1 // ignore-tidy-filelength
4 use core::convert::TryFrom;
7 /// An iterator wrapper that panics whenever `next` or `next_back` is called
8 /// after `None` has been returned.
14 fn unfuse<I: IntoIterator>(iter: I) -> Unfuse<I::IntoIter> {
15 Unfuse { iter: iter.into_iter(), exhausted: false }
18 impl<I> Iterator for Unfuse<I>
24 fn next(&mut self) -> Option<Self::Item> {
25 assert!(!self.exhausted);
26 let next = self.iter.next();
27 self.exhausted = next.is_none();
32 impl<I> DoubleEndedIterator for Unfuse<I>
34 I: DoubleEndedIterator,
36 fn next_back(&mut self) -> Option<Self::Item> {
37 assert!(!self.exhausted);
38 let next = self.iter.next_back();
39 self.exhausted = next.is_none();
46 let empty: [isize; 0] = [];
50 assert!(!xs.iter().lt(ys.iter()));
51 assert!(!xs.iter().le(ys.iter()));
52 assert!(xs.iter().gt(ys.iter()));
53 assert!(xs.iter().ge(ys.iter()));
55 assert!(ys.iter().lt(xs.iter()));
56 assert!(ys.iter().le(xs.iter()));
57 assert!(!ys.iter().gt(xs.iter()));
58 assert!(!ys.iter().ge(xs.iter()));
60 assert!(empty.iter().lt(xs.iter()));
61 assert!(empty.iter().le(xs.iter()));
62 assert!(!empty.iter().gt(xs.iter()));
63 assert!(!empty.iter().ge(xs.iter()));
66 let u = [1.0f64, 2.0];
67 let v = [0.0f64 / 0.0, 3.0];
69 assert!(!u.iter().lt(v.iter()));
70 assert!(!u.iter().le(v.iter()));
71 assert!(!u.iter().gt(v.iter()));
72 assert!(!u.iter().ge(v.iter()));
74 let a = [0.0f64 / 0.0];
78 assert!(a.iter().lt(b.iter()) == (a[0] < b[0]));
79 assert!(a.iter().le(b.iter()) == (a[0] <= b[0]));
80 assert!(a.iter().gt(b.iter()) == (a[0] > b[0]));
81 assert!(a.iter().ge(b.iter()) == (a[0] >= b[0]));
83 assert!(c.iter().lt(b.iter()) == (c[0] < b[0]));
84 assert!(c.iter().le(b.iter()) == (c[0] <= b[0]));
85 assert!(c.iter().gt(b.iter()) == (c[0] > b[0]));
86 assert!(c.iter().ge(b.iter()) == (c[0] >= b[0]));
90 fn test_multi_iter() {
91 let xs = [1, 2, 3, 4];
92 let ys = [4, 3, 2, 1];
93 assert!(xs.iter().eq(ys.iter().rev()));
94 assert!(xs.iter().lt(xs.iter().skip(2)));
99 use core::cmp::Ordering;
101 let f = |x: i32, y: i32| (x * x).cmp(&y);
102 let xs = || [1, 2, 3, 4].iter().copied();
103 let ys = || [1, 4, 16].iter().copied();
105 assert_eq!(xs().cmp_by(ys(), f), Ordering::Less);
106 assert_eq!(ys().cmp_by(xs(), f), Ordering::Greater);
107 assert_eq!(xs().cmp_by(xs().map(|x| x * x), f), Ordering::Equal);
108 assert_eq!(xs().rev().cmp_by(ys().rev(), f), Ordering::Greater);
109 assert_eq!(xs().cmp_by(ys().rev(), f), Ordering::Less);
110 assert_eq!(xs().cmp_by(ys().take(2), f), Ordering::Greater);
114 fn test_partial_cmp_by() {
115 use core::cmp::Ordering;
117 let f = |x: i32, y: i32| (x * x).partial_cmp(&y);
118 let xs = || [1, 2, 3, 4].iter().copied();
119 let ys = || [1, 4, 16].iter().copied();
121 assert_eq!(xs().partial_cmp_by(ys(), f), Some(Ordering::Less));
122 assert_eq!(ys().partial_cmp_by(xs(), f), Some(Ordering::Greater));
123 assert_eq!(xs().partial_cmp_by(xs().map(|x| x * x), f), Some(Ordering::Equal));
124 assert_eq!(xs().rev().partial_cmp_by(ys().rev(), f), Some(Ordering::Greater));
125 assert_eq!(xs().partial_cmp_by(xs().rev(), f), Some(Ordering::Less));
126 assert_eq!(xs().partial_cmp_by(ys().take(2), f), Some(Ordering::Greater));
128 let f = |x: f64, y: f64| (x * x).partial_cmp(&y);
129 let xs = || [1.0, 2.0, 3.0, 4.0].iter().copied();
130 let ys = || [1.0, 4.0, f64::NAN, 16.0].iter().copied();
132 assert_eq!(xs().partial_cmp_by(ys(), f), None);
133 assert_eq!(ys().partial_cmp_by(xs(), f), Some(Ordering::Greater));
138 let f = |x: i32, y: i32| x * x == y;
139 let xs = || [1, 2, 3, 4].iter().copied();
140 let ys = || [1, 4, 9, 16].iter().copied();
142 assert!(xs().eq_by(ys(), f));
143 assert!(!ys().eq_by(xs(), f));
144 assert!(!xs().eq_by(xs(), f));
145 assert!(!ys().eq_by(ys(), f));
147 assert!(!xs().take(3).eq_by(ys(), f));
148 assert!(!xs().eq_by(ys().take(3), f));
149 assert!(xs().take(3).eq_by(ys().take(3), f));
153 fn test_counter_from_iter() {
154 let it = (0..).step_by(5).take(10);
