使用指针作为容器迭代器是否违反标准 [英] Does Using a Pointer as a Container Iterator Violate the Standard
问题描述
Angew发表了评论使用原始指针作为迭代器类型的vector很好.那有点让我感到困惑.
Angew made a comment that a vector using a raw pointer as it's iterator type was fine. That kinda threw me for a loop.
我开始研究它，发现对vector迭代器的要求只是它们是，其中明确指出了指针符合条件:
I started researching it and found that the requirement for vector iterators was only that they are "Random Access Iterators" for which it is explicitly stated that pointers qualify:
指向数组元素的指针满足所有要求
A pointer to an element of an array satisfies all requirements
是编译器甚至出于调试目的甚至向vector提供迭代器的唯一原因，还是实际上我错过了vector的要求?
Is the only reason that compilers even provide iterators to vector for debugging purposes, or is there actually a requirement I missed on vector?
推荐答案
§24.2.1
§ 24.2.1
由于迭代器是指针的抽象，因此其语义是大多数语义的概括 C ++中的指针集.这样可以确保每个带有迭代器的函数模板都可以正常工作 常规指针.
Since iterators are an abstraction of pointers, their semantics is a generalization of most of the semantics of pointers in C++. This ensures that every function template that takes iterators works as well with regular pointers.
是的，使用指针可以满足Random Access Iterator的所有要求.
So yes, using a pointer satisfies all of the requirements for a Random Access Iterator.
std::vector出于某些原因可能提供了迭代器
std::vector likely provides iterators for a few reasons
-
标准要求.
The standard says it should.
如果像std::map或std::set这样的容器提供了迭代器，而std::vector仅提供了value_type*指针，那将很奇怪.迭代器在整个容器库中提供了一致性.
It would be odd if containers such as std::map or std::set provided iterators while std::vector provided only a value_type* pointer. Iterators provide consistency across the containers library.
它允许向量类型的特殊化，例如std::vector<bool>，其中value_type*指针将不是有效的迭代器.
It allows for specializations of the vector type eg, std::vector<bool> where a value_type* pointer would not be a valid iterator.
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