Try Effekt Online

You can immediately experiment with the Effekt language, without installing it.

Effekt is a research language, we recommend reading the paper describing important design decisions and the inner workings of Effekt.

Online Editor

Below you can find an online editor, which is enabled by clicking “edit” on the right. Please be aware that the changes are not saved!

import immutable/list
import immutable/option
import text/string
interface Greet { def sayHello(): Unit }

def helloWorld() = try {
  do sayHello()
} with Greet {
  def sayHello() = { println("Hello!"); resume(()) }


The following read-eval-print-loop gives you access to run the above contents: