ref: 2d7f3ffa770b6eb698566b6566d7e37f10193744
dir: /example.pl/
:- dynamic(math/4). math(A,B,C,D) :- D is A + B + C * A. true. likes(bob, ice). likes(sam, text). likes(sam, ice). could_be_friends(Person1, Person2) :- likes(Person1, Thing1), likes(Person2, Thing2), Thing1 = Thing2.