defaulting leading template parameters?

[Bruno Medeiros]

Sean Kelly wrote:
> d-bugmail at puremagic.com wrote:
>>
>> void testfunc(DUMMY = void, T)(int x, T a) {
>>     writefln("x = %d, a = %s", x, a);
>> }
> 
> I had no idea this was legal--it isn't in C++.  I guess the rationale is 
> that if the compiler can figure out the remaining parameters by 
> inspecting function arguments then this is not an error?
> 
> 
> Sean

Well, I've never actually learned C++ templates[*], so I my thinking 
isn't bound to what C++ can or cannot do :P . Anyway, I'm not sure I 
understand your question. At the time I just checked the docs to see 
what could be done with IFTI, and it was stated that:
"Template arguments not implicitly deduced can have default values:
   void Foo(T, U=T*)(T t) { U p; ... }
"
So in both explicit and implicit instantiation you can also have 
parameters that are deduced from other parameters. (Not the case in C++ 
then?) The DUMMY case above is just a case where such deduction is 
constant and not actually dependent on any other parameters.

[*] Well, I did a learn some of C++ templates, but only the basics, and 
only after learning D's and also usually under the perspective of D 
comparison.

-- 
Bruno Medeiros - MSc in CS/E student
http://www.prowiki.org/wiki4d/wiki.cgi?BrunoMedeiros#D