Re: template parameter can't be friend - and we hack it to be
Ralph Zhang wrote:
gcc will complain if you try to compile this:
template <class T>
class TT
{
friend class T;
};
I googled and find people saying template parameters can't be friends.
Yes, it's expressly prohibited.
So I do this:
// Add one more indirection
template <class T>
struct FriendMaker
{
typedef T Type;
};
template <class T>
class Ty
{
friend class FriendMaker<T>::Type;
Comeau does not compile it this way, saying "Type" cannot be used
in elaborate type specifier. But it compiles if I change it to
friend typename FriendMaker<T>::Type;
Can just be a fluke...
private:
int t;
};
Missing:
#include <iostream>
class A
{
public:
void f(Ty<A>& ty)
{
std::cout << ty.t;
}
};
int main()
{
Ty<A> t;
A a;
a.f(t);
}
It compiles and works! Although I've not thought about how this can be
useful, i think someone might need it some day.
Curious. Thanks for sharing!
V
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