlang.org/docs/reference/null-safety.html
- awesome modularity -- Something I'll need to look into
- a language module [that] completely abstracts the underlying runtime, and offers a set of elegant APIs that vastly improve on those available natively -- I guess the improvement in abstraction comes from the Reified Generics -- Have you got any examples of where the API is superior to that of the Kotlin one? For example, with Kotlin's extension functions Java File object has been extended with a readLines() function that returns all of the lines of a File as a List. I was impressed when I saw that. Underneath it is doing the usual BufferedReader and InputStream boiler plate work that you would normally write in Java.
- a language specification -- https://kotlinlang.org/docs/reference/
- Kotlin does not have tuples, and doesn't allow abstraction over function -arity. So no, it can't to that.
- Reified generics are simply not expensive, at least not the way Ceylon implements them. But sure, Ceylon's reified generics were implemented by Stef Epardaud who is the best programmer I've ever worked with, so I can understand if some other people find them difficult to implement efficiently.
- I'm not talking about syntax. Syntax is uninteresting. I'm talking about semantics. In Ceylon, optional types are a trivial syntax sugar for a union type, not a hacked-in special case in the type system, as they are in Kotlin, and that means that I can do more with them, for example they naturally combine with union and intersection types to do useful things.
- Your link to documentation for Kotlin does not include any specification for the language. Do you know what the word "specification" means in this context?
Finally, I strongly recommend that you take the time to read the Ceylon documentation and inform yourself about the language. You'll find lots of really interesting ideas and information in there, and I'm certain you'll love the language!
Every choice in Kotlin's design has been intentional with one idea in mind -- compromise on purity in favor of interoperability (to lower the cost of adoption). So, of course you can do more at the language level with Ceylon, but Kotlin set out to do less in that arena by design. OTOH, Kotlin has several orders of magnitude more idiomatic (or very nearly idiomatic) libraries than Ceylon.
There's a very clear tradeoff here, and Kotlin and Ceylon have been designed with very different underlying philosophies. The only point you can argue about is which language gets you more bang for the buck. Kotlin has intentionally chosen less bang for less buck, while Ceylon has chosen the opposite. Personally I believe that almost all language-level abstractions are relatively low-bang[1] -- or certainly have diminishing returns -- and therefore language purity should always be compromised for almost any other extra-linguistic feature (if it's a language designed for the industry rather than academia), and so I think that Kotlin has made the better decision and gives you almost as much bang for far less buck. But only time will tell, and arguing about this at this point is just a matter of personal preference. I can certainly see some people preferring the one and some the other.
Another way to look at it is that Ceylon was designed to appeal to Scala people, while Kotlin was designed to appeal to Java people :)
[1]: By that I mean that they're always useful for something, but in the end have a low impact on total productivity (which includes more than just writing the code).
This is simply nonsense. You made it up. There have been zero complaints about problems Ceylon has in interoperating with Java's generic types, since they simply don't exist.
I can't believe you just wrote such a longwinded comment about a nonexistent problem that you imagined out of whole cloth.
How about you actually spend some time learning the language first before commenting any more about it here or on reddit. Because it really wastes my time and raises my stress level having to correct your - probably unintentional - FUD. It's clear that you don't know Ceylon, so please stop telling everyone else stuff that you're just guessing at.
OTOH, if you want to get answers to any questions you might have you are extremely welcome to come on our Gitter channel and ask them, and I promise we're always very patient about explaining stuff there. I make that offer in complete sincerity.
As to the rest (and the lion-share) of my comment, I don't think it requires further clarification, and I don't see why you'd even think it's wrong. You've set out to create a new language with new, clean type semantics and a new runtime library, while Kotlin, in contrast, has had a different goal altogether. It doesn't even have its own concrete collection classes, so that's a radically different level of interoperability and a radically different design. That is the major difference between the languages rather than the list of features you've named in an answer to a question by someone else (and like I said, either approach has its proponents), so from my perspective it was you who was adding to the confusion, which I wanted to correct.
The answer to the question "what is the difference between Ceylon and Kotlin?" IMO (at least when the JVM target is concerned) is that Ceylon is a completely new "greenfield" language with a new, powerful type system, new semantics and a new runtime library, while Kotlin is "a better Java", a language preserving Java's semantics and standard library while solving its pressing shortcomings and providing a more modern syntax, and made to be adopted piecemeal into Java codebases. Of course there's some overlap, too, but that's the different in philosophies in broad strokes. In terms of features, some are similar (with Kotlin adopting some of Ceylon's ideas) and some are different, but that isn't the big difference.
