Re: How to return an empty aggregate

On 6 Kwi, 00:36, george.p...@[EMAIL PROTECTED]
 wrote:

> > I would create the derived (concrete) log that is *empty* and does
> > nothing and pass it as Log'Class to wherever it is expected.
> > It cannot be simpler than that.
>
> So you derive concrete from not-empty type?

I derive empty concrete from the interface:

type Log is interface;
procedure Put (L : in Log; S : in String) is abstract;

-- ...

type Null_Log is new Log with null record;
procedure Put (L : in Null_Log; S : in String) is
begin
  -- some pragma here to shut up warnings
  -- about unused parameters
  null;
end Put;

--
Maciej Sobczak *www.msobczak.com*www.inspirel.com