[PRL] proper tail recursion

[Dave Herman]

> There probably is, but surely tail recursion wouldn't correspond to
> linearity.  After all, Scheme has proper tail recursion - but it also
> has first-class continuations.  You can make tail calls from within
> continuations that have quite a few references to them, so it's not
> really linearity that gives that to us.

Yeah. Some of the designers of Clean have talked about the possibility 
of making copies of unique objects and then doing destructive updates on 
one of the copies:

http://www.xs4all.nl/~keslr/functional/clean/wish/erik.html#ErikUniqueDup

(Clean has uniqueness types, which are similar to but not the same as 
linear types. Maybe uniquness is more the property I'm talking about, 
but I'm still not totally familiar with the concept.)

This all sounds quite similar to call/cc + PTR.

Dave

PS I'm really going to bed now, honest.