scala/scala

A relaxed chat room about all things Scala. Beginner questions welcome. https://scala-lang.org/conduct/ applies

Otto Chrons

@ochrons

also, you can have interdependency with the this: U => style, for example

trait T { self: U => ... }
trait U { self: T => ... }

useful in Slick cake pattern when tables need to refer to each other but you don't want to put them all in a single trait

http://venturebeat.com/2015/12/29/google-confirms-next-android-version-wont-use-oracles-proprietary-java-apis/ in case this wasn't mentioned here yet (re: earlier discussion about Java8 on Android)

Aloïs Cochard

@aloiscochard

hi typesafe folks, (especially @jsuereth) just few minutes ago, on the #scala IRC channel (freenode) there was some rascist troll that had to be kicked. Luckily I was here, but I'm really not often in that room and sometimes there is no one to kick bots and other spammers. I just got in touch with @hippo-tiny which is from the FreeNode staff and offer his help, it would be great to get more OPs on board... I think I'm the only one active atm. We discussed a few times about giving @tpolecat and @OlegYch the ops right as well, maybe we can finally solve this as I was not able to find anyone active with "superop" access to give them necessary rights....

Dale Wijnand

@dwijnand

@tpolecat that self type of a final type is very interesting.. you can use it so that Foo is like an optional mix-in that you can only use with X.. cool

N.S. Cutler

@godenji

This message was deleted

gitter works with irc ;-)

Michiel Borkent

@borkdude

Can someone explain to me in simple terms what GenTraversableOnce stands for? Is it important to know?

Seth Tisue

@SethTisue

it’s rarely important to know. Gen stands for “general” — meaning it might or might not be a parallel collection. TraversableOnce means it might (or might not) be e.g. an Iterator which is consumed in a single pass.

soc

@soc

it basically says that it's a data strucutre which can be traversed at least once, and Gen means it has no idea whether it happens sequantially or in parallel

Seth Tisue

@SethTisue

see “hierarchy” section of http://docs.scala-lang.org/overviews/parallel-collections/architecture.html

Michiel Borkent

@borkdude

thanks

Li Haoyi

@lihaoyi

Traversable would be such a beautifully useful/general trait if it wasn't full of annoying concrete eager implementations :/

A traversable with lazy operations is the perfect dual of an iterator with lazy operations (which we have)

And would map perfectly onto Java 8 streams because that's basically what they are

Rob Norris

@tpolecat

@borkdude the collections hierarchy is legitimately baffling, so don't feel bad.

richfwebb

@richfwebb

Anyone have a recommendation for lightweight communication from scala to lua (for an API)? Tcp and cURL are the best options I've found so far.

Otto Chrons

@ochrons

HTTP is usually quite well supported

agilisticdev

@agilisticdev

Hi. I am a newly with Scala and actually reading Scala 2nd Edition and got a question on how to create an empty list. I read that Nil is a shorter way to create an empty... Why Nil? Just by its name, I would never know that Nil does that? What the explanation for Nil?

Thanks

Perry

@pfn

because Nil means empty list

Rob Norris

@tpolecat

Nil is the empty list. The one and only.

So it doesn't "create" anything; it's just a value.

agilisticdev

@agilisticdev

Thanks for you quick answer but I'll orient my question differently

Rob Norris

@tpolecat

Traditionally nil was the empty list in Lisp, so that's almost certainly where the name came from.

agilisticdev

@agilisticdev

Nil, in some languages like Objective-C means the same thing as null in Java

To me, there is no obvious relation between Nil and an empty list...

They could have used "Lon".. at it would be a acroymn for "List of Nothing"....

Martijn Hoekstra

@martijnhoekstra

I think the convention comes from Lisp, but I'm not 100% sure.

Rob Norris

@tpolecat

In FP the linked list constructors are almost always called cons and nil.

Krzysztof Pado

@povder

@agilisticdev there are a lot of new terms to learn when you start learning functional programming

agilisticdev

@agilisticdev

Oh, I do not know Lisp...

Rob Norris

@tpolecat

In Scala we write them as :: and Nil.

Krzysztof Pado

@povder

@agilisticdev If you're interested, check out https://en.wikipedia.org/wiki/Cons

agilisticdev

@agilisticdev

@povder Thanks, I'll certainly read it

Krzysztof Pado

@povder

I also recommend this course https://www.coursera.org/course/progfun

I think that this course is a very good starting point for learning functional programming and scala

agilisticdev

@agilisticdev

Thanks for your quick answer. I do not find :: and Nil very readable and easy to understand but as you guys said, these terms are used in FP, so I'll get used to it

Perry

@pfn

get used to it, and it's very readable vs alternatives

Justin du Coeur, AKA Mark Waks

@jducoeur

@agilisticdev This usage of nil is 50+ years old in the functional-programming community. It's a bit unfortunate that Objective-C used it to mean something else, but it has meant "empty list" since the early days of software -- it not only predates Objective-C, I believe it predates C...

Rob Norris

@tpolecat

correct. lisp was invented in the late 1950's

Srepfler Srdan

@schrepfler

what happened with Coursera’s progfun course this year, it was supposed to happen in September no?

nafg

@nafg

@schrepfler I think they're refactoring it ;)

@odersky can give a better answer

Seth Tisue

@SethTisue

re: progfun course, see Martin’s post at https://groups.google.com/d/msg/scala-user/mB_5PnAWRow/vt0Yv9mECwAJ

they’re actively working on it.

qifeng dai

@matrix2011

Dear all, i have a question. I know what "case class” means, but I found some single object modified by “case" yet, what does it means? as "case object Nil extends List[Nothing]” for example.

Jason Zaugg

@retronym

http://stackoverflow.com/questions/5270752/difference-between-case-object-and-object

qifeng dai

@matrix2011

thanks

Sebastian Himberger

@shimberger

is Either idiomatic to use? I am looking for a good way of error handling in the standard library

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