[debug]  ?- e_closure(nfa([0,1,2,3],[],[(0,epsilon,1),(1,epsilon,2),(2,epsilon,3),(1,epsilon,0)],0,[2]),From,To).
From = To ;
From = 0,
To = 1 ;
From = 0,
To = 2 ;
From = 0,
To = 3 ;
From = 1,
To = 2 ;
From = 1,
To = 3 ;
From = 2,
To = 3 ;
From = 1,
To = 0 ;
false.