cycling through frames in tiled layouts (and elsewhere?)

hi,

the question has been raised a few times before seemingly(?)
without a clear solution to it:

is there a lua-function to cycle through  all  frames  (i.e.
it's  currently  visible  client  window)  of a single tiled
workspace, say a 2 x 2 layout?   I  don't   mean   selection
from   some  context menu, but rather something like the be-
haviour of "Mod1+j" in `dwm'.

ioncore.goto_next(..., 'next', ...) is no good for  this  it
seems.

sure, one can _navigate_ with Mod1+Tab, N, P etc. but that's
not the same thing.

so is there a straightforward/easy way to do it?

joerg