Thread: LNK error, unresolved external...

Ok, first problem taken care of, but why these errors? They go away if I inline the functions in the header file. Thanks for any help.
Header file

Code:

#include <iostream>
using namespace std;
template <class T>
class Array  
{
public:
	Array(int = 10);
	virtual ~Array() {delete [] ptr;}
	T &operator[](int);
	int getSize() const {return size;}

private:
	T *ptr;
	int size;
};

Implementation

Code:

#include <iostream>
#include <cassert>

using namespace std;

#include "t_Array.h"

//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////

template<class T>
Array<T>::Array(int arraySize)
{
	size = (arraySize > 1 ? arraySize : 10);
	ptr = new T[size] = {0};
	assert(ptr != 0);
	cout << "This is the class template version" << endl;
}

template<class T>
T &Array<T>::operator[](int subscript)
{
	assert(1 <= subscript && subscript < size);
	return ptr[subscript];
}

Driver

Code:

#include <iostream>
using namespace std;
#include "t_Array.h"

int main()
{
	Array<double> tArray(15);

	for (int i = 0; i < tArray.getSize(); i ++)
	{
		tArray[i] = i + 0.5;
		cout << tArray[i] << endl;
	}
	return 0;
}

Errors

Code:

Compiling...
t_Array.cpp
Linking...
TempArray.obj : error LNK2001: unresolved external symbol "public: double & __thiscall Array<double>::operator[](int)" (??A?$Array@N@@QAEAANH@Z)
TempArray.obj : error LNK2001: unresolved external symbol "public: __thiscall Array<double>::Array<double>(int)" (??0?$Array@N@@QAE@H@Z)
Debug/TempArray.exe : fatal error LNK1120: 2 unresolved externals
Error executing link.exe.

TempArray.exe - 3 error(s), 0 warning(s)