function vec = next_ind_vec(vec, n)
%vec is a vector consisting of distinct positive integers <= n, in
%increasing order.
%This function is for finding all subsets of 1:n, in lex order.

l = length(vec);
i = l;
j = n;
while(i > 0 && vec(i) == j)
    i = i - 1;
    j = j - 1;
end
if i == 0
    vec = [];
    return
end
q = vec(i);
vec(i:l) = q + (1:(l - i + 1));