monad-notation-example.lisp

(defmacro monadic (&body statements)
  `(let ((m *monad*))
     (statements-of (monad m) ,@statements)))

(defun monad-example (ma mb)
  (monadic
    (get x ma)
    (get y mb)
    (val z (+ x y))
    (ret (list x y z))))

(monad-example 1 2) ; >-id-monad-> (1 2 3)

(let ((*monad* +list-monad+))
  (monad-example (list 1 2) (list 3))) ; >-> ((1 3 4) (2 3 5))

(let ((*monad* +nil-monad+))
  (monad-example 1 2)) ; >-> (1 2 3)

(let ((*monad* +nil-monad+))
  (monad-example nil 2)) ; >-> nil

(let ((*monad* +nil-monad+))
  (monad-example 1 nil)) ; >-> nil