#include <string.h> 
#include "stack.h" 


  Elem::Elem() : next(NULL),prev(NULL) {} 
  Elem::~Elem()
  {
    if(NULL != prev || NULL != next)
    {
       prev->next = next;
       next->prev = prev; 
    }
  }
  int Elem::make_tail(Elem& tail) 
  {
    int rv(1);
    if(NULL != next || NULL != tail.prev)
    {
      cout << "Trying to make a head tail relationship out of";
      cout << "inappropriate endpoints";
      rv = 0; 
    }
    else
    {
      prev = NULL;
      next = &tail;
      tail.prev = this;
      tail.next = NULL;
    }
    return(rv); 
 
  }

  Stack::Stack(int num): size(num),count(0),head(-1), tail(-1) 
  {
    array = new int[size];
  }
  Stack::~Stack()
  {
    delete[] array;
    cout <<"destructor called for a stack of size" << size << "\n";
  }

  //we may need to order the data here later, will check to see if 
  //it takes to long to decide this 
  int Stack::push(const int new_elem)
  {
    int rv(1);
    if(count == size)
    {
      cout <<"can't add to a full stack\n";
      rv = 0; 
    }
    else
    {
      int pos;
      pos =(tail + 1) % size;
      array[pos] = new_elem;
      tail = pos; 
      count++;
    }
    return(rv);
      
    
  }
  int Stack::pop() 
  {
    int rv(-1);

    if(0 == count)
    {
      cout <<"can't add to a full stack\n";
    } 
    else
    {
      rv = array[head];
      array[head] = -1; 
      head =(head + 1) % size;
      count--;
    }
    return(rv);
  }
  int Stack::is_in(const int& elem) 
  {
    int i = head;
    int rv(0);

    while(i != tail || 1 == rv)
    {
      if(elem == array[i])
        rv = 1; 
      else
        i = (i+1) % size;
    }
    return(rv);
  }