Hi,<div><br></div><div>I&#39;m still using Gambit Scheme from time to time and having a lot of fun with it.  I&#39;ve a newbie question however, I&#39;m trying to figure out the best way to structure code.  With that in mind are there any comments on the following code?  I&#39;m trying to create an &#39;object&#39; that holds a list of names, can return a random one on request that can later be returned to it.  </div>
<div><br></div><div>What&#39;s the proper Scheme way of doing this kind of thing?  Here&#39;s my stab, it returns a function that then accepts &#39;messages&#39; as parameters....</div><div><br></div><div><div><div>(define (make-name-list seed-names)</div>
<div>  </div><div>  ;; The type the list is built from</div><div>  (define-type blob-name</div><div>    name</div><div>    (random init: 0))     ; Used for sorting</div><div><br></div><div><br></div><div>    (let ((unused-name-list &#39;()))</div>
<div><br></div><div>      (define (randomise-list)  </div><div>        ; Assign each name a random number and then sort them      </div><div>        (map (lambda (x) (blob-name-random-set! x (random-integer 65536))) unused-name-list)</div>
<div>        (sort! unused-name-list (lambda (x y) </div><div>            (if (&lt; (blob-name-random x) (blob-name-random y)) #t #f))))</div><div><br></div><div><br></div><div>      ;; Put all the seed names in the list</div>
<div>      (map (lambda (x) (push (make-blob-name x) unused-name-list)) seed-names)</div><div>    </div><div><br></div><div>      (lambda (message . arguments)</div><div>        (cond ((eq? message &#39;:get-name!)</div><div>
              (if (null? unused-name-list)</div><div>                &quot;No names available&quot;</div><div>                (begin</div><div>                  (let ((name (blob-name-name (car unused-name-list))))</div><div>
                    (set! unused-name-list (cdr unused-name-list))</div><div>                    name))))  </div><div><br></div><div>              ; Add a name to the list, used to return names once they&#39;re no longer needed      </div>
<div>              ((eq? message &#39;:put-name!)</div><div>                  (push (make-blob-name (car arguments)) unused-name-list)</div><div>                  (randomise-list))</div><div><br></div><div>              ; Debug, print the internal display    </div>
<div>              ((eq? message &#39;:display)</div><div>                (display unused-name-list))</div><div><br></div><div>              (else (error &#39;name-list &quot;unrecognized message&quot;))))))</div></div><div>
<br></div><div><br></div><div>;; Test drive code.......</div><div>(define name-list (make-name-list (list &quot;Albert&quot; &quot;Bruce&quot; &quot;Clive&quot;)))</div><div>(display (name-list &#39;:get-name!))</div><div>
(name-list &#39;:put-name! &quot;David&quot;)</div><div>(name-list &#39;:put-name! &quot;Edgar&quot;)</div><div>(name-list &#39;:put-name! &quot;Frederick&quot;)</div><div><br></div><div>(display (name-list &#39;:display))</div>
<div><br></div></div><div>Some points:</div><div><br></div><div>In particular I&#39;m unhappy with the way the message arguments are accessed as (car arguments) rather than by explicit name.  I can see that being a potential cause of bugs if the number of arguments grows and they vary with each message.</div>
<div><br></div><div>I realise that the randomise-list function is probably called too often and maintaining a &#39;dirty bit&#39; would allow it to be only called when necessary when getting a name.</div><div><br></div><div>
I&#39;ve years of C/C++ programming behind me, which is probably readily apparent.  </div><div><br></div><div>How can I improve the code?</div><div><br></div><div>Thanks,</div><div>Roger.</div>