Guides and Overviews

Core Scala

Guides and overviews covering central libraries in the Scala standard library, core language features, and more.

By Martin Odersky and Lex Spoon

These pages describe the architecture of the Scala collections framework in detail. Compared to the Collections API you will find out more about the internal workings of the framework. You will also learn how this architecture helps you define your own collections in a few lines of code, while reusing the overwhelming part of collection functionality from the framework.

String Interpolation allows users to embed variable references directly in processed string literals. Here’s an example:

val name = "James"
  println(s"Hello, $name")  // Hello, James
In the above, the literal s"Hello, $name" is a processed string literal. This means that the compiler does some additional work to this literal. A processed string literal is denoted by a set of characters preceding the ". String interpolation was introduced by SIP-11, which contains all details of the implementation.

By Josh Suereth

Scala 2.10 introduced a new feature called implicit classes. An implicit class is a class marked with the implicit keyword. This keyword makes the class’ primary constructor available for implicit conversions when the class is in scope.

By Mark Harrah

Value classes are a new mechanism in Scala to avoid allocating runtime objects. This is accomplished through the definition of new AnyVal subclasses.

When two versions of Scala are binary compatible, it is safe to compile your project on one Scala version and link against another Scala version at run time. Safe run-time linkage (only!) means that the JVM does not throw a (subclass of) LinkageError when executing your program in the mixed scenario, assuming that none arise when compiling and running on the same version of Scala. Concretely, this means you may have external dependencies on your run-time classpath that use a different version of Scala than the one you’re compiling with, as long as they’re binary compatible. In other words, separate compilation on different binary compatible versions does not introduce problems compared to compiling and running everything on the same version of Scala.


Reference material on core Scala tools like Scaladoc and the Scala REPL.

Scala's API documentation generation tool.


The Scala REPL is a tool (scala) for evaluating expressions in Scala.

The scala command will execute a source script by wrapping it in a template and then compiling and executing the resulting program

Parallel and Concurrent Programming

Complete guides covering some of Scala's libraries for parallel and concurrent programming.

By Philipp Haller, Aleksandar Prokopec, Heather Miller, Viktor Klang, Roland Kuhn, and Vojin Jovanovic

Futures provide a way to reason about performing many operations in parallel– in an efficient and non-blocking way. A Future is a placeholder object for a value that may not yet exist. Generally, the value of the Future is supplied concurrently and can subsequently be used. Composing concurrent tasks in this way tends to result in faster, asynchronous, non-blocking parallel code.

By Vojin Jovanovic and Philipp Haller

To ease the migration from Scala Actors to Akka we have provided the Actor Migration Kit (AMK). The AMK consists of an extension to Scala Actors which is enabled by including the scala-actors-migration.jar on a project’s classpath. In addition, Akka 2.1 includes features, such as the ActorDSL singleton, which enable a simpler conversion of code using Scala Actors to Akka. The purpose of this document is to guide users through the migration process and explain how to use the AMK.

By Philipp Haller and Stephen Tu

This guide describes the API of the scala.actors package of Scala 2.8/2.9. The organization follows groups of types that logically belong together. The trait hierarchy is taken into account to structure the individual sections. The focus is on the run-time behavior of the various methods that these traits define, thereby complementing the existing Scaladoc-based API documentation.


Guides and overviews covering the experimental reflection API introduced in Scala 2.10, and Scala's tools for metaprogramming (def macros, macro annotations, and more), also introduced in Scala 2.10

By Heather Miller, Eugene Burmako, and Philipp Haller

Scala's runtime/compile-time reflection framework.