List Of Digits

list_of_digits.clj

;;; https://purelyfunctional.tv/issues/purelyfunctional-tv-newsletter-319-tip-shebang-scripting-with-the-clojure-cli/?__s=qn1vfepzj2qsgce6ughs

(defn number-of-digits
  "Calculates the number of digits in an integer"
  [n]
  (int (Math/ceil (Math/log10 (inc n)))))


(defn get-nth-digit
  "Gets the nth digit (zero based) from integer x"
  [n x]
  (int (mod (/ x (Math/pow 10 n)) 10)))

;; fails for zeros
(defn digits [x]
  (let [n (dec (number-of-digits x))
        k (get-nth-digit n x)
        r (Math/pow 10 n)]
    (when (>= n 0)
      (lazy-seq
       (cons k (digits (mod x r)))))))