How do I call these functions?

I am having trouble calling these functions in my cpp file. I have created the linked list and I just need to cover each of these functions. I have deleted a few of them since I already got them working. I am having trouble understanding what

Code:

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LListNode<Data>*

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portion of the functions parameter is. I just don't know what to put in there. I am sure it is really simple too. Also, I am not sure what the

Code:

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struct LListNode

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does. If anyone could help I would be extremely thankful.

Code:

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template <typename Data>
struct LListNode
{
  Data data;
  LListNode<Data>* next;

  LListNode() {next = 0;}
  LListNode (const Data& d, LListNode<Data>* nxt = 0)
    : data(d), next(nxt)
  {}
};


template <typename Data>
struct LListHeader {

  LListNode<Data>* first;

  LListHeader();

  // Add value after the indicated position
  //pre: afterThis != NULL
  void addAfter (LListNode<Data>* afterThis, const Data& value);

  // Add value before the indicated position
  //pre: beforeThis != NULL
  void addBefore (LListNode<Data>* beforeThis, const Data& value);

  // Remove value at the indicated position
  //pre: here != NULL
  void remove (LListNode<Data>* here);

  // Add value after the indicated position
  //pre: afterThis != NULL
  void removeAfter (LListNode<Data>* afterThis);

  // Search for a value. Returns null if not found
  LListNode<Data>* find (const Data& value) const;

  // Search an ordered list for a value. Returns null if not found
  LListNode<Data>* findOrdered (const Data& value) const;

  // Append another list onto the end of this one
  void append (const LListHeader<Data>& list);

};

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LListNode<Data>*
can be read as a pointer to a LListNode<Data>

struct LListNode
means you are defining a type named LListNode. the keyword struct is the same as class, with the only difference being all members are public by default (vs private for class).

Yeah...funny thing is it says the LListNode is not a type when I try to say it is.

LListNode, by itself, is not a type, since you have the struct definition inside a template definition. You can have a LListNode<int>, or a LListNode<double>, or ....

Yeah I know about the whole <int> or whatever type of linked list I want but I don't know how to call those functions and actually use them and also what the node aspect is supposed to do. I am pretty sure I created a linked list with only one node which stored numerous numbers from the array I created. I am trying to create a linked list of in that is entirely self-contained. I create the arrays by

Code:

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array[] = {1,2,3,4}

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etc. I use this array to store the data into a linked list. I am sure I need to use the node part to actually create each linked list. Could anyone help with that?

Assuming you have all those functions written, you seem to be missing "create a list", unless addAfter or addBefore can handle a 0 pointer. The preconditions say they can't. So you'll need a way to create a list -- you could make a constructor that takes a Data& to use for the head element, or you could make a constructor that takes a LListNode object (but that's no fun).

I can't alter the header file. This is provided by my professor and I am just needing to do statement coverage with gcov. Basically, what I have posted in the first post is what I have to work with. I can't be writing functions just the main function in the cpp file. This is what I have.

Well, it's not very object-oriented; but since LListHeader is a struct we can access its members. So create a LListNode<whatever> with your first data point, and create an LListHeader<whatever>. Then you can assign biglist.first = listnode (or whatever you called your actual variables). Then you can use addBefore/addAfter as appropriate.

This addToEnd would handle a 0 pointer wouldn't it?

Code:

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template <typename Data>
void LListHeader<Data>::addToEnd (const Data& value)
{
  LListNode<Data>* newNode = new LListNode<Data>(value, NULL);
  if (first == NULL)
    {
      first = newNode;
    }
  else
    {
      // Move to last node
      LListNode<Data>* current = first;
      while (current->next != NULL)
        current = current->next;

      // Link after that node
      current->next = newNode;
    }
}

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Why yes, yes it would. It can be amazing what's hiding in the woodwork sometimes.

Hmmm still using that doesn't seem to work. I have a linked list of int with the numbers 2,3,4,6 in it. Now, when I try the addInOrder function with a 5, it just puts the 5 at the beginning. Something still isn't right. Here is what I used to build my llist:

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int main(int argc, char** argv)
{
    int array[] = {2,3,4,6};
    int array2[] = {6,7,8,9};
    int listLength = 10;
    LListNode<int> listNode;
    LListHeader<int> first;

    for(int i=0; i<listLength; ++i)
    {
        first.addToEnd(array[i]);
    }
    first.addInOrder(5);
    first.display();
    return 0;
}

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Obviously still haven't used array2 yet but I am planning on using that to append the two linked lists. Am I doing something wrong in building the list? Because if I am, I don't see it :/

addToEnd should give you 2, 3, 4, 6, garbage, garbage, garbage, garbage, garbage, and garbage -- adding ten numbers to the list when you only have four elements can only lead to heartbreak. And I don't know whether addInOrder is supposed to work when the original list isn't sorted or not.

Sorry..mental mistake there. But that doesn't fix anything. And yes, the array is supposed to be ordered before we add another element to the list via addInOrder.

If you fix that, and you still get 5, 2, 3, 4, 6, then addInOrder is broken.

This is his function...so I don't know why it would be. But apparently it is. This is it

Code:

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// Add value in sorted order.
//Pre: all existing values are already ordered
template <typename Data>
void LListHeader<Data>::addInOrder (const Data& value)
{
  if (first == NULL)
    first = new LListNode<Data>(value, NULL);
  else
    {
      LListNode<Data>* current = first;
      LListNode<Data>* prev = NULL;
      while (current != NULL && value < current->data)
        {
          prev = current;
          current = current->next;
        }
      // Add between prev and current
      if (prev == NULL)
        addToFront (value);
      else
        addAfter (prev, value);
    }
}

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I myself don't see anything wrong but I guess there is!

This inOrder appears to be decreasing. If you pass in 5 for value, and the first number in the list is 2, then 5 < 2 will be false, and we won't walk the list. Is it supposed to be increasing? (If so, then that < would need to become a >.)

Ohhh yeah good eye. I guess so, but like I said, I can't change it. I guess I'll just flip my data around and treat it as decreasing. Now just one more question...how do I implement the functions that have LListNode<Data>* as parameters?

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Originally Posted by Todd88

Ohhh yeah good eye. I guess so, but like I said, I can't change it. I guess I'll just flip my data around and treat it as decreasing. Now just one more question...how do I implement the functions that have LListNode<Data>* as parameters?

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Carefully. They would be just like any other parameters; since they are pointers, that means you can modify the LListNode being pointed to, etc.

I just don't know what to put there as a parameter. Is it just LListNode<int> node? Because it's complaining at me again :/

You would need to pass a pointer to the node.

Sorry I have no idea how to do that.

Just like you would pass a pointer to anything else: with &.

Remember I can't edit the header file. I'm not sure how to pass a pointer to a node when all I have to work with is my main function. I used the addToEnd function to create my list and therefore really don't even use nodes myself. I don't know how to do this part.

What does editing the header file have to do with anything? Every variable has an address, that you can get by prefix the variable name with &. So if a function needs the address of a variable, you should give it the address of the variable.

Note also, as you can see in the addToEnd function, that the new keyword gives you a pointer to a <whatever you created>.

I'm sorry I have had the worst time with pointers and passing parameters. I am great at everything else but I can't seem to get this point. It is so frustrating because I know it's the simplest thing in the world but I just can't get it. It really makes me so mad knowing that this is simple and I can't understand!!

Edit::sorry it was just that simple. I just needed to create a node via LListNode<int>* node; and use that...I'm embarassed.