155 let xs: Vec<isize> = FromIterator::from_iter(it);
156 assert_eq!(xs, [0, 5, 10, 15, 20, 25, 30, 35, 40, 45]);
160 fn test_iterator_chain() {
161 let xs = [0, 1, 2, 3, 4, 5];
162 let ys = [30, 40, 50, 60];
163 let expected = [0, 1, 2, 3, 4, 5, 30, 40, 50, 60];
164 let it = xs.iter().chain(&ys);
167 assert_eq!(x, expected[i]);
170 assert_eq!(i, expected.len());
172 let ys = (30..).step_by(10).take(4);
173 let it = xs.iter().cloned().chain(ys);
176 assert_eq!(x, expected[i]);
179 assert_eq!(i, expected.len());
183 fn test_iterator_chain_advance_by() {
184 fn test_chain(xs: &[i32], ys: &[i32]) {
185 let len = xs.len() + ys.len();
187 for i in 0..xs.len() {
188 let mut iter = unfuse(xs).chain(unfuse(ys));
189 iter.advance_by(i).unwrap();
190 assert_eq!(iter.next(), Some(&xs[i]));
191 assert_eq!(iter.advance_by(100), Err(len - i - 1));
194 for i in 0..ys.len() {
195 let mut iter = unfuse(xs).chain(unfuse(ys));
196 iter.advance_by(xs.len() + i).unwrap();
197 assert_eq!(iter.next(), Some(&ys[i]));
198 assert_eq!(iter.advance_by(100), Err(ys.len() - i - 1));
201 let mut iter = xs.iter().chain(ys);
202 iter.advance_by(len).unwrap();
203 assert_eq!(iter.next(), None);
205 let mut iter = xs.iter().chain(ys);
206 assert_eq!(iter.advance_by(len + 1), Err(len));
209 test_chain(&[], &[]);
210 test_chain(&[], &[0, 1, 2, 3, 4, 5]);
211 test_chain(&[0, 1, 2, 3, 4, 5], &[]);
212 test_chain(&[0, 1, 2, 3, 4, 5], &[30, 40, 50, 60]);
216 fn test_iterator_chain_advance_back_by() {
217 fn test_chain(xs: &[i32], ys: &[i32]) {
218 let len = xs.len() + ys.len();
220 for i in 0..ys.len() {
221 let mut iter = unfuse(xs).chain(unfuse(ys));
222 iter.advance_back_by(i).unwrap();
223 assert_eq!(iter.next_back(), Some(&ys[ys.len() - i - 1]));
224 assert_eq!(iter.advance_back_by(100), Err(len - i - 1));
227 for i in 0..xs.len() {
228 let mut iter = unfuse(xs).chain(unfuse(ys));
229 iter.advance_back_by(ys.len() + i).unwrap();
230 assert_eq!(iter.next_back(), Some(&xs[xs.len() - i - 1]));
231 assert_eq!(iter.advance_back_by(100), Err(xs.len() - i - 1));
234 let mut iter = xs.iter().chain(ys);
235 iter.advance_back_by(len).unwrap();
236 assert_eq!(iter.next_back(), None);
238 let mut iter = xs.iter().chain(ys);
239 assert_eq!(iter.advance_back_by(len + 1), Err(len));
242 test_chain(&[], &[]);
243 test_chain(&[], &[0, 1, 2, 3, 4, 5]);
244 test_chain(&[0, 1, 2, 3, 4, 5], &[]);
245 test_chain(&[0, 1, 2, 3, 4, 5], &[30, 40, 50, 60]);
249 fn test_iterator_chain_nth() {
250 let xs = [0, 1, 2, 3, 4, 5];
251 let ys = [30, 40, 50, 60];
253 let expected = [0, 1, 2, 3, 4, 5, 30, 40, 50, 60];
254 for (i, x) in expected.iter().enumerate() {
255 assert_eq!(Some(x), xs.iter().chain(&ys).nth(i));
257 assert_eq!(zs.iter().chain(&xs).nth(0), Some(&0));
259 let mut it = xs.iter().chain(&zs);
260 assert_eq!(it.nth(5), Some(&5));
261 assert_eq!(it.next(), None);
265 fn test_iterator_chain_nth_back() {
266 let xs = [0, 1, 2, 3, 4, 5];
267 let ys = [30, 40, 50, 60];
269 let expected = [0, 1, 2, 3, 4, 5, 30, 40, 50, 60];
270 for (i, x) in expected.iter().rev().enumerate() {
271 assert_eq!(Some(x), xs.iter().chain(&ys).nth_back(i));
273 assert_eq!(zs.iter().chain(&xs).nth_back(0), Some(&5));
275 let mut it = xs.iter().chain(&zs);
276 assert_eq!(it.nth_back(5), Some(&0));
277 assert_eq!(it.next(), None);
281 fn test_iterator_chain_last() {
282 let xs = [0, 1, 2, 3, 4, 5];
283 let ys = [30, 40, 50, 60];
285 assert_eq!(xs.iter().chain(&ys).last(), Some(&60));
286 assert_eq!(zs.iter().chain(&ys).last(), Some(&60));
287 assert_eq!(ys.iter().chain(&zs).last(), Some(&60));
288 assert_eq!(zs.iter().chain(&zs).last(), None);
292 fn test_iterator_chain_count() {
293 let xs = [0, 1, 2, 3, 4, 5];
294 let ys = [30, 40, 50, 60];
296 assert_eq!(xs.iter().chain(&ys).count(), 10);
297 assert_eq!(zs.iter().chain(&ys).count(), 4);
301 fn test_iterator_chain_find() {
302 let xs = [0, 1, 2, 3, 4, 5];
303 let ys = [30, 40, 50, 60];
304 let mut iter = xs.iter().chain(&ys);
