Не работает сортировка в qt

void qSort ( RandomAccessIterator begin, RandomAccessIterator end )
Sorts the items in range [begin, end) in ascending order using the quicksort algorithm.
Example:
 QList<int> list;
 list << 33 << 12 << 68 << 6 << 12;
 qSort(list.begin(), list.end());
 // list: [ 6, 12, 12, 33, 68 ]
The sort algorithm is efficient on large data sets. It operates in linear-logarithmic time, O(n log n).
This function requires the item type (in the example above, int) to implement operator<().
If neither of the two items is "less than" the other, the items are taken to be equal. It is then undefined which one of the two items will appear before the other after the sort.
See also qStableSort() and random access iterators.