Selects the integers from a list ?- integer(a). false. ?integer(4.23). true. ?- select([1,a,3,b],R). R = [1,3] ?- select([1,[a,2],3,4],R). R = [1,3,4] select([],[]). select([H|T],[H|R]):- integer(H),select(T,R),!. select([H|T],R):- select(T,R).