Build status Latest version


  • Compile Frege code from your project's src/main/frege/ directory
  • Call Frege code from your project's Java/Scala/etc. code
  • Launch the Frege REPL with your project's classes and libraries


  • sbt 1.0.1+
  • Scala 2.4.0+

For sbt 0.13.6+ projects, use sbt-frege version 1.1.3

Getting started

Add the Frege sbt plugin to your project:


addSbtPlugin("com.earldouglas" % "sbt-frege" % "3.0.2")

Write some Frege code:


package example.HelloWorld where

main :: [String] -> IO ()
main _ = println "Hello, world!"

Build and run it:

$ sbt
> compile
> run
Hello, world!

Try it from the Frege REPL:

$ sbt
> fregeRepl

frege> import example.HelloWorld (main)

frege> main []
Hello, world!


Frege compiler

  • fregeOptions: Seq[String] - Extra options for fregec
  • fregeSource: File - Frege source directory (default src/main/frege/)
  • fregeTarget: File - Frege target directory (default target/frege/)
  • fregeCompiler: String - Full name of the Frege compiler (default frege.compiler.Main)
  • fregeLibrary: ModuleID - Frege library (fregec.jar) to use (default Frege 3.23.288)

Frege REPL

  • fregeReplVersion: String - The version of frege-repl to use (default 1.3)
  • fregeReplMainClass: String - The Frege REPL main class (default frege.repl.FregeRepl)

Though sbt-frege uses by default, Frege REPL 1.3 depends on Frege 3.23.288, so it takes priority when launching fregeRepl.