I have a simple question that should have a simple answer but I can't think of it yet. I want to process an array, a certain number of elements at a time, and wrapping round to the beginning.

Here's a diagram showing when `n` is 10 and three elements are wanted each time:

[![iterations 3 at a time](https://i.stack.imgur.com/snECK.png)](https://i.stack.imgur.com/snECK.png)

My attempts to write a simple iteration so far have failed: using `% n` gives me zeros, which don't work with Julia's one-indexing... :)