solving cubic/quartic equations non-iteratively

To R-helpers,

R offers the polyroot function for solving mentioned equations iteratively.

However, Dr Math and Mathworld (and other places) show in detail how to
solve mentioned equations non-iteratively.

Do implementations for R that are non-iterative and that solve mentioned
equations exists?

As far as I know, we don't even have the quadratic...

They can't be hard to implement, though. However, you may need to take
care that non-iterative solutions are not necessarily more precise or
even faster than iterative ones. There may be cancellation issues and
the closed-form expressions can be complicated and involve slow function
calls.

O__  ---- Peter Dalgaard             ?ster Farimagsgade 5, Entr.B
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