Re: tail recursion

[Jeff Dalton <jeff%aiai.edinburgh.ac.uk@NSFnet-Relay.AC.UK>]

> Then I define an implementation to be properly tail-recursive if,
>    for every program state P,
>       if continued execution eventually causes state P to recur,
>          and every non-tail-recursive evaluation begun since
>              the first occurrence of state P has completed
>              before the second occurrence of state P
>       then state P will recur indefinitely many times without
> 	 running out of resources

What about cases where some storage is allocated that isn't part of
the evaluation of the recursion itself?  (Reversing a list with an
accumulating parameter, say.)  What about loops that take input from
the user?  That is, when states don't recur, the definition doesn't
impose any restrictions at all on how the calls involved are
implemented.

It also seems to require garbage collection.