5 return f(l.hd) : map(f, l.tl);
13 return foldr(f, f(acc, l.hd), l.tl);
22 return filter(f, l.tl);
24 return l.hd : filter(f, l.tl);
42 foldr(\x y->x*y, 1, intList(z)),
44 foldr(\x y->x+y, 0, intList(z)),
45 "filter evens from 0..12 is: ",
46 filter(\x->x % 2 == 0, intList(12)));