template <class C, class T> void my_f(const C<T>& aContainer);

[lalebarde]

Hi all,

Is it possible and how could I define a templated method like this :

template <class C, class T> void my_f(const C<T>& aContainer);

The syntax checker is not happy saying

C is not a template

If I define it like this :

template <class C, class T> void my_f(const C& aContainer) {
  for (T c : aContainer) cout << c << " ";
}

The compiler is not happy. It says it

cannot resolve

.

The alternative would be to define it for each container :

template <class T> void my_f(const std::set<T>& aSet);
template <class T> void my_f(const std::vector<T>& aVec);

Any idea please ?

[Peter87]

I don't think you can do that because C has to be a complete type.

Containers has typedefs that you can use to get the element type from.

template <class C> void my_f(const C& aContainer)
{
	for (const typename C::value_type& c : aContainer) cout << c << " ";
}

You are using C++11 so you can also use auto to do the same thing.

template <class C> void my_f(const C& aContainer)
{
	for (const auto& c : aContainer) cout << c << " ";
}

[ne555]

template< template<class> class C, class T>
However note that, by instance, std::vector doesn't hold just one template parameter.

Peter87 wrote:

Containers has typedefs that you can use to get the element type from.

That's a lot better.
When you make your own container consider doing that typedef too.

[lalebarde]

Thanks very much Peter87.
Method 1 suffer from having to define it for each T.
Method 2 actually works with C++11.

[ne555]

¿what is the problem with method 1?