Clojure implemented on the Erlang VM.

Building clojerl requires Erlang/OTP 18+ and rebar3.

git clone https://github.com/clojerl/clojerl
cd clojerl
make

To try it out and get a sense of what you can do, you can visit Try Clojerl.

Running make repl will start the REPL and show its prompt:

Clojure 0.0.0-974.592ad8a
clje.user=>

From the REPL it's possible to start evaluating Clojure expressions:

clje.user=> (map inc (range 10))
(1 2 3 4 5 6 7 8 9 10)
clje.user=> (doc map)
-------------------------
clojure.core/map
([f] [f coll] [f c1 c2] [f c1 c2 c3] [f c1 c2 c3 & colls])
  Returns a lazy sequence consisting of the result of applying f to
  the set of first items of each coll, followed by applying f to the
  set of second items in each coll, until any one of the colls is
  exhausted.  Any remaining items in other colls are ignored. Function
  f should accept number-of-colls arguments. Returns a transducer when
  no collection is provided.
nil
clje.user=> (doc inc)
-------------------------
clojure.core/inc
([x])
  Returns a number one greater than num.
nil
clje.user=>

There are some very basic examples in the scripts/examples directory. These are meant to be references on how special forms in Clojure on the BEAM are used and how they sometimes differ from Clojure JVM.

For a very basic example of a web project please check the example-web-app repository.

The

The build tool for Clojerl project is currently rebar3, which is the official supported tool in the Erlang community.

The rebar3_clojerl plugin provides helpful commands to:

• Build a basic directory scaffolding for a new project
• Compile
• Run tests
• Start a REPL

For more information on how to use this plugin please check the documentation in rebar3_clojerl.

There is more information regarding Clojerl here, like what features does it include and how it differs from Clojure.

Erlang is a great language for building safe, reliable and scalable systems. It provides immutable, persistent data structures out of the box and its concurrency semantics are unequalled by any other language.

Clojure is a Lisp and as such comes with all the goodies Lisps provide. Apart from these Clojure also introduces powerful abstractions such as protocols, multimethods and seqs, to name a few.

Clojure was built to simplify the development of concurrent programs and some of its concurrency abstractions could be adapted to Erlang. It is fair to say that combining the power of the Erlang VM with the expressiveness of Clojure could provide an interesting, useful result to make the lives of many programmers simpler and make the world a happier place.

• Interoperability as smooth as possible, just like Clojure proper and ClojureScript do.
• Provide most Clojure abstractions.
• Provide all Erlang abstractions and toolset.
• Include a default OTP library in Clojerl.

Learn more about Erlang (and its VM), Clojure and language implementation.

This project is an experiment that I hope others will find useful. Regardless of whether it becomes a fully functional implementation of Clojure or not, I will have learned a lot along the way.

Clojerl is an experimental implementation of Clojure on the Erlang VM. Its goal is to leverage the features and abstractions of Clojure that we love (macros, collections, seq, protocols, multimethods, metadata, etc.), with the robustness the Erlang VM provides for building (distributed) systems.

Yes. LFE and Joxa were each created with very specific and different goals in mind. LFE was born to provide a LISP syntax for Erlang. Joxa was mainly created as a platform for creating DSLs that could take advantage of the Erlang VM. Its syntax was inspired by Clojure but the creators weren't interested in implementing all of Clojure's features.

Yes, they are. On one hand Clojure provides tools to handle mutable state in a sane way, while making a clear distinction between identity and state through reference types. On the other, concurrency in the Erlang VM is implemented through processes and message passing. The idea in Clojerl is to encourage the Erlang/OTP concurrency model, but support as many Clojure constructs as possible and as far as they make sense in the Erlang VM.

That is not a question, but I see what you mean :). The points he makes are of course very good. For example, when no state is shared between processes there is some communication overhead, but this isolation is also an advantage under a lot of circumstances. He also mentions here that building for the distributed case (a.k.a processes and message passing) is more complex and not always necessary, so he decided to optimise for the non-distributed case and add distribution to the parts of the system that need it. Rich Hickey calls Erlang "quite impressive", so my interpretation of these writings is that they are more about exposing the rationale behind the decisions and the trade-offs he made when designing Clojure (on the JVM), than about disregarding the actor model.

No. Some of Clojure's features are implemented by relying on the underlying mutability of the JVM and its object system. The Erlang VM provides very few mutability constructs and no support for defining new types. This makes it very hard or nearly impossible to port some features into Clojerl's implementation.

Yes, but they will need to be ported, just like for ClojureScript. In fact, most of Clojure's core namespaces were ported from the original .clj files in the Clojure JVM repository.

You can find me on twitter or lurking on Clojure's and Erlang's mailing lists.

Any feedback, comment and/or suggestion is welcome!