Hi all! I just wanted to code a template class and got the following problem: Writing this in a header file work without problems:

template<class T>
class VectorArray
{
public:
	T& operator [] (unsigned int index)
	{
		return T();
	}
};

But writing this in a header file

template<class T>
class VectorArray
{
public:
	T& operator [] (unsigned int index);
};

And this in a cpp file

template<class T>
T& VectorArray<T>::operator [] (unsigned int index);
{
	return T();
}

will give me a linking error if I call operator []: unresolved external symbol "public: int & __thiscall VectorArray::operator[](unsigned int)" I''m using MS Visual Studio .NET 2002. Thanks for every help -------------------------------------------------------- "If it looks good, it is good computer graphics" "If it looks like computer graphics, it is bad computer graphics" Corrail corrail@gmx.at ICQ#59184081

Just off the top of my head, you have a '';'' in the cpp file where it doesn''t need to be.

Change:
T& VectorArray::operator [] (unsigned int index);

to:
T& VectorArray::operator [] (unsigned int index)

and that should help.

Sorry my fault:

In my cpp file there is (without ; ):

template<class T>T& VectorArray<T>::operator [] (unsigned int index){    return T();}

--------------------------------------------------------

"If it looks good, it is good computer graphics"
"If it looks like computer graphics, it is bad computer graphics"

Corrail
corrail@gmx.at
ICQ#59184081

[edited by - Corrail on December 14, 2003 12:49:12 PM]

You can''t seperate declaration from definition with templates. Write the full implementation in the header.

Oh, didn''t know that!
Thanks a lot!

--------------------------------------------------------

"If it looks good, it is good computer graphics"
"If it looks like computer graphics, it is bad computer graphics"

Corrail
corrail@gmx.at
ICQ#59184081

Yup, what he said... I had the same problem writing all my templated functions, I had to move all code into the .h file and it all works fine now.

--- Edit ---
Just wanted to mention, I beleive other compilers allow you to do the .h/.cpp with templates without issue, but I use vc 6.0, and it only works with the implementation in the header. I beleive in .NET this is fixed, but since I don't use it, no promises that it's fixed .

[edited by - Ready4Dis on December 14, 2003 12:08:44 PM]

quote:

---

Original post by Ready4Dis
Just wanted to mention, I beleive other compilers allow you to do the .h/.cpp with templates without issue, but I use vc 6.0, and it only works with the implementation in the header. I beleive in .NET this is fixed, but since I don''t use it, no promises that it''s fixed .

---

IIRC, the export keyword should allow you to seperate prototypes and implementation like that, but there are very few compilers that support it. Certainly no version of VC++ or GCC does.

Yeah, but it''s crappy too to have to write all the code in the header. One solution is to write the implementation in a .INL file and include it in the header (which is a little more intuitive than writing it in a CPP file and excluding it from the build, and certainly nicer than writing everything in one file, even if it requires an all-dependency rebuild after any modification).

Later,
ZE.

//email me.//zealouselixir software.//msdn.//n00biez.//
miscellaneous links

As a side note, VS.NET (2002) still has the issue.

quote:

---

Original post by sbennett
IIRC, the <code>export</code> keyword should allow you to seperate prototypes and implementation like that, but there are very few compilers that support it. Certainly no version of VC++ or GCC does.

---

The current GCC supports separate linking of template implementations in cpp files, although I''m not exactly sure how to activate that behaviour. It also comes with some negative side effects.