1 // ignore-tidy-filelength
4 use core::convert::TryFrom;
9 let empty: [isize; 0] = [];
13 assert!(!xs.iter().lt(ys.iter()));
14 assert!(!xs.iter().le(ys.iter()));
15 assert!(xs.iter().gt(ys.iter()));
16 assert!(xs.iter().ge(ys.iter()));
18 assert!(ys.iter().lt(xs.iter()));
19 assert!(ys.iter().le(xs.iter()));
20 assert!(!ys.iter().gt(xs.iter()));
21 assert!(!ys.iter().ge(xs.iter()));
23 assert!(empty.iter().lt(xs.iter()));
24 assert!(empty.iter().le(xs.iter()));
25 assert!(!empty.iter().gt(xs.iter()));
26 assert!(!empty.iter().ge(xs.iter()));
29 let u = [1.0f64, 2.0];
30 let v = [0.0f64 / 0.0, 3.0];
32 assert!(!u.iter().lt(v.iter()));
33 assert!(!u.iter().le(v.iter()));
34 assert!(!u.iter().gt(v.iter()));
35 assert!(!u.iter().ge(v.iter()));
37 let a = [0.0f64 / 0.0];
41 assert!(a.iter().lt(b.iter()) == (a[0] < b[0]));
42 assert!(a.iter().le(b.iter()) == (a[0] <= b[0]));
43 assert!(a.iter().gt(b.iter()) == (a[0] > b[0]));
44 assert!(a.iter().ge(b.iter()) == (a[0] >= b[0]));
46 assert!(c.iter().lt(b.iter()) == (c[0] < b[0]));
47 assert!(c.iter().le(b.iter()) == (c[0] <= b[0]));
48 assert!(c.iter().gt(b.iter()) == (c[0] > b[0]));
49 assert!(c.iter().ge(b.iter()) == (c[0] >= b[0]));
53 fn test_multi_iter() {
54 let xs = [1, 2, 3, 4];
55 let ys = [4, 3, 2, 1];
56 assert!(xs.iter().eq(ys.iter().rev()));
57 assert!(xs.iter().lt(xs.iter().skip(2)));
62 use core::cmp::Ordering;
64 let f = |x: i32, y: i32| (x * x).cmp(&y);
65 let xs = || [1, 2, 3, 4].iter().copied();
66 let ys = || [1, 4, 16].iter().copied();
68 assert_eq!(xs().cmp_by(ys(), f), Ordering::Less);
69 assert_eq!(ys().cmp_by(xs(), f), Ordering::Greater);
70 assert_eq!(xs().cmp_by(xs().map(|x| x * x), f), Ordering::Equal);
71 assert_eq!(xs().rev().cmp_by(ys().rev(), f), Ordering::Greater);
72 assert_eq!(xs().cmp_by(ys().rev(), f), Ordering::Less);
73 assert_eq!(xs().cmp_by(ys().take(2), f), Ordering::Greater);
77 fn test_partial_cmp_by() {
78 use core::cmp::Ordering;
80 let f = |x: i32, y: i32| (x * x).partial_cmp(&y);
81 let xs = || [1, 2, 3, 4].iter().copied();
82 let ys = || [1, 4, 16].iter().copied();
84 assert_eq!(xs().partial_cmp_by(ys(), f), Some(Ordering::Less));
85 assert_eq!(ys().partial_cmp_by(xs(), f), Some(Ordering::Greater));
86 assert_eq!(xs().partial_cmp_by(xs().map(|x| x * x), f), Some(Ordering::Equal));
87 assert_eq!(xs().rev().partial_cmp_by(ys().rev(), f), Some(Ordering::Greater));
88 assert_eq!(xs().partial_cmp_by(xs().rev(), f), Some(Ordering::Less));
89 assert_eq!(xs().partial_cmp_by(ys().take(2), f), Some(Ordering::Greater));
91 let f = |x: f64, y: f64| (x * x).partial_cmp(&y);
92 let xs = || [1.0, 2.0, 3.0, 4.0].iter().copied();
93 let ys = || [1.0, 4.0, f64::NAN, 16.0].iter().copied();
95 assert_eq!(xs().partial_cmp_by(ys(), f), None);
96 assert_eq!(ys().partial_cmp_by(xs(), f), Some(Ordering::Greater));
101 let f = |x: i32, y: i32| x * x == y;
102 let xs = || [1, 2, 3, 4].iter().copied();
103 let ys = || [1, 4, 9, 16].iter().copied();
105 assert!(xs().eq_by(ys(), f));
106 assert!(!ys().eq_by(xs(), f));
107 assert!(!xs().eq_by(xs(), f));
108 assert!(!ys().eq_by(ys(), f));
110 assert!(!xs().take(3).eq_by(ys(), f));
111 assert!(!xs().eq_by(ys().take(3), f));
112 assert!(xs().take(3).eq_by(ys().take(3), f));
116 fn test_counter_from_iter() {
117 let it = (0..).step_by(5).take(10);
118 let xs: Vec<isize> = FromIterator::from_iter(it);
119 assert_eq!(xs, [0, 5, 10, 15, 20, 25, 30, 35, 40, 45]);
123 fn test_iterator_chain() {
124 let xs = [0, 1, 2, 3, 4, 5];
125 let ys = [30, 40, 50, 60];
126 let expected = [0, 1, 2, 3, 4, 5, 30, 40, 50, 60];
127 let it = xs.iter().chain(&ys);
130 assert_eq!(x, expected[i]);
133 assert_eq!(i, expected.len());
135 let ys = (30..).step_by(10).take(4);
136 let it = xs.iter().cloned().chain(ys);
139 assert_eq!(x, expected[i]);
142 assert_eq!(i, expected.len());
146 fn test_iterator_chain_nth() {
147 let xs = [0, 1, 2, 3, 4, 5];
148 let ys = [30, 40, 50, 60];
150 let expected = [0, 1, 2, 3, 4, 5, 30, 40, 50, 60];
151 for (i, x) in expected.iter().enumerate() {
152 assert_eq!(Some(x), xs.iter().chain(&ys).nth(i));
154 assert_eq!(zs.iter().chain(&xs).nth(0), Some(&0));
156 let mut it = xs.iter().chain(&zs);
157 assert_eq!(it.nth(5), Some(&5));
158 assert_eq!(it.next(), None);
162 fn test_iterator_chain_nth_back() {
163 let xs = [0, 1, 2, 3, 4, 5];
164 let ys = [30, 40, 50, 60];
166 let expected = [0, 1, 2, 3, 4, 5, 30, 40, 50, 60];
167 for (i, x) in expected.iter().rev().enumerate() {
168 assert_eq!(Some(x), xs.iter().chain(&ys).nth_back(i));
170 assert_eq!(zs.iter().chain(&xs).nth_back(0), Some(&5));
172 let mut it = xs.iter().chain(&zs);
173 assert_eq!(it.nth_back(5), Some(&0));
174 assert_eq!(it.next(), None);
178 fn test_iterator_chain_last() {
179 let xs = [0, 1, 2, 3, 4, 5];
180 let ys = [30, 40, 50, 60];
182 assert_eq!(xs.iter().chain(&ys).last(), Some(&60));
183 assert_eq!(zs.iter().chain(&ys).last(), Some(&60));
184 assert_eq!(ys.iter().chain(&zs).last(), Some(&60));
185 assert_eq!(zs.iter().chain(&zs).last(), None);
189 fn test_iterator_chain_count() {
190 let xs = [0, 1, 2, 3, 4, 5];
191 let ys = [30, 40, 50, 60];
193 assert_eq!(xs.iter().chain(&ys).count(), 10);
194 assert_eq!(zs.iter().chain(&ys).count(), 4);
198 fn test_iterator_chain_find() {
199 let xs = [0, 1, 2, 3, 4, 5];
200 let ys = [30, 40, 50, 60];
201 let mut iter = xs.iter().chain(&ys);
202 assert_eq!(iter.find(|&&i| i == 4), Some(&4));
203 assert_eq!(iter.next(), Some(&5));
204 assert_eq!(iter.find(|&&i| i == 40), Some(&40));
205 assert_eq!(iter.next(), Some(&50));
206 assert_eq!(iter.find(|&&i| i == 100), None);
207 assert_eq!(iter.next(), None);
214 impl Iterator for Toggle {
217 // alternates between `None` and `Some(())`
218 fn next(&mut self) -> Option<Self::Item> {
220 self.is_empty = false;
223 self.is_empty = true;
228 fn size_hint(&self) -> (usize, Option<usize>) {
229 if self.is_empty { (0, Some(0)) } else { (1, Some(1)) }
233 impl DoubleEndedIterator for Toggle {
234 fn next_back(&mut self) -> Option<Self::Item> {
240 fn test_iterator_chain_size_hint() {
241 // this chains an iterator of length 0 with an iterator of length 1,
242 // so after calling `.next()` once, the iterator is empty and the
243 // state is `ChainState::Back`. `.size_hint()` should now disregard
244 // the size hint of the left iterator
245 let mut iter = Toggle { is_empty: true }.chain(once(()));
246 assert_eq!(iter.next(), Some(()));
247 assert_eq!(iter.size_hint(), (0, Some(0)));
249 let mut iter = once(()).chain(Toggle { is_empty: true });
250 assert_eq!(iter.next_back(), Some(()));
251 assert_eq!(iter.size_hint(), (0, Some(0)));
255 fn test_iterator_chain_unfused() {
256 // Chain shouldn't be fused in its second iterator, depending on direction
257 let mut iter = NonFused::new(empty()).chain(Toggle { is_empty: true });
258 iter.next().unwrap_none();
259 iter.next().unwrap();
260 iter.next().unwrap_none();
262 let mut iter = Toggle { is_empty: true }.chain(NonFused::new(empty()));
263 iter.next_back().unwrap_none();
264 iter.next_back().unwrap();
265 iter.next_back().unwrap_none();
270 let xs = [0, 1, 2, 4, 5];
271 let ys = [10, 11, 12];
273 let mut it = xs.iter().zip(&ys);
274 assert_eq!(it.nth(0), Some((&0, &10)));
275 assert_eq!(it.nth(1), Some((&2, &12)));
276 assert_eq!(it.nth(0), None);
278 let mut it = xs.iter().zip(&ys);
279 assert_eq!(it.nth(3), None);
281 let mut it = ys.iter().zip(&xs);
282 assert_eq!(it.nth(3), None);
286 fn test_zip_nth_side_effects() {
287 let mut a = Vec::new();
288 let mut b = Vec::new();
289 let value = [1, 2, 3, 4, 5, 6]
296 .zip([2, 3, 4, 5, 6, 7, 8].iter().cloned().map(|n| {
302 assert_eq!(value, Some((50, 6000)));
303 assert_eq!(a, vec![1, 2, 3, 4, 5]);
304 assert_eq!(b, vec![200, 300, 400, 500, 600]);
308 fn test_zip_next_back_side_effects() {
309 let mut a = Vec::new();
310 let mut b = Vec::new();
311 let mut iter = [1, 2, 3, 4, 5, 6]
318 .zip([2, 3, 4, 5, 6, 7, 8].iter().cloned().map(|n| {
323 // The second iterator is one item longer, so `next_back` is called on it
325 assert_eq!(iter.next_back(), Some((60, 7000)));
326 assert_eq!(iter.next_back(), Some((50, 6000)));
327 assert_eq!(iter.next_back(), Some((40, 5000)));
328 assert_eq!(iter.next_back(), Some((30, 4000)));
329 assert_eq!(a, vec![6, 5, 4, 3]);
330 assert_eq!(b, vec![800, 700, 600, 500, 400]);
334 fn test_zip_nth_back_side_effects() {
335 let mut a = Vec::new();
336 let mut b = Vec::new();
337 let value = [1, 2, 3, 4, 5, 6]
344 .zip([2, 3, 4, 5, 6, 7, 8].iter().cloned().map(|n| {
349 assert_eq!(value, Some((30, 4000)));
350 assert_eq!(a, vec![6, 5, 4, 3]);
351 assert_eq!(b, vec![800, 700, 600, 500, 400]);
355 fn test_zip_next_back_side_effects_exhausted() {
356 let mut a = Vec::new();
357 let mut b = Vec::new();
358 let mut iter = [1, 2, 3, 4, 5, 6]
365 .zip([2, 3, 4].iter().cloned().map(|n| {
374 assert_eq!(iter.next_back(), None);
375 assert_eq!(a, vec![1, 2, 3, 4, 6, 5]);
376 assert_eq!(b, vec![200, 300, 400]);
380 struct CountClone(Cell<i32>);
382 fn count_clone() -> CountClone {
383 CountClone(Cell::new(0))
386 impl PartialEq<i32> for CountClone {
387 fn eq(&self, rhs: &i32) -> bool {
392 impl Clone for CountClone {
393 fn clone(&self) -> Self {
394 let ret = CountClone(self.0.clone());
395 let n = self.0.get();
402 fn test_zip_cloned_sideffectful() {
403 let xs = [count_clone(), count_clone(), count_clone(), count_clone()];
404 let ys = [count_clone(), count_clone()];
406 for _ in xs.iter().cloned().zip(ys.iter().cloned()) {}
408 assert_eq!(&xs, &[1, 1, 1, 0][..]);
409 assert_eq!(&ys, &[1, 1][..]);
411 let xs = [count_clone(), count_clone()];
412 let ys = [count_clone(), count_clone(), count_clone(), count_clone()];
414 for _ in xs.iter().cloned().zip(ys.iter().cloned()) {}
416 assert_eq!(&xs, &[1, 1][..]);
417 assert_eq!(&ys, &[1, 1, 0, 0][..]);
421 fn test_zip_map_sideffectful() {
425 for _ in xs.iter_mut().map(|x| *x += 1).zip(ys.iter_mut().map(|y| *y += 1)) {}
427 assert_eq!(&xs, &[1, 1, 1, 1, 1, 0]);
428 assert_eq!(&ys, &[1, 1, 1, 1]);
433 for _ in xs.iter_mut().map(|x| *x += 1).zip(ys.iter_mut().map(|y| *y += 1)) {}
435 assert_eq!(&xs, &[1, 1, 1, 1]);
436 assert_eq!(&ys, &[1, 1, 1, 1, 0, 0]);
440 fn test_zip_map_rev_sideffectful() {
445 let mut it = xs.iter_mut().map(|x| *x += 1).zip(ys.iter_mut().map(|y| *y += 1));
448 assert_eq!(&xs, &[0, 0, 0, 1, 1, 1]);
449 assert_eq!(&ys, &[0, 0, 0, 1]);
455 let mut it = xs.iter_mut().map(|x| *x += 1).zip(ys.iter_mut().map(|y| *y += 1));
456 (&mut it).take(5).count();
459 assert_eq!(&xs, &[1, 1, 1, 1, 1, 1]);
460 assert_eq!(&ys, &[1, 1, 1, 1]);
464 fn test_zip_nested_sideffectful() {
469 // test that it has the side effect nested inside enumerate
470 let it = xs.iter_mut().map(|x| *x = 1).enumerate().zip(&ys);
473 assert_eq!(&xs, &[1, 1, 1, 1, 1, 0]);
477 fn test_zip_nth_back_side_effects_exhausted() {
478 let mut a = Vec::new();
479 let mut b = Vec::new();
480 let mut iter = [1, 2, 3, 4, 5, 6]
487 .zip([2, 3, 4].iter().cloned().map(|n| {
496 assert_eq!(iter.nth_back(0), None);
497 assert_eq!(a, vec![1, 2, 3, 4, 6, 5]);
498 assert_eq!(b, vec![200, 300, 400]);
502 fn test_iterator_step_by() {
504 let mut it = (0..).step_by(1).take(3);
505 assert_eq!(it.next(), Some(0));
506 assert_eq!(it.next(), Some(1));
507 assert_eq!(it.next(), Some(2));
508 assert_eq!(it.next(), None);
510 let mut it = (0..).step_by(3).take(4);
511 assert_eq!(it.next(), Some(0));
512 assert_eq!(it.next(), Some(3));
513 assert_eq!(it.next(), Some(6));
514 assert_eq!(it.next(), Some(9));
515 assert_eq!(it.next(), None);
517 let mut it = (0..3).step_by(1);
518 assert_eq!(it.next_back(), Some(2));
519 assert_eq!(it.next_back(), Some(1));
520 assert_eq!(it.next_back(), Some(0));
521 assert_eq!(it.next_back(), None);
523 let mut it = (0..11).step_by(3);
524 assert_eq!(it.next_back(), Some(9));
525 assert_eq!(it.next_back(), Some(6));
526 assert_eq!(it.next_back(), Some(3));
527 assert_eq!(it.next_back(), Some(0));
528 assert_eq!(it.next_back(), None);
532 fn test_iterator_step_by_nth() {
533 let mut it = (0..16).step_by(5);
534 assert_eq!(it.nth(0), Some(0));
535 assert_eq!(it.nth(0), Some(5));
536 assert_eq!(it.nth(0), Some(10));
537 assert_eq!(it.nth(0), Some(15));
538 assert_eq!(it.nth(0), None);
540 let it = (0..18).step_by(5);
541 assert_eq!(it.clone().nth(0), Some(0));
542 assert_eq!(it.clone().nth(1), Some(5));
543 assert_eq!(it.clone().nth(2), Some(10));
544 assert_eq!(it.clone().nth(3), Some(15));
545 assert_eq!(it.clone().nth(4), None);
