I quite like the “enumerate” pattern. When indexes matter, instead of `for x in v` you would write, `for (i, x) in enumerate(v)`, then the language only needs one type of for loop as both cases use the same enumerator interface.
Yes I was thinking of something like that. Only I wish I could also know whether I is first and/or last without calling into the iterated structure. I know this looks like corner case syntactic sugar but it comes up a lot, e.g. when serializing to JSON. I guess I should write my own iterators but I want them everywhere...
