How to initialize a vector in the constructor of a class

How could I initialize a two dimensional vector in the contstructor of a class with zero values? This won't work:

#include <vector>
using namespace std;

class matrix {
 public:
  typed开发者_JS百科ef int element_type;
  matrix(int dim):data(dim, vector<int>(dim, 0)) {
  }
 private:
  vector<vector<element_type>> data;
};

Do I have to write a destructor to free the vector?

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Update: OP's code is now valid from C++11 onward.

Original answer for earlier versions of C++:

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You need to write it like this:

vector< vector<element_type> > data;

because >> is otherwise parsed as stream operator, which is invalid here. And: No, you do not need to free this in the destructor, because you aren't creating it on the heap.

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Do I have to write a destructor to free the vector?

No, because you did not acquire any resources in the constructor. That's the beauty of RAII.