C++11右值引用与完美转发及可变参数模板详解

//引用折叠限定f1实例化后总是一个左值引用
template<class T>
void f1(T& x)
{ }
//引用折叠限定f2实例化后可以是一个左值引用，也可以是一个右值引用
template<class T>
void f2(T&& x)
{ }
int main()
{
	typedef int& lref;
	typedef int&& rref;
	int n = 0;
	lref& r1 = n;//r1类型int&
	lref&& r2 = n;//r2类型int&
	rref& r3 = n;//r3类型int&
	rref&& r4 = 1;//r4类型int&&
	//即只要有左值引用折叠后就是左值引用，两个都是右值引用才是右值引用
	//没有折叠，实例化为void f1(int&x)
	f1<int>(n);
	//f1<int>(0);//err
	//折叠，实例化为void f1(int&x)
	f1<int&>(n);
	//f1<int&>(0);//err
	//折叠，实例化为void f1(int&x)
	f1<int&&>(n);
	//f1<int&&>(0);//err
	//折叠，实例化为void f1(const int&x)
	f1<const int&>(n);
	f1<const int&>(0);
	//折叠，实例化为void f1(const int&x)
	f1<const int&&>(n);
	f1<const int&&>(0);
	//没有折叠，实例化为void f2(int&&x)
	//f2<int>(n);//err
	f2<int>(0);
	//折叠，实例化为 void f2(int&x)
	f2<int&>(n);
	//f2<int&>(0);err
	//折叠，实例化为 void f2(int&&x)
	//f2<int&&>(n);err
	 f2<int&&>(0);
	return 0;
}

//方法1：
void showlist()
{
	// 编译器时递归的终⽌条件，参数包是0个时，直接匹配这个函数 
	cout << endl;
}
template<class T,class...Args>
void showlist(T t, Args...args)
{
	cout << t << " ";
	// args是N个参数的参数包 
 // 调⽤ShowList，参数包的第⼀个传给x，剩下N-1传给第⼆个参数包
	showlist(args...);
}
// 编译时递归推导解析参数 
template<class...Args>
void print(Args...args)
{
	showlist(args...);
}
//方法2：
template<class T>
const T& GetArg(const T& x)
{
	cout << x << " ";
	return x;
}
template<class...Args>
void Arguments(Args...args)
{
}
template<class...Args>
void print(Args...args)
{
	Arguments(GetArg(args)...);
}
//void Print(int x, string y, double z)
//{
// Arguments(GetArg(x), GetArg(y), GetArg(z));
//}

#pragma once
#include<iostream>
#include<assert.h>
using namespace std;
namespace bit
{
	template<class T>
	struct list_node
	{
		T _data;
		list_node* next;
		list_node* prev;
		/*list_node(const T& val = T())
			:_data(val)
			, next(nullptr)
			, prev(nullptr)
		{}*/
		list_node() = default;
		template <class... Args>
		list_node(Args&&... args)
			: next(nullptr)
			, prev(nullptr)
			, _data(forward<Args>(args)...)
		{
		}
	};
	template<class T,class ref,class ptr>
	struct list_iterator
	{
		typedef struct list_iterator<T,ref,ptr> self;
		typedef list_node<T> node;
		node* _node;
		list_iterator<T, ref, ptr>(node* nd)
			:_node(nd)
		{}
		ref& operator*()
		{
			//return _node->data;
			return _node->_data;
		}
		ptr* operator->()
		{
			return & _node->_data;
		}
		self& operator++()
		{
			_node = _node->next;
			return *this;
		}
		self& operator--()
		{
			//return _node->prev;
			_node = _node->prev;
			return *this;
		}
		self& operator++(int)
		{
			_node = _node->next;
			return *this;
		}
		self& operator--(int)
		{
			//return _node->prev;
			_node = _node->prev;
			return *this;
		}
		bool operator==(const self& s)const
		{
			return _node == s._node;
		}
		bool operator!=(const self& s)const
		{
			return _node != s._node;
		}
	};
	template<class T>
	class list
	{
	public:
		typedef list_iterator<T,T&,T*> iterator;
		typedef list_iterator<T,const T&, const T*>const_iterator;
		typedef list_node<T> node;
		list<T>()
		{
			empty_init();
		}
		void empty_init()
		{
			_head = new node;
			_head->next = _head;
			_head->prev = _head;
		}
		iterator begin()
		{
			return iterator(_head->next);
		}
		iterator end()
		{
			return iterator(_head);
		}
		const_iterator begin()const
		{
			return const_iterator(_head->next);
		}
		const_iterator end()const
		{
			return const_iterator ( _head);
		}
		template <class... Args>
		iterator insert(iterator pos, Args&&...args)
		{
			node* cur = pos._node;
			node* prev = cur->prev;
			node* newnode = new node(forward<Args>(args)...);
			newnode->next = cur;
			cur->prev = newnode;
			newnode->prev = prev;
			prev->next = newnode;
			return cur;
			++size;
		}
		template <class... Args>
		void emplace_back(Args&&... args)
		{
			insert(end(), forward<Args>(args)...);
		}
		iterator insert(iterator pos, const T& x)
		{
			node* cur = pos._node;
			node* prev = cur->prev;
			node* newnode = new node(x);
			newnode->next = cur;
			cur->prev = newnode;
			newnode->prev = prev;
			prev->next = newnode;
			return cur;
         	++size;
		}
		iterator insert(iterator pos, T&& x)
		{
			node* cur = pos._node;
			node* prev = cur->prev;
			node* newnode = new node(forward<T>(x));
			newnode->next = cur;
			cur->prev = newnode;
			newnode->prev = prev;
			prev->next = newnode;
			return cur;
			++size;
		}
		void pushback(const T& x)
		{
			insert(end(), x);
		}
		void push_back(T&& x)
		{
			insert(end(), forward<T>(x));
		}
		void pushfront(const T& x)
		{
			insert(begin(), x);
		}
		iterator erase(iterator pos)
		{
			assert(pos!=end());
			node* cur = pos._node;
			node* prev = cur->prev;
			node* next = cur->next;
			prev->next = next;
			next->prev = prev;
			delete cur;
			return next;
			--size;
		}
		void popback()
		{
			erase(--end());
		}
		void popfront()
		{
			erase(begin());
		}
		size_t size1()
		{
			return size;
		}
		bool empty()
		{
			return size == 0;
		}
		list<T>(list<T>&l)
		{
			empty_init();
			for (auto& ch : l)
			{
				pushback(ch);
			}
		}
		void swap(list<T>l)
		{
			std::swap(_head, l._head);
			std::swap(size, l.size1());
		}
		list<T>operator=(list<T>tmp)
		{
			swap(tmp);
			return *this;
		}
		void clear()
		{
			auto it = begin();
			while (it != end())
			{
				it = erase(it);
			}
		}
		~list()
		{
			clear();
			delete _head;
			_head = nullptr;
		}
	private:
		node* _head;
		size_t size;
	};
	template<class container>
	void print( const container& con)
	{
		for (auto ch : con)
		{
			cout << ch << " ";
		}
		cout << endl;
	}
}