546 assert_eq!(it.clone().nth(42), None);
550 fn test_iterator_step_by_nth_overflow() {
551 #[cfg(target_pointer_width = "8")]
553 #[cfg(target_pointer_width = "16")]
555 #[cfg(target_pointer_width = "32")]
557 #[cfg(target_pointer_width = "64")]
562 impl Iterator for &mut Test {
564 fn next(&mut self) -> Option<Self::Item> {
567 fn nth(&mut self, n: usize) -> Option<Self::Item> {
568 self.0 += n as Bigger + 1;
573 let mut it = Test(0);
574 let root = usize::MAX >> (usize::BITS / 2);
576 (&mut it).step_by(n).nth(n);
577 assert_eq!(it.0, n as Bigger * n as Bigger);
580 let mut it = Test(0);
581 (&mut it).step_by(usize::MAX).nth(5);
582 assert_eq!(it.0, (usize::MAX as Bigger) * 5);
585 let mut it = Test(0);
586 (&mut it).step_by(2).nth(usize::MAX);
587 assert_eq!(it.0, (usize::MAX as Bigger) * 2);
590 let mut it = Test(0);
591 (&mut it).step_by(1).nth(usize::MAX);
592 assert_eq!(it.0, (usize::MAX as Bigger) * 1);
596 fn test_iterator_step_by_nth_try_fold() {
597 let mut it = (0..).step_by(10);
598 assert_eq!(it.try_fold(0, i8::checked_add), None);
599 assert_eq!(it.next(), Some(60));
600 assert_eq!(it.try_fold(0, i8::checked_add), None);
601 assert_eq!(it.next(), Some(90));
603 let mut it = (100..).step_by(10);
604 assert_eq!(it.try_fold(50, i8::checked_add), None);
605 assert_eq!(it.next(), Some(110));
607 let mut it = (100..=100).step_by(10);
608 assert_eq!(it.next(), Some(100));
609 assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
613 fn test_iterator_step_by_nth_back() {
614 let mut it = (0..16).step_by(5);
615 assert_eq!(it.nth_back(0), Some(15));
616 assert_eq!(it.nth_back(0), Some(10));
617 assert_eq!(it.nth_back(0), Some(5));
618 assert_eq!(it.nth_back(0), Some(0));
619 assert_eq!(it.nth_back(0), None);
621 let mut it = (0..16).step_by(5);
622 assert_eq!(it.next(), Some(0)); // to set `first_take` to `false`
623 assert_eq!(it.nth_back(0), Some(15));
624 assert_eq!(it.nth_back(0), Some(10));
625 assert_eq!(it.nth_back(0), Some(5));
626 assert_eq!(it.nth_back(0), None);
628 let it = || (0..18).step_by(5);
629 assert_eq!(it().nth_back(0), Some(15));
630 assert_eq!(it().nth_back(1), Some(10));
631 assert_eq!(it().nth_back(2), Some(5));
632 assert_eq!(it().nth_back(3), Some(0));
633 assert_eq!(it().nth_back(4), None);
634 assert_eq!(it().nth_back(42), None);
638 fn test_iterator_step_by_nth_try_rfold() {
639 let mut it = (0..100).step_by(10);
640 assert_eq!(it.try_rfold(0, i8::checked_add), None);
641 assert_eq!(it.next_back(), Some(70));
642 assert_eq!(it.next(), Some(0));
643 assert_eq!(it.try_rfold(0, i8::checked_add), None);
644 assert_eq!(it.next_back(), Some(30));
646 let mut it = (0..100).step_by(10);
647 assert_eq!(it.try_rfold(50, i8::checked_add), None);
648 assert_eq!(it.next_back(), Some(80));
650 let mut it = (100..=100).step_by(10);
651 assert_eq!(it.next_back(), Some(100));
652 assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
657 fn test_iterator_step_by_zero() {
658 let mut it = (0..).step_by(0);
663 fn test_iterator_step_by_size_hint() {
664 struct StubSizeHint(usize, Option<usize>);
665 impl Iterator for StubSizeHint {
667 fn next(&mut self) -> Option<()> {
669 if let Some(ref mut upper) = self.1 {
674 fn size_hint(&self) -> (usize, Option<usize>) {
679 // The two checks in each case are needed because the logic
680 // is different before the first call to `next()`.
682 let mut it = StubSizeHint(10, Some(10)).step_by(1);
683 assert_eq!(it.size_hint(), (10, Some(10)));
685 assert_eq!(it.size_hint(), (9, Some(9)));
688 let mut it = StubSizeHint(10, Some(10)).step_by(3);
689 assert_eq!(it.size_hint(), (4, Some(4)));
691 assert_eq!(it.size_hint(), (3, Some(3)));
693 // larger base range, but not enough to get another element
694 let mut it = StubSizeHint(12, Some(12)).step_by(3);
695 assert_eq!(it.size_hint(), (4, Some(4)));
697 assert_eq!(it.size_hint(), (3, Some(3)));
699 // smaller base range, so fewer resulting elements
700 let mut it = StubSizeHint(9, Some(9)).step_by(3);
701 assert_eq!(it.size_hint(), (3, Some(3)));
703 assert_eq!(it.size_hint(), (2, Some(2)));
705 // infinite upper bound
706 let mut it = StubSizeHint(usize::MAX, None).step_by(1);
707 assert_eq!(it.size_hint(), (usize::MAX, None));
709 assert_eq!(it.size_hint(), (usize::MAX - 1, None));
711 // still infinite with larger step
712 let mut it = StubSizeHint(7, None).step_by(3);
713 assert_eq!(it.size_hint(), (3, None));
715 assert_eq!(it.size_hint(), (2, None));
717 // propagates ExactSizeIterator
718 let a = [1, 2, 3, 4, 5];
719 let it = a.iter().step_by(2);
720 assert_eq!(it.len(), 3);
722 // Cannot be TrustedLen as a step greater than one makes an iterator
723 // with (usize::MAX, None) no longer meet the safety requirements
724 trait TrustedLenCheck {
725 fn test(self) -> bool;
727 impl<T: Iterator> TrustedLenCheck for T {
728 default fn test(self) -> bool {
732 impl<T: TrustedLen> TrustedLenCheck for T {
733 fn test(self) -> bool {
737 assert!(TrustedLenCheck::test(a.iter()));
738 assert!(!TrustedLenCheck::test(a.iter().step_by(1)));
742 fn test_filter_map() {
743 let it = (0..).step_by(1).take(10).filter_map(|x| if x % 2 == 0 { Some(x * x) } else { None });
744 assert_eq!(it.collect::<Vec<usize>>(), [0 * 0, 2 * 2, 4 * 4, 6 * 6, 8 * 8]);
748 fn test_filter_map_fold() {
749 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
750 let ys = [0 * 0, 2 * 2, 4 * 4, 6 * 6, 8 * 8];
751 let it = xs.iter().filter_map(|&x| if x % 2 == 0 { Some(x * x) } else { None });
752 let i = it.fold(0, |i, x| {
753 assert_eq!(x, ys[i]);
756 assert_eq!(i, ys.len());
758 let it = xs.iter().filter_map(|&x| if x % 2 == 0 { Some(x * x) } else { None });
759 let i = it.rfold(ys.len(), |i, x| {
760 assert_eq!(x, ys[i - 1]);
767 fn test_iterator_enumerate() {
768 let xs = [0, 1, 2, 3, 4, 5];
769 let it = xs.iter().enumerate();
776 fn test_iterator_enumerate_nth() {
777 let xs = [0, 1, 2, 3, 4, 5];
778 for (i, &x) in xs.iter().enumerate() {
782 let mut it = xs.iter().enumerate();
783 while let Some((i, &x)) = it.nth(0) {
787 let mut it = xs.iter().enumerate();
788 while let Some((i, &x)) = it.nth(1) {
792 let (i, &x) = xs.iter().enumerate().nth(3).unwrap();
798 fn test_iterator_enumerate_nth_back() {
799 let xs = [0, 1, 2, 3, 4, 5];
800 let mut it = xs.iter().enumerate();
801 while let Some((i, &x)) = it.nth_back(0) {
805 let mut it = xs.iter().enumerate();
806 while let Some((i, &x)) = it.nth_back(1) {
810 let (i, &x) = xs.iter().enumerate().nth_back(3).unwrap();
816 fn test_iterator_enumerate_count() {
817 let xs = [0, 1, 2, 3, 4, 5];
818 assert_eq!(xs.iter().enumerate().count(), 6);
822 fn test_iterator_enumerate_fold() {
823 let xs = [0, 1, 2, 3, 4, 5];
824 let mut it = xs.iter().enumerate();
825 // steal a couple to get an interesting offset
826 assert_eq!(it.next(), Some((0, &0)));
827 assert_eq!(it.next(), Some((1, &1)));
828 let i = it.fold(2, |i, (j, &x)| {
830 assert_eq!(x, xs[j]);
833 assert_eq!(i, xs.len());
835 let mut it = xs.iter().enumerate();
836 assert_eq!(it.next(), Some((0, &0)));
837 let i = it.rfold(xs.len() - 1, |i, (j, &x)| {
839 assert_eq!(x, xs[j]);
846 fn test_iterator_filter_count() {
847 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
848 assert_eq!(xs.iter().filter(|&&x| x % 2 == 0).count(), 5);
852 fn test_iterator_filter_fold() {
853 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
854 let ys = [0, 2, 4, 6, 8];
855 let it = xs.iter().filter(|&&x| x % 2 == 0);
856 let i = it.fold(0, |i, &x| {
857 assert_eq!(x, ys[i]);
860 assert_eq!(i, ys.len());
862 let it = xs.iter().filter(|&&x| x % 2 == 0);
863 let i = it.rfold(ys.len(), |i, &x| {
864 assert_eq!(x, ys[i - 1]);
871 fn test_iterator_peekable() {
872 let xs = vec![0, 1, 2, 3, 4, 5];
874 let mut it = xs.iter().cloned().peekable();
875 assert_eq!(it.len(), 6);
876 assert_eq!(it.peek().unwrap(), &0);
877 assert_eq!(it.len(), 6);
878 assert_eq!(it.next().unwrap(), 0);
879 assert_eq!(it.len(), 5);
880 assert_eq!(it.next().unwrap(), 1);
881 assert_eq!(it.len(), 4);
882 assert_eq!(it.next().unwrap(), 2);
883 assert_eq!(it.len(), 3);
884 assert_eq!(it.peek().unwrap(), &3);
885 assert_eq!(it.len(), 3);
886 assert_eq!(it.peek().unwrap(), &3);
887 assert_eq!(it.len(), 3);
888 assert_eq!(it.next().unwrap(), 3);
889 assert_eq!(it.len(), 2);
890 assert_eq!(it.next().unwrap(), 4);
891 assert_eq!(it.len(), 1);
892 assert_eq!(it.peek().unwrap(), &5);
893 assert_eq!(it.len(), 1);
894 assert_eq!(it.next().unwrap(), 5);
895 assert_eq!(it.len(), 0);
896 assert!(it.peek().is_none());
897 assert_eq!(it.len(), 0);
898 assert!(it.next().is_none());
899 assert_eq!(it.len(), 0);
901 let mut it = xs.iter().cloned().peekable();
902 assert_eq!(it.len(), 6);
903 assert_eq!(it.peek().unwrap(), &0);
904 assert_eq!(it.len(), 6);
905 assert_eq!(it.next_back().unwrap(), 5);
906 assert_eq!(it.len(), 5);
907 assert_eq!(it.next_back().unwrap(), 4);
908 assert_eq!(it.len(), 4);
909 assert_eq!(it.next_back().unwrap(), 3);
910 assert_eq!(it.len(), 3);
911 assert_eq!(it.peek().unwrap(), &0);
912 assert_eq!(it.len(), 3);
913 assert_eq!(it.peek().unwrap(), &0);
914 assert_eq!(it.len(), 3);
915 assert_eq!(it.next_back().unwrap(), 2);
916 assert_eq!(it.len(), 2);
917 assert_eq!(it.next_back().unwrap(), 1);
918 assert_eq!(it.len(), 1);
919 assert_eq!(it.peek().unwrap(), &0);
920 assert_eq!(it.len(), 1);
921 assert_eq!(it.next_back().unwrap(), 0);
922 assert_eq!(it.len(), 0);
923 assert!(it.peek().is_none());
924 assert_eq!(it.len(), 0);
925 assert!(it.next_back().is_none());
926 assert_eq!(it.len(), 0);
930 fn test_iterator_peekable_count() {
931 let xs = [0, 1, 2, 3, 4, 5];
933 let zs: [i32; 0] = [];
935 assert_eq!(xs.iter().peekable().count(), 6);
937 let mut it = xs.iter().peekable();
938 assert_eq!(it.peek(), Some(&&0));
939 assert_eq!(it.count(), 6);
941 assert_eq!(ys.iter().peekable().count(), 1);
943 let mut it = ys.iter().peekable();
944 assert_eq!(it.peek(), Some(&&10));
945 assert_eq!(it.count(), 1);
947 assert_eq!(zs.iter().peekable().count(), 0);
949 let mut it = zs.iter().peekable();
950 assert_eq!(it.peek(), None);
954 fn test_iterator_peekable_nth() {
955 let xs = [0, 1, 2, 3, 4, 5];
956 let mut it = xs.iter().peekable();
958 assert_eq!(it.peek(), Some(&&0));
959 assert_eq!(it.nth(0), Some(&0));
960 assert_eq!(it.peek(), Some(&&1));
961 assert_eq!(it.nth(1), Some(&2));
962 assert_eq!(it.peek(), Some(&&3));
963 assert_eq!(it.nth(2), Some(&5));
964 assert_eq!(it.next(), None);
968 fn test_iterator_peekable_last() {
969 let xs = [0, 1, 2, 3, 4, 5];
972 let mut it = xs.iter().peekable();
973 assert_eq!(it.peek(), Some(&&0));
974 assert_eq!(it.last(), Some(&5));
976 let mut it = ys.iter().peekable();
977 assert_eq!(it.peek(), Some(&&0));
978 assert_eq!(it.last(), Some(&0));
980 let mut it = ys.iter().peekable();
981 assert_eq!(it.next(), Some(&0));
982 assert_eq!(it.peek(), None);
983 assert_eq!(it.last(), None);
987 fn test_iterator_peekable_fold() {
988 let xs = [0, 1, 2, 3, 4, 5];
989 let mut it = xs.iter().peekable();
990 assert_eq!(it.peek(), Some(&&0));
991 let i = it.fold(0, |i, &x| {
992 assert_eq!(x, xs[i]);
995 assert_eq!(i, xs.len());
999 fn test_iterator_peekable_rfold() {
1000 let xs = [0, 1, 2, 3, 4, 5];
1001 let mut it = xs.iter().peekable();
1002 assert_eq!(it.peek(), Some(&&0));
1003 let i = it.rfold(0, |i, &x| {
1004 assert_eq!(x, xs[xs.len() - 1 - i]);
1007 assert_eq!(i, xs.len());
1011 fn test_iterator_peekable_next_if_eq() {
1012 // first, try on references
1013 let xs = vec!["Heart", "of", "Gold"];
1014 let mut it = xs.into_iter().peekable();
1015 // try before `peek()`
1016 assert_eq!(it.next_if_eq(&"trillian"), None);
1017 assert_eq!(it.next_if_eq(&"Heart"), Some("Heart"));
1019 assert_eq!(it.peek(), Some(&"of"));
1020 assert_eq!(it.next_if_eq(&"of"), Some("of"));
1021 assert_eq!(it.next_if_eq(&"zaphod"), None);
1022 // make sure `next()` still behaves
1023 assert_eq!(it.next(), Some("Gold"));
1025 // make sure comparison works for owned values
1026 let xs = vec![String::from("Ludicrous"), "speed".into()];
1027 let mut it = xs.into_iter().peekable();
1028 // make sure basic functionality works
1029 assert_eq!(it.next_if_eq("Ludicrous"), Some("Ludicrous".into()));
1030 assert_eq!(it.next_if_eq("speed"), Some("speed".into()));
1031 assert_eq!(it.next_if_eq(""), None);
1034 /// This is an iterator that follows the Iterator contract,
1035 /// but it is not fused. After having returned None once, it will start
1036 /// producing elements if .next() is called again.
