Scala 3/Usage/Getting Started: Users

Getting Started: Users

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Trying out Dotty

In your web browser

Scastie, the online Scala playground, supports Dotty. This is an easy way to try Dotty without installing anything, directly in your browser.

sbt

The fastest way to create a new project compiled by Dotty is using sbt

Create a simple Dotty project:

$ sbt new scala/scala3.g8

Or a Dotty project that cross compiles with Scala 2:

$ sbt new scala/scala3-cross.g8

You can then start a Dotty REPL directly from your sbt project:

$ sbt
> console
scala>

For more information, see the Dotty Example Project

IDE support

Start using the Dotty IDE in any Dotty project by following the IDE guide.

Standalone installation

Releases are available for download on the Releases Section of the Dotty repository. Releases include three executables: scalac the Dotty compiler, scaladoc the Scaladoc and scala the Dotty REPL.

.
└── bin
    ├── scalac
    ├── scaladoc
    └── scala

Add these executables to your PATH and you will be able to run the corresponding commands directly from your console:

# Compile code using Dotty
$ scalac HelloWorld.scala

# Run it with the proper classpath
$ scala HelloWorld

# Start a Dotty REPL
$ scala
Starting dotty REPL...
scala>

If you're a Mac user, we also provide a homebrew package that can be installed by running:

brew install lampepfl/brew/dotty

In case you have already installed Dotty via brew, you should instead update it:

brew upgrade dotty

Scala 3 for Scripting

If you have followed the steps in "Standalone Installation" section and have the scala executable on your PATH, you can run *.scala files as scripts. Given a source named Test.scala:

@main def Test(name: String): Unit =
  println(s"Hello ${name}!")

You can run: scala Test.scala World to get an output Hello World!.

A "script" is an ordinary Scala file which contains a main method. The semantics of the scala Script.scala command is as follows:

  • Compile Script.scala with scalac into a temporary directory.
  • Detect the main method in the *.class files produced by the compilation.
  • Execute the main method.