From: "Randy Brukardt" <randy@rrsoftware.com>
Subject: Re: array from static predicate on enumerated type
Date: Fri, 12 Mar 2021 22:55:51 -0600 [thread overview]
Message-ID: <s2hgko$6u5$1@franka.jacob-sparre.dk> (raw)
In-Reply-To: 6ca041f3-2669-4497-9548-2f17666702a6n@googlegroups.com
"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.
next prev parent reply other threads:[~2021-03-13 4:55 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-12 20:49 array from static predicate on enumerated type Matt Borchers
2021-03-12 21:22 ` Egil H H
2021-03-12 22:16 ` Jeffrey R. Carter
2021-03-12 22:41 ` Dmitry A. Kazakov
2021-03-13 2:06 ` Matt Borchers
2021-03-13 4:55 ` Randy Brukardt [this message]
2021-03-15 14:16 ` Matt Borchers
2021-03-15 17:53 ` Shark8
2021-03-16 6:58 ` Randy Brukardt
2021-03-13 8:04 ` Dmitry A. Kazakov
2021-03-15 14:11 ` Matt Borchers
2021-03-15 17:48 ` Shark8
2021-03-15 20:25 ` Dmitry A. Kazakov
2021-03-16 13:27 ` Shark8
2021-03-16 14:25 ` Dmitry A. Kazakov
2021-03-17 4:05 ` Matt Borchers
2021-03-17 7:08 ` Dmitry A. Kazakov
2021-03-17 18:44 ` Matt Borchers
2021-03-17 19:41 ` Dmitry A. Kazakov
2021-03-18 1:30 ` Matt Borchers
2021-03-18 8:20 ` Dmitry A. Kazakov
2021-03-19 0:10 ` Matt Borchers
2021-03-19 8:00 ` Dmitry A. Kazakov
2021-03-18 10:15 ` Niklas Holsti
2021-03-18 10:47 ` AdaMagica
2021-03-18 11:26 ` Dmitry A. Kazakov
2021-03-19 0:34 ` Matt Borchers
2021-03-19 0:49 ` Jeffrey R. Carter
2021-03-23 1:07 ` Matt Borchers
2021-03-23 3:43 ` Randy Brukardt
2021-03-22 19:09 ` Niklas Holsti
2021-03-17 15:08 ` Shark8
2021-03-17 19:08 ` Matt Borchers
2021-03-17 20:41 ` Shark8
2021-03-18 1:04 ` Matt Borchers
2021-03-18 14:25 ` Shark8
2021-03-18 23:36 ` Matt Borchers
2022-03-16 0:38 ` Thomas
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