Question

代码如下

template<class T>
class arrayList {
public:
    // constructor, copy constructor and destructor
    arrayList(int initialCapacity = 10);
    arrayList(const arrayList<T>&);
    ~arrayList() {
        delete[] element;
    }

    class seamlessPointer;
    seamlessPointer begin() {
        return seamlessPointer(element);
    }
    seamlessPointer end() {
        return seamlessPointer(element + listSize);
    }

    // iterator for arrayList
      class iterator
      {
         public:
            // typedefs required by C++ for a bidirectional iterator
            typedef bidirectional_iterator_tag iterator_category;
            typedef T value_type;
            typedef ptrdiff_t difference_type;
            typedef T* pointer;
            typedef T& reference;

            // constructor
            iterator(T* thePosition = 0) {position = thePosition;}

            // dereferencing operators
            T& operator*() const {return *position;}
            T* operator->() const {return position;}

            // increment
            iterator& operator++();
                      {++position; return *this;}
            iterator operator++(int);

            // decrement
            iterator& operator--();
            iterator operator--(int) ;

            // equality testing
            bool operator!=(const iterator right) ;
            bool operator==(const iterator right) ;
         protected:
            T* position;
      };  // end of iterator class

        class seamlessPointer: public arrayList<T>::iterator {

        public:
            typedef random_access_iterator_tag iterator_category;
            typedef T value_type;
            typedef ptrdiff_t difference_type;
            typedef T* pointer;
            typedef T& reference;
            // constructor
            seamlessPointer(T *thePosition);
            seamlessPointer(const seamlessPointer & rhs);
            //arithmetic operators
            seamlessPointer operator+(int n) ;

            seamlessPointer operator-(int n) ;
    };

protected:
    T* element; // 1D array to hold list elements
    int arrayLength; // capacity of the 1D array
    int listSize; // number of elements in list
};

c:\wascana\mingw\bin\../lib/gcc/mingw32/4.5.0/include/c++/bits/stl_algo.h:5250:4: error: no match for 'operator-' in '__last - __first'

Answer 1

通过查看代码，您可以通过将这些typedef包含在您自己的迭代器实现中来获得正确的想法。但是，为什么在其他东西可以为你做的时候，首先要解决所有麻烦？您是否查看了iterator_traits或标准iterator？他们只是在你的代码中添加typedef，这将有助于你开发新的迭代器类型。

迭代器问题

1 个答案: