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From: Robert A Duff <bobduff@TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: Ada.Real_Time.Time_Last
Date: Sat, 18 Nov 2017 17:20:48 -0500
Organization: The World Public Access UNIX, Brookline, MA
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Xref: feeder.eternal-september.org comp.lang.ada:48998
Date: 2017-11-18T17:20:48-05:00
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Niklas Holsti <niklas.holsti@tidorum.invalid> writes:

> For various reasons, the developers of the Ada language have seen fit to
> define in the RM some standard, predefined types for which they have
> wanted to state the nature of the type, but not its full definition. For
> example, we have, in package System,
>
>    subtype Any_Priority is Integer range implementation-defined;

Yes, and Any_Priority'Last is a static expression.
Would it be static in your proposal?

Programmers need to know the priority range in order to
write pragmas Priority.  So in what sense is this
"private" information?

> This would enable all discrete-type operations on the Item type, but
> would hide (keep private) what sort of discrete type it is, as well as
> the names of the enumeration literals, if it is implemented as an
> enumerated type. The RM defines just such a type in Ada.Interrupts:
>
>    type Interrupt_Id is implementation-defined;
>
> with the explanation (RM C.3.2(13)) "The Interrupt_Id type is an
> implementation-defined discrete type used to identify interrupts."

If Interrupt_Id is an enumeration type (not true for GNAT), you don't
want to hide the names of the interrupts from clients.  If there's a
Gizmo_Device_Interrupt, then clients want to attach handlers to that by
name.

- Bob