Re: Ada OO Mechanism

[Matthew Heaney <matthew_heaney@acm.org>]

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.