STL vector vs map erase

Question

In the STL almost all containers have an erase function. The question I have is in a vector, the erase function returns an iterator pointing to the next element in the vect

Answer 1

The inconsistency is due to use. vector is a sequence having an ordering over the elements. While it's true that the elements in a map are also ordered according to some comparison criterion, this ordering is non-evident from the structure. There is no efficient way to get from one element to the next (efficient = constant time). In fact, to iterate over the map is quite expensive; either the creation of the iterator or the iterator itself involves a walk over the complete tree. This cannot be done in O(n), unless a stack is used, in which case the space required is no longer constant.

All in all, there simply is no cheap way of returning the “next” element after erasing. For sequences, there is a way.

Additionally, Rob is right. There's no need for the Map to return an iterator.