305 assert_eq!(iter.find(|&&i| i == 4), Some(&4));
306 assert_eq!(iter.next(), Some(&5));
307 assert_eq!(iter.find(|&&i| i == 40), Some(&40));
308 assert_eq!(iter.next(), Some(&50));
309 assert_eq!(iter.find(|&&i| i == 100), None);
310 assert_eq!(iter.next(), None);
317 impl Iterator for Toggle {
320 // alternates between `None` and `Some(())`
321 fn next(&mut self) -> Option<Self::Item> {
323 self.is_empty = false;
326 self.is_empty = true;
331 fn size_hint(&self) -> (usize, Option<usize>) {
332 if self.is_empty { (0, Some(0)) } else { (1, Some(1)) }
336 impl DoubleEndedIterator for Toggle {
337 fn next_back(&mut self) -> Option<Self::Item> {
343 fn test_iterator_chain_size_hint() {
344 // this chains an iterator of length 0 with an iterator of length 1,
345 // so after calling `.next()` once, the iterator is empty and the
346 // state is `ChainState::Back`. `.size_hint()` should now disregard
347 // the size hint of the left iterator
348 let mut iter = Toggle { is_empty: true }.chain(once(()));
349 assert_eq!(iter.next(), Some(()));
350 assert_eq!(iter.size_hint(), (0, Some(0)));
352 let mut iter = once(()).chain(Toggle { is_empty: true });
353 assert_eq!(iter.next_back(), Some(()));
354 assert_eq!(iter.size_hint(), (0, Some(0)));
358 fn test_iterator_chain_unfused() {
359 // Chain shouldn't be fused in its second iterator, depending on direction
360 let mut iter = NonFused::new(empty()).chain(Toggle { is_empty: true });
361 iter.next().unwrap_none();
362 iter.next().unwrap();
363 iter.next().unwrap_none();
365 let mut iter = Toggle { is_empty: true }.chain(NonFused::new(empty()));
366 iter.next_back().unwrap_none();
367 iter.next_back().unwrap();
368 iter.next_back().unwrap_none();
373 let xs = [0, 1, 2, 4, 5];
374 let ys = [10, 11, 12];
376 let mut it = xs.iter().zip(&ys);
377 assert_eq!(it.nth(0), Some((&0, &10)));
378 assert_eq!(it.nth(1), Some((&2, &12)));
379 assert_eq!(it.nth(0), None);
381 let mut it = xs.iter().zip(&ys);
382 assert_eq!(it.nth(3), None);
384 let mut it = ys.iter().zip(&xs);
385 assert_eq!(it.nth(3), None);
389 fn test_zip_nth_side_effects() {
390 let mut a = Vec::new();
391 let mut b = Vec::new();
392 let value = [1, 2, 3, 4, 5, 6]
399 .zip([2, 3, 4, 5, 6, 7, 8].iter().cloned().map(|n| {
405 assert_eq!(value, Some((50, 6000)));
406 assert_eq!(a, vec![1, 2, 3, 4, 5]);
407 assert_eq!(b, vec![200, 300, 400, 500, 600]);
411 fn test_zip_next_back_side_effects() {
412 let mut a = Vec::new();
413 let mut b = Vec::new();
414 let mut iter = [1, 2, 3, 4, 5, 6]
421 .zip([2, 3, 4, 5, 6, 7, 8].iter().cloned().map(|n| {
426 // The second iterator is one item longer, so `next_back` is called on it
428 assert_eq!(iter.next_back(), Some((60, 7000)));
429 assert_eq!(iter.next_back(), Some((50, 6000)));
430 assert_eq!(iter.next_back(), Some((40, 5000)));
431 assert_eq!(iter.next_back(), Some((30, 4000)));
432 assert_eq!(a, vec![6, 5, 4, 3]);
433 assert_eq!(b, vec![800, 700, 600, 500, 400]);
437 fn test_zip_nth_back_side_effects() {
438 let mut a = Vec::new();
439 let mut b = Vec::new();
440 let value = [1, 2, 3, 4, 5, 6]
447 .zip([2, 3, 4, 5, 6, 7, 8].iter().cloned().map(|n| {
452 assert_eq!(value, Some((30, 4000)));
453 assert_eq!(a, vec![6, 5, 4, 3]);
454 assert_eq!(b, vec![800, 700, 600, 500, 400]);
458 fn test_zip_next_back_side_effects_exhausted() {
459 let mut a = Vec::new();
460 let mut b = Vec::new();
461 let mut iter = [1, 2, 3, 4, 5, 6]
468 .zip([2, 3, 4].iter().cloned().map(|n| {
477 assert_eq!(iter.next_back(), None);
478 assert_eq!(a, vec![1, 2, 3, 4, 6, 5]);
479 assert_eq!(b, vec![200, 300, 400]);
483 struct CountClone(Cell<i32>);
485 fn count_clone() -> CountClone {
486 CountClone(Cell::new(0))
489 impl PartialEq<i32> for CountClone {
490 fn eq(&self, rhs: &i32) -> bool {
495 impl Clone for CountClone {
496 fn clone(&self) -> Self {
497 let ret = CountClone(self.0.clone());
498 let n = self.0.get();
505 fn test_zip_cloned_sideffectful() {
