use core::iter::*; #[test] fn test_iterator_skip() { let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30]; let ys = [13, 15, 16, 17, 19, 20, 30]; let mut it = xs.iter().skip(5); let mut i = 0; while let Some(&x) = it.next() { assert_eq!(x, ys[i]); i += 1; assert_eq!(it.len(), xs.len() - 5 - i); } assert_eq!(i, ys.len()); assert_eq!(it.len(), 0); } #[test] fn test_iterator_skip_doubleended() { let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30]; let mut it = xs.iter().rev().skip(5); assert_eq!(it.next(), Some(&15)); assert_eq!(it.by_ref().rev().next(), Some(&0)); assert_eq!(it.next(), Some(&13)); assert_eq!(it.by_ref().rev().next(), Some(&1)); assert_eq!(it.next(), Some(&5)); assert_eq!(it.by_ref().rev().next(), Some(&2)); assert_eq!(it.next(), Some(&3)); assert_eq!(it.next(), None); let mut it = xs.iter().rev().skip(5).rev(); assert_eq!(it.next(), Some(&0)); assert_eq!(it.rev().next(), Some(&15)); let mut it_base = xs.iter(); { let mut it = it_base.by_ref().skip(5).rev(); assert_eq!(it.next(), Some(&30)); assert_eq!(it.next(), Some(&20)); assert_eq!(it.next(), Some(&19)); assert_eq!(it.next(), Some(&17)); assert_eq!(it.next(), Some(&16)); assert_eq!(it.next(), Some(&15)); assert_eq!(it.next(), Some(&13)); assert_eq!(it.next(), None); } // make sure the skipped parts have not been consumed assert_eq!(it_base.next(), Some(&0)); assert_eq!(it_base.next(), Some(&1)); assert_eq!(it_base.next(), Some(&2)); assert_eq!(it_base.next(), Some(&3)); assert_eq!(it_base.next(), Some(&5)); assert_eq!(it_base.next(), None); let it = xs.iter().skip(5).rev(); assert_eq!(it.last(), Some(&13)); } #[test] fn test_iterator_skip_nth() { let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30]; let mut it = xs.iter().skip(0); assert_eq!(it.nth(0), Some(&0)); assert_eq!(it.nth(1), Some(&2)); let mut it = xs.iter().skip(5); assert_eq!(it.nth(0), Some(&13)); assert_eq!(it.nth(1), Some(&16)); let mut it = xs.iter().skip(12); assert_eq!(it.nth(0), None); } #[test] fn test_iterator_skip_count() { let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30]; assert_eq!(xs.iter().skip(0).count(), 12); assert_eq!(xs.iter().skip(1).count(), 11); assert_eq!(xs.iter().skip(11).count(), 1); assert_eq!(xs.iter().skip(12).count(), 0); assert_eq!(xs.iter().skip(13).count(), 0); } #[test] fn test_iterator_skip_last() { let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30]; assert_eq!(xs.iter().skip(0).last(), Some(&30)); assert_eq!(xs.iter().skip(1).last(), Some(&30)); assert_eq!(xs.iter().skip(11).last(), Some(&30)); assert_eq!(xs.iter().skip(12).last(), None); assert_eq!(xs.iter().skip(13).last(), None); let mut it = xs.iter().skip(5); assert_eq!(it.next(), Some(&13)); assert_eq!(it.last(), Some(&30)); } #[test] fn test_iterator_skip_fold() { let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30]; let ys = [13, 15, 16, 17, 19, 20, 30]; let it = xs.iter().skip(5); let i = it.fold(0, |i, &x| { assert_eq!(x, ys[i]); i + 1 }); assert_eq!(i, ys.len()); let mut it = xs.iter().skip(5); assert_eq!(it.next(), Some(&ys[0])); // process skips before folding let i = it.fold(1, |i, &x| { assert_eq!(x, ys[i]); i + 1 }); assert_eq!(i, ys.len()); let it = xs.iter().skip(5); let i = it.rfold(ys.len(), |i, &x| { let i = i - 1; assert_eq!(x, ys[i]); i }); assert_eq!(i, 0); let mut it = xs.iter().skip(5); assert_eq!(it.next(), Some(&ys[0])); // process skips before folding let i = it.rfold(ys.len(), |i, &x| { let i = i - 1; assert_eq!(x, ys[i]); i }); assert_eq!(i, 1); } #[test] fn test_skip_try_folds() { let f = &|acc, x| i32::checked_add(2 * acc, x); assert_eq!((1..20).skip(9).try_fold(7, f), (10..20).try_fold(7, f)); assert_eq!((1..20).skip(9).try_rfold(7, f), (10..20).try_rfold(7, f)); let mut iter = (0..30).skip(10); 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)); } #[test] fn test_skip_nth_back() { let xs = [0, 1, 2, 3, 4, 5]; let mut it = xs.iter().skip(2); assert_eq!(it.nth_back(0), Some(&5)); assert_eq!(it.nth_back(1), Some(&3)); assert_eq!(it.nth_back(0), Some(&2)); assert_eq!(it.nth_back(0), None); let ys = [2, 3, 4, 5]; let mut ity = ys.iter(); let mut it = xs.iter().skip(2); assert_eq!(it.nth_back(1), ity.nth_back(1)); assert_eq!(it.clone().nth(0), ity.clone().nth(0)); assert_eq!(it.nth_back(0), ity.nth_back(0)); assert_eq!(it.clone().nth(0), ity.clone().nth(0)); assert_eq!(it.nth_back(0), ity.nth_back(0)); assert_eq!(it.clone().nth(0), ity.clone().nth(0)); assert_eq!(it.nth_back(0), ity.nth_back(0)); assert_eq!(it.clone().nth(0), ity.clone().nth(0)); let mut it = xs.iter().skip(2); assert_eq!(it.nth_back(4), None); assert_eq!(it.nth_back(0), None); let mut it = xs.iter(); it.by_ref().skip(2).nth_back(3); assert_eq!(it.next_back(), Some(&1)); let mut it = xs.iter(); it.by_ref().skip(2).nth_back(10); assert_eq!(it.next_back(), Some(&1)); }