Can't print Linked List

[vkhanhvy]

Hi, I'm trying to write a function that will print out my unsorted Linked List.
When I compile the program I get the fault reading
"no operator "<<" matches these operands"
and
"binary "<<" no operator found which takes a right-hand operand of type 'ItemType' (or there is no acceptable conversion)

The program does not accept the line:

std::cout << currentPos->info << endl;

I will appreciate any help. Thank you.

#include <iostream>
#include <cstddef>

using namespace std;

enum RelationType { LESS, GREATER, EQUAL };

class ItemType {

public:
	ItemType();
	~ItemType() {};
	RelationType ComparedTo(ItemType otherItem) const;
	void GetValue() const;
	void Initialize(int number);

private:
	int value;
};

ItemType::ItemType()
{

	value = 0;
}

RelationType ItemType::ComparedTo(ItemType otherItem) const
{
	if (value < otherItem.value)
		return LESS;
	else if (value > otherItem.value)
		return GREATER;
	else return EQUAL;

}

void ItemType::GetValue() const
{
	cout << value << endl;
}


void ItemType::Initialize(int number) {
	value = number;
}

struct NodeType {

	ItemType info;
	NodeType* next;
};

class UnsortedType{
	public:
		friend struct NodeType;
		UnsortedType();
		void MakeEmpty();
		bool IsFull() const;
		int GetLength() const;
		ItemType GetItem();
		ItemType FindItem(ItemType item, bool &found);
		void PutItem(ItemType item);
		void ResetList();
		ItemType GetNextItem();
		void Print();
		
	private:
		NodeType* listData;
		int length; 
		NodeType* currentPos; 
		NodeType* nextPtr; 
		NodeType* firstPtr;
		NodeType* lastPtr; 
	
};

UnsortedType::UnsortedType()  {
	firstPtr = nullptr;
	lastPtr = nullptr; 
	listData = nullptr; 
	length = 0;
}

void UnsortedType::MakeEmpty() {

	NodeType* tempPtr;

	while (listData != NULL)
	{
		tempPtr = listData;
		listData = listData->next;
		delete tempPtr;

	}
	length = 0;
}

bool UnsortedType::IsFull() const
{
	NodeType* location;
	try
	{
		location = new NodeType;
		delete location;
		return false;
	}
	catch (bad_alloc exception)
	{

		return true;
	}
}

int UnsortedType::GetLength() const
{
	return length; 
}


ItemType UnsortedType::FindItem(ItemType item, bool& found)
{
	bool moreToSearch;
	NodeType* location;
	found = false;
	location = listData;
	moreToSearch = (location != NULL);
	
	while(moreToSearch && !found)
    {
    	switch(item.ComparedTo(location->info))
{
	case LESS:
	case GREATER: location = location->next;
		moreToSearch = (location != NULL);
		break;
	case EQUAL: found = true;
		item = location->info;
		break;
	
		}    	
		}	
		return item;
}

void UnsortedType::PutItem(ItemType item)
{
	NodeType* location;
	location = new NodeType;
	location->info = item;
	location->next = listData;
	listData = location; // aim ListData at new node 
	length++;
	
}

void UnsortedType::ResetList()
{
	currentPos = NULL; 
	
}

ItemType UnsortedType::GetNextItem()
{
	if(currentPos==NULL)
		currentPos = listData;
		else
		currentPos = currentPos->next;
		return currentPos->info;
	
}


void UnsortedType::Print() {
		
	if (GetLength() == 0) 
	{
	cout << "The list is empty." << endl;}
	NodeType *currentPos = listData;
	cout<<"The list is: "<<endl;
	while(currentPos!= nullptr)
	{
	}
	
}

int main() {
	UnsortedType List;
	UnsortedType List1;
	UnsortedType List2;
	ItemType item;
	ItemType item1; 
	ItemType item2;
	ItemType item3;
	ItemType item4;
	ItemType item5;

	item.Initialize(4);
	item1.Initialize(1);
	item2.Initialize(6);
	item3.Initialize(2);
	item4.Initialize(7);
	item5.Initialize(3);

	List.PutItem(item1);
	List.PutItem(item2);
	List.PutItem(item3);
	List.PutItem(item4);
	List.PutItem(item5);
	
	cout << "Current Items in List:" << endl; 
	List.Print();
	
	return 0;
}

[Bdanielz]

Hi welcome,

You should post your code in code tags.

I was unable to get your code to run, so I did not troubleshoot it.

Below is an example I found here.
http://www.bogotobogo.com/cplusplus/linkedlist.php#linkedlistexample1

#include <iostream>

struct Node {
    int data;
    Node *next;
};

using namespace std;


// only for the 1st Node
void initNode(struct Node *head, int n) {
    head->data = n;
    head->next = NULL;
}

// apending
void addNode(struct Node *head, int n) {
    Node *newNode = new Node;
    newNode->data = n;
    newNode->next = NULL;

    Node *cur = head;
    while (cur) {
        if (cur->next == NULL) {
            cur->next = newNode;
            return;
        }
        cur = cur->next;
    }
}

void display(struct Node *head) {
    Node *list = head;
    while (list) {
        cout << list->data << " ";
        list = list->next;
    }
    cout << endl;
    cout << endl;
}


int main() {

    struct Node *newHead;
    struct Node *head = new Node;

    initNode(head, 10);
    addNode(head, 20);
    display(head);

}

[vkhanhvy]

Thank you. The link you sent me was very useful.

[guatemala007]

In order to print custom classes such as ItemType you must overload the std::ostream operator << for instance if I had a structure defined as follows:

struct X{
    int data;
    X(int a){
        data = a;
    }
};

and I wanted to print an instance of this class I would have:

std::ostream & operator<< (std::ostream &os, X &obj) {
	return os << obj.data;
}

declared so that the ostream object known as cout has a method of printing an instance of class X.

Oh and please edit your code and surround it with code tags like the following:

[code]Put code in between here...[/code]

[vkhanhvy]

This is very useful. Thank you!

[MikeyBoy]

What would be even more useful is if you did as you've already been asked (twice!), and edit your original post to use code tags.

[vkhanhvy]

I understand the importance of using code tags. This post is old and my code is now completely different thanks to help of the people who replied to this post. I will certainly use code tags for future posts. I have marked this post as solved.