Naïve Prime Factorization in Clojure
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I saw a question about prime factorization on Stack Overflow and realized I had never attempted it before. This was what I ended up with after some playing around and tweaking.
I'd like improvements on anything here.
I know I could use a sieve instead of the naive method (I may switch later), but it was sufficient here. Is there a better way though to handle
2inprime?? I feel like it being a special case is off.Is there a better way than a full
loopfor the main function?Whatever else
(find-prime-factors 993061001)
=> [17 173 337661]
Verified against CalculatorSoup.
(ns irrelevant.prime-factorization)
(defn is-factor-of? [n multiple]
(zero? (rem n multiple)))
(defn prime? [n]
(or (= n 2) ; TODO: Eww
(->> (range 2 (inc (Math/sqrt ^double n)))
(some #(is-factor-of? n %))
(not))))
(defn primes
(->> (range)
(drop 2) ; Lower bound of 2 for the range
(filter prime?)))
(defn smallest-factor-of? [n possible-multiples]
(some #(when (is-factor-of? n %) %)
possible-multiples))
(defn find-prime-factors [n]
(loop [remaining n
remaining-primes (primes)
prime-factors ]
(if-let [small-prime (and (> remaining 1) (smallest-factor-of? remaining remaining-primes))]
(let [rest-primes (drop-while #(not= % small-prime) remaining-primes)]
(recur (long (/ remaining small-prime))
rest-primes
(conj prime-factors small-prime)))
prime-factors)))
primes clojure
asked 12 mins ago
Carcigenicate
2,67811229
add a comment |
up vote
0
down vote
favorite
I saw a question about prime factorization on Stack Overflow and realized I had never attempted it before. This was what I ended up with after some playing around and tweaking.
I'd like improvements on anything here.
I know I could use a sieve instead of the naive method (I may switch later), but it was sufficient here. Is there a better way though to handle
2inprime?? I feel like it being a special case is off.Is there a better way than a full
loopfor the main function?Whatever else
(find-prime-factors 993061001)
=> [17 173 337661]
Verified against CalculatorSoup.
(ns irrelevant.prime-factorization)
(defn is-factor-of? [n multiple]
(zero? (rem n multiple)))
(defn prime? [n]
(or (= n 2) ; TODO: Eww
(->> (range 2 (inc (Math/sqrt ^double n)))
(some #(is-factor-of? n %))
(not))))
(defn primes
(->> (range)
(drop 2) ; Lower bound of 2 for the range
(filter prime?)))
(defn smallest-factor-of? [n possible-multiples]
(some #(when (is-factor-of? n %) %)
possible-multiples))
(defn find-prime-factors [n]
(loop [remaining n
remaining-primes (primes)
prime-factors ]
(if-let [small-prime (and (> remaining 1) (smallest-factor-of? remaining remaining-primes))]
(let [rest-primes (drop-while #(not= % small-prime) remaining-primes)]
(recur (long (/ remaining small-prime))
rest-primes
(conj prime-factors small-prime)))
prime-factors)))
primes clojure
asked 12 mins ago
Carcigenicate
2,67811229
add a comment |
up vote
0
down vote
favorite
up vote
0
down vote
favorite
I saw a question about prime factorization on Stack Overflow and realized I had never attempted it before. This was what I ended up with after some playing around and tweaking.
I'd like improvements on anything here.
I know I could use a sieve instead of the naive method (I may switch later), but it was sufficient here. Is there a better way though to handle
2inprime?? I feel like it being a special case is off.Is there a better way than a full
loopfor the main function?Whatever else
(find-prime-factors 993061001)
=> [17 173 337661]
Verified against CalculatorSoup.
(ns irrelevant.prime-factorization)
(defn is-factor-of? [n multiple]
(zero? (rem n multiple)))
(defn prime? [n]
(or (= n 2) ; TODO: Eww
(->> (range 2 (inc (Math/sqrt ^double n)))
(some #(is-factor-of? n %))
(not))))
(defn primes
(->> (range)
(drop 2) ; Lower bound of 2 for the range
(filter prime?)))
(defn smallest-factor-of? [n possible-multiples]
(some #(when (is-factor-of? n %) %)
possible-multiples))
(defn find-prime-factors [n]
(loop [remaining n
remaining-primes (primes)
prime-factors ]
(if-let [small-prime (and (> remaining 1) (smallest-factor-of? remaining remaining-primes))]
(let [rest-primes (drop-while #(not= % small-prime) remaining-primes)]
(recur (long (/ remaining small-prime))
rest-primes
(conj prime-factors small-prime)))
prime-factors)))
primes clojure
asked 12 mins ago
Carcigenicate
2,67811229
I saw a question about prime factorization on Stack Overflow and realized I had never attempted it before. This was what I ended up with after some playing around and tweaking.
I'd like improvements on anything here.
I know I could use a sieve instead of the naive method (I may switch later), but it was sufficient here. Is there a better way though to handle
2inprime?? I feel like it being a special case is off.Is there a better way than a full
loopfor the main function?Whatever else
(find-prime-factors 993061001)
=> [17 173 337661]
Verified against CalculatorSoup.
(ns irrelevant.prime-factorization)
(defn is-factor-of? [n multiple]
(zero? (rem n multiple)))
(defn prime? [n]
(or (= n 2) ; TODO: Eww
(->> (range 2 (inc (Math/sqrt ^double n)))
(some #(is-factor-of? n %))
(not))))
(defn primes
(->> (range)
(drop 2) ; Lower bound of 2 for the range
(filter prime?)))
(defn smallest-factor-of? [n possible-multiples]
(some #(when (is-factor-of? n %) %)
possible-multiples))
(defn find-prime-factors [n]
(loop [remaining n
remaining-primes (primes)
prime-factors ]
(if-let [small-prime (and (> remaining 1) (smallest-factor-of? remaining remaining-primes))]
(let [rest-primes (drop-while #(not= % small-prime) remaining-primes)]
(recur (long (/ remaining small-prime))
rest-primes
(conj prime-factors small-prime)))
prime-factors)))
primes clojure
primes clojure
asked 12 mins ago
Carcigenicate
2,67811229
asked 12 mins ago
Carcigenicate
2,67811229
asked 12 mins ago
Carcigenicate
2,67811229
asked 12 mins ago
Carcigenicate
2,67811229
asked 12 mins ago
Carcigenicate
2,67811229
2,67811229
add a comment |
add a comment |
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