Class definition

[Ramzi89]

Can anyone help me find whats wrong with this class definition looks fine to me

class Cohort
{ public:
	Cohort();
	void insert(Student x);
  private:
 	 vector <string> names;
 	 vector <vector<int> >marks(3, vector <int>());
};

[Moschops]

vector <vector<int> >marks(3, vector <int>());

What's that 3 doing there?

[Ramzi89]

trying to initiate a 2d vector so that there will be 3 empty vectors in which future adresses will correspond? I thought the 3 would do this?

[Peter87]

If you are using C++11 you can do this if you use { } syntax (what is it called?)
vector <vector<int> >marks{3, vector <int>()};

otherwise you have to initialize everything in the constructor

[Ramzi89]

cool safe. X

[bbgst]

What's the matter with the 3? It constructs a vector of vector of ints with 3 elements. The only useless statements is the second argument, which is the same as the default argument, T().

http://cplusplus.com/reference/stl/vector/vector/

(And it's called an initializer list constructor)

[Moschops]

(And it's called an initializer list constructor)

(Which cannot be done in the class definition.)

[bbgst]

Yes, none will work. marks has to be initialized on the constructor. But you can move the expression to the constructor as it is:

Cohort::Cohort()
	: marks(3, vector<int>()) // use vector<int>() if you want, but it's not necessary
{
	// ..
}