1037 pub struct CycleIter<'a, T> {
1042 pub fn cycle<T>(data: &[T]) -> CycleIter<'_, T> {
1043 CycleIter { index: 0, data }
1046 impl<'a, T> Iterator for CycleIter<'a, T> {
1048 fn next(&mut self) -> Option<Self::Item> {
1049 let elt = self.data.get(self.index);
1051 self.index %= 1 + self.data.len();
1057 fn test_iterator_peekable_remember_peek_none_1() {
1058 // Check that the loop using .peek() terminates
1059 let data = [1, 2, 3];
1060 let mut iter = cycle(&data).peekable();
1063 while let Some(_) = iter.next() {
1064 let is_the_last = iter.peek().is_none();
1065 assert_eq!(is_the_last, n == data.len() - 1);
1071 assert_eq!(n, data.len());
1075 fn test_iterator_peekable_remember_peek_none_2() {
1077 let mut iter = cycle(&data).peekable();
1079 assert_eq!(iter.peek(), None);
1080 assert_eq!(iter.last(), None);
1084 fn test_iterator_peekable_remember_peek_none_3() {
1086 let mut iter = cycle(&data).peekable();
1088 assert_eq!(iter.nth(0), Some(&0));
1090 let mut iter = cycle(&data).peekable();
1092 assert_eq!(iter.peek(), None);
1093 assert_eq!(iter.nth(0), None);
1097 fn test_iterator_take_while() {
1098 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
1099 let ys = [0, 1, 2, 3, 5, 13];
1100 let it = xs.iter().take_while(|&x| *x < 15);
1103 assert_eq!(*x, ys[i]);
1106 assert_eq!(i, ys.len());
1110 fn test_iterator_skip_while() {
1111 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
1112 let ys = [15, 16, 17, 19];
1113 let it = xs.iter().skip_while(|&x| *x < 15);
1116 assert_eq!(*x, ys[i]);
1119 assert_eq!(i, ys.len());
1123 fn test_iterator_skip_while_fold() {
1124 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
1125 let ys = [15, 16, 17, 19];
1126 let it = xs.iter().skip_while(|&x| *x < 15);
1127 let i = it.fold(0, |i, &x| {
1128 assert_eq!(x, ys[i]);
1131 assert_eq!(i, ys.len());
1133 let mut it = xs.iter().skip_while(|&x| *x < 15);
1134 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
1135 let i = it.fold(1, |i, &x| {
1136 assert_eq!(x, ys[i]);
1139 assert_eq!(i, ys.len());
1143 fn test_iterator_skip() {
1144 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
1145 let ys = [13, 15, 16, 17, 19, 20, 30];
1146 let mut it = xs.iter().skip(5);
1148 while let Some(&x) = it.next() {
1149 assert_eq!(x, ys[i]);
1151 assert_eq!(it.len(), xs.len() - 5 - i);
1153 assert_eq!(i, ys.len());
1154 assert_eq!(it.len(), 0);
1158 fn test_iterator_skip_doubleended() {
1159 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
1160 let mut it = xs.iter().rev().skip(5);
1161 assert_eq!(it.next(), Some(&15));
1162 assert_eq!(it.by_ref().rev().next(), Some(&0));
1163 assert_eq!(it.next(), Some(&13));
1164 assert_eq!(it.by_ref().rev().next(), Some(&1));
1165 assert_eq!(it.next(), Some(&5));
1166 assert_eq!(it.by_ref().rev().next(), Some(&2));
1167 assert_eq!(it.next(), Some(&3));
1168 assert_eq!(it.next(), None);
1169 let mut it = xs.iter().rev().skip(5).rev();
1170 assert_eq!(it.next(), Some(&0));
1171 assert_eq!(it.rev().next(), Some(&15));
1172 let mut it_base = xs.iter();
1174 let mut it = it_base.by_ref().skip(5).rev();
1175 assert_eq!(it.next(), Some(&30));
1176 assert_eq!(it.next(), Some(&20));
1177 assert_eq!(it.next(), Some(&19));
1178 assert_eq!(it.next(), Some(&17));
1179 assert_eq!(it.next(), Some(&16));
1180 assert_eq!(it.next(), Some(&15));
1181 assert_eq!(it.next(), Some(&13));
1182 assert_eq!(it.next(), None);
1184 // make sure the skipped parts have not been consumed
1185 assert_eq!(it_base.next(), Some(&0));
1186 assert_eq!(it_base.next(), Some(&1));
1187 assert_eq!(it_base.next(), Some(&2));
1188 assert_eq!(it_base.next(), Some(&3));
1189 assert_eq!(it_base.next(), Some(&5));
1190 assert_eq!(it_base.next(), None);
1191 let it = xs.iter().skip(5).rev();
1192 assert_eq!(it.last(), Some(&13));
1196 fn test_iterator_skip_nth() {
1197 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
1199 let mut it = xs.iter().skip(0);
1200 assert_eq!(it.nth(0), Some(&0));
1201 assert_eq!(it.nth(1), Some(&2));
1203 let mut it = xs.iter().skip(5);
1204 assert_eq!(it.nth(0), Some(&13));
1205 assert_eq!(it.nth(1), Some(&16));
1207 let mut it = xs.iter().skip(12);
1208 assert_eq!(it.nth(0), None);
1212 fn test_iterator_skip_count() {
1213 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
1215 assert_eq!(xs.iter().skip(0).count(), 12);
1216 assert_eq!(xs.iter().skip(1).count(), 11);
1217 assert_eq!(xs.iter().skip(11).count(), 1);
1218 assert_eq!(xs.iter().skip(12).count(), 0);
1219 assert_eq!(xs.iter().skip(13).count(), 0);
1223 fn test_iterator_skip_last() {
1224 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
1226 assert_eq!(xs.iter().skip(0).last(), Some(&30));
1227 assert_eq!(xs.iter().skip(1).last(), Some(&30));
1228 assert_eq!(xs.iter().skip(11).last(), Some(&30));
1229 assert_eq!(xs.iter().skip(12).last(), None);
1230 assert_eq!(xs.iter().skip(13).last(), None);
1232 let mut it = xs.iter().skip(5);
1233 assert_eq!(it.next(), Some(&13));
1234 assert_eq!(it.last(), Some(&30));
1238 fn test_iterator_skip_fold() {
1239 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
1240 let ys = [13, 15, 16, 17, 19, 20, 30];
1242 let it = xs.iter().skip(5);
1243 let i = it.fold(0, |i, &x| {
1244 assert_eq!(x, ys[i]);
1247 assert_eq!(i, ys.len());
1249 let mut it = xs.iter().skip(5);
1250 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
1251 let i = it.fold(1, |i, &x| {
1252 assert_eq!(x, ys[i]);
1255 assert_eq!(i, ys.len());
1257 let it = xs.iter().skip(5);
1258 let i = it.rfold(ys.len(), |i, &x| {
1260 assert_eq!(x, ys[i]);
1265 let mut it = xs.iter().skip(5);
1266 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
1267 let i = it.rfold(ys.len(), |i, &x| {
1269 assert_eq!(x, ys[i]);
1276 fn test_iterator_take() {
1277 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
1278 let ys = [0, 1, 2, 3, 5];
1280 let mut it = xs.iter().take(ys.len());
1282 assert_eq!(it.len(), ys.len());
1283 while let Some(&x) = it.next() {
1284 assert_eq!(x, ys[i]);
1286 assert_eq!(it.len(), ys.len() - i);
1288 assert_eq!(i, ys.len());
1289 assert_eq!(it.len(), 0);
1291 let mut it = xs.iter().take(ys.len());
1293 assert_eq!(it.len(), ys.len());
1294 while let Some(&x) = it.next_back() {
1296 assert_eq!(x, ys[ys.len() - i]);
1297 assert_eq!(it.len(), ys.len() - i);
1299 assert_eq!(i, ys.len());
1300 assert_eq!(it.len(), 0);
1304 fn test_iterator_take_nth() {
1305 let xs = [0, 1, 2, 4, 5];
1306 let mut it = xs.iter();
1308 let mut take = it.by_ref().take(3);
1310 while let Some(&x) = take.nth(0) {
1315 assert_eq!(it.nth(1), Some(&5));
1316 assert_eq!(it.nth(0), None);
1318 let xs = [0, 1, 2, 3, 4];
1319 let mut it = xs.iter().take(7);
1321 while let Some(&x) = it.nth(1) {
1328 fn test_iterator_take_nth_back() {
1329 let xs = [0, 1, 2, 4, 5];
1330 let mut it = xs.iter();
1332 let mut take = it.by_ref().take(3);
1334 while let Some(&x) = take.nth_back(0) {
1336 assert_eq!(x, 3 - i);
1339 assert_eq!(it.nth_back(0), None);
1341 let xs = [0, 1, 2, 3, 4];
1342 let mut it = xs.iter().take(7);
1343 assert_eq!(it.nth_back(1), Some(&3));
1344 assert_eq!(it.nth_back(1), Some(&1));
1345 assert_eq!(it.nth_back(1), None);
1349 fn test_iterator_take_short() {
1350 let xs = [0, 1, 2, 3];
1352 let mut it = xs.iter().take(5);
1354 assert_eq!(it.len(), xs.len());
1355 while let Some(&x) = it.next() {
1356 assert_eq!(x, xs[i]);
1358 assert_eq!(it.len(), xs.len() - i);
1360 assert_eq!(i, xs.len());
1361 assert_eq!(it.len(), 0);
1363 let mut it = xs.iter().take(5);
1365 assert_eq!(it.len(), xs.len());
1366 while let Some(&x) = it.next_back() {
1368 assert_eq!(x, xs[xs.len() - i]);
1369 assert_eq!(it.len(), xs.len() - i);
1371 assert_eq!(i, xs.len());
1372 assert_eq!(it.len(), 0);
1376 fn test_iterator_scan() {
1377 // test the type inference
1378 fn add(old: &mut isize, new: &usize) -> Option<f64> {
1379 *old += *new as isize;
1382 let xs = [0, 1, 2, 3, 4];
1383 let ys = [0f64, 1.0, 3.0, 6.0, 10.0];
1385 let it = xs.iter().scan(0, add);
1388 assert_eq!(x, ys[i]);
1391 assert_eq!(i, ys.len());
1395 fn test_iterator_flat_map() {
1397 let ys = [0, 1, 2, 3, 4, 5, 6, 7, 8];
1398 let it = xs.iter().flat_map(|&x| (x..).step_by(1).take(3));
1401 assert_eq!(x, ys[i]);
1404 assert_eq!(i, ys.len());
1407 /// Tests `FlatMap::fold` with items already picked off the front and back,
1408 /// to make sure all parts of the `FlatMap` are folded correctly.
1410 fn test_iterator_flat_map_fold() {
1412 let ys = [1, 2, 3, 4, 5, 6, 7];
1413 let mut it = xs.iter().flat_map(|&x| x..x + 3);
1414 assert_eq!(it.next(), Some(0));
1415 assert_eq!(it.next_back(), Some(8));
1416 let i = it.fold(0, |i, x| {
1417 assert_eq!(x, ys[i]);
1420 assert_eq!(i, ys.len());
1422 let mut it = xs.iter().flat_map(|&x| x..x + 3);
1423 assert_eq!(it.next(), Some(0));
1424 assert_eq!(it.next_back(), Some(8));
1425 let i = it.rfold(ys.len(), |i, x| {
1426 assert_eq!(x, ys[i - 1]);
1433 fn test_iterator_flatten() {
1435 let ys = [0, 1, 2, 3, 4, 5, 6, 7, 8];
1436 let it = xs.iter().map(|&x| (x..).step_by(1).take(3)).flatten();
1439 assert_eq!(x, ys[i]);
1442 assert_eq!(i, ys.len());
1445 /// Tests `Flatten::fold` with items already picked off the front and back,
1446 /// to make sure all parts of the `Flatten` are folded correctly.
