Re: Why can't I override these functions?

["Björn Persson" <spam-away@nowhere.nil>]

Simon Wright wrote:

> The compiler should probably have said something to point you at:
> 
>    AARM 3.9.3(10), For an abstract type declared in a visible part, an
>    abstract primitive subprogram shall not be declared in the private
>    part, unless it is overriding an abstract subprogram implicitly
>    declared in the visible part. For a tagged type declared in a
>    visible part, a primitive function with a controlling result shall
>    not be declared in the private part, unless it is overriding a
>    function implicitly declared in the visible part.

I can't see how that would apply to this case. The only abstract type 
declared in a visible part is Intermediate_Definition, and the copmiler 
doesn't complain about that one. It complains about 
Typed_Parameter_Definition, which is concrete and declared in a private 
part.

> In an equivalent place in the Booch Components, I make the subprogram
> concrete and say
> 
>    function Item_At (C : Container; Index : Positive) return Item_Ptr is
>    begin
>       raise Should_Have_Been_Overridden;
>       return null;
>    end Item_At;

That workaround works for this small example, but when I applied it to 
the real library I ran into other problems instead, like "cannot find 
body of generic package "Common_Functions"". I give up. I'll have to 
live with virtually identical code in at least four places.

-- 
Björn Persson

jor ers @sv ge.
b n_p son eri nu