We already realized that iterators are, kind of, the standard interface for iterations over containers of all kinds. We just need to implement the prefix increment operator, ++, the dereference operator, *, and the object comparison operator, ==, and then we already have a primitive iterator that fits into the fancy C++11 range-based for loop.
In order to get used to this a bit more, this recipe shows how to implement an iterator that just emits a range of numbers when iterating through it. It is not backed by any container structure or anything similar. The numbers are generated ad hoc while iterating.
