4 fn test_iterator_filter_count() {
5 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
6 assert_eq!(xs.iter().filter(|&&x| x % 2 == 0).count(), 5);
10 fn test_iterator_filter_fold() {
11 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
12 let ys = [0, 2, 4, 6, 8];
13 let it = xs.iter().filter(|&&x| x % 2 == 0);
14 let i = it.fold(0, |i, &x| {
18 assert_eq!(i, ys.len());
20 let it = xs.iter().filter(|&&x| x % 2 == 0);
21 let i = it.rfold(ys.len(), |i, &x| {
22 assert_eq!(x, ys[i - 1]);
29 fn test_filter_try_folds() {
30 fn p(&x: &i32) -> bool {
33 let f = &|acc, x| i32::checked_add(2 * acc, x);
34 assert_eq!((-10..20).filter(p).try_fold(7, f), (0..10).try_fold(7, f));
35 assert_eq!((-10..20).filter(p).try_rfold(7, f), (0..10).try_rfold(7, f));
37 let mut iter = (0..40).filter(|&x| x % 2 == 1);
38 assert_eq!(iter.try_fold(0, i8::checked_add), None);
39 assert_eq!(iter.next(), Some(25));
40 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
41 assert_eq!(iter.next_back(), Some(31));
45 fn test_double_ended_filter() {
46 let xs = [1, 2, 3, 4, 5, 6];
47 let mut it = xs.iter().filter(|&x| *x & 1 == 0);
48 assert_eq!(it.next_back().unwrap(), &6);
49 assert_eq!(it.next_back().unwrap(), &4);
50 assert_eq!(it.next().unwrap(), &2);
51 assert_eq!(it.next_back(), None);