Question

#ifndef SLIST_H
#define SLIST_H
#include "llist.h"

using namespace std;

class slist:public llist{

 public:
  slist();
  int search(el_t Key);
  void replace(el_t Elem, int I);
};
#endif

That is my new class I just made that gives me the search and replace function, on top of all the inherited functions contained in llist.h

In my main…

#include "slist.h"
#include <iostream>

using namespace std;

int main(){
  slist list;
  list.addFront(4);
  cout<<list.search(4);
}

I’m trying to call addfront() which is a public function in the llist class. Then I want to call search() which is an inherited public function of the slist class. g++ gives me a few errors that I don’t understand.

slist.h: In function âint main()â:
slist.h:10: error: âslist::slist()â is protected
main.cpp:7: error: within this context

slist() is protected? Why’s that? I put it under public:

Also whats up with the this context, I’m guessing I’m just doing the whole inheritance thing totally wrong. Any help would be appreciated!

Edit: Here’s the llist class, if it helps

#ifndef LIST_H
#define LIST_H
#include <iostream>
using namespace std;

class llist{
 protected:

   typedef int el_t;
   el_t total;

  struct Node{
    int Elem;
    Node *Next;
  };

  Node *Front;
  Node *Rear;
  Node * Curr;

public:
 class Overflow{};
 class Underflow{};
 class Range{};
 llist();
 ~llist();
 bool isEmpty();
 void displayAll();
 void addRear(el_t NewNum);
 void deleteFront(el_t& OldNum);
 void addFront(el_t NewNum);
 void deleteRear(el_t& OldNum);
 void deleteIth(int I, el_t& OldNum);
 void addbeforeIth(int I, el_t newNum);
 class Overflow;

};
#endif

This is llist.cpp with only the relevant functions pasted

#include "llist.h"
#include <iostream>

using namespace std;
int total=0;

llist::llist(){
    Front=NULL;
    Rear=NULL;
    total=0;
}

llist::~llist(){
  while(Front!=NULL){
    int z;
    deleteFront(z);
  }
}
bool llist::isEmpty(){
if(Front==NULL){
  return true;
}
return false;
}
void llist::displayAll(){
 Curr=Front;
 if(isEmpty()){
   cout<<"[ empty ]"<<endl;
 }else{
  while(Curr!=NULL){\
    cout<<"curr != NuL"<<endl;
    cout<<Curr->Elem<<endl;
    Curr=Curr->Next;
  }
 }
 }



void llist::addFront(el_t NewNum){
    if(isEmpty()){
       Node *x=new Node;
       x->Next=Front;
       Rear=Front;
       Front=x;
       Front->Elem=NewNum;
        }else{
      Node *x=new Node;
      x->Next=Front;
      Front=x;
      Front->Elem=NewNum;
      ++total;
  }
  }

Answer 1

I honestly can’t see the problem but not every compiler is standard-compliant, so I would try the following:

1) Rename your class – if it works, that means it’s a because of a naming conflict.

2) Remove the using directives.

3) Remove the inheritance. If it works after this… you really need to change compilers.

4) Try #undef public before your class declaration. If it works after this… well, someone’s in for a talk with the manager.

5) Pray…