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euler / clojure / problem2.clj

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;; problem2
;; John Paulett - June 8, 2009
;;
;; 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, ...
;; Find the sum of all the even-valued terms in the sequence which do not 
;; exceed four million.

;(defn fib [maxval coll] 
;	(if (zero? coll)
;		(fib (maxval (1 2)
;	((reverse coll))
;	)

(use '[clojure.contrib.lazy-seqs :only (fibs)])

(defn sum-even-fibs [max] 
	(reduce + (for [i fibs :while (<= i max) :when (even? i)] i)))
	
;; tests
(assert (= 2 (sum-even-fibs 2)))	
(assert (= 44 (sum-even-fibs 89)))

(println (sum-even-fibs 4000000))
;; 4613732