[MustardTiger]

Scala is an OO language with FP tacked on, so it basically defaults to "make everything a pain". It was easy to justify rewriting it again because it only took two weeks to do it. A re-write is much faster than initially writing it, you're just copying yourself.

[premium-concern]

I wonder why Haskell people feel so hurt about Scala...

It's much closer to Haskell's capabilities than pretty much any other functional language.

It has better type classes, the compiler just got type inference for partially applied type constructors, it supports programming with dependent types and implicit parameters allow you to let the compiler prove almost arbitrary things.

If your definition of FP means "purity", you pretty much discarded all languages traditionally considered to be functional.

There is nothing wrong with liking Haskell more than Scala, but I think your claims are not very well-founded.

[MustardTiger]

I wonder why you assume I am a haskell person, why you assume I am "so hurt about scala", and mostly why even if those two absurd assumptions were true, that you could generalize that to "haskell people".

I am obviously not a haskell person, or I would have just used haskell rather than trying scala first. I am not hurt about scala, it simply was much less productive than haskell.

Scala is not remotely the closest to haskell. Not even the closest JVM language.

And my "claims" are my personal experience, how can they not be "very well founded". You seem to be putting some emotional context into this that has nothing to do with me.

[kmiroslav]

> It has better type classes

Haskell and Scala win and lose on different criteria but for type classes, I find Haskell's syntax and semantics infinitely more elegant, more terse and more flexible than Scala's. Defining type classes in Scala is a cacophony of syntax boiler plate riddled with implicits and brackets. Haskell is much more elegant in that area.

[premium-concern]

Scala's typeclasses are first-class values and they actually work as advertised.

Haskell's type classes are a mess because Haskell-the-spec (anti-modular, coherent) and Haskell-the-language (incoherent, "modular") work completely different and nobody cares and there us no real fix because both options suck, as soon as your project consists of more than one module.

It's the reason why no language after Haskell does type classes the Haskell way, and all of them do it similar to Scala's approach.

Could Scala have more syntax sugar? Sure! But people are more focused on getting them right first, before adding additional syntax.

[MustardTiger]

What on earth are you talking about? Tons of other languages do type classes "the haskell way". Which is also known as "type classes". Scala doesn't have type classes, it has a close approximation.

[codygman]

What other languages do type classes like Haskell?

[MustardTiger]

All of them? Who else has broken almost like typeclasses other than scala?

[premium-concern]

Not these (at least):

Idris – implicit arguments

Agda – instance arguments

OCaml – Modular implicits

:-)

[tome]

> Haskell-the-spec (anti-modular, coherent) and Haskell-the-language (incoherent, "modular") work completely different

I'm unaware of any such difference. Please explain.

[premium-concern]

The spec mandates that type class instances can only be defined together with the type class or with the corresponding data type.

While it's a very poor idea as no person except the author of the type class or the author of the data type can define a type class instance, it at least guarantees the global uniqueness and coherence of type class instances. ("There can only ever be a single typeclass instance for typeclass A and data type B.")

GHC (the only implementation that kind of matters today) takes a YOLO approach, allows as many typeclass instances as you want, doesn't bother enforcing the rules laid out in the spec. Additionally, as type class instances are not first-class values of the language a developer doesn't even have the option to make sure he is getting the instance he expects.

There exists a GHC warning for "orphan type class instances"–but as the warning triggers on everything, not only the relevant cases where multiple instances clash and break the program–it's as useful as saying "we made sure that C's goto-fail bug can never happen again by emitting a warning for every suspicions indentation – you only have to sift through 1732 warnings until you find the dangerous one!".

[dllthomas]

Your C comparison at the end is disingenuous. It is entirely possible to use the orphan instances warning to ensure coherence in an application that contains orphan instances without a single spurious warning. Simply make a habit of putting all orphan instances in a single module, and mark only that one module -fno-warn-orphans. The rest of your code can be organized appropriately. It is not ideal, but not painful.

It's true that you can't safely define orphan instances in a library, but that also should involve no "sifting through" warnings for valid uses. It is genuinely bad practice to put orphan instances in a library, even if we had global checking - it would produce cases where you simply cannot use otherwise compatible libraries in the same project.