Thread: list iterator question

Using <list>

Dose a list iterator keep an index of what number it is in the list?

About to go look through MSDN, not finding anything with google.

I found the function Distance that takes two iterators and returns the distance between them, so I could use that to find the position in the list, but I decided to just keep track of it outside of the list.

My list is a list of menu choices, and I need to know which one is the current selection, not just from the iterator, but the index from the start too.

>Dose a list iterator keep an index of what number it is in the list?
No, but you can acquire that information fairly easily by subtracting the first iterator in the list from the current one.

[edit]
My mistake. I was thinking of random access iterators rather than bidirectional iterators. For anything but a random access iterator the standard library has a function called distance in <iterator>.
[/edit]

Follow up question.


How can you loop an iterator around to make a list a circular list, what should be below...

Code:

list<object>::iterator selection;

void NextObject() {
    selection++;
    if(--something--) {
        selection = objectList.begin();
    }
}

Thats not going to work for the other direction is it?

Code:

if (selection == objectList.begin()) {
    selection = objectList.end();

got it now.

Code:

		if(selection == objectList->begin()) {
			selection = objectList->end();
			selection--;
		}
		else selection--;

thanks guys.