T Selector::sub_select(const T &x, const Selector &rhs) const {
assert(rhs.nvars() <= this->nvars());
assert(this->covers(rhs));
Selector tmp(nvars(), false);
for (uint i = 0; i < rhs.nvars(); ++i) {
tmp.add(INDX(rhs.indx(i)));
}
return tmp.select(x);
}
uint indx(uint i)const{return inc_.indx(i);}