Re: [Chicken-users] Review my Caesar Cipher?

[Daniel Carrera]

Thanks. I think it's fair to use SRF-13. Now that I learned some character functions from Phil, I think the following is nice and compact:

(define (caesar char)

  (if (not (char-alphabetic? char)) char ; Return other chars verbatim.

      (let ((i (- (char->integer (char-upcase char)) 65)))

        (integer->char (+ 65 (modulo (+ i key) 26))))))

(print (string-map caesar msg))

Cheers,

Daniel.

On 10 March 2014 16:31, Peter Bex <address@hidden> wrote:

On Mon, Mar 10, 2014 at 10:26:56AM -0500, Phil Bewig wrote:
> I would use an auxiliary function char-plus to add or subtract an offset to
> a character:
>
> (define (caesar str n)
>   (define (char-plus c)
>     (let ((alpha "ABCDEFGHIJKLMNOPQRSTUVWXYZ"))
>       (if (not (char-alphabetic? c)) c
>         (let ((i (- (char->integer (char-upcase c)) 65)))
>           (string-ref alpha (modulo (+ i n) 26))))))
>   (list->string (map char-plus (string->list str))))

If you're using srfi-13, you might as well change the final line to use
string-map:  (string-map char-plus str)

Cheers,
Peter
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