From: jsa@alexandria (Jon S Anthony)
Subject: Re: Extending A Generic Signature Package
Date: 1997/03/25
Date: 1997-03-25T00:00:00+00:00 [thread overview]
Message-ID: <JSA.97Mar24204636@alexandria> (raw)
In-Reply-To: 5gkv23INN3rn@thalamus.cis.ohio-state.edu
In article <5gvgg0INNj32@snoopy.cis.ohio-state.edu> dgibson@snoopy.cis.ohio-state.edu (david scott gibson) writes:
> In article <JSA.97Mar21200655@alexandria>,
> Jon S Anthony <jsa@alexandria> wrote:
>
> >> > declare
> >> > X : Base'Class := Get_Object;
> >> > begin
> >> > Op1(X);
> >> > end;
> >>
> >> So in this case it's clear to us and the compiler what specific type
> >> derived from Base Get_Object returns.
> >
> >No, the _specific_ type is unknown until runtime. But, whatever it
> >is, it will be in Base'Class.
>
> Hmmm. I was thinking of Get_Object as a constructor for a specific
> derived type of Base. Are you're suggesting some non-functional
> behavior here for Get_Object to be able to return any one of several
> specific derived types?
I don't know what you mean by "non-functional behavior". Certainly,
as you suggest, Get_Object could be a constructor for a specific type
in Base'Class, but I was thinking of a different situation. Suppose
it returns Base'Class and computes the object of the appropriate
specific type on the fly. Or perhaps, it dispatches (in which case it
needs a parameter of some sort) to the appropriate specific Get_Object
or some combination of these. Anyway, you get the idea.
> that this rule only applied to them. Nevertheless, I assume compilers
> may return tagged types, especially big ones, by reference. I didn't
> mean to imply that objects passed by reference should be thought of as
> "pointers". Ada seems to do a good job of making the mechanism
> transparent.
Bob answered this one.
/Jon
--
Jon Anthony
Organon Motives, Inc.
Belmont, MA 02178
617.484.3383
jsa@organon.com
prev parent reply other threads:[~1997-03-25 0:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
1997-03-17 0:00 Extending A Generic Signature Package david scott gibson
1997-03-18 0:00 ` Tucker Taft
1997-03-18 0:00 ` Alexander V. Konstantinou
1997-03-21 0:00 ` Geert Bosch
1997-03-21 0:00 ` Brian Rogoff
1997-03-22 0:00 ` Robert A Duff
1997-03-21 0:00 ` Jon S Anthony
1997-03-21 0:00 ` david scott gibson
1997-03-22 0:00 ` Robert A Duff
1997-03-22 0:00 ` Jon S Anthony
1997-03-21 0:00 ` david scott gibson
1997-03-22 0:00 ` Robert A Duff
1997-03-25 0:00 ` Jon S Anthony [this message]
replies disabled
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox