STL iterator: Assertion Error

Question

Why does the following code produce an assertion error: Expression: list iterators incompatible ?

#include <list>
using namespace std;

int main()
{
    list<int> a;
    a.push_back(1);
    list<int>::iterator iter=a.begin();
    a.erase(iter);

    iter==a.end();
}

Answer 1

What you want to do is this:

#include <list>
using namespace std;

int main()
{
    list<int> a;
    a.push_back(1);
    list<int>::iterator iter=a.begin();
    iter = a.erase(iter);
}

Answer 2

在一个给定集合的迭代a时变为无效a变化，例如，通过移除元素。

Answer 3

When erasing iter it got invalidated. I think invalid iterator can't be used for anything other than assigning to them, not even comparing them with anything. You might have wanted to use

iter = a.end();

Answer 4

the iterator is invalid after the erase. in your case erase itself returns (you drop it) the end iterator as you were deleting the last element