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From: Matthew Heaney <matthew_heaney@acm.org>
Subject: Re: Ada OO Mechanism
Date: 1999/06/08
Message-ID: <m3emjnh660.fsf@mheaney.ni.net>#1/1
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NNTP-Posting-Date: Mon, 07 Jun 1999 17:38:59 PDT
Newsgroups: comp.lang.ada
Date: 1999-06-08T00:00:00+00:00
List-Id: <comp.lang.ada>

On 07 Jun 1999 15:26:52 -0400, Hyman Rosen <hymie@prolifics.com> wrote:

> Matthew Heaney <matthew_heaney@acm.org> writes:
> > No.  The compiler has no way of knowing at compile-time how much space
> > to allocate on the stack for the return value of the function.  The size
> > is determined at run-time.
> 
> From a little further fooling around, followed by a trip to the Ada RM,
> I see that objects of class-wide type can not be record components, which
> I guess makes sense, but it doesn't seem very orthogonal to me.

I'm not sure what you mean by "doesn't seem very orthogal," but there
are pragmatic reasons for not allowing a class-wide type as a record
component.

Just as the record decl 

  type RT is
    record
      S : String;
    end record;


is illegal, so is the decl

  type RT is
    record
      O : T'Class;
    end record;


However, the declaration

  declare
    S : String := Func_Return_String;
  begin


is perfectly legal, and so is the declaration

  declare
    O : T'Class := Func_Return_T_Tic_Class;
  begin
  


In neither case is heap required.