| use core::iter::*; |
| |
| #[test] |
| fn test_filter_map() { |
| let it = (0..).step_by(1).take(10).filter_map(|x| if x % 2 == 0 { Some(x * x) } else { None }); |
| assert_eq!(it.collect::<Vec<usize>>(), [0 * 0, 2 * 2, 4 * 4, 6 * 6, 8 * 8]); |
| } |
| |
| #[test] |
| fn test_filter_map_fold() { |
| let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8]; |
| let ys = [0 * 0, 2 * 2, 4 * 4, 6 * 6, 8 * 8]; |
| let it = xs.iter().filter_map(|&x| if x % 2 == 0 { Some(x * x) } else { None }); |
| let i = it.fold(0, |i, x| { |
| assert_eq!(x, ys[i]); |
| i + 1 |
| }); |
| assert_eq!(i, ys.len()); |
| |
| let it = xs.iter().filter_map(|&x| if x % 2 == 0 { Some(x * x) } else { None }); |
| let i = it.rfold(ys.len(), |i, x| { |
| assert_eq!(x, ys[i - 1]); |
| i - 1 |
| }); |
| assert_eq!(i, 0); |
| } |
| |
| #[test] |
| fn test_filter_map_try_folds() { |
| let mp = &|x| if 0 <= x && x < 10 { Some(x * 2) } else { None }; |
| let f = &|acc, x| i32::checked_add(2 * acc, x); |
| assert_eq!((-9..20).filter_map(mp).try_fold(7, f), (0..10).map(|x| 2 * x).try_fold(7, f)); |
| assert_eq!((-9..20).filter_map(mp).try_rfold(7, f), (0..10).map(|x| 2 * x).try_rfold(7, f)); |
| |
| let mut iter = (0..40).filter_map(|x| if x % 2 == 1 { None } else { Some(x * 2 + 10) }); |
| assert_eq!(iter.try_fold(0, i8::checked_add), None); |
| assert_eq!(iter.next(), Some(38)); |
| assert_eq!(iter.try_rfold(0, i8::checked_add), None); |
| assert_eq!(iter.next_back(), Some(78)); |
| } |
| |
| #[test] |
| fn test_double_ended_filter_map() { |
| let xs = [1, 2, 3, 4, 5, 6]; |
| let mut it = xs.iter().filter_map(|&x| if x & 1 == 0 { Some(x * 2) } else { None }); |
| assert_eq!(it.next_back().unwrap(), 12); |
| assert_eq!(it.next_back().unwrap(), 8); |
| assert_eq!(it.next().unwrap(), 4); |
| assert_eq!(it.next_back(), None); |
| } |
