/* family.pl
 *
 * Example for CS 313
 *
 * to load, use "consult(family)." or the shorthand "[family]."
 */

l :- consult(family).  /* simple reload */

female(amy).
female(anna).
male(daniel).
male(peter).

parents(peter, amy, daniel).   /* child, mother, father */
parents(anna, amy, daniel).
	
sisterOf(X, Y) :-
        female(X),
        parents(X, Mother, Father),
        parents(Y, Mother, Father),
	X \= Y.

father(X) :-
        male(X),
        parents(_, _, X).

/* Try these queries:

?- sisterOf(anna, peter).
?- sisterOf(anna, amy).
?- parents(peter, X, Y).
?- sisterOf(X, anna).
?- sisterOf(X, Y).
?- father(X).

*/