[Octave-bug-tracker] [bug #43492] warning: division by zero for some nthroots of zero

[Marco Caliari]

Follow-up Comment #3, bug #43492 (project octave):

I found what the correction is: it is one step of Newton method (see
http://en.wikipedia.org/wiki/Nth_root_algorithm). I also found that without
the correction, nthroot(2^12,6) is not exactly 4 (the error is eps/2), while
it is with the correction. Anyway, it is not clear to me why a single step of
Newton method should give a better result in general. 

What it is less obvious to me is the following: both 2^(log2(2^12)/6) and
exp(log(2^12)/6) give exactly 4 but (2^12)^(1/6) not. How is it computed?

Marco

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