For those reasons, BTW, while it would be very nice to have a Kotlin spec, it isn't as necessary, as most its semantics are borrowed from Java.
Of course, you may well think that those linguistic features are a bigger difference than the design goals, but I will disagree (due to the reasons I laid out in my other comment), and no amount of Ceylon expertise is relevant to that disagreement.
Because you quite obviously have never even tried it once.
That's clear, isn't it?
"The problem with reified generics isn't their efficiency, but that they don't play nice with other generic types on the platform (which is the vast majority)."
And the context of the comment was quite clearly Ceylon interoperating with Java as anyone can verify.
I have a friendly request for you: please don't comment about Ceylon on any more hackernews or reddit threads. It's great that you like Kotlin and are having success with it. I'm happy for you. Post about how great Kotlin is on all the Kotlin threads you like.
But it's just not a good thing for anyone that you're going posting on Ceylon threads, speculating about made-up problems with Ceylon, and pretending you know Ceylon when you don't.
So please stick to the Kotlin threads is all I'm asking, OK?
This is really unproductive. Reddit and HN are discussion forums; what we want on them is more discussion, not less. We want high-quality, accurate, discussion, but if we're not getting that, the solution is to raise the quality, not reduce the volume.
In particular, the last thing i, as a reader of discussions, want is for a discussion forum to turn into a confederation of theocracies where nobody but the local priesthood are allowed to speak.
So, pron, i also have a friendly request for you: please continue to comment about Ceylon wherever you like - but make sure you've done your homework before doing so!
Specifically, if you could produce a concrete example of how Ceylon's reified generics interact poorly with Java's generics, that would be really interesting. If you could produce an example of how non-Ceylon reified generics interact poorly with Java generics, then that would be interesting, and gavinking could explain how Ceylon avoids the problem, which would also be interesting. And if you find that actually, there isn't such a problem with reified generics, that would be interesting too, not least for you.
The issue with this type of comment is that we (humans) have a set of cognitive biases which often lead us to think that we've "done [our] homework" when, in fact, we haven't. Such a person would probably actually only absorb the first portion of the quoted sentence from your post.
(Sorry for the slightly OT.)
With Ceylon, the issue is different, because the JVM -- unlike the CLR -- doesn't have a standard way of specifying reified generics (and that's a good thing, IMO, because of the "baked-in variance problem"). However, that means that none of the standard Java generic classes are first-class citizens in Ceylon world, because they don't have the reified runtime type information. This isn't a problem for Ceylon because one of its stated goals (it says so right on their website) is to replace the Java standard libraries, so this incongruence doesn't even matter to them because a Ceylon List and a Java List are not even the same type to begin with. That a Java list instance does not have a reified generic type in Ceylon is, therefore, not a problem for them, because Ceylon didn't set out to make the existing classes first-class citizens of its brand-new ecosystem.
This is why I and the Ceylon guys have this misunderstanding. They think I'm saying Ceylon has a problem, but I'm not. Ceylon has certain core design goals that may be what some people want but not others, that is all. But those design decisions do have ramifications.
BTW, the "baked-in variance" problem will not get introduced into the JVM with the addition of specialized generics for value types in Java 10, because value types can't extend other types, and so a List<int> can't also be a list of any supertype (or subtype).
This is just not true. In Ceylon when you import a Java generic class, you can do everything with it that you can do with the same class in Java.
Please stop posting incorrect things about Ceylon. You're coming off as a walking, ranting, personification of the Dunning-Kruger effect.
Of course! I have not said otherwise. I have said that you can't do with them everything you can do with Ceylon classes, hence -- not first-class citizens.
Now, I would appreciate you stop calling me names, because I haven't called you names. On the other hand, you have not addressed even a single one of the main points I've raised, except come back with great fury against some statements I've made that may not have been clear. So I would also appreciate you taking the time to understand what it is that I'm saying rather than what it is you think I'm saying, because I have not said a single bad thing about Ceylon in this entire thread (on the other hand, I have paid it and you several compliments because it really is a beautiful language), except that I believe a more compromising approach to language design would prove the more pragmatic one in the long term. Please try to understand what it is that I'm saying before blowing a fuse. We are in total agreement (on the facts, at least).
I joined this discussion to sound an observation about different design philosophies in language design (in rare agreement with a comment by Imm), then I commented to a user who asked about the differences between Ceylon and Kotlin (answer: different design goals), and you just keep calling names left and right and think I'm out to spread FUD or that I have an animosity against Ceylon. Jeez. So I will say it -- again -- just so there's no misunderstanding: Ceylon is a terrific programming language, and anyone whose goals are aligned with the language's goals should definitely give it a try!
