Monthly Archives: November 2014
The Convoluted Logic of ROT13 in CCL
Playing with CCL, the Mule Code Conversion Language, I decided to write a simple ROT13 algorithm. This turned out to be tougher than expected since CCL has no concept of the logical and and or operators; what is && and || in C derived languages.
(define-ccl-program my-ccl-rot13 '(1 ((loop (read r0) ;; The convoluted logic of rot13 in CCL. (if (r0 >= 110) ; n (if (r0 <= 122) ; z ((r0 -= 13))) ;; If we are between n-z (if (r0 >= 97) ; a (if (r0 <= 109) ; m ((r0 += 13))) ;; If we are between a-m (if (r0 >= 78) ; N (if (r0 <= 90) ; Z ((r0 -= 13))) ;; If we are between N-Z (if (r0 >= 65) ; A (if (r0 <= 77); ; M ((r0 += 13))))))) ;; If we are between A-M (write r0) (repeat))))) |
One method to tackle this, as demonstrated above, is to use the if-else construct and carefully order the comparisons.
Now, in order to do something useful with this, we define the function my-rot13-word-at-point.
(defun my-rot13-word-at-point () (interactive) (let ((word (word-at-point))) (if (stringp word) (message (ccl-execute-on-string 'my-ccl-rot13 [0 0 0 0 0 0 0 0 nil] word))))) |
And now we can do M-x my-rot13-word-at-point and we will see the word (de)cyphered in the echo area.
There is one “bug” so to speak, and that it will potentially display garbage when applied to non-ascii text, such as Japanese.
Finally, these code snippets are GPL 2 or 3 at your convenience.