506 let xs = [count_clone(), count_clone(), count_clone(), count_clone()];
507 let ys = [count_clone(), count_clone()];
509 for _ in xs.iter().cloned().zip(ys.iter().cloned()) {}
511 assert_eq!(&xs, &[1, 1, 1, 0][..]);
512 assert_eq!(&ys, &[1, 1][..]);
514 let xs = [count_clone(), count_clone()];
515 let ys = [count_clone(), count_clone(), count_clone(), count_clone()];
517 for _ in xs.iter().cloned().zip(ys.iter().cloned()) {}
519 assert_eq!(&xs, &[1, 1][..]);
520 assert_eq!(&ys, &[1, 1, 0, 0][..]);
524 fn test_zip_map_sideffectful() {
528 for _ in xs.iter_mut().map(|x| *x += 1).zip(ys.iter_mut().map(|y| *y += 1)) {}
530 assert_eq!(&xs, &[1, 1, 1, 1, 1, 0]);
531 assert_eq!(&ys, &[1, 1, 1, 1]);
536 for _ in xs.iter_mut().map(|x| *x += 1).zip(ys.iter_mut().map(|y| *y += 1)) {}
538 assert_eq!(&xs, &[1, 1, 1, 1]);
539 assert_eq!(&ys, &[1, 1, 1, 1, 0, 0]);
543 fn test_zip_map_rev_sideffectful() {
548 let mut it = xs.iter_mut().map(|x| *x += 1).zip(ys.iter_mut().map(|y| *y += 1));
551 assert_eq!(&xs, &[0, 0, 0, 1, 1, 1]);
552 assert_eq!(&ys, &[0, 0, 0, 1]);
558 let mut it = xs.iter_mut().map(|x| *x += 1).zip(ys.iter_mut().map(|y| *y += 1));
559 (&mut it).take(5).count();
562 assert_eq!(&xs, &[1, 1, 1, 1, 1, 1]);
563 assert_eq!(&ys, &[1, 1, 1, 1]);
567 fn test_zip_nested_sideffectful() {
572 // test that it has the side effect nested inside enumerate
573 let it = xs.iter_mut().map(|x| *x = 1).enumerate().zip(&ys);
576 assert_eq!(&xs, &[1, 1, 1, 1, 1, 0]);
580 fn test_zip_nth_back_side_effects_exhausted() {
581 let mut a = Vec::new();
582 let mut b = Vec::new();
583 let mut iter = [1, 2, 3, 4, 5, 6]
590 .zip([2, 3, 4].iter().cloned().map(|n| {
599 assert_eq!(iter.nth_back(0), None);
600 assert_eq!(a, vec![1, 2, 3, 4, 6, 5]);
601 assert_eq!(b, vec![200, 300, 400]);
605 fn test_iterator_step_by() {
607 let mut it = (0..).step_by(1).take(3);
608 assert_eq!(it.next(), Some(0));
609 assert_eq!(it.next(), Some(1));
610 assert_eq!(it.next(), Some(2));
611 assert_eq!(it.next(), None);
613 let mut it = (0..).step_by(3).take(4);
614 assert_eq!(it.next(), Some(0));
615 assert_eq!(it.next(), Some(3));
616 assert_eq!(it.next(), Some(6));
617 assert_eq!(it.next(), Some(9));
618 assert_eq!(it.next(), None);
620 let mut it = (0..3).step_by(1);
621 assert_eq!(it.next_back(), Some(2));
622 assert_eq!(it.next_back(), Some(1));
623 assert_eq!(it.next_back(), Some(0));
624 assert_eq!(it.next_back(), None);
626 let mut it = (0..11).step_by(3);
627 assert_eq!(it.next_back(), Some(9));
628 assert_eq!(it.next_back(), Some(6));
629 assert_eq!(it.next_back(), Some(3));
630 assert_eq!(it.next_back(), Some(0));
631 assert_eq!(it.next_back(), None);
635 fn test_iterator_step_by_nth() {
636 let mut it = (0..16).step_by(5);
637 assert_eq!(it.nth(0), Some(0));
638 assert_eq!(it.nth(0), Some(5));
639 assert_eq!(it.nth(0), Some(10));
640 assert_eq!(it.nth(0), Some(15));
641 assert_eq!(it.nth(0), None);
643 let it = (0..18).step_by(5);
644 assert_eq!(it.clone().nth(0), Some(0));
645 assert_eq!(it.clone().nth(1), Some(5));
646 assert_eq!(it.clone().nth(2), Some(10));
647 assert_eq!(it.clone().nth(3), Some(15));
648 assert_eq!(it.clone().nth(4), None);
649 assert_eq!(it.clone().nth(42), None);
653 fn test_iterator_step_by_nth_overflow() {
654 #[cfg(target_pointer_width = "8")]
656 #[cfg(target_pointer_width = "16")]
658 #[cfg(target_pointer_width = "32")]
660 #[cfg(target_pointer_width = "64")]
665 impl Iterator for &mut Test {
667 fn next(&mut self) -> Option<Self::Item> {
670 fn nth(&mut self, n: usize) -> Option<Self::Item> {
671 self.0 += n as Bigger + 1;
676 let mut it = Test(0);
677 let root = usize::MAX >> (usize::BITS / 2);
679 (&mut it).step_by(n).nth(n);
680 assert_eq!(it.0, n as Bigger * n as Bigger);
683 let mut it = Test(0);
684 (&mut it).step_by(usize::MAX).nth(5);
685 assert_eq!(it.0, (usize::MAX as Bigger) * 5);
688 let mut it = Test(0);
689 (&mut it).step_by(2).nth(usize::MAX);
690 assert_eq!(it.0, (usize::MAX as Bigger) * 2);
