Message-Id:	<199810091044.MAA51812@ieva06.lanet.lv>
From:	"Andris Pavenis" <pavenis AT lanet DOT lv>
To:	djgpp AT delorie DOT com
Date:	Fri, 9 Oct 1998 12:49:35 +0300
MIME-Version:	1.0
Subject:	Re: Templates Problem
In-reply-to:	<007f01bdf31d$ffc147e0$ef6195cc@uic>
X-mailer:	Pegasus Mail for Win32 (v3.01b)
Reply-To:	djgpp AT delorie DOT com

From:           	"Andrew Deren" <aderen AT interaccess DOT com>
To:             	"DJGPP" <djgpp AT delorie DOT com>
Subject:        	Templates Problem
Date sent:      	Thu, 8 Oct 1998 19:44:39 -0500
Send reply to:  	djgpp AT delorie DOT com

> I have created a simple linked list template.
> However, compilation goes fine, but when linking
> I get errors:
> c:/djgpp/tmp/ccaaaaaa1.o(.text+0x24):test.cpp: undefined reference to
                       ^^^^^^^^^^^^^^
Looks that You are using either gcc-2.8.0 or early version of 
DJGPP port of gcc-2.8.1. I suggest downloading the latest update
of port of gcc-2.8.1 (begin of June):
	gcc281b.zip
	gpp281b.zip
      (and other files if You need them)

Earlier versions works OK under Win9X with LFN enabled but cause
problem when LFN is not available or is disabled (LFN=N) as names
of temporary files gets truncated. Therefore this problem were not
noticed immediatelly.

> `List<int>::List(void)'
> c:/djgpp/tmp/ccaaaaaa1.o(.text+0x34):test.cpp: undefined reference to
> `List<int>::add(int *)'
> 
> I hope nobody minds posting the source here.
> Can anyone help me with that, please.
> Thank you.
> 
> ///////////////////////////////////////////////////////////////
> // FILE: list.h
> ///////////////////////////////////////////////////////////////
> #ifndef __LIST_H
> #define __LIST_H
> 
> // a single node
> template <class ListType>
> class Node
> {
>  Node(void):next(NULL), prev(NULL), elem(NULL) {}
> 
>  Node<ListType>* next;
>  Node<ListType>* prev;
>  ListType* elem;
> };
> 
> template <class ListType>
> class List
> {
> public:
>  List(void);
>  ~List(void);
> 
>  bool add(ListType* new_elem);
> 
>  int get_count(void) const { return count;}
> 
>  // sets the current to head, call get_next to start getting elements
>  void start_loop(void) {current = head;}
> 
>  // get current element and advance current to next.
>  // if there are no more element null is returned
>  ListType* get_next(void);
> 
>  // removes all the links and elements that those
>  // links refer to
>  void delete_elements(void);
> 
>  // get a value at index (1 is the first one)
>  ListType* get_at(int index);
> 
> protected:
>  int count;
> 
>  Node<ListType> *head;
>  Node<ListType> *tail;
>  Node<ListType> *current;
> };
> 
> 
> #endif // __LIST_H
> 
> ///////////////////////////////////////////////////////////////
> // FILE: list.cpp
> ///////////////////////////////////////////////////////////////
> template <class ListType>
> List<ListType>::List(void)
> :head(NULL), tail(NULL), current(NULL), count(0)
> {
> 
> }
> 
> // remove all links (does not remove instances of
> // the classes that are contained in the list.
> // Use delete_elements to do that
> template <class ListType>
> List<ListType>::~List(void)
> {
>  // delete all links
>  while (head) {
>   current = head->next;
>   delete head;
>   head = current;
>  }
> }
> 
> template <class ListType>
> bool List<ListType>::add(ListType* new_elem)
> {
>  tail->next = new Node<ListType>();
> 
>  if (!tail->next)
>   return false;
> 
>  tail = tail->next;
>  tail->elem = new_elem;
> 
>  count++;
> 
>  return true;
> }
> 
> template <class ListType>
> void List<ListType>::delete_elements(void)
> {
>  // delete all links
>  while (head) {
>   current = head->next;
>   delete head->elem;
>   delete head;
>   head = current;
>  }
>  head = tail = current = NULL;
>  count = 0;
> }
> 
> // get current element and advance current to next.
> // if there are no more element null is returned
> template <class ListType>
> ListType* List<ListType>::get_next(void)
> {
>  ListType* temp = NULL;
> 
>  if (current) {
>   temp = current->elem;
>   current = current->next;
>  }
> 
>  return temp;
> }
> 
> 
> // get a value at index (1 is the first one)
> template <class ListType>
> ListType* List<ListType>::get_at(int index)
> {
>  int i = 1;
> 
>  Node<ListType>* temp = head;
> 
>  while (temp) {
>   if (i == index)
>    return temp->elem;
> 
>   i++;
>   temp = temp->next;
>  }
> 
>  // could not find a selection at index (out of range)
>  return NULL;
> }
> 
> ///////////////////////////////////////////////////////////////
> // FILE: test.cpp (just for testing)
> ///////////////////////////////////////////////////////////////
> 
> #include <stdio.h>
> #include "list.h"
> 
> 
> int main(int argc, char** argv)
> {
>  int test1 = 3;
>  int test2 = 5;
>  int test3 = 7;
> 
>  List<int> list;
> 
>    list.add(&test1);
>    list.add(&test2);
>    list.add(&test3);
> 
>    list.start_loop();
> 
>    int *temp;
> 
>    while ((temp = list.get_next()) != NULL) {
>     printf("%d ", *temp);
>    }
> 
>    return 0;
> }
> 
> ///////////////////////////////////////////////////////////////
> 
> 
> 
> 

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