% problem 2
solve:-
fibo([2,1],Fibo),
even_sum(Fibo,Sum),
write(Sum).
even_sum([],0):-!.
even_sum([First|Rest],Sum):-
First mod 2 =:= 0,
!,
even_sum(Rest,Sum1),
Sum is First + Sum1.
even_sum([_|Rest],Sum):-
even_sum(Rest,Sum).
fibo([First|Rest],Rest):-
First >= 4000000,
!.
fibo([P1,P2|Rest],Out):-
P0 is P1 + P2,
fibo([P0,P1,P2|Rest],Out).
実行結果：
1 ?- solve.
***********************(解答伏せます)**********************
true.