unresolved external symbol

drorharush (2)
I have written a code and there is an error witch I could not fix.

The code:

triangle.h 
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#include <iostream>
using namespace std;
template<typename T>
class triangle
{
	T side1,side2,side3 ;
   public:
        triangle() {}
        triangle(T x,T y,T z):side1(x),side2(y),side3(z) {}
        bool valid();
        friend ostream& operator<< (ostream& ostr, const triangle<T>& t);
};


triangle.cpp
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#include "triangle.h"
#include <iostream>
using namespace std;
template<class T>
bool triangle<T>::valid()
{
	if(!(first>0 && second>0 && third>0))
		return false;
	if(third + second > first)
		return false;
	if(third + first > second)
		return false;
	if(first + second > third)
		return false
	return true;
}
template <typename T>
ostream& operator<< (ostream& ostr, const triangle<T>& t)
{		
   ostr<<'('<<t.side1<<','<<t.side2<<','<<t.side3<<')';
   return ostr;
}

main.cpp 
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#include "triangle.h"
#include <stdlib.h>
using namespace std;

void main()
{ 
	triangle<int> t(5,2,3);
	cout << t;

	system("PAUSE");
}


The error 
 
 
main.obj : error LNK2019: unresolved external symbol "class std::basic_ostream<char,struct std::char_traits<char> > & __cdecl operator<<(class std::basic_ostream<char,struct std::char_traits<char> > &,class triangle<int> const &)" (??6@YAAAV?$basic_ostream@DU?$char_traits@D@std@@@std@@AAV01@ABV?$triangle@H@@@Z) referenced in function _main


I have been trying to solve this for about a week now, no luck.
Any takers?
Last edited on
Disch (13742)
template function bodies cannot be defined in a separate cpp file. You must put them in the header file.


Get rid of triangle.cpp and put that in triangle.h


EDIT:
there is an error witch


Beware of those error witches. Their dark magic is very deadly!

</wiseguy>
Last edited on
closed account (zb0S216C)
Disch wrote:
"template function bodies cannot be defined in a separate cpp file. You must put them in the header file."

True. However, explicitly instantiated templates are allowed, because they are complete types.

Header:
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template <typename T>
struct Structure
{
    Structure(T const &Init = T());
    T Member;
};

Source:

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template struct Structure<int>; // Explicit Instantiation

template <>
Structure<int>::Structure(int const &Init)
    : Member(Init)
{ }

Wazzak
drorharush (2)
Thank you Disch and Framework. It has solved the problem! Like dark magic!
Disch (13742)
Yes @ Framework. I was just trying to keep my response simple =P
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