dlugosc([], 0).
dlugosc([H|T], L) :- dlugosc(T, Y), L is Y + 1.

list1(X) :- clause(X, Y), klauzula(X, Y), write('.'), nl, fail.
list1(X).

klauzula(X, true) :- !, write(X).
klauzula(X, Y) :- write(X), write(' :- '), write(Y).

test :- list1(dlugosc(_, _)).