[cmcaine]

It's correct if you want to do something `length(A)` times and want an iteration counter, but it's never better than `for idx in eachindex(A)` if what you actually want are indexes into A (which is of course the much more common case).

Julia did not initially support arrays that aren't indexed from 1 (experimental support added in Julia 0.5, I don't know when it was finalised), and at that time I'm not even sure we had something like eachindex, certainly there would be no reason why someone would use it for an array.