-- Update May 19, 2015 Clasp has a developers mailing list.

-- Update Jan 25, 2015 -- Please read regarding installing Clasp

Note: EXTERNALS_BUILD_TARGET_DIR and CLASP_BUILD_TARGET_DIR are not required any more in locals.config. There is a new variable EXTERNALS_SOURCE_DIR that you set to the path of the exterals-clang source directory.

If you have questions come ask them on IRC at freenode #clasp

Clasp is a Common Lisp implementation that interoperates with C++ and uses LLVM for just-in-time (JIT) compilation to native code. See http://drmeister.wordpress.com/2014/09/18/announcing-clasp/ for the initial announcement.

Clasp is not yet a full ANSI compliant Common Lisp - if you find differences between Clasp and the Common Lisp standard they are considered bugs in Clasp and please feel free to report them.

Libraries that clasp depends on can be obtained using the repository: externals-clasp
Currently you must build externals-clasp prior to building Clasp - we will eliminate the need for this in future releases.

Clasp needs an advanced C++ compiler that supports C++11 (minimum clang 3.5 or gcc 4.8).

Clasp also needs a very specific version of the llvm/clang 3.6 libraries that are not part of a standard release. This version of the llvm/clang3.6 is included in externals-clasp. Incidentally, the externals-clasp/llvm3.6 builds a clang3.6 compiler, which can be used by the Clasp build system to compile Clasp.

If you get lots of errors showing missing header files then you can uncomment and set CLASP_CLANG_PATH in clasp/locals.config to use the system clang (version>3.6.1). On Linux there may be the additional problem that libstd++ may need to be brought up to date.

If you experience problems with the systems above please submit an issue here or come see us on #clasp on irc.freenode.net

To build Clasp from within the top level directory do the following.

1. You need to download and build the externals-clasp repository
   

• it contains all of the external libraries that Clasp depends on and it downloads the specific version of LLVM 3.6 that Clasp needs.

2. Copy local.config.darwin or local.config.linux to local.config depending on your system

3. Edit local.config and configure it for your system. The following configuration variables affect the build process.

4. Make both the mps and boehm versions of Clasp (see note 1 for other options).

# make

If you see the error "fatal error: 'core_scrape_flag.h' file not found" just stop the build with control-C and type "make" again. It will sort itself out. It's something to do with the order in which boost-build builds things but I haven't sorted it out yet.

5. Add the directory in $CLASP_BUILD_TARGET_DIR/MacOS (OS X) or $CLASP_BUILD_TARGET_DIR/bin (linux) (from local.config) to your PATH
   

6. To run the MPS version of Clasp use

# clasp_mps_o

and to run the Boehm version of Clasp use

# clasp_boehm_o

7. When the Clasp REPL prompt appears you can type Common Lisp commands.

Starting Clasp 0.1... loading image... it takes a few seconds
Loading .clasprc
Top level.
> (defun hello-world () (print "Clasp is running.  Huzzah!!!"))

HELLO-WORLD
> (hello-world)

"Clasp is running.  Huzzah!!!"
"Clasp is running.  Huzzah!!!"
> (quit)

Clasp will run within Emacs using *inferior-lisp* and in the future Clasp will have a SLIME interface (volunteer programmers will be showered with appreciation and praise!).

Note 1: You can make just one version of Clasp

# make boostbuildv2-build 

and then to make the boehm version of Clasp use

# make clasp-boehm

or to make the mps version of Clasp use

# make clasp-mps

If you want to install the external libraries separately its more complicated because Clasp requires a particular version of LLVM/Clang3.6 which hasn't been officially released yet but is present in externals-clang. This should all become easier in a couple of months when LLVM/Clang3.6 is released.
These are the requirements as of Sep 28, 2014.
LLVM/clang 3.5 compiler
Boost build v2
boost libraries ver 1.55
Boehm 7.2
gmp-6.0.0
expat-2.0.1
zlib-1.2.8
readline-6.2

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) and the National Science Foundation (Grant number: 1300231)