Wrote myself a scheme in 48 hours, fancy that... (from the book of a remarkably similar name!)
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Wrote myself a Scheme in 48 hours, fancy that... (from the book of a remarkably similar name!).

Thanks to @bodil and @fogus for the inspiration to try my hand at building a Lisp, and thank you to Jonathan Tang and everyone that has contributed to the WikiBook in what ever capacity.

To try your own hand at this, head on over to the book and get cracking.

Binary for OSX is available on the Releases page.

Compiled using:The Glorious Glasgow Haskell Compilation System, version 7.6.3 on OSX 10.8.

Other platforms should happily compile, but you'll have to manage that for yourselves (as I'm too lazy for VMs/Docker/Vagrant right now). The following should build the executable in a cabal-dev environment to try to keep things nice and clean.

cabal-dev install

Complicated no?

I've used the mtl package for Control.Monad.Error.

Once you have a happy binary, you can either use the REPL (YES IT HAS A REPL! Omg, you have no idea how exciting it was to build a language that has it's own REPL... seriously... no idea) *ahem* by just running the binary thus:


Or alternately you can pass strings directly in for evaluation, however this process is a little weird because you have to escape everything like a champ and it becomes insufferable very quickly when dealing with strings:

./leesp "(cons \"foo\" `(bar #\b))"

head, rest, and friends are there. As well as cons, if, cond, case, a whole bunch of mathematical operations, comparison functions, atoms, and a handful of string functions: string-ref, string-set!, string-length.

You are also able to use the traditional Lisp comment styles of:

;; Inline Comments
#| and block comments ! |#
comments :D

;; No nesting support though. :(


  • 29/01/2014 WE HAVE COMMENTS!!! Woo! Added support for inline and block comments. No support for nested block comments yet, don't be greedy.
  • 13/01/2014 Added project cabal file (finally, holy hell). Began support for comments, so far it's not going so well.
  • 01/11/2013 ADDED A STANDARD LIBRARY! OMG!! This was incredibly exciting. Now it really feels like a Lisp! (There is even closure support and everything. o.O). After pulling the cord on the REPL just run the following (import "leebs/stdleeb.leesp") or (import "path/to/leeb/stdleeb.leesp") and you should have everything in the stdleeb!
  • 01/11/2013 Added support for loading text files as source files and the following file functions:open-input-file, open-output-file, close-input-port, close-output-port, read, write, read-contents, read-all.
  • 01/11/2013 Added the ability to create and store functions using define and lambda.
  • 31/10/2013 Added persistent variables from scheme, namely: define and set!.


  • Add concurrency and parallel processing primitives (selfTodo: read Hoare's CSP paper, Actor Model papers, learn more Erlang)
  • MACROS! Yeah that's right.. I went there.
  • add granular imports for leeb functionality (only, except)
  • try to implement more leebrary support (include, import, require)
  • add load process for REPL to include files (like stdleeb)
  • make it emit compilable code (ooooooo!)
  • clean up the core source
  • add support for comments. This is inexplicably annoying.
  • add standard library