1448 fn test_iterator_flatten_fold() {
1450 let ys = [1, 2, 3, 4, 5, 6, 7];
1451 let mut it = xs.iter().map(|&x| x..x + 3).flatten();
1452 assert_eq!(it.next(), Some(0));
1453 assert_eq!(it.next_back(), Some(8));
1454 let i = it.fold(0, |i, x| {
1455 assert_eq!(x, ys[i]);
1458 assert_eq!(i, ys.len());
1460 let mut it = xs.iter().map(|&x| x..x + 3).flatten();
1461 assert_eq!(it.next(), Some(0));
1462 assert_eq!(it.next_back(), Some(8));
1463 let i = it.rfold(ys.len(), |i, x| {
1464 assert_eq!(x, ys[i - 1]);
1472 let xs = [1, 2, 3, 4];
1475 let ys = xs.iter().cloned().inspect(|_| n += 1).collect::<Vec<usize>>();
1477 assert_eq!(n, xs.len());
1478 assert_eq!(&xs[..], &ys[..]);
1482 fn test_inspect_fold() {
1483 let xs = [1, 2, 3, 4];
1486 let it = xs.iter().inspect(|_| n += 1);
1487 let i = it.fold(0, |i, &x| {
1488 assert_eq!(x, xs[i]);
1491 assert_eq!(i, xs.len());
1493 assert_eq!(n, xs.len());
1497 let it = xs.iter().inspect(|_| n += 1);
1498 let i = it.rfold(xs.len(), |i, &x| {
1499 assert_eq!(x, xs[i - 1]);
1504 assert_eq!(n, xs.len());
1510 let it = (0..).step_by(1).take(cycle_len).cycle();
1511 assert_eq!(it.size_hint(), (usize::MAX, None));
1512 for (i, x) in it.take(100).enumerate() {
1513 assert_eq!(i % cycle_len, x);
1516 let mut it = (0..).step_by(1).take(0).cycle();
1517 assert_eq!(it.size_hint(), (0, Some(0)));
1518 assert_eq!(it.next(), None);
1520 assert_eq!(empty::<i32>().cycle().fold(0, |acc, x| acc + x), 0);
1522 assert_eq!(once(1).cycle().skip(1).take(4).fold(0, |acc, x| acc + x), 4);
1524 assert_eq!((0..10).cycle().take(5).sum::<i32>(), 10);
1525 assert_eq!((0..10).cycle().take(15).sum::<i32>(), 55);
1526 assert_eq!((0..10).cycle().take(25).sum::<i32>(), 100);
1528 let mut iter = (0..10).cycle();
1530 assert_eq!(iter.take(8).sum::<i32>(), 38);
1532 let mut iter = (0..10).cycle();
1534 assert_eq!(iter.take(3).sum::<i32>(), 3);
1538 fn test_iterator_nth() {
1539 let v: &[_] = &[0, 1, 2, 3, 4];
1540 for i in 0..v.len() {
1541 assert_eq!(v.iter().nth(i).unwrap(), &v[i]);
1543 assert_eq!(v.iter().nth(v.len()), None);
1547 fn test_iterator_nth_back() {
1548 let v: &[_] = &[0, 1, 2, 3, 4];
1549 for i in 0..v.len() {
1550 assert_eq!(v.iter().nth_back(i).unwrap(), &v[v.len() - 1 - i]);
1552 assert_eq!(v.iter().nth_back(v.len()), None);
1556 fn test_iterator_rev_nth_back() {
1557 let v: &[_] = &[0, 1, 2, 3, 4];
1558 for i in 0..v.len() {
1559 assert_eq!(v.iter().rev().nth_back(i).unwrap(), &v[i]);
1561 assert_eq!(v.iter().rev().nth_back(v.len()), None);
1565 fn test_iterator_rev_nth() {
1566 let v: &[_] = &[0, 1, 2, 3, 4];
1567 for i in 0..v.len() {
1568 assert_eq!(v.iter().rev().nth(i).unwrap(), &v[v.len() - 1 - i]);
1570 assert_eq!(v.iter().rev().nth(v.len()), None);
1574 fn test_iterator_last() {
1575 let v: &[_] = &[0, 1, 2, 3, 4];
1576 assert_eq!(v.iter().last().unwrap(), &4);
1577 assert_eq!(v[..1].iter().last().unwrap(), &0);
1581 fn test_iterator_len() {
1582 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1583 assert_eq!(v[..4].iter().count(), 4);
1584 assert_eq!(v[..10].iter().count(), 10);
1585 assert_eq!(v[..0].iter().count(), 0);
1589 fn test_iterator_sum() {
1590 let v: &[i32] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1591 assert_eq!(v[..4].iter().cloned().sum::<i32>(), 6);
1592 assert_eq!(v.iter().cloned().sum::<i32>(), 55);
1593 assert_eq!(v[..0].iter().cloned().sum::<i32>(), 0);
1597 fn test_iterator_sum_result() {
1598 let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
1599 assert_eq!(v.iter().cloned().sum::<Result<i32, _>>(), Ok(10));
1600 let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
1601 assert_eq!(v.iter().cloned().sum::<Result<i32, _>>(), Err(()));
1603 #[derive(PartialEq, Debug)]
1604 struct S(Result<i32, ()>);
1606 impl Sum<Result<i32, ()>> for S {
1607 fn sum<I: Iterator<Item = Result<i32, ()>>>(mut iter: I) -> Self {
1608 // takes the sum by repeatedly calling `next` on `iter`,
1609 // thus testing that repeated calls to `ResultShunt::try_fold`
1610 // produce the expected results
1611 Self(iter.by_ref().sum())
1615 let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
1616 assert_eq!(v.iter().cloned().sum::<S>(), S(Ok(10)));
1617 let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
1618 assert_eq!(v.iter().cloned().sum::<S>(), S(Err(())));
1622 fn test_iterator_sum_option() {
1623 let v: &[Option<i32>] = &[Some(1), Some(2), Some(3), Some(4)];
1624 assert_eq!(v.iter().cloned().sum::<Option<i32>>(), Some(10));
1625 let v: &[Option<i32>] = &[Some(1), None, Some(3), Some(4)];
1626 assert_eq!(v.iter().cloned().sum::<Option<i32>>(), None);
1630 fn test_iterator_product() {
1631 let v: &[i32] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1632 assert_eq!(v[..4].iter().cloned().product::<i32>(), 0);
1633 assert_eq!(v[1..5].iter().cloned().product::<i32>(), 24);
1634 assert_eq!(v[..0].iter().cloned().product::<i32>(), 1);
1638 fn test_iterator_product_result() {
1639 let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
1640 assert_eq!(v.iter().cloned().product::<Result<i32, _>>(), Ok(24));
1641 let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
1642 assert_eq!(v.iter().cloned().product::<Result<i32, _>>(), Err(()));
1645 /// A wrapper struct that implements `Eq` and `Ord` based on the wrapped
1646 /// integer modulo 3. Used to test that `Iterator::max` and `Iterator::min`
1647 /// return the correct element if some of them are equal.
1651 impl PartialEq for Mod3 {
1652 fn eq(&self, other: &Self) -> bool {
1653 self.0 % 3 == other.0 % 3
1659 impl PartialOrd for Mod3 {
1660 fn partial_cmp(&self, other: &Self) -> Option<core::cmp::Ordering> {
1661 Some(self.cmp(other))
1666 fn cmp(&self, other: &Self) -> core::cmp::Ordering {
1667 (self.0 % 3).cmp(&(other.0 % 3))
1672 fn test_iterator_product_option() {
1673 let v: &[Option<i32>] = &[Some(1), Some(2), Some(3), Some(4)];
1674 assert_eq!(v.iter().cloned().product::<Option<i32>>(), Some(24));
1675 let v: &[Option<i32>] = &[Some(1), None, Some(3), Some(4)];
1676 assert_eq!(v.iter().cloned().product::<Option<i32>>(), None);
1680 fn test_iterator_max() {
1681 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1682 assert_eq!(v[..4].iter().cloned().max(), Some(3));
1683 assert_eq!(v.iter().cloned().max(), Some(10));
1684 assert_eq!(v[..0].iter().cloned().max(), None);
1685 assert_eq!(v.iter().cloned().map(Mod3).max().map(|x| x.0), Some(8));
1689 fn test_iterator_min() {
1690 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1691 assert_eq!(v[..4].iter().cloned().min(), Some(0));
1692 assert_eq!(v.iter().cloned().min(), Some(0));
1693 assert_eq!(v[..0].iter().cloned().min(), None);
1694 assert_eq!(v.iter().cloned().map(Mod3).min().map(|x| x.0), Some(0));
1698 fn test_iterator_size_hint() {
1699 let c = (0..).step_by(1);
1700 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
1701 let v2 = &[10, 11, 12];
1704 assert_eq!((0..).size_hint(), (usize::MAX, None));
1705 assert_eq!(c.size_hint(), (usize::MAX, None));
1706 assert_eq!(vi.clone().size_hint(), (10, Some(10)));
1708 assert_eq!(c.clone().take(5).size_hint(), (5, Some(5)));
1709 assert_eq!(c.clone().skip(5).size_hint().1, None);
1710 assert_eq!(c.clone().take_while(|_| false).size_hint(), (0, None));
1711 assert_eq!(c.clone().map_while(|_| None::<()>).size_hint(), (0, None));
1712 assert_eq!(c.clone().skip_while(|_| false).size_hint(), (0, None));
1713 assert_eq!(c.clone().enumerate().size_hint(), (usize::MAX, None));
1714 assert_eq!(c.clone().chain(vi.clone().cloned()).size_hint(), (usize::MAX, None));
1715 assert_eq!(c.clone().zip(vi.clone()).size_hint(), (10, Some(10)));
1716 assert_eq!(c.clone().scan(0, |_, _| Some(0)).size_hint(), (0, None));
1717 assert_eq!(c.clone().filter(|_| false).size_hint(), (0, None));
1718 assert_eq!(c.clone().map(|_| 0).size_hint(), (usize::MAX, None));
1719 assert_eq!(c.filter_map(|_| Some(0)).size_hint(), (0, None));
1721 assert_eq!(vi.clone().take(5).size_hint(), (5, Some(5)));
1722 assert_eq!(vi.clone().take(12).size_hint(), (10, Some(10)));
1723 assert_eq!(vi.clone().skip(3).size_hint(), (7, Some(7)));
1724 assert_eq!(vi.clone().skip(12).size_hint(), (0, Some(0)));
1725 assert_eq!(vi.clone().take_while(|_| false).size_hint(), (0, Some(10)));
1726 assert_eq!(vi.clone().map_while(|_| None::<()>).size_hint(), (0, Some(10)));
1727 assert_eq!(vi.clone().skip_while(|_| false).size_hint(), (0, Some(10)));
1728 assert_eq!(vi.clone().enumerate().size_hint(), (10, Some(10)));
1729 assert_eq!(vi.clone().chain(v2).size_hint(), (13, Some(13)));
1730 assert_eq!(vi.clone().zip(v2).size_hint(), (3, Some(3)));
1731 assert_eq!(vi.clone().scan(0, |_, _| Some(0)).size_hint(), (0, Some(10)));
1732 assert_eq!(vi.clone().filter(|_| false).size_hint(), (0, Some(10)));
1733 assert_eq!(vi.clone().map(|&i| i + 1).size_hint(), (10, Some(10)));
1734 assert_eq!(vi.filter_map(|_| Some(0)).size_hint(), (0, Some(10)));
1739 let a = vec![1, 2, 3, 4, 5];
1740 let b: Vec<isize> = a.iter().cloned().collect();
1746 let v: Box<[isize]> = Box::new([1, 2, 3, 4, 5]);
1747 assert!(v.iter().all(|&x| x < 10));
1748 assert!(!v.iter().all(|&x| x % 2 == 0));
1749 assert!(!v.iter().all(|&x| x > 100));
1750 assert!(v[..0].iter().all(|_| panic!()));
1755 let v: Box<[isize]> = Box::new([1, 2, 3, 4, 5]);
1756 assert!(v.iter().any(|&x| x < 10));
1757 assert!(v.iter().any(|&x| x % 2 == 0));
1758 assert!(!v.iter().any(|&x| x > 100));
1759 assert!(!v[..0].iter().any(|_| panic!()));
1764 let v: &[isize] = &[1, 3, 9, 27, 103, 14, 11];
1765 assert_eq!(*v.iter().find(|&&x| x & 1 == 0).unwrap(), 14);
1766 assert_eq!(*v.iter().find(|&&x| x % 3 == 0).unwrap(), 3);
1767 assert!(v.iter().find(|&&x| x % 12 == 0).is_none());
1771 fn test_find_map() {
1772 let xs: &[isize] = &[];
1773 assert_eq!(xs.iter().find_map(half_if_even), None);
1774 let xs: &[isize] = &[3, 5];
1775 assert_eq!(xs.iter().find_map(half_if_even), None);
1776 let xs: &[isize] = &[4, 5];
1777 assert_eq!(xs.iter().find_map(half_if_even), Some(2));
1778 let xs: &[isize] = &[3, 6];
1779 assert_eq!(xs.iter().find_map(half_if_even), Some(3));
1781 let xs: &[isize] = &[1, 2, 3, 4, 5, 6, 7];
1782 let mut iter = xs.iter();
1783 assert_eq!(iter.find_map(half_if_even), Some(1));
1784 assert_eq!(iter.find_map(half_if_even), Some(2));
1785 assert_eq!(iter.find_map(half_if_even), Some(3));
1786 assert_eq!(iter.next(), Some(&7));
1788 fn half_if_even(x: &isize) -> Option<isize> {
1789 if x % 2 == 0 { Some(x / 2) } else { None }
1794 fn test_try_find() {
1795 let xs: &[isize] = &[];
1796 assert_eq!(xs.iter().try_find(testfn), Ok(None));
1797 let xs: &[isize] = &[1, 2, 3, 4];
1798 assert_eq!(xs.iter().try_find(testfn), Ok(Some(&2)));
1799 let xs: &[isize] = &[1, 3, 4];
1800 assert_eq!(xs.iter().try_find(testfn), Err(()));
1802 let xs: &[isize] = &[1, 2, 3, 4, 5, 6, 7];
1803 let mut iter = xs.iter();
1804 assert_eq!(iter.try_find(testfn), Ok(Some(&2)));
1805 assert_eq!(iter.try_find(testfn), Err(()));
1806 assert_eq!(iter.next(), Some(&5));
1808 fn testfn(x: &&isize) -> Result<bool, ()> {
1820 fn test_try_find_api_usability() -> Result<(), Box<dyn std::error::Error>> {
1823 let is_my_num = |s: &str, search: i32| -> Result<bool, std::num::ParseIntError> {
1824 Ok(s.parse::<i32>()? == search)
1827 let val = a.iter().try_find(|&&s| is_my_num(s, 2))?;
1828 assert_eq!(val, Some(&"2"));
1834 fn test_position() {
1835 let v = &[1, 3, 9, 27, 103, 14, 11];
1836 assert_eq!(v.iter().position(|x| *x & 1 == 0).unwrap(), 5);
1837 assert_eq!(v.iter().position(|x| *x % 3 == 0).unwrap(), 1);
1838 assert!(v.iter().position(|x| *x % 12 == 0).is_none());
1843 let xs = &[1, 2, 2, 1, 5, 9, 0, 2];
1844 assert_eq!(xs.iter().filter(|x| **x == 2).count(), 3);
1845 assert_eq!(xs.iter().filter(|x| **x == 5).count(), 1);
1846 assert_eq!(xs.iter().filter(|x| **x == 95).count(), 0);
1850 fn test_max_by_key() {
1851 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1852 assert_eq!(*xs.iter().max_by_key(|x| x.abs()).unwrap(), -10);
1857 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1858 assert_eq!(*xs.iter().max_by(|x, y| x.abs().cmp(&y.abs())).unwrap(), -10);
