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|
; LIB
(let! Maybe/just (\[a]
["Maybe" "just" a]))
(let! Maybe/nothing (\[]
["Maybe" "nothing"]))
(let! Maybe/#at (\[n seq]
(match seq
[]
(fatal! "Maybe/#at out of bounds")
otherwise
(match n
0
(head seq)
otherwise
(Maybe/#at (- n 1) (tail seq))))))
(let! Maybe/unpack (Maybe/#at 2))
(let! Maybe/kind (Maybe/#at 1))
(let! Maybe/map (\[f m]
(match (Maybe/kind m)
"just" (Maybe/just (f (Maybe/unpack m)))
"nothing" (Maybe/nothing))))
(let! Maybe/and-then (\[f m]
(match (Maybe/kind m)
"just" (f (Maybe/unpack m))
"nothing" (Maybe/nothing))))
; TESTING
;; (let! print-line! (\[s]
;; (print! (concat s "\n"))))
;; (let! a (Maybe/just 10))
;; (let! b (Maybe/nothing))
;; (Maybe/map (+ 5) a)
;; (Maybe/map (+ 5) b)
;; (Maybe/and-then (\[n] (Maybe/just (+ n 5))) a)
;; (Maybe/and-then (\[n] (Maybe/just (+ n 5))) b)
;; (let! m (Maybe/just 10))
;; (match m
;; (Maybe/just _)
;; (print-line! (fmt "found just {0}!" [(Maybe/unpack m)]))
;; (Maybe/nothing)
;; (print-line! "found nothing!"))
|
