Convert string to list_entry

Question

I have a class for lists. It's template class that takes a type of list_entry:
class cSingleList<list_entry>

I have an insert function defined as such:
public void insert(int position, list_entry entry)

What insert does is it takes an int so that we can insert a value (list_entry entry) at a certain position (int position) in the list.

Finally, I have a function:

public void read_file_insert(string filepath)
        {
            // Pre: A filepath to a file that only has integers delimited by a newline
            // and a cSingleList obejct.
            // Post: Reads the file given by the filepath and then inserts the data
            // into a cSingleList object by calling its insert function.

            string line = "";
            int index = 0;
            TextReader fin = new StreamReader(filepath);

            while ((line = fin.ReadLine()) != null)
            {
                this.insert(index, line);
                index++;
            }
        }

What this does is it reads through a file that contains integers and then we call the insert function, passing it the position we want (index) and then the value (line).

However, I always get an error stating:
Argument '2': cannot convert type 'string' to type 'list_entry'.

How can I convert a string (line) to type list_entry?

Frank · Answer

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.IO; namespace project3_FHN { class cSingleList { // This delegate will take references to other functions that take one // list_entry value as a parameter and listDelegate will pass the list_entry value // to that function public delegate void listDelegate(list_entry value); private cNode head; private int count; public cSingleList() { // Post: Creates a new cSingleList object and sets head to null head = null; count = 0; } public cSingleList(cNode nodePointer) { // Post: Creates a new cSingleList object and adds a node to the list // If head is null head will now equal the new node. Also increment count if (head == null) head = nodePointer; count++; } public cNode set_position(int position) { // Pre: Position is is a valid position in the list // Post: We create a pointer that'll point to the head of the list. We // will then start stepping through the list until we reach the position // desired. We will then return the pointer which will then be pointing // to that position. cNode pointer = head; for (int i = 0; i pointer = pointer.next; return pointer; } public void read_file_insert(string filepath) { // Pre: A filepath to a file that only has integers delimited by a newline // and a cSingleList obejct. // Post: Reads the file given by the filepath and then inserts the data // into a cSingleList object by calling its insert function. string line = ; int index = 0; TextReader fin = new StreamReader(filepath); while ((line = fin.ReadLine()) != null) { this.insert(index line); index++; } } public void insert(int position list_entry entry) { /* * Pre: A node class that has a next pointer that can be set through * a property * Post: We specify the position that we want to insert the new node * into. First we must make sure that the position desired is between * 0 and count (return an out-of-bounds error if this occurs). If it's * valid we then set a pointer (ptr) to equal head We then step through the * list in a loop until ptr reaches the position minus one (use set_pointer()). * Now we are pointing to the node just behind the position that we want. * We set the new node's pointer to point to ptr->next. Then we have * ptr->next point to the new node. We now have a new node inserted. */ const string STR_ERROR_OVERFLOW = No more memory! Overflow error!; string STR_ERROR_OUT_OF_BOUNDS = You cannot insert a node at a position that is less than zero or greater than the size of this list which is  + count; if (position count) throw new cOutOfBoundsException(STR_ERROR_OUT_OF_BOUNDS); else { cNode ptr = null; cNode newNode = new cNode (entry); if (newNode == null) throw new OverflowException(STR_ERROR_OVERFLOW); if (position > 0) { ptr = set_position(position - 1); newNode.next = ptr.next; ptr.next = newNode; } else { newNode.next = head; head = newNode; } count++; } } public void insert_sort(cDoubleList doublePtr) { /* * Pre: A pointer to a double list * Post: We sort the nodes in the list according to their data value * We'll use the insertion sort method. We'll start at the head of our * list and start inserting the nodes into the double list. */ cNode sortedHead firstUnsorted lastSorted current; int index = 0; if (head != null) { lastSorted = head; // The first element is considered sorted until further notice doublePtr.insert(0 head.retrieve()); // Insert the first element sortedHead = doublePtr.set_position(0); // This keeps track of the head of the sorted list while (lastSorted.next != null) // When this is false the list is sorted { firstUnsorted = lastSorted.next; if (firstUnsorted { doublePtr.insert(0 firstUnsorted.retrieve()); lastSorted = firstUnsorted; sortedHead = doublePtr.set_position(0); // A new sorted head has been made . . . get it. } else { current = sortedHead; current = current.next; if (current != null) { for (index = 0; firstUnsorted > current; index++) { current = current.next; if (current == null) { index++; // Because index won't be able to be added one last time since current equals null an error will be thrown instead break; // We've reached the end of the list } } } // The node is already in the correct place if (firstUnsorted == current) { doublePtr.insert(index firstUnsorted.retrieve()); lastSorted = firstUnsorted; } else { doublePtr.insert(index + 1 firstUnsorted.retrieve()); lastSorted = firstUnsorted; } } } // END OF WHILE } // END OF HEAD NOT NULL } public void traverse(listDelegate func) { listDelegate funcPointer = new listDelegate(func); for (int i = 0; i { funcPointer(set_position(i).retrieve()); } } } } I believe that's how it was. I've changed it since so that it only excepts integers but it should be pretty accurate.

Matthew Cox · Answer

Post your List_Entry class and I can help you further with the issue