void GnodePtrBag::add(Gnode *pointer)
{d_root_p = new GnodePtrBagLink(pointer,d_root_p);}
The d_root_p is a pointer to the root of a linked list held by GnodePtrBagLink. This call assigns to point to the Gnode just created. Then points the next pointer of this cell to point to the old root of the linked list. Thereby making the new pointer the root. This is done with the following GnodePtrBagLink constructor.