#Create iterators over the elements in the list Here's how to go about creating iterators for this collection. They will naturally be forward iterators, as we can't traverse the singly-linked list backwards.

First, let's declare the iterator class, and begin() and end() methods to create them:

public:
 class iterator;
 iterator begin();
 iterator end();

The state within an iterator is obviously its current Node:

template<class T>
class SingleLinkedList<T>::iterator
{
 Node* node;
}

For a forward iterator, we need to be able to dereference and to increment it; also we need to be able to compare iterators for equality, and to construct (including default-construct) instances:

template<class T>
class SingleLinkedList<T>::iterator
{
 Node* node = nullptr;
public:
 iterator(Node *node = nullptr)
 : node(node)
 {}
 bool operator!=(const iterator& other) const { return node != other.node; }
 bool operator==(const iterator& other) const { return node == other.node; }
 T& operator*() const { return node->data; }
 T& operator->() const { return node->data; }
 iterator& operator++() { node = node->next.get(); return *this; }
};
template<class T>
typename SingleLinkedList<T>::iterator SingleLinkedList<T>::begin()
{
 return head.get();
}
template<class T>
typename SingleLinkedList<T>::iterator SingleLinkedList<T>::end()
{
 return {};
}

To use with standard algorithms, we need to provide some type names that can be found by std::iterator_traits:

#include <iterator>
template<class T>
class SingleLinkedList<T>::iterator
{
public:
 using iterator_category = std::forward_iterator_tag;
 using value_type = T;
 using difference_type = std::ptrdiff_t;
 using pointer = T*;
 using reference = T&;

Then we can use iterators to simplify our code:

template <class T>
bool SingleLinkedList<T>::search(const T &x) {
 return std::find(begin(), end(), x) != end();
}

##Exercise Implement a const iterator for the list. You'll start with these methods in SingleLinkedList:

class const_iterator;
const_iterator cbegin() const;
const_iterator cend() const;
const_iterator begin() const;
const_iterator end() const;

and the iterator traits will refer to const T in place of T.

Create iterators over the elements in the list

Here's how to go about creating iterators for this collection. They will naturally be forward iterators, as we can't traverse the singly-linked list backwards.

First, let's declare the iterator class, and begin() and end() methods to create them:

public:
 class iterator;
 iterator begin();
 iterator end();

The state within an iterator is obviously its current Node:

template<class T>
class SingleLinkedList<T>::iterator
{
 Node* node;
}

For a forward iterator, we need to be able to dereference and to increment it; also we need to be able to compare iterators for equality, and to construct (including default-construct) instances:

template<class T>
class SingleLinkedList<T>::iterator
{
 Node* node = nullptr;
public:
 iterator(Node *node = nullptr)
 : node(node)
 {}
 bool operator!=(const iterator& other) const { return node != other.node; }
 bool operator==(const iterator& other) const { return node == other.node; }
 T& operator*() const { return node->data; }
 T& operator->() const { return node->data; }
 iterator& operator++() { node = node->next.get(); return *this; }
};
template<class T>
typename SingleLinkedList<T>::iterator SingleLinkedList<T>::begin()
{
 return head.get();
}
template<class T>
typename SingleLinkedList<T>::iterator SingleLinkedList<T>::end()
{
 return {};
}

To use with standard algorithms, we need to provide some type names that can be found by std::iterator_traits:

#include <iterator>
template<class T>
class SingleLinkedList<T>::iterator
{
public:
 using iterator_category = std::forward_iterator_tag;
 using value_type = T;
 using difference_type = std::ptrdiff_t;
 using pointer = T*;
 using reference = T&;

Then we can use iterators to simplify our code:

template <class T>
bool SingleLinkedList<T>::search(const T &x) {
 return std::find(begin(), end(), x) != end();
}

Exercise

Implement a const iterator for the list. You'll start with these methods in SingleLinkedList:

class const_iterator;
const_iterator cbegin() const;
const_iterator cend() const;
const_iterator begin() const;
const_iterator end() const;

and the iterator traits will refer to const T in place of T.