Accessing list element pointed by an iterator

Question

The natural answer would be to dereference the iterator and get the value. However, I'm stuck at using VC++ 2010 which doesn't allow dereferencing the list iterator (or does it?) I'm confused because, at one point, I need to dereference two list iterators and compare their values using: (*it) == (*it2) The program crashes with an error, only due to this line. I'm also dereferencing the iterator in a statement: printf("%d\n", (*it)); This works perfectly fine though. So, is there any way to access an element without dereferencing or using a cliext::list.

for (it=sList.begin(); it != sList.end(); it++)
{
    for (it2=it; it2 != sList.end(); it2++)
    {
        it2++;
        if ((*it) == (*it2))
        {
           sList.erase(it, it2);
        }
        it2--;
    }
}

The error I get is:

Debug Assertion Failed

Expression: list iterator not dereferencable

Surprisingly the same code runs without a problem when compiled on DevC++ (MinGW)

Answer 1

You can in fact dereference list iterators. If you couldn't, your comparison code wouldn't have even compiled. Most likely you're accidentally dereferencing an end iterator though rather than a valid one, causing the crash. Without more code it's hard to make further observations.

EDIT: I can't make out quite what it is you're trying to do. The code you've written erases all the elements between two equal elements. I'll assume you're actually trying to remove all the duplicate elements, and that sorting the list first for performance isn't a concern/option.

EDIT2: I saw in a comment below you really want to delete the range. Updated my code.

Then try something like this:

for (it=sList.begin(); it != sList.end(); ++it)
{
    it2 = it;
    ++it2;
    while(it2 != sList.end())
    {
        if ((*it) == (*it2))
        {
           it = it2 = sList.erase(it, it2);  // Reset it as well since it will be blown away. It'll still point to the same value it did before though.
        }
        else
            ++it2;
    }
}