function S = simple_paths(M)
u0 = '';
q0 = M.q0;

global S
S = {''};
simple_sub(M,u0,q0);
return

function simple_sub(M,u0,q0)
global S
for s = M.ALF
  q1 = dfsa_delta(M,q0,s);
  if q1~=q0
    u1 = [u0 s];
    S{end+1} = u1;
    simple_sub(M,u1,q1)
  end
end
return

function S = simple_paths0(M,u0)
if ~exist('u0','var'), 
  u0 = '';
end
if length(M.Q)==1
  S = {''};
else
  q0 = M.q0;
  S = {};
  for s = M.ALF
    q1 = dfsa_delta(M,q0,s);
    if q1~=q0
      Mq1 = M;
      Mq1.q0 = q1;
      Mq1 = minimize_dfsa(Mq1);
      Sq1 = simple_paths(Mq1);
      for i=1:length(Sq1)
        S{end+1} = Sq1{i};
        S{end+1} = [s Sq1{i}];
      end
    end
  end
end
return