I have a function I created using prolog and for some reason it always creating multi list for each element instead of one list, can someone please help me with that?
here is what I wrote:(problem is the last functin creates many lists)
father(_father,_child) :- parent(_father,_child), gender(_father,male).
mother(_mother,_child) :- parent(_mother,_child), gender(_mother,female).
couple(_woman,_man):- gender(_woman,female),gender(_man,male),parent(_man,_child),parent(_woman,_child).
parents(_woman,_man,_child) :- father(_man,_child),mother(_woman,_child).
count([],0).
count([H|T],N) :- count(T,N1) , N is N1+1.
child_to_couple(_woman,_man,_num):- couple(_woman,_man),findall(_child,parents(_woman,_man,_child),_childs),count(_childs,_num).
num_of_childs(_list):- couple(_woman,_man),setof(childrens(_man,_woman,_num),child_to_couple(_woman,_man,_num),_list).
example of data:
gender(sagi,male).
gender(limor,female).
gender(yuval,male).
gender(gilad,male).
gender(shahaf,male).
gender(yaara,female).
parent(eyal,noam).
parent(shiri,yuval2).
parent(eyal,yuval2).
parent(shiri,yonatan).
parent(eyal,yonatan).
parent(shahaf,gan).
parent(yaara,gan).
but when I run
?- num_of_childs(_x).
I get:
_x = [childrens(mordechai, miriam, 1)] ;
_x = [childrens(salax, naima, 1)] ;
_x = [childrens(eli, bella, 2)] ;
_x = [childrens(eli, bella, 2)] ;
_x = [childrens(zvi, tova, 1)] ;
_x = [childrens(avram, yokeved, 1)] ;
_x = [childrens(haim, irit, 3)] ;
_x = [childrens(haim, irit, 3)] ;
_x = [childrens(haim, irit, 3)] ;
_x = [childrens(guy, pelit, 2)] ;
_x = [childrens(guy, pelit, 2)] ;
_x = [childrens(eyal, shiri, 3)] ;
_x = [childrens(eyal, shiri, 3)] ;
_x = [childrens(eyal, shiri, 3)] ;
_x = [childrens(sagi, limor, 2)] ;
_x = [childrens(sagi, limor, 2)] ;
_x = [childrens(shahaf, yaara, 1)] ;
instead of:
_x = [childrens(sagi, limor, 2),childrens(sagi, limor, 2),childrens(shahaf, yaara, 1),..........etc]
Your num_of_childs/1 calls couple/2 before the setof/3, so you get the number of results couple/2 returns. Since child_to_couple/3 also calls couple/2 you do not in fact need it here at all.
num_of_childs(L) :- findall(childrens(M,W,N),child_to_couple(W,M,N),L).
But the big problem is that couple/2, the way you have written it, always succeeds once per child. This propagates up so that child_to_couple/2 and num_of_childs/1 also succeed multiple times.
If you change to this
couple(W,M):-
gender(W,female), gender(M,male),
( parent(M,C), parent(W,C) -> true ; false ).
You get only one result per couple, regardless of the number of children. I have the feeling there may be an even simpler way to accomplish this, but I wasn't able to find it.
?- num_of_childs(L).
L = [childrens(eyal,shiri,2),childrens(shahaf,yaara,1)] ? ;
no
Addition: using a cut would be slightly simpler but also uglier.