added example

1 files changed, 15 insertions, 0 deletions

diff --git a/examples.lisp b/examples.lisp
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+++ b/examples.lisp
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+
+(defpackage #:lt-examples
+  (:use #:cl #:lambda-toosl))
+
+
+;; 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))))))