prolog/1.pl at master · ankitajoshi15/prolog · GitHub

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parent(pam,bob).
parent(tom,bob).
parent(tom,liz).
parent(bob,ann).
parent(bob,pat).
parent(pat,jim).

female(pam).
female(liz).
female(pat).
female(ann).
male(tom).
male(bob).
male(jim).

offspring(Y,X) :-
	parent(X,Y).

mother(X,Y) :-
	parent(X,Y),
	female(X).

grandparent(X,Z):-
	parent(X,Y),
	parent(Y,Z).

sister(X,Y) :-
	parent(Z,X),
	parent(Z,Y),
	X  \= Y,
	female(X).

happy(X) :-
	parent(X,_).

hastwochildren(X) :-
	parent(X,Y),
	sister(Y,_).

grandchild(X,Y) :-
	grandparent(Y,Z).

aunt(X,Z) :-
	parent(Y,Z),
	sister(X,Y).

predecessor(X,Z) :-
	parent(X,Z).

predecessor(X,Z) :-
	parent(X,Y),
	pedecessor(Y,Z).