We routinely iterate over containers with range-base for loop, or the pre-C++11 iterator based approach:
for(auto current = container.begin(); current != container.end(); ++current)
It is usually taught as a much preferred way over the "C-ish" iterations based on index increments:
for(auto currentId = 0; currentId != container.size(); ++currentId)
Yet, what if the requirement is to iterate every N th element, for example every third?
An erroneous rewrite of the above approach would give:
// Error for(auto current = container.begin(); current != container.end(); current += 3)
Now, our programs exhibit undefined behaviour each time
(container.size() % 3) != 0.
- What would be the canonical C++ way to address such requirement?
- Can it be done reasonably with iterator based iteration?
- Should we fall-back to indexes (with comparison becoming