% ~/bin/pl
% ['examples.pl'].
% ? - can_fly(X).
%   X = tweety ; 
% halt.

thing(X) :- animal(X).
thing(X) :- plant(X).
animal(Y) :- mammal(Y).
animal(X) :- reptile(X).
animal(X) :- bird(X).
blooded(X,warm) :- mammal(X).
blooded(X,warm) :- bird(X).
blooded(X,cold) :- reptile(X).
reptile(X) :- snake(X).
mammal(X) :- dog(X).

plant(X) :- tree(X).
green(X) :- plant(X).

snake(sammy).
dog(snoopy).
bird(tweety).
tree(pine).

can_move(X) :- animal(X).
can_move(X) :- can_fly(X).
can_fly(X) :- bird(X).

good_pet(X) :- animal(X),\+ blooded(X,cold).

%%%%%%%%%%%%%%

can_fly(X) :- plane(X).
can_move(X) :- tank(X).

plane(p1).
plane(p2).
plane(p3).
tank(t1).
friendly(p1).
friendly(t1).
military(X) :- plane(X).
military(X) :- tank(X).
enemy(X) :- military(X),\+ friendly(X).

target(X) :- enemy(X).