rs(R,S,NQ,Q) :-
    (nand(S,Q,NQ,2) && true),
    (nand(R,NQ,Q,3) && true).

nand(A,B,Out,Delay) :-
    A = 1,B = 1,
    length(Delay),
    Out <- 0 .
nand(A,B,Out,Delay) :-
    A = 1,B = 0,
    length(Delay), 
    Out <- 1 .
nand(A,B,Out,Delay) :-
    A = 0,B = 1,
    length(Delay), 
    Out <- 1 .
nand(A,B,Out,Delay) :-
    A = 0,B = 0,
    length(Delay), 
    Out <- 1 .

test :- data(R,S),
    #rs(R,S,NQ,Q),
    #write((NQ,Q)).

data(R,S) :- length(4),
    read((R,S)),
    stable(R),stable(S)
 && @data(R,S).