But your N is bounded from above to 4, so pretty much anything using these functions won't be unbounded in time just because of use of these functions. If you'r

But your N is bounded from above to 4, so pretty much anything using these functions won't be unbounded in time just because of use of these functions. If you're suggesting that using nth or elt on a list of arbitrary length is a bad idea, then yes, it is, but I certainly wasn't suggesting that.