clasp Common Lisp environment
Latest commit da91d6f Oct 14, 2018

Clasp — Bringing Common Lisp and C++ Together

NOTE: April 20, 2018 - This contains a pre-release of Clasp 0.5.


Clasp is a new Common Lisp implementation that seamlessly interoperates with C++ libraries and programs using LLVM for compilation to native code. This allows Clasp to take advantage of a vast array of preexisting libraries and programs, such as out of the scientific computing ecosystem. Embedding them in a Common Lisp environment allows you to make use of rapid prototyping, incremental development, and other capabilities that make it a powerful language.

Latest Release

The upcoming release is Clasp 0.5. Changes


Building Clasp

At the moment, Clasp is supported on Linux and Mac OS X. On these systems, you should be able to build it from source.

Follow the instructions.

In case things go wrong, the quickest way to get help is to either file an issue, or to chat with us directly.

Building on most systems will take around 8-12GB of memory and ~1-2 hours with a relatively modern processor, so be prepared to watch a movie or do some other useful work until Clasp is all done. You may also want to activate a large enough swap file if your system does not have enough DRAM.

Building can be greately accelerated if you have a multi-core machine - but it requires a specially configured version of the Boehm garbage collector found here: (

Currently there are no binary releases available.

There is a docker image for a superset of Clasp called Cando

Common Lisp Ecosystem Support

Clasp supports the following major components:

Post on the issues or contact us if you're interested in changing that.

Contributing to Clasp

We very much welcome any kind of contribution to Clasp, even if it is just bug finding and testing. A lot can be done all around the project, if you want to dive into something large. See the CONTRIBUTING file for the few guidelines we've set up around contributions.

Reporting Problems

Generally you can report problems in two fashions, either by opening an issue ticket or by chatting with us directly. In both cases, though, you should have the following pieces handy in order for us to be able to help you out as quickly and painlessly as possible:

  • Your operating system name and version.
  • The branches that you're using of Clasp and Externals-Clasp.
  • A paste of the build log or failure point that you reached.
  • Patience.


Clasp has an IRC channel on Freenode called #clasp. If you have questions, problems, suggestions, or generally would like to just hang out with us devs, come and stop by!

More on Clasp

For more information on Clasp and the discussion around it, see the following sites:


Clasp was supported by:

  • The Defense Threat Reduction Agency (DOD-DTRA) (HDTRA1-09-1-0009)
  • The National Institutes of Health (NIH/NIGMS Grant number: 2R01GM067866-07A2)
  • The National Science Foundation (Grant number: 1300231)