Armed Bear

The right of the people to keep and arm bears shall not be infringed!

About ABCL

Armed Bear Common Lisp (ABCL) is an implementation of ANSI Common Lisp that runs in a Java virtual machine. It provides a runtime system, a compiler that compiles Lisp source to JVM bytecode, and an interactive REPL for program development.

ABCL is distributed under the terms of the GNU General Public License, with a special linking exception. If you link ABCL with your own program, then you do not need to release the source code for that program. However, any changes that you make to ABCL itself must be released in accordance with the terms of the GPL. The license is the same as used by GNU Classpath and J2SE (Java).

ABCL runs on platforms that support Java 1.5 (or later), including Linux, Windows, and Mac OS X.

ABCL is free software and comes with ABSOLUTELY NO WARRANTY.

The latest version is 0.0.11, released October 18, 2008.


abcl-0.0.11.tar.gz (source, 632987 bytes) (source, 1012345 bytes)


The project's Subversion repository can be checked out through anonymous access with the following command:

      $ svn co svn:// j


ABCL is a young implementation (particularly by Lisp standards). Even though a lot of energy is spent resolving issues, you may well encounter bugs. A number of people have testified to the quality of ABCL being good enough for their needs though. See the testimonials page.

ABCL 0.0.11 fails 47 out of 21702 tests in the GCL ANSI test suite. Most notable recent fixes relate to special variables handling and making sure the correct environments are used with for example LET/LET* and FLET/LABELS.

ABCL's CLOS is intolerably slow and does not handle on-the-fly redefinition of classes correctly. There is no support for the long form of DEFINE-METHOD-COMBINATION, and certain other required CLOS features are also missing. Enough CLOS is there to run ASDF and CL-PPCRE, if you're in no hurry. There's no MOP worth mentioning.

Since this is an early public release, there might be build problems as well as runtime bugs.

Please report problems to the j development mailing list (you must be subscribed to post).

The project is using several ways to test standards compliance as well as practical applicability of ABCL by using these projects' test suites as 'compliance' indicators:


The README file in the root directory of the source distribution contains instructions for building ABCL.

Java 1.5 or higher is required; Java 1.5 is recommended. There are performance issues with early versions of Java 1.6. To build ABCL, you'll need the full JDK; the JRE is not enough.
Recent performance tests have shown Java 1.6 Update 10 - a Release Candidate as of this writing - to be as fast as Java 1.5.

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