24 lines
836 B
Common Lisp
24 lines
836 B
Common Lisp
(defun encipher-char (ch key)
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(let*
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((c (char-code ch))
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(la (char-code #\a)) (lz (char-code #\z))
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(ua (char-code #\A)) (uz (char-code #\Z))
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(base (cond
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((and (>= c la) (<= c lz)) la)
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((and (>= c ua) (<= c uz)) ua)
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(t nil))))
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(if base (code-char (+ (mod (+ (- c base) key) 26) base)) ch)))
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(defun caesar-cipher (str key)
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(map 'string #'(lambda (c) (encipher-char c key)) str))
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(defun caesar-decipher (str key) (caesar-cipher str (- key)))
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(let* ((original-text "The five boxing wizards jump quickly")
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(key 3)
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(cipher-text (caesar-cipher original-text key))
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(recovered-text (caesar-decipher cipher-text key)))
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(format t " Original: ~a ~%" original-text)
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(format t "Encrypted: ~a ~%" cipher-text)
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(format t "Decrypted: ~a ~%" recovered-text))
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