Section Fcore_digits.
Variable beta : radix.
Definition Zdigit n k := Z.rem (Z.quot n (Zpower beta k)) beta.

Theorem Zdigit_ge_Zpower_pos :
forall e n,
(0 <= n < Zpower beta e)%Z ->
forall k, (e <= k)%Z -> Zdigit n k = Z0.