1862 fn test_min_by_key() {
1863 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1864 assert_eq!(*xs.iter().min_by_key(|x| x.abs()).unwrap(), 0);
1869 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1870 assert_eq!(*xs.iter().min_by(|x, y| x.abs().cmp(&y.abs())).unwrap(), 0);
1876 // sum the first five values
1877 let partial_sum = xs.by_ref().take(5).fold(0, |a, b| a + b);
1878 assert_eq!(partial_sum, 10);
1879 assert_eq!(xs.next(), Some(5));
1884 let xs = [2, 4, 6, 8, 10, 12, 14, 16];
1885 let mut it = xs.iter();
1888 assert!(it.rev().cloned().collect::<Vec<isize>>() == vec![16, 14, 12, 10, 8, 6]);
1893 let xs = [2, 4, 6, 8];
1895 let mut it = xs.iter().copied();
1896 assert_eq!(it.len(), 4);
1897 assert_eq!(it.next(), Some(2));
1898 assert_eq!(it.len(), 3);
1899 assert_eq!(it.next(), Some(4));
1900 assert_eq!(it.len(), 2);
1901 assert_eq!(it.next_back(), Some(8));
1902 assert_eq!(it.len(), 1);
1903 assert_eq!(it.next_back(), Some(6));
1904 assert_eq!(it.len(), 0);
1905 assert_eq!(it.next_back(), None);
1910 let xs = [2, 4, 6, 8];
1912 let mut it = xs.iter().cloned();
1913 assert_eq!(it.len(), 4);
1914 assert_eq!(it.next(), Some(2));
1915 assert_eq!(it.len(), 3);
1916 assert_eq!(it.next(), Some(4));
1917 assert_eq!(it.len(), 2);
1918 assert_eq!(it.next_back(), Some(8));
1919 assert_eq!(it.len(), 1);
1920 assert_eq!(it.next_back(), Some(6));
1921 assert_eq!(it.len(), 0);
1922 assert_eq!(it.next_back(), None);
1926 fn test_cloned_side_effects() {
1929 let iter = [1, 2, 3]
1939 assert_eq!(count, 2);
1943 fn test_double_ended_map() {
1944 let xs = [1, 2, 3, 4, 5, 6];
1945 let mut it = xs.iter().map(|&x| x * -1);
1946 assert_eq!(it.next(), Some(-1));
1947 assert_eq!(it.next(), Some(-2));
1948 assert_eq!(it.next_back(), Some(-6));
1949 assert_eq!(it.next_back(), Some(-5));
1950 assert_eq!(it.next(), Some(-3));
1951 assert_eq!(it.next_back(), Some(-4));
1952 assert_eq!(it.next(), None);
1956 fn test_double_ended_enumerate() {
1957 let xs = [1, 2, 3, 4, 5, 6];
1958 let mut it = xs.iter().cloned().enumerate();
1959 assert_eq!(it.next(), Some((0, 1)));
1960 assert_eq!(it.next(), Some((1, 2)));
1961 assert_eq!(it.next_back(), Some((5, 6)));
1962 assert_eq!(it.next_back(), Some((4, 5)));
1963 assert_eq!(it.next_back(), Some((3, 4)));
1964 assert_eq!(it.next_back(), Some((2, 3)));
1965 assert_eq!(it.next(), None);
1969 fn test_double_ended_zip() {
1970 let xs = [1, 2, 3, 4, 5, 6];
1971 let ys = [1, 2, 3, 7];
1972 let a = xs.iter().cloned();
1973 let b = ys.iter().cloned();
1974 let mut it = a.zip(b);
1975 assert_eq!(it.next(), Some((1, 1)));
1976 assert_eq!(it.next(), Some((2, 2)));
1977 assert_eq!(it.next_back(), Some((4, 7)));
1978 assert_eq!(it.next_back(), Some((3, 3)));
1979 assert_eq!(it.next(), None);
1983 fn test_double_ended_filter() {
1984 let xs = [1, 2, 3, 4, 5, 6];
1985 let mut it = xs.iter().filter(|&x| *x & 1 == 0);
1986 assert_eq!(it.next_back().unwrap(), &6);
1987 assert_eq!(it.next_back().unwrap(), &4);
1988 assert_eq!(it.next().unwrap(), &2);
1989 assert_eq!(it.next_back(), None);
1993 fn test_double_ended_filter_map() {
1994 let xs = [1, 2, 3, 4, 5, 6];
1995 let mut it = xs.iter().filter_map(|&x| if x & 1 == 0 { Some(x * 2) } else { None });
1996 assert_eq!(it.next_back().unwrap(), 12);
1997 assert_eq!(it.next_back().unwrap(), 8);
1998 assert_eq!(it.next().unwrap(), 4);
1999 assert_eq!(it.next_back(), None);
2003 fn test_double_ended_chain() {
2004 let xs = [1, 2, 3, 4, 5];
2005 let ys = [7, 9, 11];
2006 let mut it = xs.iter().chain(&ys).rev();
2007 assert_eq!(it.next().unwrap(), &11);
2008 assert_eq!(it.next().unwrap(), &9);
2009 assert_eq!(it.next_back().unwrap(), &1);
2010 assert_eq!(it.next_back().unwrap(), &2);
2011 assert_eq!(it.next_back().unwrap(), &3);
2012 assert_eq!(it.next_back().unwrap(), &4);
2013 assert_eq!(it.next_back().unwrap(), &5);
2014 assert_eq!(it.next_back().unwrap(), &7);
2015 assert_eq!(it.next_back(), None);
2017 // test that .chain() is well behaved with an unfused iterator
2018 struct CrazyIterator(bool);
2019 impl CrazyIterator {
2020 fn new() -> CrazyIterator {
2021 CrazyIterator(false)
2024 impl Iterator for CrazyIterator {
2026 fn next(&mut self) -> Option<i32> {
2036 impl DoubleEndedIterator for CrazyIterator {
2037 fn next_back(&mut self) -> Option<i32> {
2042 assert_eq!(CrazyIterator::new().chain(0..10).rev().last(), Some(0));
2043 assert!((0..10).chain(CrazyIterator::new()).rev().any(|i| i == 0));
2047 fn test_rposition() {
2048 fn f(xy: &(isize, char)) -> bool {
2052 fn g(xy: &(isize, char)) -> bool {
2056 let v = [(0, 'a'), (1, 'b'), (2, 'c'), (3, 'b')];
2058 assert_eq!(v.iter().rposition(f), Some(3));
2059 assert!(v.iter().rposition(g).is_none());
2063 fn test_rev_rposition() {
2064 let v = [0, 0, 1, 1];
2065 assert_eq!(v.iter().rev().rposition(|&x| x == 1), Some(1));
2070 fn test_rposition_panic() {
2071 let v: [(Box<_>, Box<_>); 4] = [(box 0, box 0), (box 0, box 0), (box 0, box 0), (box 0, box 0)];
2073 v.iter().rposition(|_elt| {
2083 fn test_double_ended_flat_map() {
2085 let v = [5, 6, 7, 8];
2086 let mut it = u.iter().flat_map(|x| &v[*x..v.len()]);
2087 assert_eq!(it.next_back().unwrap(), &8);
2088 assert_eq!(it.next().unwrap(), &5);
2089 assert_eq!(it.next_back().unwrap(), &7);
2090 assert_eq!(it.next_back().unwrap(), &6);
2091 assert_eq!(it.next_back().unwrap(), &8);
2092 assert_eq!(it.next().unwrap(), &6);
2093 assert_eq!(it.next_back().unwrap(), &7);
2094 assert_eq!(it.next_back(), None);
2095 assert_eq!(it.next(), None);
2096 assert_eq!(it.next_back(), None);
2100 fn test_double_ended_flatten() {
2102 let v = [5, 6, 7, 8];
2103 let mut it = u.iter().map(|x| &v[*x..v.len()]).flatten();
2104 assert_eq!(it.next_back().unwrap(), &8);
2105 assert_eq!(it.next().unwrap(), &5);
2106 assert_eq!(it.next_back().unwrap(), &7);
2107 assert_eq!(it.next_back().unwrap(), &6);
2108 assert_eq!(it.next_back().unwrap(), &8);
2109 assert_eq!(it.next().unwrap(), &6);
2110 assert_eq!(it.next_back().unwrap(), &7);
2111 assert_eq!(it.next_back(), None);
2112 assert_eq!(it.next(), None);
2113 assert_eq!(it.next_back(), None);
2117 fn test_double_ended_range() {
2118 assert_eq!((11..14).rev().collect::<Vec<_>>(), [13, 12, 11]);
2119 for _ in (10..0).rev() {
2120 panic!("unreachable");
2123 assert_eq!((11..14).rev().collect::<Vec<_>>(), [13, 12, 11]);
2124 for _ in (10..0).rev() {
2125 panic!("unreachable");
2131 assert_eq!((0..5).collect::<Vec<_>>(), [0, 1, 2, 3, 4]);
2132 assert_eq!((-10..-1).collect::<Vec<_>>(), [-10, -9, -8, -7, -6, -5, -4, -3, -2]);
2133 assert_eq!((0..5).rev().collect::<Vec<_>>(), [4, 3, 2, 1, 0]);
2134 assert_eq!((200..-5).count(), 0);
2135 assert_eq!((200..-5).rev().count(), 0);
2136 assert_eq!((200..200).count(), 0);
2137 assert_eq!((200..200).rev().count(), 0);
2139 assert_eq!((0..100).size_hint(), (100, Some(100)));
2140 // this test is only meaningful when sizeof usize < sizeof u64
2141 assert_eq!((usize::MAX - 1..usize::MAX).size_hint(), (1, Some(1)));
2142 assert_eq!((-10..-1).size_hint(), (9, Some(9)));
2143 assert_eq!((-1..-10).size_hint(), (0, Some(0)));
2145 assert_eq!((-70..58).size_hint(), (128, Some(128)));
2146 assert_eq!((-128..127).size_hint(), (255, Some(255)));
2148 (-2..isize::MAX).size_hint(),
2149 (isize::MAX as usize + 2, Some(isize::MAX as usize + 2))
2154 fn test_char_range() {
2157 let from = if cfg!(miri) { char::from_u32(0xD800 - 10).unwrap() } else { '\0' };
2158 let to = if cfg!(miri) { char::from_u32(0xDFFF + 10).unwrap() } else { char::MAX };
2159 assert!((from..=to).eq((from as u32..=to as u32).filter_map(char::from_u32)));
2160 assert!((from..=to).rev().eq((from as u32..=to as u32).filter_map(char::from_u32).rev()));
2162 assert_eq!(('\u{D7FF}'..='\u{E000}').count(), 2);
2163 assert_eq!(('\u{D7FF}'..='\u{E000}').size_hint(), (2, Some(2)));
2164 assert_eq!(('\u{D7FF}'..'\u{E000}').count(), 1);
2165 assert_eq!(('\u{D7FF}'..'\u{E000}').size_hint(), (1, Some(1)));
2169 fn test_range_exhaustion() {
2171 assert!(r.is_empty());
2172 assert_eq!(r.next(), None);
2173 assert_eq!(r.next_back(), None);
2174 assert_eq!(r, 10..10);
2177 assert_eq!(r.next(), Some(10));
2178 assert_eq!(r.next(), Some(11));
2179 assert!(r.is_empty());
2180 assert_eq!(r, 12..12);
2181 assert_eq!(r.next(), None);
2184 assert_eq!(r.next_back(), Some(11));
2185 assert_eq!(r.next_back(), Some(10));
2186 assert!(r.is_empty());
2187 assert_eq!(r, 10..10);
2188 assert_eq!(r.next_back(), None);
2190 let mut r = 100..10;
2191 assert!(r.is_empty());
2192 assert_eq!(r.next(), None);
2193 assert_eq!(r.next_back(), None);
2194 assert_eq!(r, 100..10);
2198 fn test_range_inclusive_exhaustion() {
2199 let mut r = 10..=10;
2200 assert_eq!(r.next(), Some(10));
2201 assert!(r.is_empty());
2202 assert_eq!(r.next(), None);
2203 assert_eq!(r.next(), None);
2205 assert_eq!(*r.start(), 10);
2206 assert_eq!(*r.end(), 10);
2207 assert_ne!(r, 10..=10);
2209 let mut r = 10..=10;
2210 assert_eq!(r.next_back(), Some(10));
2211 assert!(r.is_empty());
2212 assert_eq!(r.next_back(), None);
2214 assert_eq!(*r.start(), 10);
2215 assert_eq!(*r.end(), 10);
2216 assert_ne!(r, 10..=10);
2218 let mut r = 10..=12;
2219 assert_eq!(r.next(), Some(10));
2220 assert_eq!(r.next(), Some(11));
2221 assert_eq!(r.next(), Some(12));
2222 assert!(r.is_empty());
2223 assert_eq!(r.next(), None);
2225 let mut r = 10..=12;
2226 assert_eq!(r.next_back(), Some(12));
2227 assert_eq!(r.next_back(), Some(11));
2228 assert_eq!(r.next_back(), Some(10));
2229 assert!(r.is_empty());
2230 assert_eq!(r.next_back(), None);
2232 let mut r = 10..=12;
2233 assert_eq!(r.nth(2), Some(12));
2234 assert!(r.is_empty());
2235 assert_eq!(r.next(), None);
2237 let mut r = 10..=12;
2238 assert_eq!(r.nth(5), None);
2239 assert!(r.is_empty());
2240 assert_eq!(r.next(), None);
2242 let mut r = 100..=10;
2243 assert_eq!(r.next(), None);
2244 assert!(r.is_empty());
2245 assert_eq!(r.next(), None);
2246 assert_eq!(r.next(), None);
2247 assert_eq!(r, 100..=10);
2249 let mut r = 100..=10;
2250 assert_eq!(r.next_back(), None);
2251 assert!(r.is_empty());
2252 assert_eq!(r.next_back(), None);
2253 assert_eq!(r.next_back(), None);
2254 assert_eq!(r, 100..=10);
2258 fn test_range_nth() {
2259 assert_eq!((10..15).nth(0), Some(10));
2260 assert_eq!((10..15).nth(1), Some(11));
2261 assert_eq!((10..15).nth(4), Some(14));
2262 assert_eq!((10..15).nth(5), None);
2265 assert_eq!(r.nth(2), Some(12));
2266 assert_eq!(r, 13..20);
2267 assert_eq!(r.nth(2), Some(15));
2268 assert_eq!(r, 16..20);
2269 assert_eq!(r.nth(10), None);
2270 assert_eq!(r, 20..20);
2274 fn test_range_nth_back() {
2275 assert_eq!((10..15).nth_back(0), Some(14));
2276 assert_eq!((10..15).nth_back(1), Some(13));
2277 assert_eq!((10..15).nth_back(4), Some(10));
2278 assert_eq!((10..15).nth_back(5), None);
2279 assert_eq!((-120..80_i8).nth_back(199), Some(-120));
2282 assert_eq!(r.nth_back(2), Some(17));
2283 assert_eq!(r, 10..17);
2284 assert_eq!(r.nth_back(2), Some(14));
2285 assert_eq!(r, 10..14);
2286 assert_eq!(r.nth_back(10), None);
2287 assert_eq!(r, 10..10);
2291 fn test_range_from_nth() {
2292 assert_eq!((10..).nth(0), Some(10));
2293 assert_eq!((10..).nth(1), Some(11));
2294 assert_eq!((10..).nth(4), Some(14));
2297 assert_eq!(r.nth(2), Some(12));
2298 assert_eq!(r, 13..);
2299 assert_eq!(r.nth(2), Some(15));
2300 assert_eq!(r, 16..);
2301 assert_eq!(r.nth(10), Some(26));
2302 assert_eq!(r, 27..);
2304 assert_eq!((0..).size_hint(), (usize::MAX, None));
2307 fn is_trusted_len<I: TrustedLen>(_: I) {}
2310 fn test_range_from_take() {
2311 let mut it = (0..).take(3);
2312 assert_eq!(it.next(), Some(0));
2313 assert_eq!(it.next(), Some(1));
2314 assert_eq!(it.next(), Some(2));
2315 assert_eq!(it.next(), None);
2316 is_trusted_len((0..).take(3));
2317 assert_eq!((0..).take(3).size_hint(), (3, Some(3)));
2318 assert_eq!((0..).take(0).size_hint(), (0, Some(0)));
2319 assert_eq!((0..).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
2323 fn test_range_from_take_collect() {
2324 let v: Vec<_> = (0..).take(3).collect();
2325 assert_eq!(v, vec![0, 1, 2]);
2329 fn test_range_inclusive_nth() {
