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

[Daniel Carrera]

With the last suggestion from Alex, and a tip to use cond-expand from Kon, I have settled on the following:

-----------------------------

;

; Works with Chicken Scheme and Gauche.

;

(cond-expand (chicken (use srfi-13))

             (gauche  (use srfi-13)))

 

(define msg "The quick brown fox jumps over the lazy dog.")

(define key 13)

 

(define (caesar char)

  (define A (char->integer #\A))

  (define Z (char->integer #\Z))

  (define a (char->integer #\a))

  (define z (char->integer #\z))

  (define c (char->integer char))

  (integer->char

    (cond ((<= A c Z) (+ A (modulo (+ key (- c A)) 26)))

          ((<= a c z) (+ a (modulo (+ key (- c a)) 26)))

          (else c)))) ; Return other characters verbatim.

 

(print (string-map caesar msg))

-----------------------------

I tried to include more Schemes, but Chibi doesn't seem to have SRFI-13, Racket doesn't support SRFI-0 (cond-expand), and Stklos is case-insensitive. There are other schemes that support both SRFI-0 and 13, but AFAICT they are not active. Even Stklos seems to have gone into a slumber 2.5 years ago. I have updated the Rosetta Code page. Since this code includes a lot of advice from experienced Schemers, I have removed the "novice" note.

http://rosettacode.org/wiki/Caesar_cipher#Scheme

Cheers,

Daniel.

On 11 March 2014 02:09, Alex Shinn <address@hidden> wrote:

(integer->char

 (cond ((<= A c Z) (+ A (modulo (+ key (- c A)) 26)))

          ((<= a c z) (+ a (modulo (+ key (- c A)) 26)))

          (else c)))

--
When an engineer says that something can't be done, it's a code phrase that means it's not fun to do.