next prev函数怎么用啊

#include <bits/stdc++.h>
using namespace std;
vector <int> a;
int main(){
	for(int i = 0; i < 10; ++i) a.push_back(i), cout<<a[i]<<" "; cout<<'\n';
	// 0 1 2 3 4 5 6 7 8 9 
	vector<int>::iterator iter = a.begin();
	cout<<*iter<<'\n';
	advance(iter,6);
	cout<<*iter<<'\n';
	advance(iter,-1);
	cout<<*iter<<'\n';
	
	cout<<*iter.next()<<*iter.prev();//这里报错了
	return 0;
}