[Irit]

> Is this still needed?

It's not needed for geometric_mean. It's still a reasonable feature request, but it would be non-trivial effort to put a good quality implementation together - C doesn't have this function, so we can't simply wrap it like we did for cbrt. But at least IEEE 754 does specify a "rootn" function, so we know what the behaviour should be in all the various special cases.

cbrt probably covers a good proportion of use-cases for rootn (those that weren't already satisfied by sqrt).

NumPy seems to have survived without needing a rootn function so far, which seems like an indication that it's not a really pressing need.

Let's close, and re-open or open a new issue if someone discovers another good use-case.