From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.5-pre1 (2020-06-20) on ip-172-31-74-118.ec2.internal X-Spam-Level: X-Spam-Status: No, score=-1.9 required=3.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.5-pre1 Path: eternal-september.org!reader02.eternal-september.org!gandalf.srv.welterde.de!news.jacob-sparre.dk!franka.jacob-sparre.dk!pnx.dk!.POSTED.rrsoftware.com!not-for-mail From: "Randy Brukardt" Newsgroups: comp.lang.ada Subject: Re: array from static predicate on enumerated type Date: Fri, 12 Mar 2021 22:55:51 -0600 Organization: JSA Research & Innovation Message-ID: References: <89128f73-fcc5-4e57-8067-d09877ba0211n@googlegroups.com> <6ca041f3-2669-4497-9548-2f17666702a6n@googlegroups.com> Injection-Date: Sat, 13 Mar 2021 04:55:52 -0000 (UTC) Injection-Info: franka.jacob-sparre.dk; posting-host="rrsoftware.com:24.196.82.226"; logging-data="7109"; mail-complaints-to="news@jacob-sparre.dk" X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2900.5931 X-RFC2646: Format=Flowed; Original X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.7246 Xref: reader02.eternal-september.org comp.lang.ada:61508 List-Id: "Matt Borchers" writes: >I do want a map or hash table, but in this case, I was hoping that Ada >would handle the mapping for me ... Ada is not some sort of magic wand. What you want requires a complex data structure, and using an array (as defined in Ada) for it is not practical (mainly because of the slice operation of which I've complained previously). >...such that I did not have to instantiate such a complexity for a simple >example. Ada was designed to provide high-quality (that is, fast) code. If you want a language with a high degree of abstraction -- Ada isn't it. And in such a language, you wouldn't have arrays (in the Ada sense) at all - you would only have maps and sequences. And if you think a single instance is "such complexity", I have no idea what you would want -- a map instance is simpler to write than an array type declaration (and *much* simpler under the covers). Do you also never use Unchecked_Deallocation?? It's harder to instantiate than an Ordered_Map. >I was a bit surprised after discovering Static_Predicate that the Ada >language >syntax was essentially useless in dealing with it in a consistent way. I was in favor of set constraints rather than Static_Predicates, mainly because of the value problems Dmitry commented on. But even those would have been illegal in arrays -- an array makes a lousy way to describe a map. Anyway, subtypes with Static Predicates work for case statements, memberships, an for loops; they're only disallowed for arrays. I don't think anyone should be writing an array in a modern language (outside of interfacing to something outside of that language) - it's a mixed up data structure that only makes sense because of historical reasons. >I like the idea of creating non-contiguous enumerated sub-types. Static predicates do that fine. Just don't use them with obsolete data structures. :-) Randy.