%There are 8 candidates, A, B, C, D, E, F, G, H, for an expedition to the North Pole. Only 6 candidates have to be selected: one biologist, hydrologist, weather forecaster, telegraphist, mechanician and doctor.
%E and G can carry duties of a biologist,
%B and F - a hydrologist,
%F and G - a weather forecaster,
%C and D - a telegraphist,
%C and H - a mechanician, and
%A and D - a doctor.
%However, the candidates chosen can not share the duties.
%Find possible candidate groups, if

%F can only go together with B,
%D - with H and C,
%C can not go with G, and
%A not with B.

group(A,B,C,D,E,F) :-
    bio(A),
    hydro(B),
    weath(C),
    tel(D),
    mech(E),
    doc(F).
    no_doubles([A,B,C,D,E,F]).
    rules(G),

bio(e).
bio(g).
hydro(b).
hydro(f).
weath(f).
weath(g).
tel(c).
tel(d).
mech(c).
mech(h).
doc(a).
doc(d).

no_doubles([]).
no_doubles([A|B]) :-
    not(contains(A,B)),
    no_doubles(B).

takeout(A,[A|B],B).
takeout(A,[B|C],[B|D]) :-
    takeout(A,C,D).

contains(A,[A|_]).
contains(_,[]) :- false.
contains(A,[_|C]) :-
    contains(A,C).

rules(contains(f,G)) :-
    contains(b,G),
    takeout(f,G,NG),
    rules(NG).
rules(contains(d,G)) :-
    contains(h,G),
    contains(c,G),
    takeout(d,G,NG),
    rules(NG).
rules(contains(c,G)) :-
    not(contains(g,G)),
    takeout(c,G,NG),
    rules(NG).
rules(contains(a,G)) :-
    not(contains(b,G)),
    takeout(a,G,NG),
    rules(NG).
rules(_).