std :: list implementation&指针化学。 [英] std::list implementation & pointer arithemetic.

问题描述

根据我的理解，std :: vector分配/解除分配它需要的所有内存，每次它的元素增长或收缩，因此指针算术可以用于迭代矢量元素。

As I understand it, std::vector allocates/de-allocates all the memory it requires each time it's elements grows or shrinks, therefore pointer arithmetic can be used to iterate the vector elements.

std :: list另一方面使用双链表，每个元素指向下一个和上一个元素。

std::list on the other hand uses a double linked list, with each element pointing to the next and previous element.

假设（可能是错误的）std :: list动态分配它的内存，所以内存被分配，如果需要的话，递增。如何std :: list仍然能够提供指针算术作为迭代它的元素的方法。

Assuming(possibly wrongly) that std::list allocates it's memory dynamically, so memory is allocated, if and when required, incrementally. How is std::list still able to offer pointer arithmetic as a means to iterate it's elements?.

推荐答案

可以假设 std :: list :: iterator 是指向列表元素的指针的容器 struct iterator {list :: element * current}; 。一个元素有指向下一个和前一个的指针，如 struct element {list :: element * next，* previous}; 当你递增迭代器时，指向下一个元素。像链接列表中的 it-> current = it-> current-> next 。没有涉及指针算术。

Roughly speaking, you can assume an std::list::iterator to be a container for pointer to a list element struct iterator { list::element *current };. And an element has pointers to the next and previous, like struct element { list::element *next, *previous }; When you increment that iterator, it just reassigns this pointer to point to the next element. Like it->current = it->current->next in linked lists. No pointer arithmetics involved.

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