c++ "no appropriate default constructor available" error using template class data member

Question

I made a template class Grid(where i said in the header file that the default for T is float), i quoted a part of the source file:

#include"Grid.h"

template <class T>
Grid<T>::Grid(unsigned int rows=1, unsigned int columns=1)
:Rows(rows),Columns(columns)
{
reset();
}

template<class T>
Grid<T>::~Grid(){}

template <class T>
void Grid<T>::reset()
{
vector<T> vec(Rows * Columns,T());
matrix = vec;
}

And the other member functions can read/change a value of matrix or cout it.

Grid.h:

template<typename T=float> class Grid{

public:
        Grid(unsigned int, unsigned int);
        ~Grid();
        T getValue(unsigned int, unsigned int);
        void setValue(unsigned int, unsigned int, T);
        void reset();
        void write();

private:
        unsigned int Rows;
        unsigned int Columns;
        vector<T> matrix;
};

I found on the internet that in order to use a template class I needed to #include Grid.cpp as well as Grid.h, and doing this I can use the clas Grid and its member functions in my main(). I also put a preprocessor wrapper arround Grid.cpp.

Now, when I try to build a new class PDEProblem, without inheritance but using members from type Grid I get errors:

    Error   2   error C2512: 'Grid<>' : no appropriate default constructor available      c:\users\...  15  

    Error   3   error C2512: 'Grid<T>' : no appropriate default constructor available   c:\users\...    15  
4   IntelliSense: no default constructor exists for class "Grid<float>" c:\Users\...    15

PDEProblem.h:

#include"grid.h"
#include"grid.cpp"

class PDEProblem: Grid<>
{
public:
PDEProblem(unsigned int,unsigned int);
~PDEProblem();
//some more other data members

private:
Grid<char> gridFlags;
Grid<> grid;
unsigned int Rows;
unsigned int Columns;
void conPot(unsigned int, unsigned int);
void conFlag(unsigned int, unsigned int);
};

PDEProblem.cpp:

#include"grid.h"
#include"grid.cpp"
#include "PDEProblem.h"

PDEProblem::PDEProblem(unsigned int rows=1,unsigned int columns=1)
    :Rows(rows), Columns(columns)
{
    conPot(rows, columns);
    conFlag(rows,columns);
}

PDEProblem::~PDEProblem(){}

void PDEProblem::conPot(unsigned int rows, unsigned int columns)
{
    grid=Grid<>(rows,columns);
}

void PDEProblem::conFlag(unsigned int rows, unsigned int columns)
 {gridFlags=Grid<char>(rows,columns);
    // some stuff with a few if and for loops which sets some elements of gridFlags to 1 and the others to 0
}

How can I fix this? It seems to me that I have defaults for everything relevant? Thank you

Answer 1

With my compiler (Visual Studio 2010) and your code, I can make your error go away by moving the default parameter values from the function definition to the function prototype. Specifically:

Grid.h

template<typename T=float> class Grid{

public:
    Grid(unsigned int rows = 1, unsigned int columns = 1);
...
};

Grid.cpp

template <class T>
Grid<T>::Grid(unsigned int rows, unsigned int columns)
:Rows(rows),Columns(columns)
{
reset();
}