Templatise a class over itself?

[TheDestroyer]

Hello guys :),

Is this ever possible? I need it, but not so sure it would be supported in C++. I have inside my class a container for the class itself I'm creating. But I want to be free in choosing the container type using templates:

class MyClass
{
    vector<myClass> myVec;
    //rest removed for brevity
};

So I want to have the freedom of choosing the container to be a vector, deque, list, queue, or any other STL container using templates. Is that possible? is there a trick to do it?

Thank you for any efforts :)

[tition]

The code you gave compiles as a charm on my system (gcc with code::blocks on ubuntu), and seems to work just fine (but please be careful with doing stuff such as

MyClass x;
x.myVec.push_back(x);

Can you explain what is the purpose of this class?

[zwA4jE8b]

#include <iostream>
#include <vector>
#include <list>

template <class dtype>
class one
{
public:
	one(){two = new dtype;}
	dtype* two;
};

int main()
{
	one<std::vector<int>> a;
	a.two->push_back(5);

	one<std::list<float>> b;
	b.two->push_back(4);

	std::cout << a.two->front() << " " << b.two->front();
	std::cin.get();
	return 0;
}

#include <iostream>
#include <vector>
#include <list>

template <class dtype>
class one
{
public:
	one(){}
	dtype two;
};

int main()
{
	one<std::vector<int>> a;
	a.two.push_back(5);

	one<std::list<float>> b;
	b.two.push_back(4);

	std::cout << a.two.front() << " " << b.two.front();
	std::cin.get();
	return 0;
}

[tition]

#include<iostream>
#include<vector>

class Weirdclass
{
  public:
  std::vector<Weirdclass> x;
  void printMe(int recDepth)
  { std::cout << "\n";
    for (int j=0; j<recDepth; j++)
        std::cout << "\t";
    std::cout << "I am nested in depth " << recDepth << "; My size is: " <<  this->x.size() << " My elements are: ";
    for (unsigned int i=0; i<this->x.size(); i++)
      this->x[i].printMe(recDepth+1);
  }
};

int main()
{ Weirdclass A;
  for (int i=0; i<5; i++)
    A.x.push_back(A);
  A.printMe(0);
  int i;
  std::cin >> i;

  return 0;
}

[zwA4jE8b]

this also might help

http://cplusplus.com/doc/tutorial/templates/

[TheDestroyer]

Thank you for your fast answer.

But the code I wrote isn't what I'm looking for. I want to yet "templatise" over my container. So I expect something like:

template<T>
class MyClass
{
    T<myClass> myVec;
    //rest removed for brevity
};

int main()
{
    MyClass<vector> x;
    MyClass<deque> y;
    MyClass<list> z;
    x.myVec.push_back(x);
    y.myVec.push_front(y);
    z.myVec.insert(z,...);
}

It looks stupid what I wrote, for sure. Because vector is not a class, but vector<double> is a class. I just wrote it that way to explain what I'm looking for.

Any ideas? :-)

Correction: code at list corrected

[TheDestroyer]

If this is impossible to be done, please let me know!

[tition]

It does look impossible to me... what about simply calling the template class in a different manner?

#include<iostream>
#include<vector>

template <class T>
class Weirdclass
{
  public:
  T a;
};


int main()
{ Weirdclass<std::vector<Weirdclass<std::vector<int> > > > x;

  return 0;
}

[TheDestroyer]

Thank you for your answer.

Not really... having ever an int inside isn't a good idea! sorry!

I need it to be of the same class! and as you have noticed, it appears to be an infinite series of template calls!

any other ideas?

[LB]

@tition's original post: what is wrong with that code? It won't lead to recursion if that's what you think.

And yes it is impossible unless you get clever with C++11's variadic template parameters ;)

[TheDestroyer]

Thank you for your reply, L B.

But how do you think variadic templates parameters could help? I see the main problem here is the infinite recursions of template definitions required, or in other words the circular template defition that never ends!

container -> needs MyClass type
MyClass -> needs container type

I don't see how variadic template parameters could help. Please explain!!!!

[LB]

If you can give a template parameter of the depth you can recurs to the point of your choosing.

[TheDestroyer]

The depth is unlimited. How can I give such a parameter?