693 let mut it = Test(0);
694 (&mut it).step_by(1).nth(usize::MAX);
695 assert_eq!(it.0, (usize::MAX as Bigger) * 1);
699 fn test_iterator_step_by_nth_try_fold() {
700 let mut it = (0..).step_by(10);
701 assert_eq!(it.try_fold(0, i8::checked_add), None);
702 assert_eq!(it.next(), Some(60));
703 assert_eq!(it.try_fold(0, i8::checked_add), None);
704 assert_eq!(it.next(), Some(90));
706 let mut it = (100..).step_by(10);
707 assert_eq!(it.try_fold(50, i8::checked_add), None);
708 assert_eq!(it.next(), Some(110));
710 let mut it = (100..=100).step_by(10);
711 assert_eq!(it.next(), Some(100));
712 assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
716 fn test_iterator_step_by_nth_back() {
717 let mut it = (0..16).step_by(5);
718 assert_eq!(it.nth_back(0), Some(15));
719 assert_eq!(it.nth_back(0), Some(10));
720 assert_eq!(it.nth_back(0), Some(5));
721 assert_eq!(it.nth_back(0), Some(0));
722 assert_eq!(it.nth_back(0), None);
724 let mut it = (0..16).step_by(5);
725 assert_eq!(it.next(), Some(0)); // to set `first_take` to `false`
726 assert_eq!(it.nth_back(0), Some(15));
727 assert_eq!(it.nth_back(0), Some(10));
728 assert_eq!(it.nth_back(0), Some(5));
729 assert_eq!(it.nth_back(0), None);
731 let it = || (0..18).step_by(5);
732 assert_eq!(it().nth_back(0), Some(15));
733 assert_eq!(it().nth_back(1), Some(10));
734 assert_eq!(it().nth_back(2), Some(5));
735 assert_eq!(it().nth_back(3), Some(0));
736 assert_eq!(it().nth_back(4), None);
737 assert_eq!(it().nth_back(42), None);
741 fn test_iterator_step_by_nth_try_rfold() {
742 let mut it = (0..100).step_by(10);
743 assert_eq!(it.try_rfold(0, i8::checked_add), None);
744 assert_eq!(it.next_back(), Some(70));
745 assert_eq!(it.next(), Some(0));
746 assert_eq!(it.try_rfold(0, i8::checked_add), None);
747 assert_eq!(it.next_back(), Some(30));
749 let mut it = (0..100).step_by(10);
750 assert_eq!(it.try_rfold(50, i8::checked_add), None);
751 assert_eq!(it.next_back(), Some(80));
753 let mut it = (100..=100).step_by(10);
754 assert_eq!(it.next_back(), Some(100));
755 assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
760 fn test_iterator_step_by_zero() {
761 let mut it = (0..).step_by(0);
766 fn test_iterator_step_by_size_hint() {
767 struct StubSizeHint(usize, Option<usize>);
768 impl Iterator for StubSizeHint {
770 fn next(&mut self) -> Option<()> {
772 if let Some(ref mut upper) = self.1 {
777 fn size_hint(&self) -> (usize, Option<usize>) {
782 // The two checks in each case are needed because the logic
783 // is different before the first call to `next()`.
785 let mut it = StubSizeHint(10, Some(10)).step_by(1);
786 assert_eq!(it.size_hint(), (10, Some(10)));
788 assert_eq!(it.size_hint(), (9, Some(9)));
791 let mut it = StubSizeHint(10, Some(10)).step_by(3);
792 assert_eq!(it.size_hint(), (4, Some(4)));
794 assert_eq!(it.size_hint(), (3, Some(3)));
796 // larger base range, but not enough to get another element
797 let mut it = StubSizeHint(12, Some(12)).step_by(3);
798 assert_eq!(it.size_hint(), (4, Some(4)));
800 assert_eq!(it.size_hint(), (3, Some(3)));
802 // smaller base range, so fewer resulting elements
803 let mut it = StubSizeHint(9, Some(9)).step_by(3);
804 assert_eq!(it.size_hint(), (3, Some(3)));
806 assert_eq!(it.size_hint(), (2, Some(2)));
808 // infinite upper bound
809 let mut it = StubSizeHint(usize::MAX, None).step_by(1);
810 assert_eq!(it.size_hint(), (usize::MAX, None));
812 assert_eq!(it.size_hint(), (usize::MAX - 1, None));
814 // still infinite with larger step
815 let mut it = StubSizeHint(7, None).step_by(3);
816 assert_eq!(it.size_hint(), (3, None));
818 assert_eq!(it.size_hint(), (2, None));
820 // propagates ExactSizeIterator
821 let a = [1, 2, 3, 4, 5];
822 let it = a.iter().step_by(2);
823 assert_eq!(it.len(), 3);
825 // Cannot be TrustedLen as a step greater than one makes an iterator
826 // with (usize::MAX, None) no longer meet the safety requirements
827 trait TrustedLenCheck {
828 fn test(self) -> bool;
