The Common Lisp Cookbook – Getting started

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The Common Lisp Cookbook – Getting started

Easy steps to install a development environment and start a project.

Want a 2-clicks install ? Then get Portacle, a portable and multi-platform Common Lisp environment. It ships Emacs25, SBCL (the implementation), Quicklisp (package manager), SLIME (IDE) and Git. It’s the most straightforward way to get going !

Install an implementation

With your package manager

In doubt, just get SBCL:

apt-get install sbcl

Common Lisp has been standardized via an ANSI document, so it can be implemented in different ways: see Wikipedia’s list of implementations.

The following implementations are packaged for Debian and probably for your distro:

There is also:

and older implementations:

With Roswell

Roswell is:

You’ll find several ways of installation on its wiki (Debian package, Windows installer, Brew/Linux Brew,…).

With Docker

If you already know Docker, you can get started with Common Lisp pretty quickly. The daewok/lisp-devel-docker image comes with recent versions of SBCL, CCL, ECL and ABCL, plus Quicklisp installed in the home (/home/lisp) so than we can ql:quickload libraries straight away.

It works on GNU/Linux, Mac and Windows.

The following command will download the required image (around 400MB), put your local sources inside the Docker image where indicated and drop you into an SBCL REPL:

docker run --rm -it -v /path/to/local/code:/usr/local/share/common-lisp/source daewok/lisp-devel:base sbcl

But we still want to develop from our Emacs and SLIME, so we need to connect SLIME to the Lisp inside Docker. See slime-docker for a library that helps on setting that up.

On Windows

All implementations above can be installed on Windows.

Portacle is multiplatform and works on Windows.

You can also try:

Start a REPL

Just launch the implementation executable on the command line to enter the REPL (Read Eval Print Loop), i.e. the interactive interpreter.

Quit with (quit) or ctr-d (on some implementations).

Here is a sample session:

user@debian:~$ sbcl
This is SBCL 1.3.14.debian, an implementation of ANSI Common Lisp.
More information about SBCL is available at <>.

SBCL is free software, provided as is, with absolutely no warranty.
It is mostly in the public domain; some portions are provided under
BSD-style licenses.  See the CREDITS and COPYING files in the
distribution for more information.
* (+ 1 2)

* (quit)

You can slightly enhance the REPL (the arrow keys do not work, it has no history,…) with rlwrap:

apt-get install rlwrap


rlwrap sbcl

But we’ll setup our editor to offer a better experience instead of working in this REPL. See editor-support.

Lisp is interactive by nature, so in case of an error we enter the debugger. This can be annoying in certain cases so you might want to use SBCL’s --disable-debugger option.

Tip: the CLISP implementation has a better default REPL for the terminal (readline capabilities, completion of symbols). You can even use clisp -on-error abort to have error messages without the debugger. It’s handy to try things out, but we recommend to set-up one’s editor and to use SBCL or CCL for production.


Common Lisp has hundreds of libraries available under a free software license. See:

Some terminology

Install Quicklisp

Quicklisp is more than a package manager, it is also a central repository (a dist) that ensures that all libraries build together.

It provides its own dist but it is also possible to build our own.

To install it, we can either:

1- run this command, anywhere:

curl -O

and enter a Lisp REPL and load this file:

sbcl --load quicklisp.lisp


2- install the Debian package:

apt-get install cl-quicklisp

and load it, from a REPL:

(load "/usr/share/common-lisp/source/quicklisp/quicklisp.lisp")

Then, in both cases, still from the REPL:


This will create the ~/quicklisp/ directory, where Quicklisp will maintain its state and downloaded projects.

If you wish, you can install Quicklisp to a different location. For instance, to install it to a hidden folder on Unix systems:

(quicklisp-quickstart:install :path "~/.quicklisp")

If you want Quicklisp to always be loaded in your Lisp sessions, run (ql:add-to-init-file): this adds the right stuff to the init file of your CL implementation. Otherwise, you have to run (load "~/quicklisp/setup.lisp") in every session if you want to use Quicklisp or any of the libraries installed through it.

