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

[Alex Shinn]

On Tue, Mar 11, 2014 at 6:16 AM, Daniel Carrera <address@hidden> wrote:

On 10 March 2014 20:04, Daniel Carrera <address@hidden> wrote:

I am trying to write an R7RS-compliant version. R7RS would give me "import", as well as char->integer and integer->char. The problem I'm having is that my code does not work when I compile it, or when I use "csi -s", but it works perfectly well when I paste it directly into the csi REPL.

After a tip from Erik, I have isolated the issue. The (import) only works correctly if you first run (use posix). My REPL was loading posix because I loaded readline. The following code compiles and runs correctly:

(use posix)

;

; Unicode-safe. Requires an R7RS-compliant Scheme.

;

(import (srfi 13)) ; String library.

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

(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))

  (cond ((and (>= c A) (<= c Z)) (integer->char (+ A (modulo (+ key (- c A)) 26))))

        ((and (>= c a) (<= c z)) (integer->char (+ a (modulo (+ key (- c a)) 26))))

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

(integer->char

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

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

          (else c)))

 

(print (string-map caesar msg))

Cheers,

Daniel.

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