Re: [Jscheme-user] treating #null as #f in conditionals?

[Ken A. <kan...@bb...>]

Thanks for your description of #null.  Its interesting that Scheme, and functional languages can get along without it.  Why is that?  I think Common Lisp had a #null called NIL.

My plan was that #null and #f would be distinct objects, but that #null would be treated as #f.  in conditionals.

The problem with Rusty and Geof's macros is you need to provide ifj, andj, orj, notj, and condj.  Here's a piece of code that's written in this style:

       (let ((effective (.getNotamEffectiveDtg n))
             (expire (.getNotamExpireDtg n)))
         (if (andj effective expire)
             (prefix " WEF " (string-append (.substring effective 2) "-"
                                            (.substring expire 2)))
             (ifj expire (prefix " TIL " (.substring expire 2))
                  (ifj effective (prefix " WEF " (.substring effective 2)))))))

which i don't like.

treating #null like #f in conditions lets  java collections return #null but let you write code like (if (member x y) ... or (if (.get table key) ...

k
At 04:16 PM 11/4/2004 -0500, Alan Donovan wrote:
>I agree; I think it's much cleaner to keep #null distinct from #f.