append([],A,A).
append([H,T],A,[H|S]):-append(T,A,S).
append(A,X,L).

subset([],_).
subset([X|R],L):-member(X,L),subset(R,L).

member(A,[A|_]).

member(A,[H|T]):-member(A,T).
%?-member(1,[1]).

between(A,A,Y):-A=<Y.
between(A,X,Y):-X<Y,X1 is X + 1, between(A,X1,Y).

%?-between(A,7,10),write(A).

e(0).
e(X):-X is Y+2,e(Y),write(X).
?-e(6).