Ray Dillinger scripsit:

> Okay, I got that far.  But as I said, my problem is getting an exact 
> result while taking a qth root.  That's the part I don't know how to 
> do, except by getting lucky in interval division.

Oh.  Easy-peasy.  Get a quick upper bound for the qth root, call it y,
then do a binary search over the interval 1 .. y.  You can memoize the
fixnum-sized powers of q, too.

The classic square-root-by-hand algorithm works like this too, except
that it does a "decimal search" instead of binary search.  It's a close
relative of the long division algorithm.

-- 
John Cowan    http://ccil.org/~cowan    [email protected]
Mr. Henry James writes fiction as if it were a painful duty.  --Oscar Wilde

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