Our coding guidelines prefer const_iterator, because they are a little faster compared to a normal iterator. It seems like the compiler optimizes the code when you use const_iterator.
Is this really correct? If yes, what really happens internally that makes const_iterator faster?.
EDIT: I wrote small test to check const_iterator vs iterator and found varying results:
For iterating 10,000 objects const_terator was taking a few milliseconds (around 16 ms) less. But not always. There were iterations in which both were equal.
If nothing else, a const_iterator reads better, since it tells anyone reading the code "I'm just iterating over this container, not messing with the objects contained".
That's a great big win, never mind any performance differences.