Programming Forums > Application Development > C++

-=PARADOX=- · Jan 22nd, 2006, 8:17 AM

Hi there,

I'm trying to make a linked list with templates

LinkedList.h

template <class Tipo>
class CLinkedList
{
	template <class Tipo>
	class No
	{
	public:
		const Tipo *p;
		No<Tipo> *next;
	};
	No<Tipo> *top;
	No<Tipo> *tail;
public:
	CLinkedList(void);
	virtual ~CLinkedList(void);
	virtual void add(const Tipo &);
	virtual bool remove(const Tipo &);
	virtual void showAll();
};

When I compile it it gives me the following errors:

(Toggle Plain Text)

error LNK2019: unresolved external symbol "public: virtual __thiscall CLinkedList<int>::~CLinkedList<int>(void)" (??1?$CLinkedList@H@@UAE@XZ) referenced in function _main

error LNK2019: unresolved external symbol "public: virtual void __thiscall CLinkedList<int>::showAll(void)" (?showAll@?$CLinkedList@H@@UAEXXZ) referenced in function _main

error LNK2019: unresolved external symbol "public: __thiscall CLinkedList<int>::CLinkedList<int>(void)" (??0?$CLinkedList@H@@QAE@XZ) referenced in function _main

Can someone help me with this?

thanks

-=PARADOX=- · Jan 22nd, 2006, 9:53 AM

Well, it seems that C++ doesn't like templates in modules...

I've copy the definition code of the .h to the .cpp and everything works fine!

Can someone tell me why?

Animatronic · Jan 22nd, 2006, 9:56 AM

Where are definitions for:

virtual ~CLinkedList(void);
virtual void add(const Tipo &);
virtual bool remove(const Tipo &);
virtual void showAll();

for most compilers template definitions need tobe available to every source file, so the function definitions should be present in the header file, either inside the class declaration or after.

Also are you sure you want to make them virtual, I cant see a reason to inherit off of the class.

No<Tipo> *top;
No<Tipo> *tail;

Shouldn't that be either head/tail or top/bottom

.

The second template <class Tipo> in your class declaration is redundant.

const Tipo *p;

Are you sure you want to make that const, it would mean that you could only ever get const access to your data inside your linklist. Also why make it a pointer that will mean an extra call to malloc/new on insert, when you could just have the object itself.

edit:
You need to place the code in the headers for most compilers because the compiler neesd to generate the complete code for the class, in that source file, when it meets a instantiation of a template.

-=PARADOX=- · Jan 22nd, 2006, 11:07 AM

Thanks for info

Jessehk · Jan 22nd, 2006, 1:10 PM

Maybe it was just me, but I was unsure about the winking smilie. I didn't know what you were trying to imply.

Maybe just use a smilie-face smilie to show appreciation (

).

Jan 22nd, 2006, 8:17 AM	#1
-=PARADOX=- Programmer Join Date: Oct 2005 Location: Portugal Posts: 53 Rep Power: 3	Linked List Hi there, I'm trying to make a linked list with templates LinkedList.h (Toggle Plain Text) template <class Tipo> class CLinkedList { template <class Tipo> class No { public: const Tipo p; No<Tipo> next; }; No<Tipo> top; No<Tipo> tail; public: CLinkedList(void); virtual ~CLinkedList(void); virtual void add(const Tipo &); virtual bool remove(const Tipo &); virtual void showAll(); }; template <class Tipo> class CLinkedList { template <class Tipo> class No { public: const Tipo p; No<Tipo> next; }; No<Tipo> top; No<Tipo> tail; public: CLinkedList(void); virtual ~CLinkedList(void); virtual void add(const Tipo &); virtual bool remove(const Tipo &); virtual void showAll(); }; When I compile it it gives me the following errors: (Toggle Plain Text) error LNK2019: unresolved external symbol "public: virtual __thiscall CLinkedList<int>::~CLinkedList<int>(void)" (??1?$CLinkedList@H@@UAE@XZ) referenced in function _main error LNK2019: unresolved external symbol "public: virtual void __thiscall CLinkedList<int>::showAll(void)" (?showAll@?$CLinkedList@H@@UAEXXZ) referenced in function _main error LNK2019: unresolved external symbol "public: __thiscall CLinkedList<int>::CLinkedList<int>(void)" (??0?$CLinkedList@H@@QAE@XZ) referenced in function _main error LNK2019: unresolved external symbol "public: virtual __thiscall CLinkedList<int>::~CLinkedList<int>(void)" (??1?$CLinkedList@H@@UAE@XZ) referenced in function _main error LNK2019: unresolved external symbol "public: virtual void __thiscall CLinkedList<int>::showAll(void)" (?showAll@?$CLinkedList@H@@UAEXXZ) referenced in function _main error LNK2019: unresolved external symbol "public: __thiscall CLinkedList<int>::CLinkedList<int>(void)" (??0?$CLinkedList@H@@QAE@XZ) referenced in function _main Can someone help me with this? thanks

Jan 22nd, 2006, 1:10 PM	#5
Jessehk The Oblivious One Join Date: May 2005 Location: Ontario, Canada Posts: 630 Rep Power: 4	Maybe it was just me, but I was unsure about the winking smilie. I didn't know what you were trying to imply. Maybe just use a smilie-face smilie to show appreciation ( ). __________________ Dr. Zoidberg: [ecstatic] I'm going to a movie... with FRIENDS!

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Jan 22nd, 2006, 9:53 AM	#2
-=PARADOX=- Programmer Join Date: Oct 2005 Location: Portugal Posts: 53 Rep Power: 3	Well, it seems that C++ doesn't like templates in modules... I've copy the definition code of the .h to the .cpp and everything works fine! Can someone tell me why?

Jan 22nd, 2006, 9:56 AM	#3
Animatronic Programmer Join Date: Jun 2005 Posts: 99 Rep Power: 4	Where are definitions for: virtual ~CLinkedList(void); virtual void add(const Tipo &); virtual bool remove(const Tipo &); virtual void showAll(); for most compilers template definitions need tobe available to every source file, so the function definitions should be present in the header file, either inside the class declaration or after. Also are you sure you want to make them virtual, I cant see a reason to inherit off of the class. No<Tipo> top; No<Tipo> tail; Shouldn't that be either head/tail or top/bottom . The second template <class Tipo> in your class declaration is redundant. const Tipo *p; Are you sure you want to make that const, it would mean that you could only ever get const access to your data inside your linklist. Also why make it a pointer that will mean an extra call to malloc/new on insert, when you could just have the object itself. edit: You need to place the code in the headers for most compilers because the compiler neesd to generate the complete code for the class, in that source file, when it meets a instantiation of a template.

Jan 22nd, 2006, 11:07 AM	#4
-=PARADOX=- Programmer Join Date: Oct 2005 Location: Portugal Posts: 53 Rep Power: 3	Thanks for info

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