fib.clj

;Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:
;1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
;By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.
;Extra: Give a solution in two different languages.

(def fib (cons 0 (cons 1 (lazy-seq (map + fib (rest fib))))))
(def answer (->> fib
                 (take-while #(<= % 4000000))
                 (filter even?)
                 (reduce +)))