It adds the following in your (for example) ~/.sbclrc:

  (let ((quicklisp-init (merge-pathnames "quicklisp/setup.lisp"
    (when (probe-file quicklisp-init)
      (load quicklisp-init)))

Install libraries

In the REPL:

(ql:quickload "package-name")

and voilà. See Quicklisp’s documentation for more commands.

Note also that dozens of Common Lisp libraries are packaged in Debian. The package names usually begin with the cl- prefix (use apt-cache search --names-only "^cl-.*" to list them all).

For example, in order to use the CL-PPCRE library (for regular expressions), one should first install the cl-ppcre package.

Then, in SBCL and ECL, it can be used with:

(require "asdf")
(require "cl-ppcre")
(cl-ppcre:regex-replace "fo+" "foo bar" "frob")

See more:

Advanced dependencies management

You can drop Common Lisp projects into any of those folders:

For a complete list, see




A library installed here is automatically available for every project.

Providing our own version of a library. Cloning projects.

Given the property above, we can clone any library into the local-projects directory and it will be found by ASDF (and Quicklisp) and available right-away:

(asdf:load-system "system")


(ql:quickload "system")

The practical different between the two is that ql:quickload first tries to fetch the system from the Internet if it is not already installed.

How to work with local versions of libraries

If we need libraries to be installed locally, for only one project, or in order to easily ship a list of dependencies with an application, we can use Qlot.

Quicklisp also provides Quicklisp bundles. They are self-contained sets of systems that are exported from Quicklisp and loadable without involving Quicklisp.

At last, there’s Quicklisp controller to help us build dists.

Working with projects

Now that we have Quicklisp and our editor ready, we can start writing Lisp code in a file and interacting with the REPL.

But what if we want to work with an existing project or create a new one, how do we proceed, what’s the right sequence of defpackage, what to put in the .asd file, how to load the project into the REPL ?

Creating a new project

Some project builders help to scaffold the project structure. We like cl-project that also sets up a tests skeleton.

In short:

(ql:quickload "cl-project")
(cl-project:make-project #P"./path-to-project/root/")

it will create a directory structure like this:

|-- my-project.asd
|-- my-project-test.asd
|-- README.markdown
|-- src
|   `-- my-project.lisp
`-- tests
    `-- my-project.lisp

Where my-project.asd resembles this:

(defsystem "my-project"
  :version "0.1.0"
  :author ""
  :license ""
  :depends-on ()  ;; <== list of Quicklisp dependencies
  :components ((:module "src"
                ((:file "my-project"))))
  :description ""
     (subpathname *load-pathname* "README.markdown"))
  :in-order-to ((test-op (test-op "my-project-test"))))

and src/my-project.lisp this:

(defpackage footest
  (:use :cl))
(in-package :footest)

How to load an existing project

You have created a new project, or you have an existing one, and you want to work with it on the REPL, but Quicklisp doesn’t know it. How can you do ?

Well first, if you create it or clone it into one of ~/common-lisp, ~/.local/share/common-lisp/source/ or ~/quicklisp/local-projects, you’ll be able to (ql:quickload …) it with no further ado.

Otherwise you’ll need to compile and load its system definition (.asd) first. In SLIME with the slime-asdf contrib loaded, type C-c C-k (slime-compile-and-load-file) in the .asd, then you can (ql:quickload …) it.

Usually you want to “enter” the system in the REPL at this stage:

(use-package :my-project)

Lastly, you can compile or eval the sources (my-project.lisp) with C-c C-k or C-c C-c (slime-compile-defun) in a form, and see its result in the REPL.

Another solution is to use ASDF’s list of known projects:

(pushnew "~/path-to-project/root/" asdf:*central-registry* :test #'equal)

and since ASDF is integrated into Quicklisp, we can quickload our project.

Happy hacking !

More settings

You might want to set SBCL’s default encoding format to utf-8:

(setf sb-impl::*default-external-format* :utf-8)

You can add this to your ~/.sbclrc.

If you dislike the REPL to print all symbols upcase, add this:

(setf *print-case* :downcase)

Beware that this might break some packages like Mito. Avoid doing this in production.

Read more


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