class template specialization and inheritance

[mki]

Thanks for your answers!

Edward Diener Wrote:

> Bill Baxter wrote:
> > Edward Diener wrote:
> >> mki wrote:
> >>> Hello!
> >>>
> >>> I just discovered the template syntax of D. I am very exited about 
> >>> its simplicity compared to C++.
> >>>
> >>> Now I ran into a template behavior I do not understand. This code:
> >>  > snip...
> >>> class C(TT:A!(T)) {
> >>>     static void tellMe() {
> >>>         writefln("derived from A!(T).");
> >>>     }
> >>> }
> >>
> >> Huh ! What is T above ? I do not think that your use of T should be 
> >> legal. Are you sure you did not mean 'class C(TT:A!(TT)) { etc.' ?
> > 
> > I think it's supposed to be legal using:
> > 
> > class C(TT:A!(T), T)
> 
> This makes sense since T is another template parameter. In the original, 
> quoted further above, there was no second template parameter of T, which 
> should generate a compiler error.

I don't see why the original
class C(TT:A!(T))
shouldn't be legal.

in C++ style syntax I would have

//primary template
template<typename T>
class C {};

//template specialization of C
template<typename TT, typename T>
class C<TT:A<T> > ... ;

(Of course this isn't legal either, because C++ doesn't have the colon-syntax.)

Now D does away with primary templates, so the first part can be skipped completely in D.
Furthermore, D does not need the line
template<typename TT, typename T>
because the template parameters of the specialization can be completely deduced from the expression C<TT:A<T> >. All undeclared symbols are template parameters.

So to my understanding,
C(TT:A(T))
should be legal D and should have the sense I indicated with the C++ style syntax above. Also notice that there is no compiler error message on this expression.

For my programming purpose, the important thing is that C(TT:A(T)) is a specialization of C(T), but the suggested C(TT:A(T),T) is _not_.
For this reason, I really need the first variant, and not the second one.


I would like to hear further opinions on this. I my understanding correct, or not?