use core::iter::*; #[test] fn test_iterator_take() { let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19]; let ys = [0, 1, 2, 3, 5]; let mut it = xs.iter().take(ys.len()); let mut i = 0; assert_eq!(it.len(), ys.len()); while let Some(&x) = it.next() { assert_eq!(x, ys[i]); i += 1; assert_eq!(it.len(), ys.len() - i); } assert_eq!(i, ys.len()); assert_eq!(it.len(), 0); let mut it = xs.iter().take(ys.len()); let mut i = 0; assert_eq!(it.len(), ys.len()); while let Some(&x) = it.next_back() { i += 1; assert_eq!(x, ys[ys.len() - i]); assert_eq!(it.len(), ys.len() - i); } assert_eq!(i, ys.len()); assert_eq!(it.len(), 0); } #[test] fn test_iterator_take_nth() { let xs = [0, 1, 2, 4, 5]; let mut it = xs.iter(); { let mut take = it.by_ref().take(3); let mut i = 0; while let Some(&x) = take.nth(0) { assert_eq!(x, i); i += 1; } } assert_eq!(it.nth(1), Some(&5)); assert_eq!(it.nth(0), None); let xs = [0, 1, 2, 3, 4]; let mut it = xs.iter().take(7); let mut i = 1; while let Some(&x) = it.nth(1) { assert_eq!(x, i); i += 2; } } #[test] fn test_iterator_take_nth_back() { let xs = [0, 1, 2, 4, 5]; let mut it = xs.iter(); { let mut take = it.by_ref().take(3); let mut i = 0; while let Some(&x) = take.nth_back(0) { i += 1; assert_eq!(x, 3 - i); } } assert_eq!(it.nth_back(0), None); let xs = [0, 1, 2, 3, 4]; let mut it = xs.iter().take(7); assert_eq!(it.nth_back(1), Some(&3)); assert_eq!(it.nth_back(1), Some(&1)); assert_eq!(it.nth_back(1), None); } #[test] fn test_take_advance_by() { let mut take = (0..10).take(3); assert_eq!(take.advance_by(2), Ok(())); assert_eq!(take.next(), Some(2)); assert_eq!(take.advance_by(1), Err(0)); assert_eq!((0..0).take(10).advance_by(0), Ok(())); assert_eq!((0..0).take(10).advance_by(1), Err(0)); assert_eq!((0..10).take(4).advance_by(5), Err(4)); let mut take = (0..10).take(3); assert_eq!(take.advance_back_by(2), Ok(())); assert_eq!(take.next(), Some(0)); assert_eq!(take.advance_back_by(1), Err(0)); assert_eq!((0..2).take(1).advance_back_by(10), Err(1)); assert_eq!((0..0).take(1).advance_back_by(1), Err(0)); assert_eq!((0..0).take(1).advance_back_by(0), Ok(())); assert_eq!((0..usize::MAX).take(100).advance_back_by(usize::MAX), Err(100)); } #[test] fn test_iterator_take_short() { let xs = [0, 1, 2, 3]; let mut it = xs.iter().take(5); let mut i = 0; assert_eq!(it.len(), xs.len()); while let Some(&x) = it.next() { assert_eq!(x, xs[i]); i += 1; assert_eq!(it.len(), xs.len() - i); } assert_eq!(i, xs.len()); assert_eq!(it.len(), 0); let mut it = xs.iter().take(5); let mut i = 0; assert_eq!(it.len(), xs.len()); while let Some(&x) = it.next_back() { i += 1; assert_eq!(x, xs[xs.len() - i]); assert_eq!(it.len(), xs.len() - i); } assert_eq!(i, xs.len()); assert_eq!(it.len(), 0); } #[test] fn test_take_try_folds() { let f = &|acc, x| i32::checked_add(2 * acc, x); assert_eq!((10..30).take(10).try_fold(7, f), (10..20).try_fold(7, f)); assert_eq!((10..30).take(10).try_rfold(7, f), (10..20).try_rfold(7, f)); let mut iter = (10..30).take(20); assert_eq!(iter.try_fold(0, i8::checked_add), None); assert_eq!(iter.next(), Some(20)); assert_eq!(iter.try_rfold(0, i8::checked_add), None); assert_eq!(iter.next_back(), Some(24)); let mut iter = (2..20).take(3); assert_eq!(iter.try_for_each(Err), Err(2)); assert_eq!(iter.try_for_each(Err), Err(3)); assert_eq!(iter.try_for_each(Err), Err(4)); assert_eq!(iter.try_for_each(Err), Ok(())); let mut iter = (2..20).take(3).rev(); assert_eq!(iter.try_for_each(Err), Err(4)); assert_eq!(iter.try_for_each(Err), Err(3)); assert_eq!(iter.try_for_each(Err), Err(2)); assert_eq!(iter.try_for_each(Err), Ok(())); }