i have the fallowing class of object with a class a data structure which i use in main combined. The ADT(abstract data type) is a linked list. After i read from file the input data and create and object which at print looks just fine after a print. after i push_back() the 3-rd int variable get initializated to 0. So example and code: Example: ex.in:

1 7 31
2 2 2
3 3 3

now i create objects from each line, which at print look as they suppose, but after push_back():

1 7 0
2 2 0
3 3 0

Class.h:

class RAngle
{
private:
    int x,y,l,b;            
public:
    int solution,prec;
    RAngle(){
        x = y = solution = prec = b = l =0;
    }

    RAngle(int i,int j,int k){
        x = i;
        y = j;
        l = k;
        solution = 0; prec=0; b=0;
    }
    friend ostream& operator << (ostream& out, const RAngle& ra){
    out << ra.x << " " << ra.y << " " << ra.l <<endl;
    return out;
}

friend istream& operator >>( istream& is, RAngle& ra){
    is >> ra.x;
    is >> ra.y;
    is >> ra.l;
    return is ;
}
};

ADT.h:

template <class T>
class List
{
private:
    struct Elem
    {
        T data;
        Elem* next;
    };

    Elem* first;

    T pop_front(){
    if (first!=NULL)
    {
        T aux = first->data;
        first = first->next;
        return aux;
    }

    T a;
    return a;
}


    void push_back(T data){
    Elem *n = new Elem;
    n->data = data;
    n->next = NULL;
    if (first == NULL)
    {
        first = n;
        return ;
    }
    Elem *current;
    for(current=first;current->next != NULL;current=current->next);
    current->next = n;
}

Main.cpp(after i call this function in main which prints object as they suppose to be the x var(from RAngle class) changes to 0 in all cases.)

void readData(List <RAngle> &l){
    RAngle r;
    ifstream f_in;
f_in.open("ex.in",ios::in);

for(int i=0;i<10;++i){
    f_in >> r;
    cout << r;
    l.push_back(r);

}