c++ - Linked list, add node to end -

i'm working on project , given function complete

void addtoend(node*& head, string newval)  effect:  adds new node tail end of list  precondition: head pointer first node in list (list may empty) postcondition: list contains 1 more node 

my question string newval for?

the value_type of class of type double i'm confused string newval for. can't set newval in node because of 2 different types.

this have far. i'm not sure if im going in right direction.

node *temp = new node; temp = head;  while(temp->link() != null){     temp = temp->link(); }  head->set_link(temp); 

i'm not sure use string in block of code.

link() returns member variable node* link_field set_link() sets new link link_field

well, we're guessing somehow expect turn string double function std::stod.

as list manipulation code, there's few problems:

node *temp = new node; temp = head; 

this creates new node, puts pointer in temp, overwrites temp head, losing (leaking) new node. don't that.

while(temp->link() != null){     temp = temp->link(); } 

this close, might not work. problem need keep track of real node pointer, not copy.

normally, in linked list api using pointers instead of references, "add node" function looks like:

void addtoend(node** head, string newval) {     while(*head)         head = &((*head)->next);     *head = new node;     (*head)->value = newval;     (*head)->next = 0; } 

note if list empty, passed-in head pointer altered point new node. if list not empty, last next pointer altered instead.

the api you're given (i.e. link , set_link methods) doesn't allow this, because head pointer not node , functions require node. you've got little differently, namely have handle empty list case separately.

void addtoend(node*& head, string newval) {     // create node.     node* newnode = new node;     newnode->value = std::stod(newval);     newnode->set_link(0);      if(!head) // empty list?     {         head = newnode;         return;     }      // find last node.     node* item = head;     while(item->link())         item = item->link();     item->set_link(newnode); }