python - 如何在C++中创建一个可迭代的类？

Question

我有一个链表代码:

#include <iostream>
class Node
{
private:
    /* data */
public:
    int value;
    Node* next;
    Node(int value){
        this->value = value;
        this->next = nullptr;
    }
};

class LinkedList
{
private:
    /* data */
public:
    Node *start;

    LinkedList(){
        this->start = nullptr;
    }

    void insert(int value){
        Node *node = new Node(value);
        if (this->start == nullptr)
        {
            this->start = node; 
        }else
        {
            Node* temp = this->start;
            while (temp->next != nullptr)
            {
                temp = temp->next;
            }
            temp->next = node;
        }
        
        

    }

    void print(){
        Node* temp = this->start;
        while (temp != nullptr)
        {
            std::cout<<temp->value<<std::endl;
            temp = temp->next;
        }
        
    }

    void __iter__(){
        Node* node = this->start;
        while (node)
        {
            yield node;
            node = node->next;
        }
        
    }
};

int main(int argc, char const *argv[])
{
    LinkedList listed;
    listed.insert(4);
    listed.insert(7);
    listed.insert(9);
    listed.insert(6);
    listed.print();

    return 0;
}

如您所见，我的 LinkedList 类中有 __iter__ 方法，但我发现 yield 未定义在 C++ 中使用，所以我的控制台只显示:

info.cpp: In member function 'void LinkedList::__iter__()':
info.cpp:59:13: error: 'yield' was not declared in this scope
   59 |             yield node;
      |             ^~~~~

我正在引用下一段Python代码:

def __iter__(self):
        node = self.start
        while node:
            yield node
            node = node.next

希望您能帮我解决这个问题，谢谢。

Answer 1

看看这个来源:https://en.cppreference.com/w/cpp/iterator/iterator

它是这么说的

std::iterator is the base class provided to simplify definitions of the required types for iterators.

此外:

此来源https://cplusplus.com/reference/iterator/iterator/

为您提供以下示例:

// std::iterator example
#include <iostream>     // std::cout
#include <iterator>     // std::iterator, std::input_iterator_tag

class MyIterator : public std::iterator<std::input_iterator_tag, int>
{
  int* p;
public:
  MyIterator(int* x) :p(x) {}
  MyIterator(const MyIterator& mit) : p(mit.p) {}
  MyIterator& operator++() {++p;return *this;}
  MyIterator operator++(int) {MyIterator tmp(*this); operator++(); return tmp;}
  bool operator==(const MyIterator& rhs) const {return p==rhs.p;}
  bool operator!=(const MyIterator& rhs) const {return p!=rhs.p;}
  int& operator*() {return *p;}
};

int main () {
  int numbers[]={10,20,30,40,50};
  MyIterator from(numbers);
  MyIterator until(numbers+5);
  for (MyIterator it=from; it!=until; it++)
    std::cout << *it << ' ';
  std::cout << '\n';

  return 0;
}

它包括通过 #include <iterator> 的迭代器，将其操作定义为 public然后在main里面函数有效地使用了它。您将需要应用类似的东西，但您将需要在 operator++ 的指针之间步进。方法。