Error in Family Tree using Prolog

Question

I have some issues in my family tree. As required, I need to create predicates on father, mother, son, daughter, grandfather, sibling, aunt, uncle, cousin, spouse, parent_of based on the facts of Male, Female, parent_of.

male(jerry).
male(stuart).
male(warren).
male(peter).
female(kather).
female(maryalice).
female(ann).
brother(jerry,stuart).
brother(jerry,kather).
brother(peter, warren).
sister(ann, maryalice).
sister(kather,jerry).
parent_of(warren,jerry).
parent_of(maryalice,jerry).

father(X,Y) :- male(X), parent_of(X,Y).
mother(X,Y) :- female(X), parent_of(X,Y).
son(X,Y) :- male(X), parent_of(Y,X).
daughter(X,Y) :- female(X), parent_of(Y,X).
grandfather(X,Y) :- father(X,P), parent_of(P,Y).
sibling(X,Y):- parent_of(P,X), parent_of(P,Y), X\=Y.
aunt(X,Y) :- sister(X,P), parent_of(P,Y).
uncle(X,Y) :- brother(X,P), parent_of(P,Y).
cousin(X,Y):- sibling(P,Q), parent_of(P,X), parent_of(Q,Y).
spouse(X,Y) :- parent_of(X,P), parent_of(Y,P).
parent_of(X,Y) :- male(X), father(X,Y); female(X), mother(X,Y).

The parent_of predicate gives me an error. Clasues of parent_of/2 are not together in the source file. When I ignore the error and run a query ?- sibling(jerry, stuart), it gives me an error out of local stack. Anyone know how to solve this problem. Your help will be appreicated. Thanks.

C.B. C.B. · Accepted Answer · 2014-03-28T15:14:21

Problem 1

The parent_of predicate gives me an error. Clasues of parent_of/2 are not together in the source file.

Simply place definitions of the predicate right next to eachother

Change

parent_of(warren,jerry).
parent_of(maryalice,jerry).

...
spouse(X,Y) :- parent_of(X,P), parent_of(Y,P).
parent_of(X,Y) :- male(X), father(X,Y); female(X), mother(X,Y).

to

parent_of(warren,jerry).
parent_of(maryalice,jerry).
parent_of(X,Y) :- male(X), father(X,Y); female(X), mother(X,Y).
...
spouse(X,Y) :- parent_of(X,P), parent_of(Y,P).

Problem 2

?- sibling(jerry, stuart), it gives me an error out of local stack.

You have a circular logic error. You define parent_of\2 in terms of father\2 and father\2 in terms of parent_of\2. This will cause each to circle off into Prolog never-never-land.

Error in Family Tree using Prolog

1 Answers