If you think I have posted something that is incorrect or can be misunderstood, please add your correction politely. Why politely? Because you just might have misinterpreted my intentions or my words, and by being polite you might avoid saying things you may regret. Even if you really think that I'm trying to hurt your language or just so stupid that I keep making the same mistakes over and over, still keep a polite tone, because other readers of the discussion may not have the same interpretation as you.
And this is why creators of languages should refrain from participating in discussions about the language they created. Especially when they post so much stuff and they seem to be the only person in the 100+ messages defending the language.
Either Ceylon stands on its own merits and other people will come to correct misconceptions about it or... there's simply not enough people who care about it.
There's no truth in that. Sure, it's possible that there are some differences in how we both do interop, and that some things are easier in one or the other, but overall you've no basis for claiming that, and I strongly suspect you haven't tried Ceylon for interop at all or you would not say that.
When you do try and find interop things that we should improve, please let us know in our issue tracker and we'll do our best to fix it.
Meanwhile, please stop with the FUD.
There are no "some differences", but a radically different philosophy which is at the very core of the language's design. A Kotlin list is a Java list and vice-versa; a Kotlin map is a Java map and vice-versa; a Kotlin set is a Java set and vice-versa. The same, BTW, is true for Clojure, but unlike Clojure, Kotlin doesn't just keep the interfaces, but also the implementations. Kotlin hardly even has a standard library. The Java standard libraries are Kotlin's standard libraries (modulo some extension methods). Ceylon has its own standard libraries, and, in general, Java libraries are not idiomatic Ceylon libraries. That Ceylon even has CeylonList/JavaList types shows how the two approaches are worlds apart. Comparing it to Kotlin in that regard is ridiculous, and I don't even know why you'd try. It is one of Ceylon's strengths that it has its own library, and one of Kotlin's that it doesn't. Each appeals to different needs, and I don't see why you feel you should blur the differences.
> When you do try and find interop things that we should improve
It's not about that. You may think that Ceylon's Java interop is great. It may be just the right amount of interoperability that you want. But claiming it is anywhere near Kotlin's is just preposterous. I didn't say that Ceylon's Java interop is bad, but it's just not even in the same ballpark as Koltin's. But that's OK, because the two languages have different philosophies.
> Meanwhile, please stop with the FUD.
Please stop calling it FUD. I have never, ever said people shouldn't use Ceylon, that it's a bad language or even that Kotlin is better. I have emphasized the big difference in design goals between the two languages that makes them very different in practice: Ceylon has an advanced, very elegant, beautiful type system, while Kotlin has many thousands of libraries. Where is the FUD?
OTOH, instead of calling it FUD, and since this is a Ceylon thread, I would very much like to hear a justification for Ceylon's design; not the choices of the particular language features -- I will readily admit that Ceylon is the best language ever devised by man -- but why being better at the language/typesystem level, without offering a new paradigm warrants switching a language in the first place. After all, it doesn't offer anything radical when it comes to concurrency (like Clojure or Erlang or Go) or functional purity/equational reasoning (like Haskell). It's just cleaner and more elegant than Java or Scala. OCaml is another such beautiful, well-designed language, but, perhaps sadly, it has hardly seen any adoption. Why do you believe that is enough to get people to switch to a new language? For example, I know that Joe Armstrong thought a lot about the problem of fault-tolerant systems, and he came up with the idea of isolating failure; Rich Hickey thought a lot about state and identity and came up with Clojure's data structures and controlled mutation. Their reasoning is fascinating. What is that behind Ceylon's (I can tell you the reasoning behind Kotlin)? Did you reach the conclusion that a major obstacle to building modern software at this point in time is deficiencies in the type system? I'm not mocking, and I'm not saying it isn't, but unlike in Clojure's, Erlang's, Rust's and Kotlin's case (or Haskell or Scala), I've just never seen the Ceylon philosophy explained.
I've read Ceylon's guiding principles, but they haven't answered the question. If simply doing the same thing better justifies starting over, then supposing Ceylon takes off, in a few years Ceylon, too, will accumulate cruft, and its design mistakes (in the language or libraries) will become apparent. What will Ceylon advocate then? Backwards compatibility or breaking changes (or maybe a new language altogether)? And if the idea is to start over every 20 years -- I can see the merit in that argument -- why not a whole new paradigm? Is everything OK except mistakes in library design and the type system?
You don't have to answer, and you can either address or ignore my views -- but please don't call them FUD.
The only example you give is that they don't have their own standard library. I agree it's a difference, but you really think that makes it worlds apart?
