iterator和const_iterator以及节点Node是类List中嵌套类
iterator继承来自const_iterator
const_iterator里面有Node* current变量以及retrieve()函数
重点来了!!!!!!!!!!!!!!!!!!!
iterator好像看不到上述的那个变量以及函数
编译器一直报错
希望高手帮忙指点一下(限于篇幅已经把一些不相关的函数已经删除)
#include
using namespace std;
template
class List{
private:
struct Node
{
Object data;
Node *prev;
Node *next;
Node(const Object&d=Object(),Node *p=NULL,Node *n=NULL)
:data(d),prev(p),next(n){}
};
public:
class const_iterator
{
public:
const_iterator():current(NULL)
{}
protected://
Node *current;
Object &retrieve()const
{
return current->data;
}
const_iterator(Node *p):current(p)
{}
friend class List<Object>;
};
class iterator:public const_iterator
{
public:
iterator()
{}
Object & operator*()
{
return retrieve();//
/*
List.cpp:64:37: error: there are no arguments to ‘retrieve’ that depend on a template parameter, so a declaration of ‘retrieve’ must be available [-fpermissive]
return retrieve();
*/
}
const Object& operator*()const
{
return const_iterator::operator*();
}
iterator &operator++()
{
current = current->next; //////// 看不到current
return *this;
/*List.cpp:64:37: note: (if you use ‘-fpermissive’, G++ will accept your code, but allowing the use of an undeclared name is deprecated)
List.cpp: In member function ‘List::iterator& List::iterator::operator++()’:
List.cpp:72:21: error: ‘current’ was not declared in this scope
/
}
iterator operator++(int)
{
iterator old = *this;
++(*this);
return old;
}
protected:
iterator(Node p):const_iterator(p)
{}
friend class List<Object>;
};
public:
private:
int theSize;
Node *head;
Node *tail;
};
int main()
{
return 0;
}
protected://
Node *current;
只有在派生类中才可以通过派生类对象访问基类的protected成员
List.cpp:64:37: error: there are no arguments to ‘retrieve’
这个错误猜测也是同样错误，方便提供源码，帮你看一下嘛？
#include
using namespace std;
template
class List{
private:
struct Node
{
Object data;
Node prev;
Node *next;
Node(const Object&d=Object(),Node *p=NULL,Node *n=NULL)
:data(d),prev(p),next(n){}
};
public:
class const_iterator
{
public:
const_iterator():current(NULL)
{}
const Object& operator()const
{
return retrieve();
}
const_iterator& operator++()
{
current = current->next;
return *this;
}
const_iterator operator++(int)
{
const_iterator old = *this;
++(*this);
return old;
}
bool operator== (const const_iterator &rhs)const
{
return current==rhs.current;
}
bool operator !=(const const_iterator &rhs)const
{
return !(*this == rhs);
}
protected://
Node *current;
Object & retrieve()const
{
return current->data;
}
const_iterator(Node *p):current(p)
{}
friend class List<Object>;
};
class iterator:public const_iterator
{
public:
iterator()
{}
Object & operator*()
{
return retrieve();//retrieve
/*
List.cpp:64:37: error: there are no arguments to ‘retrieve’ that depend on a template parameter, so a declaration of ‘retrieve’ must be available [-fpermissive]
return retrieve();
*/
}
const Object& operator*()const
{
return const_iterator::operator*();
}
iterator &operator++()
{
current = current->next; //////// 看不到current
return *this;
/*List.cpp:64:37: note: (if you use ‘-fpermissive’, G++ will accept your code, but allowing the use of an undeclared name is deprecated)
List.cpp: In member function ‘List::iterator& List::iterator::operator++()’:
List.cpp:72:21: error: ‘current’ was not declared in this scope
/
}
iterator operator++(int)
{
iterator old = *this;
++(*this);
return old;
}
protected:
iterator(Node p):const_iterator(p)
{}
friend class List<Object>;
};
public:
List()
{
init();
}
void init()
{
theSize = 0;
head = new Node;
tail = new Node;
head->next = tail;
tail->prev = head;
}
~List()
{
clear();
delete head;
delete tail;
}
List(const List &rhs)
{
init();
*this = rhs;
}
const List& operator=(const List &rhs)
{
if(this == &rhs)
return *this;
clear();
for(const_iterator itr=rhs.begin();itr!=rhs.end();++itr)
push_back(*itr);
return *this;
}
/////////////////////////////////////////////////
iterator begin()
{
return iterator(head->next);
}
const_iterator begin()const
{
return const_iterator(head->next);
}
iterator end()
{
return iterator(tail);
}
const_iterator end()const
{
return const_iterator(tail);
}
int size()const
{
return theSize;
}
bool empty()const
{
return size()==0;
}
void clear()
{
while(!empty())
pop_front();
}
Object &front()
{
return *begin();
}
const Object &front()const
{
return *begin();
}
Object &back()
{
return *--end();
}
const Object& back()const
{
return *--end();
}
void push_front(const Object &x)
{
insert(end(),x);
}
void push_back(const Object &x)
{
insert(begin());
}
void pop_front()
{
erase(begin());
}
void pop_back()
{
erase(--end());
}
iterator insert(iterator itr,const Object &x)
{
/*Node * newNode = new Node(x,p->prev,p);
p->prev->next = newNode;
p->prev = nowNode ;*/
Node * p = itr.current;
theSize++;
return iterator(p->prev=p->prev->next= new Node(x,p->prev,p));
}
iterator erase(iterator itr)
{
Node *p = itr.current;
iterator retVal(p->next);
p->prev->next = p->next;
p->next->prev = p->prev;
delete p;
theSize--;
return retVal;
}
iterator erase(iterator start,iterator end)
{
for(iterator itr=start;itr!=end;)
itr = erase(itr);
return end;
}
private:
int theSize;
Node *head;
Node *tail;
};
int main()
{
return 0;
1. }