% Create a 2*N+1 dimensional Hermitian tridiagonal matrix
% (from J. H. Wilkinson) that has a *nearly* double eigenvalue.

 N = 10;

 A = diag([N:-1:0 1:N]) + diag(ones(2*N,1),1) + diag(ones(2*N,1),-1);

 ew = eig(A)
 gap = ew(2:end)-ew(1:end-1)
