Thread: Question about using erase() with lists (STL)

Hi,
I want to remove one element pointed by iterator from a list. I read that when I use erase() on such list with precise iterator, then it returns the iterator for the element after which I removed. But now my question: is it correct not to catch what erase returns?
Example:

Code:

#include <cstdio>
#include <list>

using namespace std;

int main()
{
        list<int>       L;
        for(int i = 0; i < 5; i++)
                L.push_back(i+1);
        for(list<int>::iterator i = L.begin(); i != L.end(); i++)
                printf("%d\n", (*i));
        printf(".\n");
        for(list<int>::iterator i = L.begin(); i != L.end(); i++)
        {
                if((*i)==3)
                        printf("Hola!\n");
                if((*i)==2)
                {
                        L.erase(i); // or i=L.erase(i);
                        printf("%d\n", (*i));
                }
        }
        for(list<int>::iterator i = L.begin(); i != L.end(); i++)
                printf("%d\n", (*i));
        return 0;
}

Becouse when there is
L.erase(i);
then printf() prints "2" but this "2" is not on the list yet... so something here is wired? But when I have i=L.erase(i); then printf() prints "3" (next element) what is correct - but then I have to do i-- not to omit one possition in the loop, right? (If I don't i-- then in the moment there will be i++ so element with "3" will be omitted in the loop - no "Hola" at the output.). Can anyone explain me that?
Regards.

>> is it correct not to catch what erase returns?

It is legal, but it won't work as you expect. Magos' version is the common way to erase in a loop.

Obviously this is because erase returns the next valid position after the erased element, and the for loop does i++ skipping that valid position. That while loop only increments the iterator when erase does not do it itself.