A Leiningen plugin to compile Frege (http://www.frege-lang.org) code.
Clojure Frege
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project.clj Ensure we are in interactive mode when running Frege code! Feb 10, 2015



Moved to https://github.com/Frege/frege-lein-plugin


A Leiningen plugin to compile Frege (http://www.frege-lang.org) code.


Add [lein-fregec "3.22.367-i"] to :plugins in your project.clj. The version of lein-fregec matches the version of the Frege compiler it is compatible with and uses.

Set :frege-source-paths to the location(s) of your Frege source files. Default is the current directory but I highly recommend using src/frege and structuring your projects that way (although the hello example relies on current directory).

Run lein fregec to compile Frege source files to .class files.

The output of compilation will go to the :compile-path directory, which defaults to target/classes/ in Leiningen.

You may specify additional Frege compiler options via :fregec-options in project.clj (as a vector of strings) or via the command line. Note that command line options for Leiningen tasks start with : (and are converted to - options automatically):

lein fregec :v

This will pass -v to the Frege compiler (verbose mode). If you want to see the full list of options being passed to the Frege compiler, set the DEBUG environment variable to true:

DEBUG=true lein fregec

This will also display the exact version of the Frege compiler that the plugin is using.

Run lein uberjar to compile Frege source files and create a JAR file in the target/ folder. You need to ensure that Frege compilation is part of the :uberjar profile in project.clj:

:profiles {:uberjar {:aot :all
                     :prep-tasks ["fregec" "compile"]}}

This tells Leiningen to run the fregec task and the compile task before building the JAR file. That will run the Frege compiler and also compile any Clojure code in the project.

Also, in order to include the Frege runtime in the resulting JAR file, you will need the following dependency in your project.clj file:

:dependencies [[com.theoryinpractise.frege/frege "3.22.367-g2737683"]]

The version here should exactly match that displayed by lein-fregec when you use the DEBUG=true environment variable!

This tells Leiningen that your project depends on Frege, and it will package it into the standalone JAR it produces. The standalone JAR can be run as follows:

java -cp target/frege-hello-0.1.0-SNAPSHOT-standalone.jar Hello

This assumes your project.clj starts out like this:

(defproject frege-hello "0.1.0-SNAPSHOT"

You can also run your (pure Frege) code by specifying :run and the class name (followed by any arguments for your main method):

lein fregec :run Hello

There will also be a non-standalone JAR will which does not contain the Frege runtime.

An example of a pure Frege project can be found in the hello directory which is a self-contained Leiningen project with its own README.

An example of mixed Clojure / Frege usage can be found in the example directory which is also a self-contained project.


Copyright (c) 2014-2015 Sean Corfield

Distributed under the Eclipse Public License, the same as Clojure.