d(p(A,B), p(Da,Db)) :- d(A,Da), d(B,Db).
d(t(A,B), p(t(A,Db),t(Da,B))) :- d(A,Da), d(B,Db).

d(x,1).
d(Y,0).

?d(p(t(x,3),4),Ans), write(answer), write(Ans).