> You can accept the points I made or discuss them, but this is just moving the goalposts AGAIN.

I am really not. My claim is a general one about Scala's kitchen-sink design philosophy, and why it's inappropriate for an "big engineering" language, as opposed to fast development languages like Ruby or Perl, yet it is you who insist on focusing on detail, which is part of the problem. So I responded to the detail.

> Why should that happen?

Sorry, I made a mistake there. The compilation will break when you try to pass the object to a method that accepts that structural type.

> It's pretty damning to see that in the few months in which macros existed, more useful functionality was written than for Java annotation processing ever.

You are most certainly wrong here, though I can't prove it. You're forgetting that 99.9% of Java code is not open-source. In the organizations where I previously worked we used annotation processing where needed.

> Again, just because you don't see the benefit or the reasoning behind it, doesn't mean that the brightest minds in our profession are all wrong.

Those brightest minds are usually the brightest minds in PL research. I don't think it's a coincidence that most of the languages designed by them, while brilliant in some respects, are not widely adopted in the industry. You can only attribute some of that to marketing. I also do not think it's a coincidence that all languages developed at Google, a company that knows a thing or two about large scale development, follow the Java philosophy.

I am not a PL researcher and not particularly interested in PL research aside from learning a thing or two about the potential of programming languages, but I am very much interested in moving the software development industry forward. Some of the things PL researchers focus on I find to be genuine problems with software development – like taming concurrency, which Haskell does a good job at though perhaps at an unacceptable cost to the industry, and Clojure and Erlang do an excellent job with despite their lack of PL researchers – while other areas, like developer productivity, I find to be the wrong problems to focus on.

Let me explain the last point because I think it's important. We have some good languages (Ruby, Python) that are excellent for productivity, and are extensively used in some domains. Where those languages fail - concurrency, large-scale engineering - productivity is less of an issue.

But then I found Clojure (and, mind you, I personally prefer static typing and think it's generally better for engineering, though I recognize this is just a means to an end), and saw a language that is probably as "productive" as Ruby, yet actually tackles the big issues (like making sure some careless team member does not introduce a very hard to find race condition).

I think Scala takes powerful though complex features and channels them – unlike, say, Haskell – into all the wrong places (productivity), and at the same time makes it impossible for a mere mortal to understand how a basic collection is written. You can argue details all you want with me, and say that you could do this and could do that, but a language that makes collections the domain of experts without at least fixing the real hard issues, is just plain misguided.

> I am really not. My claim is a general one about Scala's kitchen-sink design philosophy, and why it's inappropriate for an "big engineering" language, as opposed to fast development languages like Ruby or Perl, yet it is you who insist on focusing on detail, which is part of the problem. So I responded to the detail.

And that claim is just not defensible in any kind of way. Have a look at C# and C++. Both of them are magnitudes more kitchen-sinky than Scala by pretty much every measurable metric. Both of them are considered to be “big engineering languages”. Don't believe me, look into the spec.

Scala is certainly not the language which ships features which have been explicitly designed for working with the MS Office API for example. I can give you dozens more if you want.

> You are most certainly wrong here, though I can't prove it. You're forgetting that 99.9% of Java code is not open-source. In the organizations where I previously worked we used annotation processing where needed.

Well, there is certainly Scala code which isn't open-source, too. That doesn't mean that looking at the existing, available software out there is not a reasonable metric.

Anyway, even if that point was wrong, I have mentioned a lot of issues concerning Java's annotations processing and pretty much every item should be a deal-breaker if the goal wasn't to ship a failed experiment. People use Java annotation processing, because the alternatives are even worse, not because Java annotation processing is so great.

> Those brightest minds are usually the brightest minds in PL research. I don't think it's a coincidence that most of the languages designed by them, while brilliant in some respects, are not widely adopted in the industry.

Those are the brightest minds which shipped most of the stuff which made C# great. I wouldn't call C# PL research by any means.

> while other areas, like developer productivity, I find to be the wrong problems to focus on.

Developer productivity is certainly not the sole focus of Scala. But developer productivity means that people have more time to look at the hard problems they are trying to solve instead of fighting the language and shipping the business value they are paid for instead of wasting time on unrelated issues.

A language which has e. g. concurrency done right, but is so painful to deal with that everyone writes single-threaded code to get home early, is completely useless.

> but a language that makes collections the domain of experts without at least fixing the real hard issues, is just plain misguided.

Scala's collections are the most pleasant ones I have worked with and I think most people will disagree on that. I also think that Scala's trade-off on letting the library authors solve hard problems once instead of letting every user deal with them on their own each and every time they use it is a reasonable trade-off.

In other languages you would probably have to implement every operation yourself if you wanted to define a new collection type. Mostly tedious, error-prone work. In Scala instead, you understand the CanBuildFrom facility once and get almost the complete implementation for free, overriding only the operations you care about. Note that understanding CanBuildFrom is a one-time effort, while in other languages you will hit those issues every time you want to create a new collection type. Again, seems like a reasonable trade-off to me.

BTW, when I said developer productivity I didn't mean actual productivity (which is harder to quantify, as it includes all time spent on testing and maintenance throughout the lifetime of the project), but "developer productivity" as it's become known in PL vernacular to mean less boilerplate and fewer LOC.

