Re: Classwide Parameter?

[Matthew Heaney <matthewjheaney@earthlink.net>]

matthias_k <nospam@digitalraid.com> writes:

> Matthew Heaney wrote:
> > matthias_k <nospam@digitalraid.com> writes:
> >
> >>Thanks for that answer. However, I'm still having problems (I have
> >>rewritten the code to be in one single package now):
> >>
> >><snip>
> >>package Graphics is
> >>
> >>    type Shape is abstract tagged null record;
> >>    procedure Draw (Obj: Shape'Class);
> > Get rid of this operation.  It's a "class-wide" operation (like a
> > static
> > method in C++), and hence the operation isn't primitive for the type
> > (and therefore doesn't dispatch).
> >
> 
> Oha? I thought it would be analogous to 'virtual' in C++, not static.

I should have said: "change the type from Shape'Class to Shape, and
optionally declare the operation as abstract."

In Ada, you don't need to say "virtual".  An operation for a type is
"primitive" whenever it has the type as a parameter or return type, and
the operation is declared in the same package as the type.

To make a "static" method in Ada, declare the parameter as T'Class.


> And btw.: What does dispatch mean? :) Is that the Ada term for dynamic
> binding?

Yes.