;; declare lambda
($ a (-> (x) (* x 2)))
(assert-eq? 14 (a 7))

;; high order function
($ b (-> (x y) (x (x y))))
(assert-eq? 12 (b a 3))

;; calling function literal
(assert-eq? 7 ( (-> (x y) (+ x y 1)) 2 4 ))

;; syntaxic sugar for function declaration
($ (c n) (* 2 n))
(assert-eq? 18 (c 9))

;; inner variable
($ (d x) ($ y 3) (+ x y))
(assert-eq? 7 (d 4))

;; recursivity
($ (e n)
  (if (eq? 0 n) 1
      (* n (e (- n 1)))))

(assert-eq? 120 (e 5))

;; self keyword
(assert-eq? 720 ((-> (x)
            (if (eq? x 0)
                1
                (* x (self (- x 1))))) 6))