/**
?- traverse([i,am,happy],[[i,eat,apple],[apple,makes_me,happy]],Facts2).

Yes
traverse([i, am,happy],[[i,eat,apple],[apple,makes_me,happy], [i, eat, appleseed], [appleseed, is_in, apple]], _L207).
**/

/** 

traverse(+Proposition,+Facts,-Facts2)

Proposition is form [Subject,Verb,Object]
Facts is in form of list of [Proposition]

**/

%%traverse(_,[],_):-fail.
traverse([Subject,_,Object],Facts,Facts2) :- 
	traverse1(Subject,Object1,Facts,Facts1), traverse1(Object1,Object,Facts1,Facts2).

/**

traverse(+Proposition,+Facts,-Facts2)

As for traverse

**/

traverse1(Subject,Object,Facts,Facts3) :-
	delete(Facts,[Subject,_,Object],Facts2), traverse2([Subject,_,Object],Facts2,Facts3),!.

/**  
%%traverse2(_,[],_):-fail.
traverse2([+Proposition,+Terminator],+Facts,-Facts1) 

where terms are described as for traverse/1.

**/

 
traverse2([Subject,_,Object],Facts,Facts3) :-
	member([Subject,_,Object1],Facts), member([Object1,_,Object],Facts),
	traverse([Subject,_,Object],Facts,Facts3).
traverse2([Subject,_,Object],Facts,Facts) :-
	not(member([Subject,_,Object1],Facts)),not(member([Object1,_,Object],Facts)).