> For the first iteration, after considering your input, I'd go with
> "init function", "get random row", "end function", without imposing an
> index, but somehow passing a (COND or similar) arg to the init
> function.

For the first iteration I'd go without a condition. You, probably
shouldn't add an API that you won't use, and in the first iteration you
won't use it, right? It can be added later when needed.