Scala Days – key note

It may not be a great surprise, but the opening key note is held by Martin Odersky. I don’t feel much expectation, more or less everyone expects he’s going to repeat the opening speech of the last Scala conference in New York.
In this post I’ll just summarize the content, my considerations will be in a next one.
Scala days are going to be attended by some 1000 people. Conf app is, of course written in Scala and swift (and it’s open source) courtesy of 47 degrees.

Odersky enters with son et lumier effect, halfway between a disco and an alien abduction… Maybe both.
First he shows a steady growth of the language. Scala jobs get a little over the line. There is no comparison with Java, of course, but there is no drop in popularity.
He will talk about the future, next, mid and distant futures.
What’s next? Scala center, Scala 2.12 , Scala libraries.
Scala center is a vendor neutral initiative supported by several partners that promotes Scala, and undertakes projects that benefit all the Scala community.
Scala 2.12 is the next release of the language, about to be completed. Optimized for Java 8. Shorter code and faster execution.
This release will arrive mid year. Older Java versions will be supported by Scala 2.11 that, in turn, will be supported for quite a while.
Not many new features: 33. Main contributors are from the community.
Martin’s book “Programming in Scala” will be updated to 3rd edition to include release 2.12 of the language.

In the farther future: 2.13 will focus on libraries – Scala collections, simpler, lazy, integrated with Spark. Backward compatible.

Split Scala stdlib into core and platform. Stdlib was much prototypal with the idea that wouldn’t have lasted long.

Scala js, and Scala native.

The dot is the foundation of Scala. a mini language, small enough that programs written in this language can be machine proof. Much of the language can be encoded in this language. 8 years in the working. Language work can be done with much more confidence.


Type soundness, properties of code can be demonstrated (the examples say that an expression of type T produces a value of type T).
Dotty a language close to Scala compiler that produces dot code. Generics are processed with dot. Not ready for industry, but if you want to try something cool…
Goal: Best language Martin knows how to make.

Dropped: procedure syntax. Rewrite tool that will take care of translating. DelayedInit.
Macros – of was just a long run example. There will be an alternative.
Early initializers – for stuff that needs to be initialized before the base trait.
Existential Types forSome.
General Type Projection T#x.

Added: intersection and union types- types T&U just the common properties of the two types. T|U will have either the properties of T or the properties of U.

Function arity adaptation. ((a,b) =>a+b)

Static method for object.

Non blocking lazy Vals: locking time is much shorter now. Avoiding deadlocks.
@volatile for thread shared lazy vals.

Multiversal equality type safe equality and inequality operators. Named type parameters – partial type parametrization.

Motivations better foundation, safer,…

SBT integration. Repl with syntax highlighting. Intellij. Doc generation. Linker.

Scala meta – will replace macros and meta programming. Inline and meta. Executed by the compiler.
Implicit function types . used to compose … Just more mess.

Effect checking a->b pure function, a=>b impure. Checked by the compiler.

Nullable types T? =T | Null. Types coming from Java will have a ? Because they have side effect. It is an alternative to monads.

Generic programming.

Guard rails – how to prevent the programmers to misuse or abuse the language. Strategic Scala style: principle of least power. Strategic Scala style.

Libraries that inject bad behavior (eg implicit conversion). Implicit conversions will make a style error if public.

Syntax flexibily. Even Martin regrets the space syntax. Add @infix annotation if the author intends it to be used as infix and give a style error in other cases.

Operators are regretted as well . @infix will have the option to give names to such operators.

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