I mean, in Ceylon you can also use the JDK, so I don't quite see the big thing, but even then, OK that's one difference (and it's a justified one too, but fine, OK). That's really the thing that makes you say that we have Java interop a world apart? I understand it may be an important point for you, but I don't understand how you can extrapolate that it's so important for everyone.
> while Kotlin has many thousands of libraries. Where is the FUD?
There. Right there ;)
Yes. Well, it's one of the symptoms. Let me explain, but instead of using my own words, let me quote Ceylon's website:
Ceylon is a new programming language that's deeply influenced by Java, designed by people who are unapologetic fans of Java... But much of our frustration is not even with the Java language itself. The extremely outdated class libraries that form the Java SE SDK are riddled with problems. Developing a great SDK is a top priority of the project... Java interoperability is a major priority for the project. However, since Ceylon will be based on its own modular SDK, making a clean break from the legacy Java SDK, Ceylon will require new frameworks designed especially for Ceylon.
In one of the comments, Gavin King, Ceylon's chief designer, explains what differentiates Ceylon from other attempts:
What's going to be very challenging is the _platform_: the libraries and frameworks. This is where most of the potential value of this project resides, but it's where we have relatively more work to do than other projects which simply aim to leverage the Java SDK "as is".
So (my words now), Ceylon is a new language with a new ecosystem. It is a greenfield project that also can interoperate with "legacy" Java libraries. Kotlin is fundamentally different, as Gavin Kind correctly notes. It's decided from the get go that the Java ecosystem is the Kotlin ecosystem. That any Java library is an idiomatic Kotlin library and will be treated the same way as if it were written in Kotlin (that goal has not been achieved 100%, but certainly 95%). That meant that any language feature that would have made the Java ecosystem different from the Kotlin ecosystem was intentionally left out. For Ceylon, the goal was different. A new better language and a new better SDK. When interoperability was concerned, wrapper types were introduced and sometimes language features (that are not recommended for Ceylon code) like use-site variance, too. That is a completely different perspective with major implications. Kotlin really does have many thousands of Koltin libraries; Ceylon doesn't. OTOH, Ceylon is a more comprehensively designed language with less compromises.
I can speak from experience. I'm the author of several Java libraries. Some of them have hundreds of API classes and thousands of methods. Making those libraries "Kotlin idiomatic" was zero effort, and adding all the necessary "Kotlin bling" (e.g. cool use of inline functions which are Kotlin's poor-man's macros) took a couple hundred lines of code, none of which were really necessary. Clojure, BTW, is similar, but less ambitious in that regard. As all Clojure collections are Java collections and vice-versa, Rich Hickey specifically said that Java libraries should not be wrapped, as many can be used as-is, simply passing in and getting out plain Clojure types. Ceylon is different. If I have a library working with Java collections (which is pretty much all of them), any use by Ceylon code would feel foreign and may require wrapping or other special handling. But that is by design. It says so right there on the Ceylon website. How can any of that be FUD?
> There. Right there ;)
I see. Then consider changing the Ceylon website because it's just full of FUD about replacing the ecosystem. I might be guilty of spreading it, but I'm not the source.
It is not. You're a fabulist. Your behavior on this thread is worse than obnoxious.
>> I can speak from experience. I'm the author of several Java libraries. Some of them have hundreds of API classes and thousands of methods.
You can use them in Ceylon with no problems at all.
Please stop lying about Ceylon and please stop putting words in our mouths. Thanks.
This is quite clearly not true, and yet another assertion that you just made up and stated as fact. We're Java not Scala developers, and we designed Ceylon for other people like us. Don't try to tell me what my own motivations were.
In fact, it's very difficult to imagine, even charitably, why you would possibly be motivated to make such a claim unless you were deliberately trying to spread misinformation.
Syntax-wise, Ceylon is not a very pretty language at first glance. LHS types and semi-colons. Not really a lot to like from a syntax perspective for your average Scala developer I think.
But that's just my opinion.
You can form types like Object&T, and if T is an optional type of form S|Null, then that is reduced automatically to the type S by the typechecker. But if T is not an optional type, then it just remains T.
Very useful to be able to do this kind of trick in generic code.
And note that nothing here was using any special reasoning about Null: this is all just the totally generic reasoning for union types in general.
- problem of null: Ceylon uses union types to union between the class in question (ex String) and Null, which is a type separate from Object. Therefore, the typesystem enforces this. And yes, Ceylon has the exists operator, which means you can do if (exists stringOrNull) to instanceof/cast at the same time.
