Управление не переходит в конструктор односвязного списка

#include <iostream>
 
using namespace std;
 
struct Single_node
{
Single_node *next;
int val;
Single_node(){}
Single_node(int x)
{
val= x;
}
Single_node(int x, Single_node *y)
{
val = x;
next = y;
}
};
 
class Single_list
{
    Single_node *head;
    Single_node *tail;
public:
Single_list()
{
head = new Single_node;
tail = head;
}
 
Single_list(int);
 
~Single_list();
 
bool is_empty()
{
return head == tail;
}
 
void add_front(int new_node)
{
head = new Single_node(new_node,head);
}
 
int remove_front();
 
bool find(int);
 
int get_nth(int);
 
int size();
};
 
void print_slist(Single_list& ref)
{
int n = ref.size();
for(int i = 0; i<n; i++)
cout<<ref.get_nth(i)<<" ";
cout<<endl;
}
 
int main()
{
Single_list list;
for(int i = 0; i<5; i++)
{
list.add_front(i);
print_slist(list);
}
while(!list.is_empty())
{
print_slist(list);
list.remove_front();
}
system("pause");
return 0;
}
//------------------------
Single_list::Single_list(int x)
{
    tail = new Single_node;
    head = new Single_node(x);
    head->next = tail;
}
 
Single_list::~Single_list()
{
    while(head != tail)
    {
    Single_node *temp;
    temp = head->next;
    delete head;
    head = temp;
    }
    delete head;
}
 
int Single_list::remove_front()
{
    int temp_val = head->val;
    Single_node *temp_p = head;
    head = head->next;
    delete temp_p;
    return temp_val;
}
 
bool Single_list::find(int we_need)
{
    Single_node *current = head;
    while (current != tail)
    if(current->val == we_need)
    return true;
    else current = current->next;
    return false;
}
 
int Single_list::get_nth(int n)
{
    Single_node *current = head;
    for(int i = 0; i<n; i++)
    current = current->next;
    return current->val;
}
 
int Single_list::size()
{
    Single_node *current = head;
    int sz = 0;
    while(current != tail)
    {
        current = current->next;
        sz++;
    }
    return sz;
}