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(defpackage #:lt-examples
(:use #:cl #:lambda-tools))
;; http://rosettacode.org/wiki/Luhn_test_of_credit_card_numbers
(defun luhn (n)
(flet ((sum-dig (x) (if (> x 9) (- x 9) x)))
(>> n #'reverse
#$(map 'list #'digit-char-p $char)
#$(mapcar #'*
(loop :for i :upto (length $digits) :collect (1+ (mod i 2)))
$digits)
#$(zerop (mod (apply #'+ (mapcar #'sum-dig $digits)) 10)))))
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