Two parameter template acting differently from one parameter in call - c++

Question

For an assignment (this is a fairly small part I've been stuck on, I'm not asking for anyone to do the homework), we were supplied with the following code and its call in the main file:
template <class number_type>
class Point {
public:
Point(const number_type& x_, const number_type& y_) : x(x_),y(y_) {}
// REPRESENTATION
number_type x;
number_type y;
};
template <class number_type, class label_type>
class QuadTree {
public:
QuadTree(const number_type& number_, const label_type& label_) : number(number_), label(label_){}
number_type number;
label_type label;
};
int main() {
std::vector< std::pair<Point<int>,char> > simple_points;
QuadTree<int,char> simple;
}
However, using a very similar style to the supplied coding produces a "no matching function" error in my terminal:
I'm confused as to why it doesnt work in this case, as well as what I can do to fix it.
As a note, we are not allowed to use c++11, structs, and a few other tools. Also, we are not permitted to change anything in the "main" function, so QuadTree simple; MUST stay as-is
main.cpp: In function ‘void simple_test()’:
main.cpp:110:22: error: no matching function for call to ‘QuadTree<int, char>::QuadTree()’
QuadTree<int,char> simple;
^
main.cpp:110:22: note: candidates are:
In file included from main.cpp:14:0:
quad_tree.h:56:5: note: QuadTree<number_type, label_type>::QuadTree(const number_type&, const label_type&) [with number_type = int; label_type = char]
QuadTree(const number_type& number_, const label_type& label_) : number(number_), label(label_){}
^
quad_tree.h:56:5: note: candidate expects 2 arguments, 0 provided
quad_tree.h:54:7: note: QuadTree<int, char>::QuadTree(const QuadTree<int, char>&)
class QuadTree {
^
quad_tree.h:54:7: note: candidate expects 1 argument, 0 provided

Answer 1

This code:
QuadTree<int,char> simple;
is attempting to call the default constructor. However, since you provide a constructor, the default constructor is implicitly deleted. The constructor you provided is:
QuadTree(const number_type& number_, const label_type& label_)
So you'd have to do:
QuadTree<int, char> simple(42, 'C');

Answer 2

Your QuadTree constructor takes 2 parameters, but you probably (based on your error message) have a definition like
QuadTree<int,char> simple;
which declares an object with no parameters passed to the constructor. You need to do something like
QuadTree<int, char> simple(2, 'a'); // need to specify the parameters
Note that because you defined a constructor, the compiler does not generate a default one for you anymore.