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 <peter....@xs4all.nl> 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
> --
> http://www.more-magic.net
>
--
When an engineer says that something can't be done, it's a code phrase that
means it's not fun to do.
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