Week 8-ROT13 on DrRocket

There are many codes that exist, some are well known and hard to decode, like Morse code, and some is relatively easy, like rot13. Rot 13 is to convert a character to another. For example, A can be converted to N. The definition can be written in DrRocket below:

(define (rot13 c)

  (cond

    [(char<=? #\A c #\M) (integer->char (+ 13 (char->integer c)))]

    [(char<=? #\a c #\m) (integer->char (+ 13 (char->integer c)))]

    [(char<=? #\N c #\Z) (integer->char (- (char->integer c) 13))]

    [(char<=? #\n c #\z) (integer->char (- (char->integer c) 13))]

    [else c]))

Therefore, “I Love You!” can be translated into rot13 language "V Ybir Lbh!"