From: adam@irvine.com (Adam Beneschan)
Subject: Re: Renaming an abstract function
Date: 16 Nov 2001 19:08:04 -0800
Date: 2001-11-17T03:08:05+00:00 [thread overview]
Message-ID: <b4682ab7.0111161908.1d330e1@posting.google.com> (raw)
In-Reply-To: uvggau5ro.fsf@gsfc.nasa.gov
Stephen Leake <stephen.a.leake.1@gsfc.nasa.gov> wrote in message news:<uvggau5ro.fsf@gsfc.nasa.gov>...
> "Nick Roberts" <nickroberts@adaos.worldonline.co.uk> writes:
>
> > When given the program:
> >
> > package Test1 is
> > type T is abstract tagged limited private;
> > function P (X, Y: in T) return T is abstract;
> > function "*" (A, B: in T) return T renames P; -- error line
> > private
> > type T is abstract tagged limited null record;
> > end;
> >
> > GNAT 3.12p on Windows 95 returns the error message:
> >
> > function that returns abstract type must be abstract
> >
> > Is this a bug in: (a) GNAT; (b) the RM95; or (c) my brain?
>
> Same error in gnat 3.14 (you should at least upgrade to 3.13p).
>
> RM 8.5.4 (2) says:
>
> 2. subprogram_renaming_declaration ::=
> subprogram_specification renames callable_entity_name;
>
> The term "callable_entity_name" is not mentioned elsewhere in the
> reference manual, which I find odd.
Note that "callable_entity" is in italics, while "name" is not. In RM
notation, that means that the language expects the syntax of a "name"
(defined in 4.1), while "callable_entity" is a description that tells
you what the name has to represent. I guess if you're searching a
text file version of the RM, there's probably no indication that part
of it is in italics. "callable entity" is easily found in the index.
A "callable entity" is defined (in 6(2)) to be a subprogram or entry.
Thus an abstract subprogram is a callable entity even though you can't
really call it.
I don't see any prohibition on renaming an abstract subprogram.
However, renaming subprograms don't quite take on all the
characteristics of the subprograms they rename; see 8.5.4(12) for
instance. I suspect that has something to do with why renaming an
abstract subprogram could lead to an error, but I don't have time
right this minute to look into it further.
-- Adam
next prev parent reply other threads:[~2001-11-17 3:08 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-11-15 23:52 Renaming an abstract function Nick Roberts
2001-11-16 14:52 ` Stephen Leake
2001-11-17 3:08 ` Adam Beneschan [this message]
2001-11-17 17:47 ` Egil Harald Hoevik
2001-11-17 18:33 ` Stephen Leake
2001-11-17 22:00 ` Mark Biggar
2001-11-17 23:17 ` Nick Roberts
2001-11-19 15:38 ` Stephen Leake
2001-11-22 3:14 ` Nick Roberts
2001-11-23 15:40 ` Stephen Leake
2001-11-24 3:55 ` Nick Roberts
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