Vigenère cipher: Difference between revisions

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@@ Line 957: / Line 957: @@
   (string-upcase (remove-if-not 'alpha-char-p s)))
-(defun vigenere (txt key &key decode &aux (d (if decode -1 1)))
+(defun vigenere (txt key &key plain &aux (p (if plain -1 1)))
   (let ((txt (strip txt)) (key (strip key)) (i -1))
     (map 'string
       (lambda (c)
         (setf i (mod (1+ i) (length key)))
-        (char +a+ (mod (+ (position c +a+) (* d (position (elt key i) +a+))) 26)))
+        (char +a+ (mod (+ (position c +a+) (* p (position (elt key i) +a+))) 26)))
       txt)))</lang>
@@ Line 968: / Line 968: @@
 <pre>(vigenere "« Through the Looking-Glass »" "Lewis Carroll")
-(vigenere "ELNWMIHKYSWZZOEVYILRJG" "Lewis Carroll" :decode t)</pre>
+(vigenere "ELNWMIHKYSWZZOEVYILRJG" "Lewis Carroll" :plain t)</pre>
 {{out}}
 <pre>