ex24.in

formulas(sos).

  % 1. everyone is like him/herself.
  (all x (islike(x,x))).

  % 2. if someone is a member of a club, then they want to be a member and the club will accept them.
  (all x (all y (ismember(x,y) -> (want(x,y) & accept(y,x))))).

  % 3. groucho does not want to be a member of any club that will accept anyone like him.
  (all x ((exists y (accept(x,y) & islike(y, groucho))) -> -want(groucho, x))).

end_of_list.

formulas(goals).

  % 4. groucho is not a member of any club.
  (all x (-ismember(groucho, x))).

end_of_list.