830 impl<T: Iterator> TrustedLenCheck for T {
831 default fn test(self) -> bool {
835 impl<T: TrustedLen> TrustedLenCheck for T {
836 fn test(self) -> bool {
840 assert!(TrustedLenCheck::test(a.iter()));
841 assert!(!TrustedLenCheck::test(a.iter().step_by(1)));
845 fn test_filter_map() {
846 let it = (0..).step_by(1).take(10).filter_map(|x| if x % 2 == 0 { Some(x * x) } else { None });
847 assert_eq!(it.collect::<Vec<usize>>(), [0 * 0, 2 * 2, 4 * 4, 6 * 6, 8 * 8]);
851 fn test_filter_map_fold() {
852 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
853 let ys = [0 * 0, 2 * 2, 4 * 4, 6 * 6, 8 * 8];
854 let it = xs.iter().filter_map(|&x| if x % 2 == 0 { Some(x * x) } else { None });
855 let i = it.fold(0, |i, x| {
856 assert_eq!(x, ys[i]);
859 assert_eq!(i, ys.len());
861 let it = xs.iter().filter_map(|&x| if x % 2 == 0 { Some(x * x) } else { None });
862 let i = it.rfold(ys.len(), |i, x| {
863 assert_eq!(x, ys[i - 1]);
870 fn test_iterator_enumerate() {
871 let xs = [0, 1, 2, 3, 4, 5];
872 let it = xs.iter().enumerate();
879 fn test_iterator_enumerate_nth() {
880 let xs = [0, 1, 2, 3, 4, 5];
881 for (i, &x) in xs.iter().enumerate() {
885 let mut it = xs.iter().enumerate();
886 while let Some((i, &x)) = it.nth(0) {
890 let mut it = xs.iter().enumerate();
891 while let Some((i, &x)) = it.nth(1) {
895 let (i, &x) = xs.iter().enumerate().nth(3).unwrap();
901 fn test_iterator_enumerate_nth_back() {
902 let xs = [0, 1, 2, 3, 4, 5];
903 let mut it = xs.iter().enumerate();
904 while let Some((i, &x)) = it.nth_back(0) {
908 let mut it = xs.iter().enumerate();
909 while let Some((i, &x)) = it.nth_back(1) {
913 let (i, &x) = xs.iter().enumerate().nth_back(3).unwrap();
919 fn test_iterator_enumerate_count() {
920 let xs = [0, 1, 2, 3, 4, 5];
921 assert_eq!(xs.iter().enumerate().count(), 6);
925 fn test_iterator_enumerate_fold() {
926 let xs = [0, 1, 2, 3, 4, 5];
927 let mut it = xs.iter().enumerate();
928 // steal a couple to get an interesting offset
929 assert_eq!(it.next(), Some((0, &0)));
930 assert_eq!(it.next(), Some((1, &1)));
931 let i = it.fold(2, |i, (j, &x)| {
933 assert_eq!(x, xs[j]);
936 assert_eq!(i, xs.len());
938 let mut it = xs.iter().enumerate();
939 assert_eq!(it.next(), Some((0, &0)));
940 let i = it.rfold(xs.len() - 1, |i, (j, &x)| {
942 assert_eq!(x, xs[j]);
949 fn test_iterator_filter_count() {
950 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
951 assert_eq!(xs.iter().filter(|&&x| x % 2 == 0).count(), 5);
955 fn test_iterator_filter_fold() {
956 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
957 let ys = [0, 2, 4, 6, 8];
958 let it = xs.iter().filter(|&&x| x % 2 == 0);
959 let i = it.fold(0, |i, &x| {
960 assert_eq!(x, ys[i]);
963 assert_eq!(i, ys.len());
965 let it = xs.iter().filter(|&&x| x % 2 == 0);
966 let i = it.rfold(ys.len(), |i, &x| {
967 assert_eq!(x, ys[i - 1]);
974 fn test_iterator_peekable() {
975 let xs = vec![0, 1, 2, 3, 4, 5];
977 let mut it = xs.iter().cloned().peekable();
978 assert_eq!(it.len(), 6);
979 assert_eq!(it.peek().unwrap(), &0);
980 assert_eq!(it.len(), 6);
981 assert_eq!(it.next().unwrap(), 0);
982 assert_eq!(it.len(), 5);
983 assert_eq!(it.next().unwrap(), 1);
984 assert_eq!(it.len(), 4);
985 assert_eq!(it.next().unwrap(), 2);
986 assert_eq!(it.len(), 3);
987 assert_eq!(it.peek().unwrap(), &3);
988 assert_eq!(it.len(), 3);
989 assert_eq!(it.peek().unwrap(), &3);
990 assert_eq!(it.len(), 3);
991 assert_eq!(it.next().unwrap(), 3);
992 assert_eq!(it.len(), 2);
993 assert_eq!(it.next().unwrap(), 4);
994 assert_eq!(it.len(), 1);
995 assert_eq!(it.peek().unwrap(), &5);
996 assert_eq!(it.len(), 1);
997 assert_eq!(it.next().unwrap(), 5);
998 assert_eq!(it.len(), 0);
999 assert!(it.peek().is_none());
1000 assert_eq!(it.len(), 0);
1001 assert!(it.next().is_none());
1002 assert_eq!(it.len(), 0);
1004 let mut it = xs.iter().cloned().peekable();
1005 assert_eq!(it.len(), 6);
1006 assert_eq!(it.peek().unwrap(), &0);
1007 assert_eq!(it.len(), 6);
