I hadn't realised that tail-recursion optimisations could operate in a 'mixed environment'. That is to say, the last time I took the time to investigate the mechanisms involved, they seemed to only operate in an all-or-nothing manner. I remember several long articles/series in Byte, JoACM and others about techniques for ensuring that tail-recursion wasn't inhibited. That only goes to show how long I have been suffering under the delusion that TR wasn't a useful technique outside of those languages that make a virtue of it.

I'm long overdue taking the time to re-visit the issue I think. Thanks. Now I'm off in search of a nice self-contained example of a mixed recursion/TR algorithm to play with:)