Specifying eponymous template "internal parameter"

[Simen Kjaeraas]

On 2013-55-08 09:01, monarch_dodra <monarchdodra at gmail.com> wrote:

> Sometimes (especially in phobos), one defines a parametrized template,  
> that resolves to a templated function.
>
> This is a nifty trick, because it allows specifying a vararg before the  
> current type parameter, eg:
>
> //----
> auto r = [1, 2, 3];
> auto m = map!("++a", "--a")(r);
> //----
>
> As you can see, the template guessed the type of r, even though we used  
> a vararg. This would not have worked with a single template function.
>
> My question though: I have a similar use case, but I NEED to be able to  
> explicitly specify the type of r: as such:
>
> //----
> auto m = fun!("++a", "--a", ubyte)(1);
> auto m = fun!("++a", "--a")!(ubyte)(1);
> auto m = fun!("++a", "--a").fun!ubyte(1);
> //----
> None of them work. In this specific case, I *need* to specify that 1 is  
> of type ubyte, but I really can't do it :/
>
> Simplified example: in my use case, it is a "immutable(int[])": Failure  
> to specify the type means the compiler strips tail immutability...
>
> The only workaround I can find to make such a thing, is to *not* use  
> eponymous temples, and explicitly call an inner function. This is ugly  
> as sin, and it makes specifying the internal parameter mandatory.
>
> Any thoughts?

A non-eponymous template is currently the only way to do this. Strangely,  
this works:

   alias fun2 = fun!("++a", "--a");
   auto m = fun2!(ubyte)(1);

-- 
Simen