#include <iostream>
#include <vector>
#include <algorithm>
template <typename T>
class _iterator
{
T* ptr;
public:
using iterator_category = std::random_access_iterator_tag;
using value_type = T;
using reference = T&;
using pointer = T*;
using difference_type = unsigned long long;
_iterator(T* ptr) : ptr(ptr) {}
reference operator* () { return *ptr; }
pointer operator->() { return ptr; }
_iterator& operator++() { ptr++; return *this; }
_iterator& operator--() { ptr--; return *this; }
difference_type operator-(const _iterator& it) { return this->ptr - it.ptr; }
_iterator operator+(const difference_type& diff) { return _iterator(ptr + diff); }
_iterator operator-(const difference_type& diff) { return _iterator(ptr - diff); }
bool operator==(const _iterator& it) { return this->ptr == it.ptr; }
bool operator!=(const _iterator& it) { return this->ptr != it.ptr; }
bool operator< (const _iterator& it) { return this->ptr < it.ptr; }
operator _iterator<const T>() const { return _iterator<const T>(ptr); }
};
template <typename T>
class X
{
std::vector<T> data;
public:
using iterator = _iterator<T>;
using const_iterator = _iterator<const T>;
void push_back(T t)
{
data.push_back(t);
}
iterator begin()
{
return iterator(&data[0]);
}
iterator end()
{
return iterator(&data[0] + data.size());
}
};
int main()
{
X<int> x;
for (int i = 9; i >= 0; i--)
x.push_back(i);
// 1 ------------------------------------------------------------------------
// C2780 'void std::_Sort_unchecked(_RanIt,_RanIt,iterator_traits<_Iter>::difference_type,_Pr)': expects 4 arguments - 3 provided
// C2672 '_Sort_unchecked': no matching overloaded function found
// C2678 binary '-': no operator found which takes a left - hand operand of type 'const _RanIt' (or there is no acceptable conversion)
std::sort(x.begin(), x.end());
// 2 ------------------------------------------------------------------------
// C2666 '_iterator<T>::operator -': 2 overloads have similar conversions
// C2512 '_iterator<T>': no appropriate default constructor available
for (X<int>::iterator it = x.end() - 1; it >= x.begin(); --it)
std::cout << *it << ' ';
std::cout << std::endl;
}
我正在尝试为自定义容器编写随机访问迭代器。我面临几个问题:
错误写在与它对应的每一段代码之上。另外我不确定我定义的方式
iterator
和 const_iterator
是否有效。我在这里做错了什么以及如何解决它们?
最佳答案
// C2678 binary '-': no operator found which takes a left - hand operand of type 'const _RanIt' (or there is no acceptable conversion)
如果您将以下函数标记为
const
:difference_type operator-(const _iterator& it) const { return this->ptr - it.ptr; }
您将开始解决一些问题。我没有检查这是否涵盖了所有情况。但总的来说,尽你所能
const
有很大帮助。
关于c++ - 如何编写可与 STL 算法一起使用的随机访问自定义迭代器?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/61208870/