Sha256: b235fc8c268b063ea29cc993b24423012af6a3dc72cbd6ee42f27e474c354002
Contents?: true
Size: 786 Bytes
Versions: 396
Compression:
Stored size: 786 Bytes
Contents
(defmodule luhn
(export (valid? 1)
(create 1)
(checksum 1)))
(defun valid? (number) (== (rem (checksum number) 10) 0))
(defun create (number)
(lists:flatten `(,number ,(- #\: (rem (checksum (++ number "0")) 10)))))
(defun checksum (number)
(checksum
(lists:reverse
(lists:filter
(lambda (c)
(=< #\0 c #\9))
number))
'odd
0))
(defun checksum
([() _ total] total)
([(cons h reversed-number) 'odd total]
(checksum reversed-number 'even (- (+ total h) #\0)))
([(cons h reversed-number) 'even total] (when (< h #\5))
(checksum reversed-number 'odd (+ total (* (- h #\0) 2))))
([(cons h reversed-number) 'even total] (when (>= h #\5))
(checksum reversed-number 'odd (- (+ total (* (- h #\0) 2)) 9))))
Version data entries
396 entries across 396 versions & 1 rubygems