Matrix operation, constructor problem

I would like to put another question about matrix operations...

template <typename T>
struct TMatrix
{
    typedef std::vector < std::vector <T> > Type;
};


template <typename T>
class Mat开发者_运维技巧rix
{
    private:
            typename TMatrix <T>::Type items;       
            const unsigned int rows_count;          
            const unsigned int columns_count;   

    public:
             template <typename U>
             //Error, see bellow please
             Matrix ( const Matrix <U> &M ): 
                  rows_count ( M.getRowsCount() ), columns_count ( M.getColumnsCount() ), items ( M.getItems()){} 
             unsigned int getRowsCount() const {return rows_count;}
             unsigned int getColumnsCount() const {return columns_count;}
             typename TMatrix <T>::Type const & getItems () const {return items;}
             typename TMatrix <T>::Type & getItems ()  {return items;}  

Compiling the code, the compiler stops here:

Matrix ( const Matrix <U> &M ):  
      rows_count ( M.getRowsCount() ), columns_count ( M.getColumnsCount() ), items ( M.getItems()){}  //Error

and shows the following error:

Error   79  error C2664: 'std::vector<_Ty>::vector(const std::allocator<_Ty> &)' : cannot convert parameter 1 from 'const std::vector<_Ty>' to 'const std::allocator<_Ty> &'

But I do not know, why... Thanks again for your help...

Updated question:

Compiling the code

template <class T>
template <typename U>
Matrix <T> :: Matrix ( const Matrix <U> &M )
: rows_count ( M.getRowsCount() ), columns_count ( M.getColumnsCount() ), items ( M.getItems().begin(), M.getItems().end()){}

with the following result:

Error   132 error C2664: 'std::vector<_Ty>::vector(const std::allocator<_Ty> &)' : 
cannot convert parameter 1 from 'const std::vector<_Ty>' to 'const std::allocator<_Ty> &'
c:\program files\microsoft visual studio 10.0\vc\include\xmemory    208

---

Your templated constructor Matrix<T>::Matrix<U>(const Matrix<U> &M) is designed to construct a Matrix<T> given a Matrix<U>. It does this by invoking the constructor vector<vector<T>>(vector<vector<U>>) in the initializer list.

The problem is that std::vector does not provide a mixed-type constructor.

I don't know how to solve this in the initializer list. You might do it in the body of the constructor. Here are updates to your public interface to allow this:

Matrix() : rows_count(), columns_count(), items() {}
template <typename U>
Matrix ( const Matrix <U> M ):
    rows_count ( M.getRowsCount() ), columns_count ( M.getColumnsCount() ), items ( ) {
    for(int i = 0; i < M.getItems().size(); i++) {
        items.push_back(std::vector<T>(M.getItems()[i].begin(),M.getItems()[i].end()));
    }
}

---

You forgot to #include <vector> at the top and a }; at the end of the file. When I add these to the code, it compiles just fine on my computer.