Hi, there! Please bear with me as I am very new to Closure (this is my
second program ever) but have a kind of solid Haskell background.
I was trying to get a version of this Haskell code:
divides x y = mod x y == 0
primeub x = div x (if even x then 2 else 3)
isprime primes x = all (not . divides x) (lowerprimes x)
where
lowerprimes x = takeWhile (<= primeub x) primes
primes = 2 : filter (isprime primes) [3..]
which works fine. E.g.: take 10 primes == [2,3,5,7,11,13,17,19,23,29]. In
Closure, I got this:
(defn divides? [x y] (zero? (mod x y)))
(defn prime-ub [x] (/ x (if (even? x) 2 3)))
(defn lower-primes [primes x] (let [ub (prime-ub x)]
(take-while #(<= % ub) primes)))
(defn prime? [primes x] (not-any? #(divides? x %)(lower-primes primes x)))
(defn primes [] (let [primes' (atom nil)]
(reset! primes' (cons 2 (filter #(prime? @primes' %) (drop
3 (range)))))))
However, I am getting (take 10 (primes)) == (2 3 5 7 9 11 13 15 17 19)
(please notice the undesirable presence of 9 and 15 there...).
Any ideas why this is happening? Thanks in advance.
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