2330 assert_eq!((10..=15).nth(0), Some(10));
2331 assert_eq!((10..=15).nth(1), Some(11));
2332 assert_eq!((10..=15).nth(5), Some(15));
2333 assert_eq!((10..=15).nth(6), None);
2335 let mut exhausted_via_next = 10_u8..=20;
2336 while exhausted_via_next.next().is_some() {}
2338 let mut r = 10_u8..=20;
2339 assert_eq!(r.nth(2), Some(12));
2340 assert_eq!(r, 13..=20);
2341 assert_eq!(r.nth(2), Some(15));
2342 assert_eq!(r, 16..=20);
2343 assert_eq!(r.is_empty(), false);
2344 assert_eq!(ExactSizeIterator::is_empty(&r), false);
2345 assert_eq!(r.nth(10), None);
2346 assert_eq!(r.is_empty(), true);
2347 assert_eq!(r, exhausted_via_next);
2348 assert_eq!(ExactSizeIterator::is_empty(&r), true);
2352 fn test_range_inclusive_nth_back() {
2353 assert_eq!((10..=15).nth_back(0), Some(15));
2354 assert_eq!((10..=15).nth_back(1), Some(14));
2355 assert_eq!((10..=15).nth_back(5), Some(10));
2356 assert_eq!((10..=15).nth_back(6), None);
2357 assert_eq!((-120..=80_i8).nth_back(200), Some(-120));
2359 let mut exhausted_via_next_back = 10_u8..=20;
2360 while exhausted_via_next_back.next_back().is_some() {}
2362 let mut r = 10_u8..=20;
2363 assert_eq!(r.nth_back(2), Some(18));
2364 assert_eq!(r, 10..=17);
2365 assert_eq!(r.nth_back(2), Some(15));
2366 assert_eq!(r, 10..=14);
2367 assert_eq!(r.is_empty(), false);
2368 assert_eq!(ExactSizeIterator::is_empty(&r), false);
2369 assert_eq!(r.nth_back(10), None);
2370 assert_eq!(r.is_empty(), true);
2371 assert_eq!(r, exhausted_via_next_back);
2372 assert_eq!(ExactSizeIterator::is_empty(&r), true);
2376 fn test_range_len() {
2377 assert_eq!((0..10_u8).len(), 10);
2378 assert_eq!((9..10_u8).len(), 1);
2379 assert_eq!((10..10_u8).len(), 0);
2380 assert_eq!((11..10_u8).len(), 0);
2381 assert_eq!((100..10_u8).len(), 0);
2385 fn test_range_inclusive_len() {
2386 assert_eq!((0..=10_u8).len(), 11);
2387 assert_eq!((9..=10_u8).len(), 2);
2388 assert_eq!((10..=10_u8).len(), 1);
2389 assert_eq!((11..=10_u8).len(), 0);
2390 assert_eq!((100..=10_u8).len(), 0);
2394 fn test_range_step() {
2395 #![allow(deprecated)]
2397 assert_eq!((0..20).step_by(5).collect::<Vec<isize>>(), [0, 5, 10, 15]);
2398 assert_eq!((1..21).rev().step_by(5).collect::<Vec<isize>>(), [20, 15, 10, 5]);
2399 assert_eq!((1..21).rev().step_by(6).collect::<Vec<isize>>(), [20, 14, 8, 2]);
2400 assert_eq!((200..255).step_by(50).collect::<Vec<u8>>(), [200, 250]);
2401 assert_eq!((200..-5).step_by(1).collect::<Vec<isize>>(), []);
2402 assert_eq!((200..200).step_by(1).collect::<Vec<isize>>(), []);
2404 assert_eq!((0..20).step_by(1).size_hint(), (20, Some(20)));
2405 assert_eq!((0..20).step_by(21).size_hint(), (1, Some(1)));
2406 assert_eq!((0..20).step_by(5).size_hint(), (4, Some(4)));
2407 assert_eq!((1..21).rev().step_by(5).size_hint(), (4, Some(4)));
2408 assert_eq!((1..21).rev().step_by(6).size_hint(), (4, Some(4)));
2409 assert_eq!((20..-5).step_by(1).size_hint(), (0, Some(0)));
2410 assert_eq!((20..20).step_by(1).size_hint(), (0, Some(0)));
2411 assert_eq!((i8::MIN..i8::MAX).step_by(-(i8::MIN as i32) as usize).size_hint(), (2, Some(2)));
2412 assert_eq!((i16::MIN..i16::MAX).step_by(i16::MAX as usize).size_hint(), (3, Some(3)));
2413 assert_eq!((isize::MIN..isize::MAX).step_by(1).size_hint(), (usize::MAX, Some(usize::MAX)));
2417 fn test_step_by_skip() {
2418 assert_eq!((0..640).step_by(128).skip(1).collect::<Vec<_>>(), [128, 256, 384, 512]);
2419 assert_eq!((0..=50).step_by(10).nth(3), Some(30));
2420 assert_eq!((200..=255u8).step_by(10).nth(3), Some(230));
2424 fn test_range_inclusive_step() {
2425 assert_eq!((0..=50).step_by(10).collect::<Vec<_>>(), [0, 10, 20, 30, 40, 50]);
2426 assert_eq!((0..=5).step_by(1).collect::<Vec<_>>(), [0, 1, 2, 3, 4, 5]);
2427 assert_eq!((200..=255u8).step_by(10).collect::<Vec<_>>(), [200, 210, 220, 230, 240, 250]);
2428 assert_eq!((250..=255u8).step_by(1).collect::<Vec<_>>(), [250, 251, 252, 253, 254, 255]);
2432 fn test_range_last_max() {
2433 assert_eq!((0..20).last(), Some(19));
2434 assert_eq!((-20..0).last(), Some(-1));
2435 assert_eq!((5..5).last(), None);
2437 assert_eq!((0..20).max(), Some(19));
2438 assert_eq!((-20..0).max(), Some(-1));
2439 assert_eq!((5..5).max(), None);
2443 fn test_range_inclusive_last_max() {
2444 assert_eq!((0..=20).last(), Some(20));
2445 assert_eq!((-20..=0).last(), Some(0));
2446 assert_eq!((5..=5).last(), Some(5));
2447 let mut r = 10..=10;
2449 assert_eq!(r.last(), None);
2451 assert_eq!((0..=20).max(), Some(20));
2452 assert_eq!((-20..=0).max(), Some(0));
2453 assert_eq!((5..=5).max(), Some(5));
2454 let mut r = 10..=10;
2456 assert_eq!(r.max(), None);
2460 fn test_range_min() {
2461 assert_eq!((0..20).min(), Some(0));
2462 assert_eq!((-20..0).min(), Some(-20));
2463 assert_eq!((5..5).min(), None);
2467 fn test_range_inclusive_min() {
2468 assert_eq!((0..=20).min(), Some(0));
2469 assert_eq!((-20..=0).min(), Some(-20));
2470 assert_eq!((5..=5).min(), Some(5));
2471 let mut r = 10..=10;
2473 assert_eq!(r.min(), None);
2477 fn test_range_inclusive_folds() {
2478 assert_eq!((1..=10).sum::<i32>(), 55);
2479 assert_eq!((1..=10).rev().sum::<i32>(), 55);
2481 let mut it = 44..=50;
2482 assert_eq!(it.try_fold(0, i8::checked_add), None);
2483 assert_eq!(it, 47..=50);
2484 assert_eq!(it.try_fold(0, i8::checked_add), None);
2485 assert_eq!(it, 50..=50);
2486 assert_eq!(it.try_fold(0, i8::checked_add), Some(50));
2487 assert!(it.is_empty());
2488 assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
2489 assert!(it.is_empty());
2491 let mut it = 40..=47;
2492 assert_eq!(it.try_rfold(0, i8::checked_add), None);
2493 assert_eq!(it, 40..=44);
2494 assert_eq!(it.try_rfold(0, i8::checked_add), None);
2495 assert_eq!(it, 40..=41);
2496 assert_eq!(it.try_rfold(0, i8::checked_add), Some(81));
2497 assert!(it.is_empty());
2498 assert_eq!(it.try_rfold(0, i8::checked_add), Some(0));
2499 assert!(it.is_empty());
2501 let mut it = 10..=20;
2502 assert_eq!(it.try_fold(0, |a, b| Some(a + b)), Some(165));
2503 assert!(it.is_empty());
2504 assert_eq!(it.try_fold(0, |a, b| Some(a + b)), Some(0));
2505 assert!(it.is_empty());
2507 let mut it = 10..=20;
2508 assert_eq!(it.try_rfold(0, |a, b| Some(a + b)), Some(165));
2509 assert!(it.is_empty());
2510 assert_eq!(it.try_rfold(0, |a, b| Some(a + b)), Some(0));
2511 assert!(it.is_empty());
2515 fn test_range_size_hint() {
2516 assert_eq!((0..0usize).size_hint(), (0, Some(0)));
2517 assert_eq!((0..100usize).size_hint(), (100, Some(100)));
2518 assert_eq!((0..usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
2520 let umax = u128::try_from(usize::MAX).unwrap();
2521 assert_eq!((0..0u128).size_hint(), (0, Some(0)));
2522 assert_eq!((0..100u128).size_hint(), (100, Some(100)));
2523 assert_eq!((0..umax).size_hint(), (usize::MAX, Some(usize::MAX)));
2524 assert_eq!((0..umax + 1).size_hint(), (usize::MAX, None));
2526 assert_eq!((0..0isize).size_hint(), (0, Some(0)));
2527 assert_eq!((-100..100isize).size_hint(), (200, Some(200)));
2528 assert_eq!((isize::MIN..isize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
2530 let imin = i128::try_from(isize::MIN).unwrap();
2531 let imax = i128::try_from(isize::MAX).unwrap();
2532 assert_eq!((0..0i128).size_hint(), (0, Some(0)));
2533 assert_eq!((-100..100i128).size_hint(), (200, Some(200)));
2534 assert_eq!((imin..imax).size_hint(), (usize::MAX, Some(usize::MAX)));
2535 assert_eq!((imin..imax + 1).size_hint(), (usize::MAX, None));
2539 fn test_range_inclusive_size_hint() {
2540 assert_eq!((1..=0usize).size_hint(), (0, Some(0)));
2541 assert_eq!((0..=0usize).size_hint(), (1, Some(1)));
2542 assert_eq!((0..=100usize).size_hint(), (101, Some(101)));
2543 assert_eq!((0..=usize::MAX - 1).size_hint(), (usize::MAX, Some(usize::MAX)));
2544 assert_eq!((0..=usize::MAX).size_hint(), (usize::MAX, None));
2546 let umax = u128::try_from(usize::MAX).unwrap();
2547 assert_eq!((1..=0u128).size_hint(), (0, Some(0)));
2548 assert_eq!((0..=0u128).size_hint(), (1, Some(1)));
2549 assert_eq!((0..=100u128).size_hint(), (101, Some(101)));
2550 assert_eq!((0..=umax - 1).size_hint(), (usize::MAX, Some(usize::MAX)));
2551 assert_eq!((0..=umax).size_hint(), (usize::MAX, None));
2552 assert_eq!((0..=umax + 1).size_hint(), (usize::MAX, None));
2554 assert_eq!((0..=-1isize).size_hint(), (0, Some(0)));
2555 assert_eq!((0..=0isize).size_hint(), (1, Some(1)));
2556 assert_eq!((-100..=100isize).size_hint(), (201, Some(201)));
2557 assert_eq!((isize::MIN..=isize::MAX - 1).size_hint(), (usize::MAX, Some(usize::MAX)));
2558 assert_eq!((isize::MIN..=isize::MAX).size_hint(), (usize::MAX, None));
2560 let imin = i128::try_from(isize::MIN).unwrap();
2561 let imax = i128::try_from(isize::MAX).unwrap();
2562 assert_eq!((0..=-1i128).size_hint(), (0, Some(0)));
2563 assert_eq!((0..=0i128).size_hint(), (1, Some(1)));
2564 assert_eq!((-100..=100i128).size_hint(), (201, Some(201)));
2565 assert_eq!((imin..=imax - 1).size_hint(), (usize::MAX, Some(usize::MAX)));
2566 assert_eq!((imin..=imax).size_hint(), (usize::MAX, None));
2567 assert_eq!((imin..=imax + 1).size_hint(), (usize::MAX, None));
2572 let mut it = repeat(42);
2573 assert_eq!(it.next(), Some(42));
2574 assert_eq!(it.next(), Some(42));
2575 assert_eq!(it.next(), Some(42));
2576 assert_eq!(repeat(42).size_hint(), (usize::MAX, None));
2580 fn test_repeat_take() {
2581 let mut it = repeat(42).take(3);
2582 assert_eq!(it.next(), Some(42));
2583 assert_eq!(it.next(), Some(42));
2584 assert_eq!(it.next(), Some(42));
2585 assert_eq!(it.next(), None);
2586 is_trusted_len(repeat(42).take(3));
2587 assert_eq!(repeat(42).take(3).size_hint(), (3, Some(3)));
2588 assert_eq!(repeat(42).take(0).size_hint(), (0, Some(0)));
2589 assert_eq!(repeat(42).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
2593 fn test_repeat_take_collect() {
2594 let v: Vec<_> = repeat(42).take(3).collect();
2595 assert_eq!(v, vec![42, 42, 42]);
2599 fn test_repeat_with() {
2600 #[derive(PartialEq, Debug)]
2601 struct NotClone(usize);
2602 let mut it = repeat_with(|| NotClone(42));
2603 assert_eq!(it.next(), Some(NotClone(42)));
2604 assert_eq!(it.next(), Some(NotClone(42)));
2605 assert_eq!(it.next(), Some(NotClone(42)));
2606 assert_eq!(repeat_with(|| NotClone(42)).size_hint(), (usize::MAX, None));
2610 fn test_repeat_with_take() {
2611 let mut it = repeat_with(|| 42).take(3);
2612 assert_eq!(it.next(), Some(42));
2613 assert_eq!(it.next(), Some(42));
2614 assert_eq!(it.next(), Some(42));
2615 assert_eq!(it.next(), None);
2616 is_trusted_len(repeat_with(|| 42).take(3));
2617 assert_eq!(repeat_with(|| 42).take(3).size_hint(), (3, Some(3)));
2618 assert_eq!(repeat_with(|| 42).take(0).size_hint(), (0, Some(0)));
2619 assert_eq!(repeat_with(|| 42).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
2623 fn test_repeat_with_take_collect() {
2625 let v: Vec<_> = repeat_with(|| {
2632 assert_eq!(v, vec![1, 2, 4, 8, 16]);
2636 fn test_successors() {
2637 let mut powers_of_10 = successors(Some(1_u16), |n| n.checked_mul(10));
2638 assert_eq!(powers_of_10.by_ref().collect::<Vec<_>>(), &[1, 10, 100, 1_000, 10_000]);
2639 assert_eq!(powers_of_10.next(), None);
2641 let mut empty = successors(None::<u32>, |_| unimplemented!());
2642 assert_eq!(empty.next(), None);
2643 assert_eq!(empty.next(), None);
2649 assert_eq!(it.len(), 3);
2650 assert_eq!(it.next(), Some(0));
2651 assert_eq!(it.len(), 2);
2652 assert_eq!(it.next(), Some(1));
2653 assert_eq!(it.len(), 1);
2654 assert_eq!(it.next(), Some(2));
2655 assert_eq!(it.len(), 0);
2656 assert_eq!(it.next(), None);
2657 assert_eq!(it.len(), 0);
2658 assert_eq!(it.next(), None);
2659 assert_eq!(it.len(), 0);
2660 assert_eq!(it.next(), None);
2661 assert_eq!(it.len(), 0);
2665 fn test_fuse_nth() {
2667 let mut it = xs.iter();
2669 assert_eq!(it.len(), 3);
2670 assert_eq!(it.nth(2), Some(&2));
2671 assert_eq!(it.len(), 0);
2672 assert_eq!(it.nth(2), None);
2673 assert_eq!(it.len(), 0);
2677 fn test_fuse_last() {
2681 assert_eq!(it.len(), 3);
2682 assert_eq!(it.last(), Some(&2));
2686 fn test_fuse_count() {
2690 assert_eq!(it.len(), 3);
2691 assert_eq!(it.count(), 3);
2692 // Can't check len now because count consumes.
