lucy:~/451/F2007/Prolog> prolog
GNU Prolog 1.2.18
By Daniel Diaz
Copyright (C) 1999-2004 Daniel Diaz
| ?- [family].
compiling /home/jglenn/451/F2007/Prolog/family.pl for byte code...
/home/jglenn/451/F2007/Prolog/family.pl compiled, 18 lines read - 2365 bytes written, 6 ms

yes
| ?- spouse(steve,sandi).

yes
| ?- spouse(sandi,steve).

no
| ?- married(sandi,steve).

yes
| ?- married(X,Y).

X = steve
Y = sandi ? ;

X = sandi
Y = steve

yes
| ?- grandparent(X,Y).

X = dorothy
Y = liisa ? a

X = dorothy
Y = john

X = dorothy
Y = traci

X = olive
Y = traci

yes
| ?- son(X,Y).

X = steve
Y = dorothy ? a

no
| ?-

family.pl

father(steve,liisa).
father(steve,john).
father(steve,traci).
mother(judy,liisa).
mother(judy,john).
mother(sandi,traci).
mother(dorothy,steve).
mother(olive,sandi).
spouse(steve,sandi).

married(X,Y) :- spouse(X,Y).
married(X,Y) :- spouse(Y,X).
parent(X,Y) :- father(X,Y).
parent(X,Y) :- mother(X,Y).
grandparent(X,Y) :- parent(X,Z),parent(Z,Y).

male(X) :- father(X,_), !.
son(X,Y) :- parent(Y,X),male(X).