phowat / bodol

The common BODil Oriented Language

BODOL

This is my language experiment.

Preliminary goals which may or may not be possible to combine:

• Pure functional language.
• Homoiconic in the Lisp tradition.
• Built on the traditional Lisp primitives.
• Hindley-Milner flavoured type system.
• Currying function calls.
• Pattern matching.

This is a work in progress. Don't expect it to even run its own test suite.

Inspiration

Clojure is great, but sometimes I miss static typing. Haskell is great, but sometimes I miss Lisp's elegantly simple syntax. Shen is a splendid compromise, but I found myself wishing it came with Haskell's uncompromising purity and Standard ML's straightforward type system. BODOL is my attempt at crossbreeding the three, with Shen obviously the major influence.

A Taste of BODOL

Functional hello world:

(ƒ factorial
  0 -> 1
  n -> (* n (factorial (- n 1))))

(ƒ fibonacci
  0 -> 0
  1 -> 1
  n -> (+ (fibonacci (- n 1)) (fibonacci (- n 2))))

More advanced pattern matching:

(ƒ map
   f () -> ()
   f (head . tail) -> (cons (f head) (map f tail)))

(= '(2 3 4) (map (λ a -> (+ a 1)) '(1 2 3))))

Currying:

(ƒ triplet a b c -> (list a b c))
(define one-and (triplet 1))
(define one-and-two-and (one-and 2))
(= '(1 2 3) (one-and-two-and 3))

Take a look at the theoretically comprehensive test suite for examples of all the currently defined language features.

Test Drive

The BODOL prototype interpreter is written in Clojure, so you'll need to install Leiningen in order to run it. Optionally, you may also want to install rlwrap for a better line editing experience. Once that's done, check out the BODOL repo, cd over there and type:

$ ./repl
BODOL version 0.0.0
You are in a maze of twisty little passages, all alike.
→→

If you're discouraged by the curious absence of λ and ƒ on your keyboard, you can substitute Clojure's fn and defn or Common Lisp's lambda and defun respectively.

If you're using Emacs, I find this helps:

;; Keybindings for λ and ƒ
(global-set-key (kbd "M-l") (lambda () (interactive) (insert "\u03bb"))) ;lambda
(global-set-key (kbd "M-f") (lambda () (interactive) (insert "\u0192"))) ;function

;; Launch the BODOL REPL in an inferior-lisp buffer
(defun bodol-repl ()
  (interactive)
  (run-lisp "<path to your BODOL repo>/repl"))

On Vim, to achieve the same ƒ and λ keybindings:

" Keybindings for λ and ƒ
:inoremap <A-l> <C-v>u3bb<Space>
:inoremap <A-f> <C-v>u192<Space>