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petermd/luhn.cljs

Created January 21, 2015 12:58
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luhn.cljs
(defn sum-digits [num]
(+ (quot num 10) (mod num 10)))
(defn sum-doubleeven [idx num]
(sum-digits (if (even? idx) num (* num 2))))
(defn luhn? [num]
(zero? (mod (reduce + (map-indexed sum-doubleeven (reverse num))) 10)))
(defn test-luhn []
(map luhn? ["49927398716","49927398717","1234567812345678","1234567812345670"]))
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