// cout << "recursion to leftchild at l = " << l << ", symbol = " << (uchar)symbol << ", rank0 = " << bitmap->rank0(pos) << ", rank1 = " << bitmap->rank1(pos) << endl;
// check left child for symbols <= givenSymbol
// cout << "recursion to leftchild at l = " << l << ", symbol = " << (uchar)symbol << ", rank0 = " << bitmap->rank0(pos) << ", rank1 = " << bitmap->rank1(pos) << endl;
// check left child for symbols <= givenSymbol