const 与c++指针 - 计算机学习指南

[giscus[bot]]

const 与c++指针 - 计算机学习指南

计算机学习指南，这里有从网络上收集的计算机各种方面的知识技能，可供查阅和学习

https://cs.meowrain.cn/Blogs/meowrain/c%2B%2B/const%E4%B8%8Ec%2B%2B%E6%8C%87%E9%92%88/

[meowrain]

做个笔记

/*
A const Pointer
*/

//------------------------------------------------------------
//constant pointer to a non-constant int
// This means that the pointer `p` is constant, i.e.,
// it cannot be reassigned to point to a different memory location. However, the value it points to can be modified. For example, you can change the value of `*p`,
// but you cannot make `p` point to a different memory location.
int * const p; 
//------------------------------------------------------------


//------------------------------------------------------------
// non-constant pointer to a constant int
//which means that the value which pointer p point can not be changed because it is constant.
// But pointer p can point to another memory location.
// The Writing method below are same;
const int* p;
int const* p;

//------------------------------------------------------------
// constant pointer to a constant int
// which means that the pointer can not point to another memory location,at the same time,the value p points also can not be changed.
// The pointer and the value it points are all constant
const int* const p;
int const* const p;
//------------------------------------------------------------

[meowrain]

就看const是不是在p左边，挨着就是常量指针，不挨着就是指向常量得指针😊

[meowrain]

const Iterators

iterators act like pointers
for example: const vector<int>::iterator itr acts like int* const itr,it is just a constant pointer point to a memory location,
which means that we can not let itr point to a new memory location,But we can use it to change the value it points

Let's see the code

#include <iostream>
#include <vector>

int main(void) {
	std::vector<int> v{1,2,3,4,5};
	const vector<int>::iterator itr = v.begin();
	itr++; // compile wrong!
	*itr = 15; //compile successfully!
	return 0;
}