From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Thread: 103376,db88d0444fafe8eb X-Google-Attributes: gid103376,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news1.google.com!news4.google.com!newsfeed2.dallas1.level3.net!news.level3.com!newsfeed-00.mathworks.com!nntp.TheWorld.com!not-for-mail From: Robert A Duff Newsgroups: comp.lang.ada Subject: Re: Surprise in array concatenation Date: 07 Sep 2005 16:09:45 -0400 Organization: The World Public Access UNIX, Brookline, MA Message-ID: References: <1125610942.747981.280770@f14g2000cwb.googlegroups.com> <431d6095$0$24157$9b4e6d93@newsread4.arcor-online.net> <83u0gx87j0.fsf@skynet.be> NNTP-Posting-Host: shell01.theworld.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: pcls4.std.com 1126123785 12686 192.74.137.71 (7 Sep 2005 20:09:45 GMT) X-Complaints-To: abuse@TheWorld.com NNTP-Posting-Date: Wed, 7 Sep 2005 20:09:45 +0000 (UTC) User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2 Xref: g2news1.google.com comp.lang.ada:4509 Date: 2005-09-07T16:09:45-04:00 List-Id: Thierry Pirot writes: > Robert A Duff writes: > > > It breaks the abstraction called "subprogram". As I showed in my > > example, a procedure is handed an integer value (X'First), which is an > > offset from the beginning of some object it knows nothing about, and > > should know nothing about. > > > Do you mean : > the calling subprogram knows about that object (of which a slice is passed) and > the called subprogram doesn't and shouldn't ? Yes, that's exactly what I mean. > I tend to agree, however, if I got it right, I wonder : > what about a recursive subprogram ? > It is both the called and calling program. Good point. And what about the case where there's no recursion, but the callee _should_ know about that array which was sliced? The answer must be some sort of a "subarray" abstraction, which carries with it the original array (or a reference to it). I haven't thought this through... > (This may indeed be a bit sophistic, > actually I have found Ada's passing of slice bounds quite elegant > within recursive subprograms > --- wherein a string is conveniently rendered a recursive object by > Ada's slices, i.e. strings include slices which are (sub)strings). Yes, in rare cases, including the recursive case you mention, I have found some use for slices that remember their bounds within the original array. But in _most_ cases, I've found it an error-prone annoyance. > Take it Easy Don't worry Be Happy Good advice. :-) - Bob