The Nat module in the Num library is not documented in the official
documentation, but is documented in the 1992 tech report by Valérie
Ménissier-Morain. I would ilke to use Ocaml-only library for big
integers which has bit shifting operations. Big_int does not, but Nat
does. Is Nat stable and "safe to use" by people who are neither
French, nor at INRIA, nor are they Ocaml developers?

Before someone tells me I should use GMP and/or MPFR: I am already
using them, I am just rewriting a piece of code so that it can be
optionally compiled with pure ocaml.

Best regards,

Andrej