Can't understand templates

[Sly via Digitalmars-d-learn]

OK, so we *can* have overlapping templates in one fits better
than another, just like in C++. I still don't understand how to
read this signature:
Point!T getResponse(T: Point!T)(string question)


On Friday, 28 November 2014 at 23:59:07 UTC, Ali Çehreli wrote:
> On 11/28/2014 12:36 PM, Sly wrote:
>
> > Let's take a simpler example from earlier in the tutorial,
> where
> > Point is a non-template struct:
> >
> >
> > // The general definition of the function template (same as
> > before)
> > T getResponse(T)(string question)
> > {
> [...]
> > }
>
> That definition would work with any type T. So, it is general: 
> it accepts any type.
>
> > // The specialization of the function template for Point
> > T getResponse(T : Point)(string question)
> > {
> [...]
> > }
>
> That definition is for T that matches Point (i.e. Point itself 
> in this example). So, it is special: it accepts only that type.
>
> > auto center = getResponse!Point("Where is the center?");
> >
> > Doesn't getResponse!Point match both declarations?
>
> True but the call is dispatched to the most special of all of 
> the matches. It is very briefly explained through a reference 
> to C++:
>
> "The template picked to instantiate is the one that is most 
> specialized that fits the types of the TemplateArgumentList. 
> Determine which is more specialized is done the same way as the 
> C++ partial ordering rules. If the result is ambiguous, it is 
> an error."
>
> See the "Specialization" heading here:
>
>   http://dlang.org/template.html
>
> Ali