// CSCI 2720			Data Structures			     Spring 2004
//
// 				 PtrToPtrToNode
//
// Contains sample code for a private helper insert function which is part of an
// ordered linked list of integers, in order to illustrate the use of the 
// Node** type.  This is close in spirit to the "locative" data type used by
// Lewis and Denenberg in their text. 

// ----------- one function implementation from the ***.cc file below ---------- 

// iterative insert  --  private
int OrdList::Insert(int new_value, Node * &T) {

  Node **P = &T;              // start by pointing to the input pointer

  while ( *P && new_value < (*P)->Value)  // advance along list 
    P = &((*P)->Next);

  if ( *P && new_value == (*P)->Value)  // new_value already in list  
    return 0;

  (*P) = new Node(new_value, *P);  // insert new_value into the list,
			           // locating it in a new Node		

  if ( !(*P) )
    error("out of space for Insert");  // defined elsewhere; prints error
			// message to cerr and calls exit( ) to end the 
			// program in case memory was not available for new Node

  return 1; // new_value successfully inserted into list

}  // end of Insert(int, Node*&)

// Notice that using Node** P, insertion at the beginning and end do not
// require special cases in the code.  The work is performed by the private
// helper function Insert(int, Node*&) so that the public member function
// Insert(int) can call it with a reference to the head of the list, which
// should be kept as protected or private in the class OrdList.