If you are new to Emacs, you may find the Emacs Starter Kit helpful. GNU Emacs 23 or 24 is recommended; forks like XEmacs and Aquamacs are not supported but may work.

If you already have your own Emacs configuration, you will need to get package.el in order to install the necessary elisp libraries. If you are using Emacs 24 or the Emacs Starter Kit you will already have it installed. You'll also need to add Marmalade as a package source. (This repo is added by the Emacs Starter Kit since 2011-04-12.)

• Download package.el to your ~/.emacs.d/ directory (create it if necessary).
• Make sure that your ~/.emacs file contains the following or equivalent:
• Reload your ~/.emacs file or restart Emacs.
• Invoke M-x package-refresh-contents

When you have package.el available (either from Emacs Starter Kit or following the above steps), install clojure-mode by pressing M-x package-install and choosing clojure-mode.

Open or create a Clojure .clj file, and you should find that clojure-mode enabled since built-in functions and forms are syntax-highlighted.

There are multiple approaches for interacting with a live Clojure process:

• SLIME and Swank Clojure: a rich, complex mode that provides various commands to communicate with an external Clojure instance via a socket.
• inferior-lisp: a simple mode that will start a Clojure instance as a subprocess and then communicates with its REPL via stdin/stdout pipes.

In both cases, you need to launch a Clojure instance with the correct classpath settings. This is most commonly done using a build tool such as Leiningen. For instructions see the Build Tools section of Getting Started.

SLIME and Swank Clojure

If you are using Leiningen and a recent version of clojure-mode, you can invoke M-x clojure-jack-in to begin a Slime session for the current project.

The most commonly-used key bindings are C-c C-k to compile the current file, M-. to jump to a definition, and C-c M-p to change the namespace of the repl session.

For more key bindings and other details see the swank-clojure readme.

Automated VM Setup

If you don't mind working in a virtual machine, you can get a fully-automated VM set up with Emacs configured using Slime and Swank-Clojure using Vagrant: https://github.com/Seajure/emacs-clojure-vagrant

inferior-lisp

The simplest way to eval expressions at a Clojure REPL is to set Clojure to be your inferior-lisp program (inferior as in a subprocess, not as in worse-than) as follows:

• M-x describe-variable inferior-lisp-program
• Customize the variable to point to a command that launches a Clojure REPL. You can use an absolute path, or a relative path that will be interpreted relative to the current directory in emacs. For example:
  • java -cp path/to/clojure.jar clojure.main for a basic repl (no rlwrap/jline needed)
  • lein repl for a Leiningen project
  • cake repl for a Cake project
  • mvn clojure:repl for a Maven project
  • script/repl for the labrepl tutorial project.
• M-x inferior-lisp (or C-c C-z)
• Use C-x C-e at the end of an expression to evaluate it, showing the result in the inferior-lisp buffer. C-c C-l will load the current file. C-M-x can evaluate a whole def form.