On 2023-02-18 03:52:51 +0000, Oscar Benjamin wrote: > On Sat, 18 Feb 2023 at 01:47, Chris Angelico <ros...@gmail.com> wrote: > > On Sat, 18 Feb 2023 at 12:41, Greg Ewing via Python-list > > > To avoid it you would need to use an algorithm that computes nth > > > roots directly rather than raising to the power 1/n. > > > > > > > It's somewhat curious that we don't really have that. We have many > > other inverse operations - addition and subtraction (not just "negate > > and add"), multiplication and division, log and exp - but we have > > exponentiation without an arbitrary-root operation. For square roots, > > that's not a problem, since we can precisely express the concept > > "raise to the 0.5th power", but for anything else, we have to raise to > > a fractional power that might be imprecise. > > Various libraries can do this. Both SymPy and NumPy have cbrt for cube roots:
Yes, but that's a special case. Chris was talking about arbitrary
(integer) roots. My calculator has a button labelled [x√y], but my
processor doesn't have an equivalent operation. Come to think of it, it
doesn't even have a a y**x operation - just some simpler operations
which can be used to implement it. GCC doesn't inline pow(y, x) on
x86/64 - it just calls the library function.
hp
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