Question

If I put this code in a .cpp file and run it, it runs just fine:

#include <iostream>
#include <vector>
#include <string>


using namespace std;

typedef vector<int> row;
typedef vector<row> myMatrix;

void main()
{
    //cout << endl << "test" << endl;
    myMatrix mat(2,2);

    mat[0][1] = 2;

    cout << endl << mat[0][1] << endl;
}

But, if I make a .h and a .cpp file with the .h file like this, it gives me boatloads of errors.

#ifndef _grid_
#define _grid_

#include<iostream>
#include<vector>
#include<string>

using namespace std;

typedef vector<int> row;
typedef vector<row> myMatrix;

class grid
{
    public:

        grid();

        ~grid();

        int getElement(unsigned int ri, unsigned int ci);

        bool setElement(unsigned int ri, unsigned int ci, unsigned int value);


    private:

        myMatrix sudoku_(9,9);
};

#endif

These are some of the errors I get:

warning C4091: 'typedef ' : ignored on left of 'int' when no variable is declared
error C4430: missing type specifier - int assumed. Note: C++ does not support default-int

Answer 1

You need to qualify vector as std::vector.

It works in the .cpp file because you use using namespace std; (do not use using namespace in a header file).

Furthermore, your declaration of the member variable is incorrect. It should just be:

myMatrix sudoku_;

If you want to set its dimensions, you need to do so in the constructor.