How do I enable continuations in Scala?

Question

Question says it all.

(Yet, the details of how to get access to the shift and reset operations has changed over the years. Old blog entries and Stack Overflow answers may have out of date information.)

See also What are Scala continuations and why use them? which talks about what you might want to do with shift and reset once you have them.

Answer 1

Scala 2.11

The easiest way is to use sbt:

scalaVersion := "2.11.6"

autoCompilerPlugins := true

addCompilerPlugin(
  "org.scala-lang.plugins" % "scala-continuations-plugin_2.11.6" % "1.0.2")

libraryDependencies +=
  "org.scala-lang.plugins" %% "scala-continuations-library" % "1.0.2"

scalacOptions += "-P:continuations:enable"

In your code (or the REPL), do import scala.util.continuations._

You can now use shift and reset to your heart's content.

historical information for Scala 2.8, 2.9, 2.10

You have to start scala (or scalac) with the -P:continuations:enable flag.

In your code, do import scala.util.continuations._

You can now use shift and reset to your heart's content.

If you're using sbt 0.7, see https://groups.google.com/forum/#!topic/simple-build-tool/Uj-7zl9n3f4

If you're using sbt 0.11+, see https://gist.github.com/1302944

If you're using maven, see http://scala-programming-language.1934581.n4.nabble.com/scala-using-continuations-plugin-with-2-8-0-RC1-and-maven-td2065949.html#a2065949

Answer 2

Non SBT solution:

scala -Xpluginsdir /.../scala/lib/ -P:continuations:enable

Works on scala 2.11.6, but the plugin/library said that it will no longer be included with Scala 2.12