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Union Types, done in a lightweight 'anonymous' fashion. Awesome! Some languages go the discriminated type union route. If I had to chose I would take the this o

Union Types, done in a lightweight 'anonymous' fashion. Awesome! Some languages go the discriminated type union route. If I had to chose I would take the this over a that alternative. Typescript continues to push forward. Hopefully this leads to the construct being adopted by more languages. Rust has the heavier version, maybe they will adopt this before they release instead and then they can replace their gussied up Either/Err type with unions. Maybe someday the Scala team will see the light and we will get them as well. Sadly I am not holding my breath, adopting innovations like union types were what drew me to Scala. Something like this isn't even on the docket for the next several years at a minimum. All the innovation in syntax died following the terrible 2013 scaladays keynote that "challenged" the Scala community to suck as hard as Java by 2018. It's really a shame that martin didn't decide to just implement union types when he implemented tuples years ago, now the language is probably too ossified to ever adopt them for fear they'll be another XML.

frowaway001 12y ago
> Maybe someday the Scala team will see the light and we will get them as well. Sadly I am not holding my breath, adopting innovations like union types were what drew me to Scala. Something like this isn't even on the docket for the next several years at a minimum. ??? Union types are already announced and will ship in a future version of Scala. If you can't wait you can use dotc instead of scalac, and play with union types today. (A commit to share the newest scalac-backend between scalac and dotc just entered the pull request queue and should close one of the largest missing pieces.)
- benjaminjackman 12y ago
  That's awesome! I must have missed that announcement where it will come sooner than the next several years. Can you point me to it? The last I heard was in the roadmap [http://www.scala-lang.org/news/roadmap-next http://www.scala-lang.org/news/roadmap-next] and the earliest it is to be expected is in "Don Giovanni" which is not 2.12 or 2.13 but 2.14 which is, what, 4-5 years away at this point? Unfortunately, we can't use dotc, we use Scala for a decently large project (220KLOC using wc -l) started back in the late 2.6/early 2.7 days which is gradually being ported to cross compile in ScalaJS. Having said that I will look into it for a side project. That's how our use of ScalaJS started. I had been attempting to use Typescript, but after giving it a shot, ScalaJS clearly beat it in every regard for our use cases, (well until the union types, but ScalaJs is still very very far ahead for us). Thanks for the heads up!
  - frowaway001 12y ago
    I think this is the announcement I had in mind, I'd just take the published roadmap with a grain of salt, because usually things ship when they are ready and fit into the whole picture. As seen in dotty, the basic stuff around union types is already working, so I'd be pretty surprised if it didn't ship earlier, especially because there is a demonstrated need for HLists, and shipping HLists without union types ... could be done, but why? Additionally, a lot of things mentioned in "Don Giovanni" are already ready-to-ship today (sans a few minor requirements). For instance Giovanni's 1.3, 2.1, (some parts of 2.4 already shipped with 2.11), (approaches for 5.1 were already discussed and benchmarked), 5.1/5.2 (will happen when targeting Java 10). My recommendation is to take that roadmap as a bottom line, but be prepared for drastic changes. My current guess is that if work gets done at the current speed, it might be possible to move things to earlier releases and subsequently eliminate a whole release in between, e. g. shipping the features of three releases in two. But that's all just my educated guess.
    - benjaminjackman 12y ago
      Sweet I will definitely check out dotty then! Thanks for taking the time to catch me up. I'll move to guardedly optimistic we'll see union types in Scala this decade :) Are HLists shipping soon too? I was under the impression they would have to wait for Giovanni as well, I need to start reading internals again I guess. Re: 5.1/5.2(miniboxing/value classes) => Java 10 is going to get structs then I am guessing? I read the rough draft of that a few months back, looks pretty complicated but it seems to have thought through the corner cases. It is a godsend if you need that level of performance. As an aside: it's funny you mention 1.3(Procedure Syntax) and 2.1(Result types are mandatory for Implicit definitions). They are actually the two changes that are far and away the worst for us from Giovanni so it's frustrating to see them be implemented first. This is because we have thousands of lines for our serialization framework that run afoul of 2.1 which look like this: object Foo {implicit val ser = SerBuilder.forCase(this.apply _)} case class Foo(x : Int) And thousands upon thousands that use procedure syntax. (We should write with less side-effects, I agree.) However when we do have side effects we want them to visually separate themselves from all the non unit returning methods. Procedure syntax does that and conveys the inherit difference between a procedure and function, via quickly scannable visual signaling. So that the procedures don't blend in to the : Blah = .... sea of functions, and all while being 8 less keypresses.

