类 : expected initializer before '*' : 的 C++ 错误

Question

我正在实现一个列表(只是为了好玩):

#include <iostream>

template <class T>
class list {

private:
    struct node {
        T data;
        struct node *next, *prev;
    } head;

    unsigned int length;

public:

    class iterator {

    private:
        node *ptr;

    public:
        iterator ();
        inline T& operator *();
        inline iterator operator ++();
        inline iterator operator ++(int);
        inline iterator operator --();
        inline iterator operator --(int);

    };

    list ();
    //~list ()

    inline unsigned int size () const;
    inline bool empty () const;
    inline iterator begin ();
    inline iterator end ();
    inline T& front ();
    inline T& back ();
    //void insert (iterator position, const T &x);
    //void push_back (const T &x);
    //void push_front (const T &x);
    //void pop_back ();
    //void pop_front ();

};

template <class T>
inline list<T>::iterator::iterator () {

    ptr = NULL;

}

template <class T>
inline T& list<T>::iterator::operator*() {

    return ptr->data;

}


template <class T>
inline iterator list<T>::iterator::operator++() {

    ptr = ptr->next;
    return *this;

}

template <class T>
inline iterator list<T>::iterator::operator++(int) {

    iterator tmp = ptr;
    ptr = ptr->next;
    return tmp;

}

template <class T>
inline iterator list<T>::iterator::operator --() {

    ptr = ptr->prev;
    return *this;

}

template <class T>
inline iterator list<T>::iterator::operator --(int) {

    iterator tmp = ptr;
    ptr = ptr->prev;
    return tmp;

}

////////////////////
////////////////////

template <class T>
inline list<T>::list () {

    head.next = &head;
    head.prev = &head;
    length = 0;


}

template <class T>
inline unsigned int list<T>::size () const {

    return length;

}

template <class T>
inline bool list<T>::empty () const {

    return length == 0;

}

template <class T>
inline iterator list<T>::begin () {

    return head->next;

}

template <class T>
inline iterator list<T>::end () {

    return &head;

}

template <class T>
inline T& list<T>::front () {

    return *begin();

}

template <class T>
inline T& list<T>::back () {

    return *(--end());

}

我遇到了这个错误:

list.h:64: error: expected initializer before ‘list’
list.h:72: error: expected initializer before ‘list’
list.h:81: error: expected initializer before ‘list’
list.h:89: error: expected initializer before ‘list’
list.h:125: error: expected initializer before ‘list’
list.h:132: error: expected initializer before ‘list’

不，我没有漏掉分号。

有什么想法吗？

Answer 1

因为你的定义是类外的，所以嵌套类型迭代器不在范围内；您需要限定对 iterator

的引用

template <class T>
inline iterator list<T>::iterator::operator++() {

应该是

template <class T>
inline typename list<T>::iterator list<T>::iterator::operator++() {