2696 fn test_fuse_fold() {
2698 let it = xs.iter(); // `FusedIterator`
2699 let i = it.fuse().fold(0, |i, &x| {
2700 assert_eq!(x, xs[i]);
2703 assert_eq!(i, xs.len());
2705 let it = xs.iter(); // `FusedIterator`
2706 let i = it.fuse().rfold(xs.len(), |i, &x| {
2707 assert_eq!(x, xs[i - 1]);
2712 let it = xs.iter().scan((), |_, &x| Some(x)); // `!FusedIterator`
2713 let i = it.fuse().fold(0, |i, x| {
2714 assert_eq!(x, xs[i]);
2717 assert_eq!(i, xs.len());
2722 let mut it = once(42);
2723 assert_eq!(it.next(), Some(42));
2724 assert_eq!(it.next(), None);
2728 fn test_once_with() {
2729 let count = Cell::new(0);
2730 let mut it = once_with(|| {
2731 count.set(count.get() + 1);
2735 assert_eq!(count.get(), 0);
2736 assert_eq!(it.next(), Some(42));
2737 assert_eq!(count.get(), 1);
2738 assert_eq!(it.next(), None);
2739 assert_eq!(count.get(), 1);
2740 assert_eq!(it.next(), None);
2741 assert_eq!(count.get(), 1);
2746 let mut it = empty::<i32>();
2747 assert_eq!(it.next(), None);
2751 fn test_chain_fold() {
2755 let mut iter = xs.iter().chain(&ys);
2757 let mut result = Vec::new();
2758 iter.fold((), |(), &elt| result.push(elt));
2759 assert_eq!(&[2, 3, 1, 2, 0], &result[..]);
2763 fn test_steps_between() {
2764 assert_eq!(Step::steps_between(&20_u8, &200_u8), Some(180_usize));
2765 assert_eq!(Step::steps_between(&-20_i8, &80_i8), Some(100_usize));
2766 assert_eq!(Step::steps_between(&-120_i8, &80_i8), Some(200_usize));
2767 assert_eq!(Step::steps_between(&20_u32, &4_000_100_u32), Some(4_000_080_usize));
2768 assert_eq!(Step::steps_between(&-20_i32, &80_i32), Some(100_usize));
2769 assert_eq!(Step::steps_between(&-2_000_030_i32, &2_000_050_i32), Some(4_000_080_usize));
2771 // Skip u64/i64 to avoid differences with 32-bit vs 64-bit platforms
2773 assert_eq!(Step::steps_between(&20_u128, &200_u128), Some(180_usize));
2774 assert_eq!(Step::steps_between(&-20_i128, &80_i128), Some(100_usize));
2775 if cfg!(target_pointer_width = "64") {
2776 assert_eq!(Step::steps_between(&10_u128, &0x1_0000_0000_0000_0009_u128), Some(usize::MAX));
2778 assert_eq!(Step::steps_between(&10_u128, &0x1_0000_0000_0000_000a_u128), None);
2779 assert_eq!(Step::steps_between(&10_i128, &0x1_0000_0000_0000_000a_i128), None);
2781 Step::steps_between(&-0x1_0000_0000_0000_0000_i128, &0x1_0000_0000_0000_0000_i128,),
2787 fn test_step_forward() {
2788 assert_eq!(Step::forward_checked(55_u8, 200_usize), Some(255_u8));
2789 assert_eq!(Step::forward_checked(252_u8, 200_usize), None);
2790 assert_eq!(Step::forward_checked(0_u8, 256_usize), None);
2791 assert_eq!(Step::forward_checked(-110_i8, 200_usize), Some(90_i8));
2792 assert_eq!(Step::forward_checked(-110_i8, 248_usize), None);
2793 assert_eq!(Step::forward_checked(-126_i8, 256_usize), None);
2795 assert_eq!(Step::forward_checked(35_u16, 100_usize), Some(135_u16));
2796 assert_eq!(Step::forward_checked(35_u16, 65500_usize), Some(u16::MAX));
2797 assert_eq!(Step::forward_checked(36_u16, 65500_usize), None);
2798 assert_eq!(Step::forward_checked(-110_i16, 200_usize), Some(90_i16));
2799 assert_eq!(Step::forward_checked(-20_030_i16, 50_050_usize), Some(30_020_i16));
2800 assert_eq!(Step::forward_checked(-10_i16, 40_000_usize), None);
2801 assert_eq!(Step::forward_checked(-10_i16, 70_000_usize), None);
2803 assert_eq!(Step::forward_checked(10_u128, 70_000_usize), Some(70_010_u128));
2804 assert_eq!(Step::forward_checked(10_i128, 70_030_usize), Some(70_040_i128));
2806 Step::forward_checked(0xffff_ffff_ffff_ffff__ffff_ffff_ffff_ff00_u128, 0xff_usize),
2810 Step::forward_checked(0xffff_ffff_ffff_ffff__ffff_ffff_ffff_ff00_u128, 0x100_usize),
2814 Step::forward_checked(0x7fff_ffff_ffff_ffff__ffff_ffff_ffff_ff00_i128, 0xff_usize),
2818 Step::forward_checked(0x7fff_ffff_ffff_ffff__ffff_ffff_ffff_ff00_i128, 0x100_usize),
2824 fn test_step_backward() {
2825 assert_eq!(Step::backward_checked(255_u8, 200_usize), Some(55_u8));
2826 assert_eq!(Step::backward_checked(100_u8, 200_usize), None);
2827 assert_eq!(Step::backward_checked(255_u8, 256_usize), None);
2828 assert_eq!(Step::backward_checked(90_i8, 200_usize), Some(-110_i8));
2829 assert_eq!(Step::backward_checked(110_i8, 248_usize), None);
2830 assert_eq!(Step::backward_checked(127_i8, 256_usize), None);
2832 assert_eq!(Step::backward_checked(135_u16, 100_usize), Some(35_u16));
2833 assert_eq!(Step::backward_checked(u16::MAX, 65500_usize), Some(35_u16));
2834 assert_eq!(Step::backward_checked(10_u16, 11_usize), None);
2835 assert_eq!(Step::backward_checked(90_i16, 200_usize), Some(-110_i16));
2836 assert_eq!(Step::backward_checked(30_020_i16, 50_050_usize), Some(-20_030_i16));
2837 assert_eq!(Step::backward_checked(-10_i16, 40_000_usize), None);
2838 assert_eq!(Step::backward_checked(-10_i16, 70_000_usize), None);
2840 assert_eq!(Step::backward_checked(70_010_u128, 70_000_usize), Some(10_u128));
2841 assert_eq!(Step::backward_checked(70_020_i128, 70_030_usize), Some(-10_i128));
2842 assert_eq!(Step::backward_checked(10_u128, 7_usize), Some(3_u128));
2843 assert_eq!(Step::backward_checked(10_u128, 11_usize), None);
2845 Step::backward_checked(-0x7fff_ffff_ffff_ffff__ffff_ffff_ffff_ff00_i128, 0x100_usize),
2851 fn test_rev_try_folds() {
2852 let f = &|acc, x| i32::checked_add(2 * acc, x);
2853 assert_eq!((1..10).rev().try_fold(7, f), (1..10).try_rfold(7, f));
2854 assert_eq!((1..10).rev().try_rfold(7, f), (1..10).try_fold(7, f));
2856 let a = [10, 20, 30, 40, 100, 60, 70, 80, 90];
2857 let mut iter = a.iter().rev();
2858 assert_eq!(iter.try_fold(0_i8, |acc, &x| acc.checked_add(x)), None);
2859 assert_eq!(iter.next(), Some(&70));
2860 let mut iter = a.iter().rev();
2861 assert_eq!(iter.try_rfold(0_i8, |acc, &x| acc.checked_add(x)), None);
2862 assert_eq!(iter.next_back(), Some(&60));
2866 fn test_cloned_try_folds() {
2867 let a = [1, 2, 3, 4, 5, 6, 7, 8, 9];
2868 let f = &|acc, x| i32::checked_add(2 * acc, x);
2869 let f_ref = &|acc, &x| i32::checked_add(2 * acc, x);
2870 assert_eq!(a.iter().cloned().try_fold(7, f), a.iter().try_fold(7, f_ref));
2871 assert_eq!(a.iter().cloned().try_rfold(7, f), a.iter().try_rfold(7, f_ref));
2873 let a = [10, 20, 30, 40, 100, 60, 70, 80, 90];
2874 let mut iter = a.iter().cloned();
2875 assert_eq!(iter.try_fold(0_i8, |acc, x| acc.checked_add(x)), None);
2876 assert_eq!(iter.next(), Some(60));
2877 let mut iter = a.iter().cloned();
2878 assert_eq!(iter.try_rfold(0_i8, |acc, x| acc.checked_add(x)), None);
2879 assert_eq!(iter.next_back(), Some(70));
2883 fn test_chain_try_folds() {
2884 let c = || (0..10).chain(10..20);
2886 let f = &|acc, x| i32::checked_add(2 * acc, x);
2887 assert_eq!(c().try_fold(7, f), (0..20).try_fold(7, f));
2888 assert_eq!(c().try_rfold(7, f), (0..20).rev().try_fold(7, f));
2891 assert_eq!(iter.position(|x| x == 5), Some(5));
2892 assert_eq!(iter.next(), Some(6), "stopped in front, state Both");
2893 assert_eq!(iter.position(|x| x == 13), Some(6));
2894 assert_eq!(iter.next(), Some(14), "stopped in back, state Back");
2895 assert_eq!(iter.try_fold(0, |acc, x| Some(acc + x)), Some((15..20).sum()));
2897 let mut iter = c().rev(); // use rev to access try_rfold
2898 assert_eq!(iter.position(|x| x == 15), Some(4));
2899 assert_eq!(iter.next(), Some(14), "stopped in back, state Both");
2900 assert_eq!(iter.position(|x| x == 5), Some(8));
2901 assert_eq!(iter.next(), Some(4), "stopped in front, state Front");
2902 assert_eq!(iter.try_fold(0, |acc, x| Some(acc + x)), Some((0..4).sum()));
2905 iter.by_ref().rev().nth(14); // skip the last 15, ending in state Front
2906 assert_eq!(iter.try_fold(7, f), (0..5).try_fold(7, f));
2909 iter.nth(14); // skip the first 15, ending in state Back
2910 assert_eq!(iter.try_rfold(7, f), (15..20).try_rfold(7, f));
2914 fn test_map_try_folds() {
2915 let f = &|acc, x| i32::checked_add(2 * acc, x);
2916 assert_eq!((0..10).map(|x| x + 3).try_fold(7, f), (3..13).try_fold(7, f));
2917 assert_eq!((0..10).map(|x| x + 3).try_rfold(7, f), (3..13).try_rfold(7, f));
2919 let mut iter = (0..40).map(|x| x + 10);
2920 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2921 assert_eq!(iter.next(), Some(20));
2922 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2923 assert_eq!(iter.next_back(), Some(46));
2927 fn test_filter_try_folds() {
2928 fn p(&x: &i32) -> bool {
2931 let f = &|acc, x| i32::checked_add(2 * acc, x);
2932 assert_eq!((-10..20).filter(p).try_fold(7, f), (0..10).try_fold(7, f));
2933 assert_eq!((-10..20).filter(p).try_rfold(7, f), (0..10).try_rfold(7, f));
2935 let mut iter = (0..40).filter(|&x| x % 2 == 1);
2936 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2937 assert_eq!(iter.next(), Some(25));
2938 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2939 assert_eq!(iter.next_back(), Some(31));
2943 fn test_filter_map_try_folds() {
2944 let mp = &|x| if 0 <= x && x < 10 { Some(x * 2) } else { None };
2945 let f = &|acc, x| i32::checked_add(2 * acc, x);
2946 assert_eq!((-9..20).filter_map(mp).try_fold(7, f), (0..10).map(|x| 2 * x).try_fold(7, f));
2947 assert_eq!((-9..20).filter_map(mp).try_rfold(7, f), (0..10).map(|x| 2 * x).try_rfold(7, f));
2949 let mut iter = (0..40).filter_map(|x| if x % 2 == 1 { None } else { Some(x * 2 + 10) });
2950 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2951 assert_eq!(iter.next(), Some(38));
2952 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2953 assert_eq!(iter.next_back(), Some(78));
2957 fn test_enumerate_try_folds() {
2958 let f = &|acc, (i, x)| usize::checked_add(2 * acc, x / (i + 1) + i);
2959 assert_eq!((9..18).enumerate().try_fold(7, f), (0..9).map(|i| (i, i + 9)).try_fold(7, f));
2960 assert_eq!((9..18).enumerate().try_rfold(7, f), (0..9).map(|i| (i, i + 9)).try_rfold(7, f));
2962 let mut iter = (100..200).enumerate();
2963 let f = &|acc, (i, x)| u8::checked_add(acc, u8::checked_div(x, i as u8 + 1)?);
2964 assert_eq!(iter.try_fold(0, f), None);
2965 assert_eq!(iter.next(), Some((7, 107)));
2966 assert_eq!(iter.try_rfold(0, f), None);
2967 assert_eq!(iter.next_back(), Some((11, 111)));
2971 fn test_peek_try_folds() {
2972 let f = &|acc, x| i32::checked_add(2 * acc, x);
2974 assert_eq!((1..20).peekable().try_fold(7, f), (1..20).try_fold(7, f));
2975 assert_eq!((1..20).peekable().try_rfold(7, f), (1..20).try_rfold(7, f));
2977 let mut iter = (1..20).peekable();
2978 assert_eq!(iter.peek(), Some(&1));
2979 assert_eq!(iter.try_fold(7, f), (1..20).try_fold(7, f));
2981 let mut iter = (1..20).peekable();
2982 assert_eq!(iter.peek(), Some(&1));
2983 assert_eq!(iter.try_rfold(7, f), (1..20).try_rfold(7, f));