- elegant APIs - With regard to file I/O: https://modules.ceylon-lang.org/modules/ceylon.io/1.1.0/doc
- language spec - Ceylon's is much more detailed: http://ceylon-lang.org/documentation/1.1/spec/html_single/
FTR I am not sure I believe that explanation. I was with Gavin a few years ago when Andrey Breslav asked us if we were going to implement reified generics (we had not yet at the time) because they were having trouble implementing it and so if we were not going to implement it, they would not bother.
We haven't talked about this conversation publicly in the past because to be brutally honest most of it would make them look really bad, and it's likely that we won't, but this anecdote was very relevant to the discussion about reified generics.
My guess is they tried and failed, strictly based on this conversation. It's possible that they really considered it too expensive, but I since that's not backed by public experiments and our own experiments tell us it's not that expensive for the benefits it gives us, I don't _have_ to believe them ;)
The article was an overly verbose 2000 word wall of text.
On a slightly different note(and no idea if this goes against HN guidelines) but you've got a fairly argumentative tone. If you're really interested in seeing the language flourish I'd try not being as combative.
Community is just as important as how well a language is designed and based on the tone of a lot of the sub-threads here I'm not really inclined to look into Ceylon any further.
I would really advise him to try and ignore most of them if he wants to keep his sanity though. (serious, been there, done that.) Especially since I think that the language looks quite promising.
Sometimes, it's ok to correct things even if a little harshly though. People will always find a dumb argument anyway.
For example, the T|Null thing doesn't give you code composability of the type monad transformers do -- at least as far as I understand it[1]. (I'm sure there are other things, but that's the first thing that popped into my head.)
FTR, I am a typed-FP weenie, but I still find Ceylon quite interesting, though I haven't done anything non-trivial in it yet.
[1] I still haven't fully understood the (experimental) HKT support, so maybe that can accomodate this?
But it's true I never built a big ceylon project, so I can't say I know how that works out in practice.
Curious if this work is still fruitful, now that Google has abandoned its plans to integrate Dart VM into chrome. http://techcrunch.com/2015/03/25/google-will-not-integrate-i...
* Hello World web application
* Simple online store implementation (authN, database access via ORM layer, logging)
* Todo MVC implementation
* RESTful/XML/SOAP web services
* RESTful/XML/SOAP clients
* Examples for writing AngularJS and React front-ends with Ceylon back-end services, with info on how to host such as to minimize and cache assets and server-side query caching and either side-loading or multi-table joined/extended data structures, updating and reading/accessing those data structures partially.
* Examples for easily timestamping and userstamping models
* Examples for using testing frameworks: unit, integration, (web) acceptance
Here's what I found in looking for that:
* This hello world: http://ceylon-lang.org/documentation/tour/basics/
* No Ceylon JS example at http://todomvc.com/ but this Todo list: https://github.com/vietj/cayla-mvvm/blob/master/source/io/ca...
* Two examples in what I assume is the official examples git repo at: https://github.com/ceylon/ceylon-examples containing N-queens and Game of Life only.
Also, I'd want to see benchmarks. Show me how much it is "like" performance of equivalent Java, Dart, and JS as is claimed by comparing to maybe a Play Framework app, the Dart example client-server https://www.dartlang.org/server/google-cloud-platform/app-en... , and a simple MEAN stack and/or full-stack example using ReactJS.
In addition to those examples, I'd want to see a larger community behind it with a variety of projects, e.g. specialized ORM, larger web app/services framework, simple web app/service framework each that have their own communities using it.
I think it is cool, but I don't think it is even in the same ballpark with solutions/combinations like Play+Scala, MEAN, Rails, Elixir+Phoenix, etc. for wide application in web/services.
- http://taiar.github.io/log/2015/10/09/ceylon-programming-lan...
- http://taiar.github.io/log/2015/10/23/ceylon-programming-lan...
Basic toy stuff but has some points on Java interoperability and explores other language aspects.
==
String name => firstName + " " + lastName;
And an assignment:
String name = firstName + " " + lastName;
In the first example, the expression is recomputed every time name is evaluated. In the second example, the expression is computed once and the result assigned to name.
==
A function which looks like just a variable and recomputed each time! Happy debugging my code, suckers!
...that's just not ever an issue.
but, I dont know if thats really the case though (I dont know ceylon). I think that fat arrow line would just become a no op instead, creating a lambda and throwing it away immediately ("name" being the param name in the lambda and nothing more).
Part of me is intrigued by the excellent modularity story.
Part of me is excited to try out the type system.
Most of me wonders if I'll get time or an opportunity to explore.
Overall, this generation of languages is pretty exciting!