Problem description, from Project Euler
Find the difference between the sum of the squares of the first N natural numbers and the square of the sum.
This one actually seemed to be easier than the others. No filters required!
(defn problem06 [upper] (defn sq [n] (* n n)) (def l (range 1 (+ upper 1))) (- (sq (reduce + l)) (reduce + (map sq l)) ) )
The biggest hangup I had was that when I originally read the problem, I thought I’d need a power function, and then spent at least 15 minutes determining there was no Clojure core power function. I found some alternatives here:
; for integers (cuz it's faster) (. (. java.math.BigInteger (valueOf 2)) (pow 5)) ; for doubles (. java.lang.Math (pow 2 -3))