// you can cut and paste
// or you can exec this file all at once via exec('filename')
// Add a semi-colon to reduce the output.
//
// Sets as column vectors
// For n small
n = 100;
// The universe
U = ones(n,1);
// The empty set
E = zeros(n,0);
// or 
E(n) = 0;
// A = [ 3, 9, 11 ]
A([3,9,11]) = 1;
// B = odds <= n
B(1:2:n) = 1;
// Which elements does A have?
find(A>0)