And I guess we'll just agree to disagree, because I think we disagree about what's important even more than we disagree about the merit of each feature in Scala on its own. I believe Scala's tradeoffs are very misguided (and yeah, C++ is certainly similar) while you think they're justified. I believe that even an excellent feature should be left out of a language if it increases its complexity and the benefits do not solve a problem I care about every day, while you might think it's OK to increase a language's complexity even for features that won't be used so often. I think that in modern software development, application developers are better served by an opinionated language (especially when it comes to concurrency) while infrastructure software developers (assuming your software environment allows to easily mix languages) can certainly live with some annoying boilerplate if the language "closer to the metal", but both value simplicity; you might think that "one language to rule them all" with few constraints is preferable even at some cost to both types of developers.

> I believe that even an excellent feature should be left out of a language if it increases its complexity and the benefits do not solve a problem I care about every day, while you might think it's OK to increase a language's complexity even for features that won't be used so often.

No, I don't think we disagree here at all and I think it's one of the design principles behind the language.

“do not solve a problem I care about every day” is just another phrase for “anything I'm remotely unfamiliar with”. And again, just because you decided to not invest the time to understand thing X, doesn't mean all daily users of X are idiots.

You couldn't offer much here except structural types, so let me just take it is an example. Structural types were not “added” to the language because they are “so great and useful”, but because it eliminated an inconsistency where one would have types which one could express and a subset of types which would be e. g. a valid type for a method's parameter.

Treating types consistently is a huge reduction in complexity for users because they don't have to divide types into types which can be used everywhere and types which can't be used everywhere. If you think this is just an academic idea, have a look at the weird corner cases this creates in Java where you can call methods on an instance directly, but if you assign that instance, the methods seem to not exist anymore.

Ceylon, by the way not only agrees on that with Scala, but the designers marked this as one of their pillars of language philosophy (principal types).

Almost everything you can do in Java is probably easier and more consistent in Scala. Claiming that those things which Java can't do (e. g. having a remotely useful type system (1), typeclasses, ...) make the language simpler is just trying to ignore that problems are not solved by wishing them to go away. Those things just crop up in an ugly way elsewhere, be it in ridiculously complicated frameworks, in bytecode manipulation, etc.

(1) There is a reason proponents of dynamically-typed languages bring up Java when they explain what's wrong with static typing.

> “do not solve a problem I care about every day” is just another phrase for “anything I'm remotely unfamiliar with”. And again, just because you decided to not invest the time to understand thing X, doesn't mean all daily users of X are idiots.

I wasn't calling anyone an idiot, and I don't know who you are, buddy, but I'm starting to get the feeling that I might have some years experience over you; perhaps even a decade, so chill.

Look, you can go on believing Scala is simple all you want for whatever measure of simplicity you define; Martin Odersky even tried using grammar size as a measure (personally, I wouldn't go for consistency as a measure, though, because machine language is also very consistent, but YMMV...)

Then, you can try to get the team working on the next aircraft-carrier control system (or a huge mail routing system or air traffic control software) to adopt Scala, and see how fast they throw you out the window.

> Claiming that those things which Java can't do (e. g. having a remotely useful type system (1), typeclasses, ...)

Again with the features. I don't care about what type system a language has and how mathematically correct it is. I care about writing maintainable, correct and efficient code. Types might help achieve those goals, but it's not as if the more "correct" the type system is, the better those goals will be served. Why? some of the reasons are cultural, some have to do with the way humans think, and some have to do with the way computers "think".

You think Scala helps achieve those goals, I think Scala is detrimental to them. I abandoned Scala about 5 years ago and I have no intention of using it again, especially now when there are languages which I find superior to Scala in every respect that I think matters. If you feel Scala works for you I'm not going to convince you otherwise. For me and for the organizations I've worked for it didn't work at all.

> You think Scala helps achieve those goals, I think Scala is detrimental to them. I abandoned Scala about 5 years ago and I have no intention of using it again, especially now when there are languages which I find superior to Scala in every respect that I think matters. If you feel Scala works for you I'm not going to convince you otherwise. For me and for the organizations I've worked for it didn't work at all.

I think this explains all of it. The thing you are talking about has pretty much no resemblance with Scala today. You can bash Scala-from-5-years-ago as much as you want as long as you stop misleading people that your claims are in any way relevant to what Scala is today.

Really, look at how your extrapolations from pre-historic Scala versions worked out til now. You only embarrassed yourself. I recommend being honest next time and just sharing your experience about Scala 2.5/2.6/2.7. I think we could all have a good time telling war stories, considering how hilariously unstable the compiler was at that time.

Dude, look, I stopped using Scala because it's gotten sooo much worse worse with each version; whatever coherence it had at first, it quickly shed away in a frenzy of misguided notions about what developers really need. I actually liked it in the early days. My claims are my view, as someone who's been developing software professionally for over two decades. I am well aware that there are those who disagree. Of course, you are entitled to your opinion. It could be the best damn language in the world for you, but it sucks for many, many others. I can tell you that some companies looked at Scala carefully and rejected it; some adopted it only to discard it a couple of years later. You should accept the undeniable fact that Scala does not appeal to some knowledgeable, experienced people, even after they consider it carefully. And it's OK - I like many things that other people don't like, and they have good reasons not to like them. I would concede that Clojure, too (and I really think Clojure is an exceptionally well designed language), does not have a very broad appeal; neither does Scala.

Use it in peace. If 5 years from now a significant portion of the software development community is using Scala, then you were right and I was wrong; if not, you'd better recheck your convictions. Maybe the language you like so much doesn't solve problems that hurt badly enough, or doesn't solve them well enough, for people to pay the price of its complexity and lack of coherence.

Either way, Scala has certainly taught us a few things and we can learn from its mistakes. Maybe some of the lessons will be used to create a language that works for me and those who see things my way, too.