PPT Slide
next_to( X , Y ) : - adjacent( X , Y ) .
next_to( X , Y ) : - adjacent( Y , X ) .
connected( A , B ) : - connect_mark( A , B , [ A ] ) .
connect_mark( A , B , MarkedList ) : -
nonmember( B , MarkedList ) ,
print( [ B | MarkedList ] ) .
connect_mark( A , B , MarkedList ) : -
nonmember( C , MarkedList ) ,
connect_mark( C , B , [ C | Marked List ] ) .
nonmember( X , L ) : - not( member ( X , L ) ) .