2985 let mut iter = [100, 20, 30, 40, 50, 60, 70].iter().cloned().peekable();
2986 assert_eq!(iter.peek(), Some(&100));
2987 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2988 assert_eq!(iter.peek(), Some(&40));
2990 let mut iter = [100, 20, 30, 40, 50, 60, 70].iter().cloned().peekable();
2991 assert_eq!(iter.peek(), Some(&100));
2992 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2993 assert_eq!(iter.peek(), Some(&100));
2994 assert_eq!(iter.next_back(), Some(50));
2996 let mut iter = (2..5).peekable();
2997 assert_eq!(iter.peek(), Some(&2));
2998 assert_eq!(iter.try_for_each(Err), Err(2));
2999 assert_eq!(iter.peek(), Some(&3));
3000 assert_eq!(iter.try_for_each(Err), Err(3));
3001 assert_eq!(iter.peek(), Some(&4));
3002 assert_eq!(iter.try_for_each(Err), Err(4));
3003 assert_eq!(iter.peek(), None);
3004 assert_eq!(iter.try_for_each(Err), Ok(()));
3006 let mut iter = (2..5).peekable();
3007 assert_eq!(iter.peek(), Some(&2));
3008 assert_eq!(iter.try_rfold((), |(), x| Err(x)), Err(4));
3009 assert_eq!(iter.peek(), Some(&2));
3010 assert_eq!(iter.try_rfold((), |(), x| Err(x)), Err(3));
3011 assert_eq!(iter.peek(), Some(&2));
3012 assert_eq!(iter.try_rfold((), |(), x| Err(x)), Err(2));
3013 assert_eq!(iter.peek(), None);
3014 assert_eq!(iter.try_rfold((), |(), x| Err(x)), Ok(()));
3018 fn test_skip_while_try_fold() {
3019 let f = &|acc, x| i32::checked_add(2 * acc, x);
3020 fn p(&x: &i32) -> bool {
3023 assert_eq!((1..20).skip_while(p).try_fold(7, f), (6..20).try_fold(7, f));
3024 let mut iter = (1..20).skip_while(p);
3025 assert_eq!(iter.nth(5), Some(11));
3026 assert_eq!(iter.try_fold(7, f), (12..20).try_fold(7, f));
3028 let mut iter = (0..50).skip_while(|&x| (x % 20) < 15);
3029 assert_eq!(iter.try_fold(0, i8::checked_add), None);
3030 assert_eq!(iter.next(), Some(23));
3034 fn test_take_while_folds() {
3035 let f = &|acc, x| i32::checked_add(2 * acc, x);
3036 assert_eq!((1..20).take_while(|&x| x != 10).try_fold(7, f), (1..10).try_fold(7, f));
3037 let mut iter = (1..20).take_while(|&x| x != 10);
3038 assert_eq!(iter.try_fold(0, |x, y| Some(x + y)), Some((1..10).sum()));
3039 assert_eq!(iter.next(), None, "flag should be set");
3040 let iter = (1..20).take_while(|&x| x != 10);
3041 assert_eq!(iter.fold(0, |x, y| x + y), (1..10).sum());
3043 let mut iter = (10..50).take_while(|&x| x != 40);
3044 assert_eq!(iter.try_fold(0, i8::checked_add), None);
3045 assert_eq!(iter.next(), Some(20));
3049 fn test_skip_try_folds() {
3050 let f = &|acc, x| i32::checked_add(2 * acc, x);
3051 assert_eq!((1..20).skip(9).try_fold(7, f), (10..20).try_fold(7, f));
3052 assert_eq!((1..20).skip(9).try_rfold(7, f), (10..20).try_rfold(7, f));
3054 let mut iter = (0..30).skip(10);
3055 assert_eq!(iter.try_fold(0, i8::checked_add), None);
3056 assert_eq!(iter.next(), Some(20));
3057 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
3058 assert_eq!(iter.next_back(), Some(24));
3062 fn test_skip_nth_back() {
3063 let xs = [0, 1, 2, 3, 4, 5];
3064 let mut it = xs.iter().skip(2);
3065 assert_eq!(it.nth_back(0), Some(&5));
3066 assert_eq!(it.nth_back(1), Some(&3));
3067 assert_eq!(it.nth_back(0), Some(&2));
3068 assert_eq!(it.nth_back(0), None);
3070 let ys = [2, 3, 4, 5];
3071 let mut ity = ys.iter();
3072 let mut it = xs.iter().skip(2);
3073 assert_eq!(it.nth_back(1), ity.nth_back(1));
3074 assert_eq!(it.clone().nth(0), ity.clone().nth(0));
3075 assert_eq!(it.nth_back(0), ity.nth_back(0));
3076 assert_eq!(it.clone().nth(0), ity.clone().nth(0));
3077 assert_eq!(it.nth_back(0), ity.nth_back(0));
3078 assert_eq!(it.clone().nth(0), ity.clone().nth(0));
3079 assert_eq!(it.nth_back(0), ity.nth_back(0));
3080 assert_eq!(it.clone().nth(0), ity.clone().nth(0));
3082 let mut it = xs.iter().skip(2);
3083 assert_eq!(it.nth_back(4), None);
3084 assert_eq!(it.nth_back(0), None);
3086 let mut it = xs.iter();
3087 it.by_ref().skip(2).nth_back(3);
3088 assert_eq!(it.next_back(), Some(&1));
3090 let mut it = xs.iter();
3091 it.by_ref().skip(2).nth_back(10);
3092 assert_eq!(it.next_back(), Some(&1));
3096 fn test_take_try_folds() {
3097 let f = &|acc, x| i32::checked_add(2 * acc, x);
3098 assert_eq!((10..30).take(10).try_fold(7, f), (10..20).try_fold(7, f));
3099 assert_eq!((10..30).take(10).try_rfold(7, f), (10..20).try_rfold(7, f));
3101 let mut iter = (10..30).take(20);
3102 assert_eq!(iter.try_fold(0, i8::checked_add), None);
3103 assert_eq!(iter.next(), Some(20));
3104 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
3105 assert_eq!(iter.next_back(), Some(24));
3107 let mut iter = (2..20).take(3);
3108 assert_eq!(iter.try_for_each(Err), Err(2));
3109 assert_eq!(iter.try_for_each(Err), Err(3));
3110 assert_eq!(iter.try_for_each(Err), Err(4));
3111 assert_eq!(iter.try_for_each(Err), Ok(()));
3113 let mut iter = (2..20).take(3).rev();
3114 assert_eq!(iter.try_for_each(Err), Err(4));
3115 assert_eq!(iter.try_for_each(Err), Err(3));
3116 assert_eq!(iter.try_for_each(Err), Err(2));
3117 assert_eq!(iter.try_for_each(Err), Ok(()));
3121 fn test_flat_map_try_folds() {
3122 let f = &|acc, x| i32::checked_add(acc * 2 / 3, x);
3123 let mr = &|x| (5 * x)..(5 * x + 5);
3124 assert_eq!((0..10).flat_map(mr).try_fold(7, f), (0..50).try_fold(7, f));
3125 assert_eq!((0..10).flat_map(mr).try_rfold(7, f), (0..50).try_rfold(7, f));
3126 let mut iter = (0..10).flat_map(mr);
3128 iter.next_back(); // have front and back iters in progress
3129 assert_eq!(iter.try_rfold(7, f), (1..49).try_rfold(7, f));
3131 let mut iter = (0..10).flat_map(|x| (4 * x)..(4 * x + 4));
3132 assert_eq!(iter.try_fold(0, i8::checked_add), None);
3133 assert_eq!(iter.next(), Some(17));
3134 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
3135 assert_eq!(iter.next_back(), Some(35));
3139 fn test_flatten_try_folds() {
3140 let f = &|acc, x| i32::checked_add(acc * 2 / 3, x);
3141 let mr = &|x| (5 * x)..(5 * x + 5);
3142 assert_eq!((0..10).map(mr).flatten().try_fold(7, f), (0..50).try_fold(7, f));
3143 assert_eq!((0..10).map(mr).flatten().try_rfold(7, f), (0..50).try_rfold(7, f));
3144 let mut iter = (0..10).map(mr).flatten();
3146 iter.next_back(); // have front and back iters in progress
3147 assert_eq!(iter.try_rfold(7, f), (1..49).try_rfold(7, f));
3149 let mut iter = (0..10).map(|x| (4 * x)..(4 * x + 4)).flatten();
3150 assert_eq!(iter.try_fold(0, i8::checked_add), None);
3151 assert_eq!(iter.next(), Some(17));
3152 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
3153 assert_eq!(iter.next_back(), Some(35));
3157 fn test_functor_laws() {
3159 fn identity<T>(x: T) -> T {
3162 assert_eq!((0..10).map(identity).sum::<usize>(), (0..10).sum());
3165 fn f(x: usize) -> usize {
3168 fn g(x: usize) -> usize {
3171 fn h(x: usize) -> usize {
3174 assert_eq!((0..10).map(f).map(g).sum::<usize>(), (0..10).map(h).sum());
3178 fn test_monad_laws_left_identity() {
3179 fn f(x: usize) -> impl Iterator<Item = usize> {
3180 (0..10).map(move |y| x * y)
3182 assert_eq!(once(42).flat_map(f.clone()).sum::<usize>(), f(42).sum());
3186 fn test_monad_laws_right_identity() {
3187 assert_eq!((0..10).flat_map(|x| once(x)).sum::<usize>(), (0..10).sum());
3191 fn test_monad_laws_associativity() {
3192 fn f(x: usize) -> impl Iterator<Item = usize> {
3195 fn g(x: usize) -> impl Iterator<Item = usize> {
3199 (0..10).flat_map(f).flat_map(g).sum::<usize>(),
3200 (0..10).flat_map(|x| f(x).flat_map(g)).sum::<usize>()
3205 fn test_is_sorted() {
3206 assert!([1, 2, 2, 9].iter().is_sorted());
3207 assert!(![1, 3, 2].iter().is_sorted());
3208 assert!([0].iter().is_sorted());
3209 assert!(std::iter::empty::<i32>().is_sorted());
3210 assert!(![0.0, 1.0, f32::NAN].iter().is_sorted());
3211 assert!([-2, -1, 0, 3].iter().is_sorted());
3212 assert!(![-2i32, -1, 0, 3].iter().is_sorted_by_key(|n| n.abs()));
3213 assert!(!["c", "bb", "aaa"].iter().is_sorted());
3214 assert!(["c", "bb", "aaa"].iter().is_sorted_by_key(|s| s.len()));
3218 fn test_partition() {
3219 fn check(xs: &mut [i32], ref p: impl Fn(&i32) -> bool, expected: usize) {
3220 let i = xs.iter_mut().partition_in_place(p);
3221 assert_eq!(expected, i);
3222 assert!(xs[..i].iter().all(p));
3223 assert!(!xs[i..].iter().any(p));
3224 assert!(xs.iter().is_partitioned(p));
3225 if i == 0 || i == xs.len() {
3226 assert!(xs.iter().rev().is_partitioned(p));
3228 assert!(!xs.iter().rev().is_partitioned(p));
3232 check(&mut [], |_| true, 0);
3233 check(&mut [], |_| false, 0);
3235 check(&mut [0], |_| true, 1);
3236 check(&mut [0], |_| false, 0);
3238 check(&mut [-1, 1], |&x| x > 0, 1);
3239 check(&mut [-1, 1], |&x| x < 0, 1);
3241 let ref mut xs = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
3242 check(xs, |_| true, 10);
3243 check(xs, |_| false, 0);
3244 check(xs, |&x| x % 2 == 0, 5); // evens
3245 check(xs, |&x| x % 2 == 1, 5); // odds
3246 check(xs, |&x| x % 3 == 0, 4); // multiple of 3
3247 check(xs, |&x| x % 4 == 0, 3); // multiple of 4
3248 check(xs, |&x| x % 5 == 0, 2); // multiple of 5
3249 check(xs, |&x| x < 3, 3); // small
3250 check(xs, |&x| x > 6, 3); // large
3253 /// An iterator that panics whenever `next` or next_back` is called
3254 /// after `None` has already been returned. This does not violate
3255 /// `Iterator`'s contract. Used to test that iterator adaptors don't
3256 /// poll their inner iterators after exhausting them.
3257 struct NonFused<I> {
3262 impl<I> NonFused<I> {
3263 fn new(iter: I) -> Self {
3264 Self { iter, done: false }
3268 impl<I> Iterator for NonFused<I>
3272 type Item = I::Item;
3274 fn next(&mut self) -> Option<Self::Item> {
3275 assert!(!self.done, "this iterator has already returned None");
3276 self.iter.next().or_else(|| {
3283 impl<I> DoubleEndedIterator for NonFused<I>
3285 I: DoubleEndedIterator,
3287 fn next_back(&mut self) -> Option<Self::Item> {
3288 assert!(!self.done, "this iterator has already returned None");
3289 self.iter.next_back().or_else(|| {
3297 fn test_peekable_non_fused() {
3298 let mut iter = NonFused::new(empty::<i32>()).peekable();
3300 assert_eq!(iter.peek(), None);
3301 assert_eq!(iter.next_back(), None);
3305 fn test_flatten_non_fused_outer() {
3306 let mut iter = NonFused::new(once(0..2)).flatten();
3308 assert_eq!(iter.next_back(), Some(1));
3309 assert_eq!(iter.next(), Some(0));
3310 assert_eq!(iter.next(), None);
3314 fn test_flatten_non_fused_inner() {
3315 let mut iter = once(0..1).chain(once(1..3)).flat_map(NonFused::new);
3317 assert_eq!(iter.next_back(), Some(2));
3318 assert_eq!(iter.next(), Some(0));
3319 assert_eq!(iter.next(), Some(1));
3320 assert_eq!(iter.next(), None);