From: "Randy Brukardt" <randy@rrsoftware.com>
Subject: Re: Making sense of predicates
Date: Wed, 23 Oct 2013 22:58:18 -0500
Date: 2013-10-23T22:58:18-05:00 [thread overview]
Message-ID: <l4a5sv$8oa$1@loke.gir.dk> (raw)
In-Reply-To: b4d93d01-c200-404f-a414-71258ef8318c@googlegroups.com
"Shark8" <onewingedshark@gmail.com> wrote in message
news:b4d93d01-c200-404f-a414-71258ef8318c@googlegroups.com...
...
> IOW, why is the predicate required to be dynamic when, for example,
> "subtype Number_String is Array(Positive range <>) of Digit_Character" or
> "subtype short_String is String(1..255)" is not a dynamic-predicate?
Because the idea of a "static predicate" was a hack to allow certain
(scalar) predicates in for loops and case statements. All predicates were
originally supposed to be dynamic; there was a set constraint proposed to
handle the static set cases. Most people (not me) preferred having
predicates handle sets, that required two kinds of predicate to avoid
maintenance hazards.
Maybe we'll extend them someday, but I think we'd have to have a compelling
use case. And adding new kinds of constraints (such as an array element
constraint) would have a much higher bar than extending existing kinds of
constraints (such as a way to have a static one-ended unconstrained array).
Randy.
next prev parent reply other threads:[~2013-10-24 3:58 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-21 19:51 Making sense of predicates Dmitry A. Kazakov
2013-10-22 4:35 ` Randy Brukardt
2013-10-22 8:19 ` Dmitry A. Kazakov
2013-10-22 12:53 ` Georg Bauhaus
2013-10-22 13:38 ` Dmitry A. Kazakov
2013-10-22 20:38 ` Georg Bauhaus
2013-10-24 4:03 ` Randy Brukardt
2013-10-24 7:26 ` Dmitry A. Kazakov
2013-10-22 7:14 ` Shark8
2013-10-22 7:35 ` Jacob Sparre Andersen
2013-10-22 17:26 ` Shark8
2013-10-23 7:56 ` Jacob Sparre Andersen
2013-10-24 3:58 ` Randy Brukardt [this message]
2013-10-22 8:11 ` Dmitry A. Kazakov
2013-10-22 7:20 ` Jacob Sparre Andersen
2013-10-22 7:57 ` Dmitry A. Kazakov
2013-10-22 14:52 ` Dan'l Miller
2013-10-22 16:30 ` Dmitry A. Kazakov
2013-10-22 17:15 ` Dan'l Miller
2013-10-22 19:26 ` Dmitry A. Kazakov
2013-10-22 19:49 ` J-P. Rosen
2013-10-22 21:30 ` Dan'l Miller
2013-10-23 9:25 ` Dmitry A. Kazakov
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