🚀 go-pugleaf

girod@tele.nokia.fi (Marc Girod @ kpd) writes

 > This made me wonder whether it was possible to overload template
 > definitions, such as:
 > 
 > template <class A> class X {};
 > template <class A, class B> class X {};
 > 
 > X<int> x1;       //from the first template
 > X<int, int> x2;  //from the second
 > 
 > I checked with g++ v2.2.2, and was surprised to notice that the
 > overriding of the templates was legal, but thus hid the former
 > declaration, without any warning. The result was thus an error, at
 > delaration time of x1:
 > 
 > incorrect number of parameters (1, should be 2) in template expansion
 > 
 > Well, I had a look in ARM, and couldn't find anything better than:
 > 
 > p 347
 > 14.5c Declarations and Definitions
 > "There must be exactly one definition for each template of a given
 > name in a program."


How about (pg343):

	A class template name must be unique in a program and may not
	be declared to refer to any other template, class, function,
	value, or type in the same scope.

 > This sounds like g++ was right (apart from allowing the superseeding
 > to occur, additionally without warning).

No. That seems to be a g++ bug.

 > But now, why? What would be the problem? Wouldn't it be more natural
 > to allow template name overloading?

It would be nice to be able to overload templates, but to do this we'd
have to work out the exact overloading rules. That is not a trivial task,
it hasn't been done, and there may be fundamental problems lurking.
Hence the prohibition.