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Swank/slime support for clojure

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Swank Clojure

Swank Clojure is a server that allows SLIME (the Superior Lisp Interaction Mode for Emacs) to connect to Clojure projects. To use it you must launch a swank server, then connect to it from within Emacs.


If you just want a standalone swank server with no third-party libraries, you can just install swank-clojure using Leiningen.

$ lein plugin install swank-clojure 1.3.0
$ ~/.lein/bin/swank-clojure

M-x slime-connect

If you put ~/.lein/bin on your $PATH it's even more convenient.

You can also start a swank server from inside your project:

$ lein swank # you can specify PORT and HOST optionally

Note that the lein-swank plugin now comes with Swank Clojure; it does not need to be specified as a separate dependency any more.

If you're using Maven, add this to your pom.xml under the <dependencies> section:


Then you can launch a swank server like so:

$ mvn -o clojure:swank

Note that due to a bug in clojure-maven-plugin, you currently cannot include it as a test-scoped dependency; it must be compile-scoped. You also cannot change the port from Maven; it's hard-coded to 4005.

Put this in your Emacs configuration to get syntax highlighting in the slime repl:

(add-hook 'slime-repl-mode-hook 'clojure-mode-font-lock-setup)

Connecting with SLIME

Install the "slime-repl" package using package.el. If you are using Emacs 23, it's best to get the latest version of package.el from Emacs trunk. Then add Marmalade as an archive source:

(add-to-list 'package-archives
             '("marmalade" . "") t)

Then you can do M-x package-list-packages. Go down to slime-repl and mark it with i. Execute the installation by pressing x.

When you perform the installation, you will see warnings related to the byte-compilation of the packages. This is normal; the packages will work just fine even if there are problems byte-compiling it upon installation.

Then you should be able to connect to the swank server you launched:

M-x slime-connect

It will prompt you for your host (usually localhost) and port. It may also warn you that your SLIME version doesn't match your Swank version; this should be OK.

Having old versions of SLIME either manually installed or installed using a system-wide package manager like apt-get may cause issues.

SLIME Commands

Commonly-used SLIME commands:

  • C-c TAB: Autocomplete symbol at point
  • C-x C-e: Eval the form under the point
  • C-c C-k: Compile the current buffer
  • C-c C-l: Load current buffer and force dependent namespaces to reload
  • M-.: Jump to the definition of a var
  • C-c S-i: Inspect a value
  • C-c C-m: Macroexpand the call under the point
  • C-c C-d C-d: Look up documentation for a var
  • C-c C-z: Switch from a Clojure buffer to the repl buffer
  • C-c M-p: Switch the repl namespace to match the current buffer
  • C-c C-c: Interrupt the current function call in the repl
  • C-c C-w c: List all callers of a given function

Pressing "v" on a stack trace a debug buffer will jump to the file and line referenced by that frame if possible.

Note that SLIME was designed to work with Common Lisp, which has a distinction between interpreted code and compiled code. Clojure has no such distinction, so the load-file functionality is overloaded to add :reload-all behaviour.


You can embed Swank Clojure in your project, start the server from within your own code, and connect via Emacs to that instance:

(ns my-app
  (:require [swank.swank]))
(swank.swank/start-repl) ;; optionally takes a port argument

Then use M-x slime-connect to connect from within Emacs.

You can also start the server directly from the "java" command-line launcher if you AOT-compile it and specify "swank.swank" as your main class.

Debug Repl

For now, see Hugo Duncan's blog for an explanation of this excellent feature. Further documentation to come.


Previous versions of Swank Clojure bundled an Elisp library called swank-clojure.el that provided ways to launch your swank server from within your Emacs process. It's much more reliable to launch the server from your build tool, so this has been removed.


The mailing list and clojure channel on Freenode are the best places to bring up questions/issues.

Contributions are preferred as either Github pull requests or using "git format-patch". Please use standard indentation with no tabs, trailing whitespace, or lines longer than 80 columns. See this post on submitting good patches for some tips. If you've got some time on your hands, reading this style guide wouldn't hurt either.


Copyright (C) 2008-2011 Jeffrey Chu, Phil Hagelberg, Hugo Duncan, and contributors

Licensed under the EPL. (See the file COPYING.)

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