person(doreen). person(donna).
person(danny). person(david).

across(danny,david). across(david,danny).
across(doreen,donna). across(donna,doreen).

beside(X,Y) :- \+ across(X,Y).

uniq_people(A,B,C,D) :-
    person(A), person(B),
    \+ A=B,
    person(C),
    \+ A=C, \+ B=C,
    person(D),
    \+ A=D, \+ B=D, \+ C=D.

solution(Pizza) :-
    uniq_people(Pizza,Lasagna,Chicken,Steak),
    uniq_people(Coke,Milk,Water,Coffee),

    \+ doreen=Steak,
    beside(doreen,Steak),
    Chicken=Coke,
    across(Lasagna,Milk),
    \+ david=Coffee,
    donna=Water,
    \+ danny=Steak,

    write(Pizza), write(' ordered Pizza'), nl,
    write(Lasagna), write(' ordered Lasagna'), nl,
    write(Chicken), write(' ordered Chicken'), nl,
    write(Steak), write(' ordered Steak'),nl,
    nl,
    write(Coke), write(' ordered Coke'), nl,
    write(Milk), write(' ordered Milk'), nl,
    write(Water), write(' ordered Water'),nl,
    write(Coffee), write(' ordered Coffee'),nl.