?- nr_vowel([],X). X = 0 ?- nr_vowel([a,r,e,d,i],X). X = 3 ?- nr_vowel([m,r],X). X = 0 ?- nr_vowel([s,e,e,d],X). X = 2
vowel(X):- member(X,[a,e,i,o,u]). nr_vowel([],0). nr_vowel([X|T],N):- vowel(X),nr_vowel(T,N1),N is N1+1,!. nr_vowel([X|T],N):- nr_vowel(T,N).