frowaway001 12y ago

> Maybe someday the Scala team will see the light and we will get them as well. Sadly I am not holding my breath, adopting innovations like union types were what drew me to Scala. Something like this isn't even on the docket for the next several years at a minimum. ??? Union types are already announced and will ship in a future version of Scala. If you can't wait you can use dotc instead of scalac, and play with union types today. (A commit to share the newest scalac-backend between scalac and dotc just entered the pull request queue and should close one of the largest missing pieces.)

benjaminjackman 12y ago
That's awesome! I must have missed that announcement where it will come sooner than the next several years. Can you point me to it? The last I heard was in the roadmap [http://www.scala-lang.org/news/roadmap-next http://www.scala-lang.org/news/roadmap-next] and the earliest it is to be expected is in "Don Giovanni" which is not 2.12 or 2.13 but 2.14 which is, what, 4-5 years away at this point? Unfortunately, we can't use dotc, we use Scala for a decently large project (220KLOC using wc -l) started back in the late 2.6/early 2.7 days which is gradually being ported to cross compile in ScalaJS. Having said that I will look into it for a side project. That's how our use of ScalaJS started. I had been attempting to use Typescript, but after giving it a shot, ScalaJS clearly beat it in every regard for our use cases, (well until the union types, but ScalaJs is still very very far ahead for us). Thanks for the heads up!
- frowaway001 12y ago
  I think this is the announcement I had in mind, I'd just take the published roadmap with a grain of salt, because usually things ship when they are ready and fit into the whole picture. As seen in dotty, the basic stuff around union types is already working, so I'd be pretty surprised if it didn't ship earlier, especially because there is a demonstrated need for HLists, and shipping HLists without union types ... could be done, but why? Additionally, a lot of things mentioned in "Don Giovanni" are already ready-to-ship today (sans a few minor requirements). For instance Giovanni's 1.3, 2.1, (some parts of 2.4 already shipped with 2.11), (approaches for 5.1 were already discussed and benchmarked), 5.1/5.2 (will happen when targeting Java 10). My recommendation is to take that roadmap as a bottom line, but be prepared for drastic changes. My current guess is that if work gets done at the current speed, it might be possible to move things to earlier releases and subsequently eliminate a whole release in between, e. g. shipping the features of three releases in two. But that's all just my educated guess.
  - benjaminjackman 12y ago
    Sweet I will definitely check out dotty then! Thanks for taking the time to catch me up. I'll move to guardedly optimistic we'll see union types in Scala this decade :) Are HLists shipping soon too? I was under the impression they would have to wait for Giovanni as well, I need to start reading internals again I guess. Re: 5.1/5.2(miniboxing/value classes) => Java 10 is going to get structs then I am guessing? I read the rough draft of that a few months back, looks pretty complicated but it seems to have thought through the corner cases. It is a godsend if you need that level of performance. As an aside: it's funny you mention 1.3(Procedure Syntax) and 2.1(Result types are mandatory for Implicit definitions). They are actually the two changes that are far and away the worst for us from Giovanni so it's frustrating to see them be implemented first. This is because we have thousands of lines for our serialization framework that run afoul of 2.1 which look like this: object Foo {implicit val ser = SerBuilder.forCase(this.apply _)} case class Foo(x : Int) And thousands upon thousands that use procedure syntax. (We should write with less side-effects, I agree.) However when we do have side effects we want them to visually separate themselves from all the non unit returning methods. Procedure syntax does that and conveys the inherit difference between a procedure and function, via quickly scannable visual signaling. So that the procedures don't blend in to the : Blah = .... sea of functions, and all while being 8 less keypresses.