madlisp/mad/fib.mad
2020-10-17 14:15:14 +07:00

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;; Functions to calculate Fibonacci numbers
;; Slow recursive version
(def slowFib (fn (n) (if (< n 2) n (+ (slowFib (- n 1)) (slowFib (- n 2))))))
;; Return the sum of the last 2 numbers in a sequence
(def sumOfLast (fn (l) (+ (last l) (penult l))))
;; Faster version, return vector of n numbers, tail call optimized
(def fibListRec (fn (n l) (if (< (len l) n) (fibListRec n (push l (sumOfLast l))) l)))
(def fibList (fn (n) (fibListRec n [0 1])))
(def fastFib (fn (n) (sumOfLast (fibList n))))