protected void loadLogs(DoubleArrayList to, int last) {
double logF = 0.;
int i = 1;
if (to.size() == 0) { // factorial 0!=1, 1!=1
to.add(logF);
} else {
logF = to.last();
i = to.size();
}
for (; i <= last; i++) {
logF += Math.log(i);
to.add(logF);
}
}
public double calc(int n) {
if (n >= SAVED_LOGS.size()) {
loadLogs(SAVED_LOGS, n + STEP_FORWARD);
}
return SAVED_LOGS.get(n);
}