Question

I am working on a homework assignment where we aren’t allowed to use any STL containers. My implementation of LinkedList is a collection of Nodes that are chained together with pointers. I have another class called ContinuousList which has a data member LinkedList whose Nodes contain pointers to Nodes in various other LinkedLists. I’m trying to assign the return value of a function that returns a pointer to a Node to a variable that is also a pointer to a Node, but it is saying that is invalid and I don’t understand why I can’t do that.

template <typename ValueType>
struct Node
{
    Node();
    std::string m_key;
    ValueType m_value;
    Node<ValueType>* m_next;
};

The linked list class:

template <typename ValueType>
class LinkedList
{
public:
    Node<ValueType>* begin()
    {
        return m_head;
    }
private:
    Node<ValueType>* m_head;
};

ContinuousList:

template <typename ValueType>
class ContinuousList
{
public:
    ValueType* iterate(std::string& key)
    {
        m_curr = m_collection.begin(); // Error occurs here

        ...
    }
private:
    LinkedList<Node<ValueType>*> m_collection;
    Node<ValueType>* m_curr;
};

Full error message

1>          error C2440: '=' : cannot convert from 'Node<ValueType> *' to 'Node<ValueType> *'
1>          with
1>          [
1>              ValueType=Node<bool> *
1>          ]
1>          and
1>          [
1>              ValueType=bool
1>          ]
1>          Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
1>          while compiling class template member function 'bool *ContinuousList<ValueType>::iterate(std::string &)'
1>          with
1>          [
1>              ValueType=bool
1>          ]
1>          see reference to class template instantiation 'ContinuousList<ValueType>' being compiled
1>          with
1>          [
1>              ValueType=bool
1>          ]

Answer 1

    LinkedList<Node<ValueType>*> m_collection;

this

is making m_head be

      Node<Node<ValueType>*>*

Which is not what you want.

    m_curr = m_collection.begin()
    Node<ValueType> = Node<Node<ValueType>*>*

if

    Node<Node<ValueType>*>* 

was what you wanted, use

m_collection.begin()->m_value;

or use

    LinkedList<ValueType>, 

and it will return Node

Though I may just be really tired…. =D