1008 assert_eq!(it.next_back().unwrap(), 5);
1009 assert_eq!(it.len(), 5);
1010 assert_eq!(it.next_back().unwrap(), 4);
1011 assert_eq!(it.len(), 4);
1012 assert_eq!(it.next_back().unwrap(), 3);
1013 assert_eq!(it.len(), 3);
1014 assert_eq!(it.peek().unwrap(), &0);
1015 assert_eq!(it.len(), 3);
1016 assert_eq!(it.peek().unwrap(), &0);
1017 assert_eq!(it.len(), 3);
1018 assert_eq!(it.next_back().unwrap(), 2);
1019 assert_eq!(it.len(), 2);
1020 assert_eq!(it.next_back().unwrap(), 1);
1021 assert_eq!(it.len(), 1);
1022 assert_eq!(it.peek().unwrap(), &0);
1023 assert_eq!(it.len(), 1);
1024 assert_eq!(it.next_back().unwrap(), 0);
1025 assert_eq!(it.len(), 0);
1026 assert!(it.peek().is_none());
1027 assert_eq!(it.len(), 0);
1028 assert!(it.next_back().is_none());
1029 assert_eq!(it.len(), 0);
1033 fn test_iterator_peekable_count() {
1034 let xs = [0, 1, 2, 3, 4, 5];
1036 let zs: [i32; 0] = [];
1038 assert_eq!(xs.iter().peekable().count(), 6);
1040 let mut it = xs.iter().peekable();
1041 assert_eq!(it.peek(), Some(&&0));
1042 assert_eq!(it.count(), 6);
1044 assert_eq!(ys.iter().peekable().count(), 1);
1046 let mut it = ys.iter().peekable();
1047 assert_eq!(it.peek(), Some(&&10));
1048 assert_eq!(it.count(), 1);
1050 assert_eq!(zs.iter().peekable().count(), 0);
1052 let mut it = zs.iter().peekable();
1053 assert_eq!(it.peek(), None);
1057 fn test_iterator_peekable_nth() {
1058 let xs = [0, 1, 2, 3, 4, 5];
1059 let mut it = xs.iter().peekable();
1061 assert_eq!(it.peek(), Some(&&0));
1062 assert_eq!(it.nth(0), Some(&0));
1063 assert_eq!(it.peek(), Some(&&1));
1064 assert_eq!(it.nth(1), Some(&2));
1065 assert_eq!(it.peek(), Some(&&3));
1066 assert_eq!(it.nth(2), Some(&5));
1067 assert_eq!(it.next(), None);
1071 fn test_iterator_peekable_last() {
1072 let xs = [0, 1, 2, 3, 4, 5];
1075 let mut it = xs.iter().peekable();
1076 assert_eq!(it.peek(), Some(&&0));
1077 assert_eq!(it.last(), Some(&5));
1079 let mut it = ys.iter().peekable();
1080 assert_eq!(it.peek(), Some(&&0));
1081 assert_eq!(it.last(), Some(&0));
1083 let mut it = ys.iter().peekable();
1084 assert_eq!(it.next(), Some(&0));
1085 assert_eq!(it.peek(), None);
1086 assert_eq!(it.last(), None);
1090 fn test_iterator_peekable_fold() {
1091 let xs = [0, 1, 2, 3, 4, 5];
1092 let mut it = xs.iter().peekable();
1093 assert_eq!(it.peek(), Some(&&0));
1094 let i = it.fold(0, |i, &x| {
1095 assert_eq!(x, xs[i]);
1098 assert_eq!(i, xs.len());
1102 fn test_iterator_peekable_rfold() {
1103 let xs = [0, 1, 2, 3, 4, 5];
1104 let mut it = xs.iter().peekable();
1105 assert_eq!(it.peek(), Some(&&0));
1106 let i = it.rfold(0, |i, &x| {
1107 assert_eq!(x, xs[xs.len() - 1 - i]);
1110 assert_eq!(i, xs.len());
1114 fn test_iterator_peekable_next_if_eq() {
1115 // first, try on references
1116 let xs = vec!["Heart", "of", "Gold"];
1117 let mut it = xs.into_iter().peekable();
1118 // try before `peek()`
1119 assert_eq!(it.next_if_eq(&"trillian"), None);
1120 assert_eq!(it.next_if_eq(&"Heart"), Some("Heart"));
1122 assert_eq!(it.peek(), Some(&"of"));
1123 assert_eq!(it.next_if_eq(&"of"), Some("of"));
1124 assert_eq!(it.next_if_eq(&"zaphod"), None);
1125 // make sure `next()` still behaves
1126 assert_eq!(it.next(), Some("Gold"));
1128 // make sure comparison works for owned values
1129 let xs = vec![String::from("Ludicrous"), "speed".into()];
1130 let mut it = xs.into_iter().peekable();
1131 // make sure basic functionality works
1132 assert_eq!(it.next_if_eq("Ludicrous"), Some("Ludicrous".into()));
1133 assert_eq!(it.next_if_eq("speed"), Some("speed".into()));
1134 assert_eq!(it.next_if_eq(""), None);
1138 fn test_iterator_peekable_mut() {
1139 let mut it = vec![1, 2, 3].into_iter().peekable();
1140 if let Some(p) = it.peek_mut() {
1145 assert_eq!(it.collect::<Vec<_>>(), vec![5, 2, 3]);
1148 /// This is an iterator that follows the Iterator contract,
1149 /// but it is not fused. After having returned None once, it will start
1150 /// producing elements if .next() is called again.
