Passing values to inner class via template arguments C++ - c++

Question

Trying to pass the value to nested class via template agrument,and have some confusion:
template<typename A,typename B>
class outter{
int a;
T* p;
////...////
template<typename N=int> class inner;
inner do_something(){
return inner<a>(p)
}
}
template<typename T,typename A, typename N=int>
class outter<T,A>::inner<N>{
sz=N;
}
Task is to create an iterator for vector with range control.
For now im stuck in inner class template declaration and passing arguments. Please, i need advance if that possible. Thanks!

Answer 1

For the inner class, you have template <typename N>, which means that your N is a type, not a value, hence, you cannot assign it to a value.
To solve your issue, try having template <int N> class inner; and also fix the same way at the bottom template<typename T, typename A, int N>
Edit
Just noticed, that at the bottom you have the inner class definition. What you want this sz to be? is it a value or type? In case you want this to be a value, you should write
template<typename T,typename A, int N> // this last int determines also the type to be used down below v
class outter<T,A>::inner<N>{
int sz=N; // this int comes from the upper side ^
}
If you want the sz to be a type defining the sizes within the inner class, then keep the upper and bottom parts to be <..., typename N = int> and put using before sz=N;
template<typename T,typename A, typename N=int>
class outter<T,A>::inner<N>{
using sz=N;
}
If you want to have N type and value be specified through templates, please follow this example:
template </*outer template params*/>
class outer {
template <typename SIZE_TYPE, SIZE_TYPE VALUE = SIZE_TYPE()>
class inner;
};
template </*outer template params*/, typename SIZE_TYPE, SIZE_TYPE VALUE = SIZE_TYPE()>
class outer</*params*/>::inner<SIZE_TYPE, VALUE> {
using size_type = SIZE_TYPE;
size_type my_value = VALUE;
}
Edit 2
In case you want to understand what happens here, please read more about the template instantiation.