Linked List Operations

[dudicus14]

So I've got a linked list data base using templates which compiles fine and lets me print out a list of all states and lets me search for a person and print all that persons data(since these methods work, I left them out below to save space) Below I have find_state, print_person, and print_people_in_state methods, what I need them to collectively be able to do is to (given a user input of state) print out the info on all the people from that particular state. However right now when I run it, nothing happens. How can I fix this. Any help would be appreciated. Thanks

-if you want to run the code yourself here is a link to the file that i named data.txt (http://rabbit.eng.miami.edu/class/een118/labs/152/dbfile1.txt)

#include <iostream>
#include <string>
#include <string.h>
#include <fstream>
using namespace std;


struct person
{
    int dob,ss_number;
    string fname, lname,state;
    
    person()
    { }
    person(int a, int b, string c, string d, string e)
    {dob=a; ss_number=b; fname=c; lname=d; state=e;}
};


struct state
{
    string sname;
    person*P;
    
    
    state()
    {}
    state(string a)
    {sname=a;}
};

template<typename T>struct Link
{
    T*data;
    Link*extradata;
    Link*next;
    
    Link()
    {}
    Link(T*a,Link<T>*C=NULL)
    {
        data=a;
        next=C;
        
    }
    
};
template<typename T>
struct List
{int length;
    Link<T>*Head,*tail;
    List(Link<T>*h=NULL, Link<T>*t=NULL)
    {
        Head=h;
        tail=t;
        length=0;
    }
    
    void add(T*object)
    {
        {   if (Head == NULL && tail == NULL)
        {   Link<T> * newlink = new Link<T>(object);
            Head = newlink;
            tail = Head;  }
        else
        {   Link<T> * newlink = new Link<T>(object);
            tail->next = newlink;
            tail=newlink;} }
    }
void print_people_in_state(string search)
{

   Link<state>*temp=Head;
   if(temp!==NULL)
       {
          if(temp->data->P->state==search)
             {
               cout<<temp->data->P->fname<<endl;
              }
       //  temp=temp->next;
}}




};
List<person>*person_from_file(string file)//reads file and creates linked list of people
{
    List<person>* newlist=new List<person>();
    //        Link<T> * head=NULL;
    //        Link<T> * temp=NULL;
    ifstream fin;
    fin.open("data.txt");
    if (fin.fail())
        cout<<"file not found\n";
    if (!fin.fail())
    {
        while(true)
        {
            int a,b;
            string c,d,e;
            fin>>a>>b>>c>>d>>e;
            if (fin.fail())break;
            person * p=new person(a,b,c,d,e);
            newlist->add(p);
            
            
        }
    }
    else
        cout<<"Can't open file";
    fin.close();
    return newlist;
}
List<state>*state_from_file(string file)//reads file and creates linked list of states
{
    List<state>* newlist=new List<state>();
    //        Link<T> * head=NULL;
    //        Link<T> * temp=NULL;
    ifstream fin;
    fin.open("data.txt");
    if (fin.fail())
        cout<<"file not found\n";
    if (!fin.fail())
    {
        while(true)
        {
            int a,b;
            string c,d,e;
            fin>>a>>b>>c>>d>>e;
            if (fin.fail())break;
            state * s=new state(e);
            newlist->add(s);
            
            
        }
    }
    else
        cout<<"Can't open file";
    fin.close();
    return newlist;
}

int main()
{List<person>*A = person_from_file("data.txt");
 List<state> *B= state_from_file("data.txt");
   
  
    
       B->print_people_in_state("TX");
    
    
    
    return 0;
}

[LB]

Those functions should not exist. What if your linked list template was instantiated with T == double? Would it make sense to search a list of numbers for a specific state, or print the people in the numbers? The point of generic programming is that you should not be concerned with the objects you are dealing with.

[dudicus14]

Sorry I accidentally uploaded my old code. I just changed it to where it's only one function. However it still doesnt work. It compiles but gets a seg fault

[LB]

I still see "print_people_in_state" inside your template class. As I said, this is wrong. It would be fine as a free function (that is, not a member of the class).