Question

Look at the function below. I want to pass a vector of factors and test if any of the elements in the vector is a factor of x. How do I do that?

(defn multiple?
  "Takes a seq of factors, and returns true if x is multiple of any factor."
  ([x & factors] (for [e m] ))
  ([x factor] (= 0 (rem x factor))))

Answer 1

You could try using some and map:

(defn multiple? [x & factors]
  (some zero? (map #(rem x %) factors)))

Also some returns nil if all tests fail, if you need it to actually return false, you could put a true? in there:

(defn multiple? [x & factors]
  (true? (some zero? (map #(rem x %) factors))))

---

Note that some short-circuits and map is lazy, so multiple? stops as soon as a match is found. e.g. the following code tests against the sequence 1,2,3,4,....

=> (apply multiple? 10 (map inc (range)))
true

Obviously this computation can only terminate if multiple? doesn’t test against every number in the sequence.