Template with equivalent function names

[Jonathan M Davis]

On Sunday 15 August 2010 20:18:27 Andrej Mitrovic wrote:
> This isn't a question but more of an observation. Here's an interesting
> template from the docs:
> 
> template Foo(T, R...)
> {
>     void Foo(T t, R r)
>     {
> 	writeln(t);
> 	static if (r.length)	// if more arguments
> 	    Foo(r);		// do the rest of the arguments
>     }
> }
> 
> void main()
> {
>     Foo(1, 'a', 6.8);
> }
> 
> What really intrigues me here is not the tuples which I already get, but
> the fact that Foo is a function template. But if I remove the inner Foo()
> function then it's not a function template anymore so the call in main
> won't work. The inner function must have the same name as the template,
> apparently (it doesn't even state this in the docs from what I can tell!).
> 
> There seem to be plenty of ways of making templates, sometimes you
> explicitly add the template keyword, sometimes not.. I kind of wish the
> syntax was more unified in this regard.
> 
> Well anyway, that page (http://www.digitalmars.com/d/2.0/template.html)
> reveals some really powerfull stuff you can do with templates. If only
> template error messages were as exciting to look at! :p

TDPL does discuss it, and it's highly useful. Of course, in this case, you might 
as well make the function itself a template function instead of putting it in a 
template, but it's highly useful and definitely used in Phobos to have a template 
with the same name as one of its members. Functions like Format!() would be a 
prime example. Usually, the member with the same name is an enum which then 
replaces the template when instantiatied. It's _highly_ useful for generating 
stuff at compile-time.

Regardless, I'm sure that the docs could be updated and fleshed out with regards 
to templates. I'd guess that part of the problem is that the more experienced D 
users pretty much never read them, and the folks who would be qualified and 
arguably have the responsibility to keep them up-to-date are very busy with 
other D-related stuff that needs doing.

- Jonathan M Davis