baseSampler static method
Sample z0 in {0, 1, ..., 18} with a distribution very close to the
half-Gaussian D_{Z+, 0, maxSigma}.
Reads _rcdtPrec >> 3 == 9 bytes and interprets them as a little-endian
unsigned BigInt; z0 is the number of rcdt entries strictly greater
than that value.
Implementation
static int baseSampler(RandomBytes rb) {
final u = _bytesToBigIntLE(rb(_rcdtPrec >> 3));
var z0 = 0;
for (final elt in rcdt) {
if (u < elt) z0 += 1;
}
return z0;
}