我有一个分配,我需要在其中进行linkedlist and traververver的模板类。类遍历的类需要是一个界面,该接口声明某些集合类的索引和迭代功能。我不确定如何为迭代器制作接口,以便linkedlist可以使用它。我在想
template <class T, class U>
class ITraversible {
public:
virtual U begin() noexcept = 0;
virtual U end() noexcept = 0;
virtual T& operator[](int) = 0;
};
,然后在linkedlist标头文件中我要做:
template <class T>
class LinkedList : public ITraversible<T,typename LinkedList<T>::iterator> {
struct node {
T data;
node* next, *prev;
explicit node(const T&);
void connect(node*);
};
node *head, *tail;
int n;
public:
/*************************ITERATOR************************/
class iterator : public std::iterator<std::bidirectional_iterator_tag, node*> {
typename LinkedList<T>::node* itr;
explicit iterator(node*) noexcept;
friend class LinkedList;
public:
iterator& operator++();
iterator operator++(int);
iterator& operator--();
iterator operator--(int);
bool operator==(const iterator&) const noexcept;
bool operator!=(const iterator&) const noexcept;
T& operator*() const noexcept;
T& operator->() const noexcept;
};
/**********************************************************/
LinkedList() noexcept;
LinkedList(std::initializer_list<T>);
LinkedList(const LinkedList&);
LinkedList(LinkedList&&) noexcept;
~LinkedList() noexcept;
LinkedList& operator=(LinkedList) noexcept;
template <class A>
friend void swap(LinkedList<A>&, LinkedList<A>&);
void add(const T&);
void removeAt(int);
int size() const noexcept;
bool operator==(const LinkedList&) const noexcept;
bool operator!=(const LinkedList&) const noexcept;
virtual T& operator[](int) override;
virtual iterator begin() noexcept override;
virtual iterator end() noexcept override;
};
但随后可遍历模板具有两个参数,它应该只有一个。这是我应该做的吗?请记住,我是模板和迭代器的新手。
创建接口时,您需要钉住正在返回的内容的静态类型。这些行为可能会动态不同,但是除了使用子类型关系时,您不能更改其他类型。
就个人而言,我认为此练习在C 上下文中不明智。使用Java或C#时,May May 是有意义的。但是,可以获得类似的行为。绘制的草图将是这样的(尽管这应该有效它会很慢):
template <typename T>
struct iterator_base {
virtual iterator_base() {}
virtual iterator_base<T>* do_clone() = 0;
virtual T& do_value() = 0;
virtual void do_next() = 0;
virtual bool do_equal() = 0;
// other operations to implement operator--, operator[], ...
};
template <typename It>
class iterator: iterator_base<typename std::iterator_traits<It>::value_type> {
typedef typename std::iterator_traits<It>::value_type> type;
It it;
iterator_base<type>* do_clone() { return new iterator<It>(*this); }
type& do_value() { return *this->it; }
void do_next() { ++this->it; }
bool do_equal(iterator_base<type>* other) {
return this->it == static_cast<iterator<It>>(other)->it;
}
};
template <typename T>
class poly_iterator {
std::unique_ptr<iterator_base<T>> ptr;
public:
poly_iterator(iterator_base<T>* ptr): ptr(ptr) {}
poly_iterator(poly_iterator const& other): ptr(other.ptr->clone()) {}
poly_iterator& operator= (poly_iterator other) {
other.swap(this);
return *this;
}
void swap(poly_iterator& other) { swap(this->ptr, other.ptr); }
T& operator*() { return this->ptr->value(); }
T* operator->() { return &this->operator*(); }
poly_iterator& operator++() { this->ptr->next(); return *this; }
poly_iterator operator++(int) {
poly_iterator rc(*this);
this->operator++();
return rc;
}
bool operator== (poly_iterator const& other) {
return this->ptr->equal(other.ptr.ptr());
}
bool operator!= (poly_iterator const& other) {
return !(*this == other);
}
// other operations
};
// define a suitable specialization of std::iterator_traits<poly_iterator<T>>
template <typename T>
class ITraversible {
virtual iterator_base<T>* do_begin() = 0;
virutal iterator_base<T>* do_end() = 0;
public:
poly_iterator<T> begin() { return this->do_begin(); }
poly_iterator<T> end() { return this->do_end(); }
// other operations
};
template <typename T>
class List: public ITraversible<T> {
std::list<T> list;
iterator_base<T>* do_begin() {
return iterator<std::list<T>::iterator>(list.begin());
}
iterator_base<T>* do_end() {
return iterator<std::list<T>::iterator>(list.end());
}
public:
// whatever is needed to fill the list
};