Well, for some reason your iteration triggered stream case.
And AFAICS the error message is true: there is no 'swhile'
in algebra. It seems that corresponding code remains
unimplemented. To say the truth, implementation of this
looks like can of worms. And we have a lot of things that
could be improved, so this one waits for more attention.
To say the truth, getting iteration for generators to work seem
more important. And IMO interation over stream should be
special case of interation using generators. But when I
looked at this there seemed to be almost no interest
(you basicaly wrote that if our generators can not do
all what Aldor generators do, then they are not interesting).
So some initial work is done, but I moved to other things.
--
Waldek Hebisch