Sha256: 4ffc90b0c0e96c8426e0b635da6335204195c705283e2efd5d956c9c064fdceb
Contents?: true
Size: 945 Bytes
Versions: 289
Compression:
Stored size: 945 Bytes
Contents
(ns luhn
(:require [clojure.string :as string]))
(defn to-reversed-digits
"returns a lazy sequence of least to most significant digits of n"
[n]
(->> [n 0]
(iterate (fn [[i _]] [(quot i 10) (mod i 10)]))
(take-while (complement #{[0 0]}))
(map second)
rest))
(defn checksum
"returns the luhn checksum of n, assuming it has a check digit"
[n]
(-> (->> n
to-reversed-digits
(map * (cycle [1 2]))
(map #(if (>= % 10) (- % 9) %))
(apply +))
(mod 10)))
(defn string->long
"Strips any non-digit characters and converts the string into a Long"
[n]
(-> n (string/replace #"[^0-9]+" "") Long/parseLong))
(defn valid?
"whether n has a valid luhn check-digit"
[n]
; Numbers with non digit/whitespace or only 1 digit are invalid
(if (or (re-find #"[^0-9\s]+" n) (>= 1 (count (string/trim n))))
false
(zero? (-> n string->long checksum))))
Version data entries
289 entries across 289 versions & 1 rubygems