4 fn test_map_try_folds() {
5 let f = &|acc, x| i32::checked_add(2 * acc, x);
6 assert_eq!((0..10).map(|x| x + 3).try_fold(7, f), (3..13).try_fold(7, f));
7 assert_eq!((0..10).map(|x| x + 3).try_rfold(7, f), (3..13).try_rfold(7, f));
9 let mut iter = (0..40).map(|x| x + 10);
10 assert_eq!(iter.try_fold(0, i8::checked_add), None);
11 assert_eq!(iter.next(), Some(20));
12 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
13 assert_eq!(iter.next_back(), Some(46));
17 fn test_double_ended_map() {
18 let xs = [1, 2, 3, 4, 5, 6];
19 let mut it = xs.iter().map(|&x| x * -1);
20 assert_eq!(it.next(), Some(-1));
21 assert_eq!(it.next(), Some(-2));
22 assert_eq!(it.next_back(), Some(-6));
23 assert_eq!(it.next_back(), Some(-5));
24 assert_eq!(it.next(), Some(-3));
25 assert_eq!(it.next_back(), Some(-4));
26 assert_eq!(it.next(), None);