Modified Version of node_expand

node_expand(N,NL) :-
 node_state_of(N,S),
 stn(S,SL),
 sl2nl(SL,NL).

% sl2nl(SL, NL)
% list of states SL => list of nodes NL

sl2nl([],[]).

sl2nl([S|Y],[N|NL]) :-
 node_new(N),
 node_state_of(N,S),
 sl2nl(Y,NL).