..........
The point is, people keep insisting that there are a vast number of
algorithms which are best expressed using recursion and which require TCO to
be practical, and yet when asked for examples they either can't give any
examples at all, or they give examples that are not well-suited to
recursion. Or, at best, examples which are equally good when written either
using recursion or iteration.
I do believe that such examples surely must exist. But I'm yet to see one.
....
I believe the classic answer is Ackermann's function
http://demonstrations.wolfram.com/RecursionInTheAckermannFunction/
which is said to be not "primitive recursive" ie cannot be unwound into loops;
not sure whether that implies it has to be recursively defined or can perhaps be
broken down some other way. For more eye-glazing
http://math.stackexchange.com/questions/75296/what-is-the-difference-between-total-recursive-and-primitive-recursive-functions
--
Robin Becker
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