1151 pub struct CycleIter<'a, T> {
1156 pub fn cycle<T>(data: &[T]) -> CycleIter<'_, T> {
1157 CycleIter { index: 0, data }
1160 impl<'a, T> Iterator for CycleIter<'a, T> {
1162 fn next(&mut self) -> Option<Self::Item> {
1163 let elt = self.data.get(self.index);
1165 self.index %= 1 + self.data.len();
1171 fn test_iterator_peekable_remember_peek_none_1() {
1172 // Check that the loop using .peek() terminates
1173 let data = [1, 2, 3];
1174 let mut iter = cycle(&data).peekable();
1177 while let Some(_) = iter.next() {
1178 let is_the_last = iter.peek().is_none();
1179 assert_eq!(is_the_last, n == data.len() - 1);
1185 assert_eq!(n, data.len());
1189 fn test_iterator_peekable_remember_peek_none_2() {
1191 let mut iter = cycle(&data).peekable();
1193 assert_eq!(iter.peek(), None);
1194 assert_eq!(iter.last(), None);
1198 fn test_iterator_peekable_remember_peek_none_3() {
1200 let mut iter = cycle(&data).peekable();
1202 assert_eq!(iter.nth(0), Some(&0));
1204 let mut iter = cycle(&data).peekable();
1206 assert_eq!(iter.peek(), None);
1207 assert_eq!(iter.nth(0), None);
1211 fn test_iterator_take_while() {
1212 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
1213 let ys = [0, 1, 2, 3, 5, 13];
1214 let it = xs.iter().take_while(|&x| *x < 15);
1217 assert_eq!(*x, ys[i]);
1220 assert_eq!(i, ys.len());
1224 fn test_iterator_skip_while() {
1225 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
1226 let ys = [15, 16, 17, 19];
1227 let it = xs.iter().skip_while(|&x| *x < 15);
1230 assert_eq!(*x, ys[i]);
1233 assert_eq!(i, ys.len());
1237 fn test_iterator_skip_while_fold() {
1238 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
1239 let ys = [15, 16, 17, 19];
1240 let it = xs.iter().skip_while(|&x| *x < 15);
1241 let i = it.fold(0, |i, &x| {
1242 assert_eq!(x, ys[i]);
1245 assert_eq!(i, ys.len());
1247 let mut it = xs.iter().skip_while(|&x| *x < 15);
1248 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
1249 let i = it.fold(1, |i, &x| {
1250 assert_eq!(x, ys[i]);
1253 assert_eq!(i, ys.len());
1257 fn test_iterator_skip() {
1258 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
1259 let ys = [13, 15, 16, 17, 19, 20, 30];
1260 let mut it = xs.iter().skip(5);
1262 while let Some(&x) = it.next() {
1263 assert_eq!(x, ys[i]);
1265 assert_eq!(it.len(), xs.len() - 5 - i);
1267 assert_eq!(i, ys.len());
1268 assert_eq!(it.len(), 0);
1272 fn test_iterator_skip_doubleended() {
1273 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
1274 let mut it = xs.iter().rev().skip(5);
1275 assert_eq!(it.next(), Some(&15));
1276 assert_eq!(it.by_ref().rev().next(), Some(&0));
1277 assert_eq!(it.next(), Some(&13));
1278 assert_eq!(it.by_ref().rev().next(), Some(&1));
1279 assert_eq!(it.next(), Some(&5));
1280 assert_eq!(it.by_ref().rev().next(), Some(&2));
1281 assert_eq!(it.next(), Some(&3));
1282 assert_eq!(it.next(), None);
1283 let mut it = xs.iter().rev().skip(5).rev();
1284 assert_eq!(it.next(), Some(&0));
1285 assert_eq!(it.rev().next(), Some(&15));
1286 let mut it_base = xs.iter();
1288 let mut it = it_base.by_ref().skip(5).rev();
1289 assert_eq!(it.next(), Some(&30));
1290 assert_eq!(it.next(), Some(&20));
1291 assert_eq!(it.next(), Some(&19));
1292 assert_eq!(it.next(), Some(&17));
1293 assert_eq!(it.next(), Some(&16));
1294 assert_eq!(it.next(), Some(&15));
1295 assert_eq!(it.next(), Some(&13));
1296 assert_eq!(it.next(), None);
1298 // make sure the skipped parts have not been consumed
1299 assert_eq!(it_base.next(), Some(&0));
1300 assert_eq!(it_base.next(), Some(&1));
1301 assert_eq!(it_base.next(), Some(&2));
1302 assert_eq!(it_base.next(), Some(&3));
1303 assert_eq!(it_base.next(), Some(&5));
1304 assert_eq!(it_base.next(), None);
1305 let it = xs.iter().skip(5).rev();
1306 assert_eq!(it.last(), Some(&13));
1310 fn test_iterator_skip_nth() {
1311 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
1313 let mut it = xs.iter().skip(0);
1314 assert_eq!(it.nth(0), Some(&0));
1315 assert_eq!(it.nth(1), Some(&2));
1317 let mut it = xs.iter().skip(5);
1318 assert_eq!(it.nth(0), Some(&13));
1319 assert_eq!(it.nth(1), Some(&16));
1321 let mut it = xs.iter().skip(12);
1322 assert_eq!(it.nth(0), None);
1326 fn test_iterator_skip_count() {
1327 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
1329 assert_eq!(xs.iter().skip(0).count(), 12);
1330 assert_eq!(xs.iter().skip(1).count(), 11);
1331 assert_eq!(xs.iter().skip(11).count(), 1);
1332 assert_eq!(xs.iter().skip(12).count(), 0);
1333 assert_eq!(xs.iter().skip(13).count(), 0);
1337 fn test_iterator_skip_last() {
1338 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
1340 assert_eq!(xs.iter().skip(0).last(), Some(&30));
1341 assert_eq!(xs.iter().skip(1).last(), Some(&30));
1342 assert_eq!(xs.iter().skip(11).last(), Some(&30));
1343 assert_eq!(xs.iter().skip(12).last(), None);
1344 assert_eq!(xs.iter().skip(13).last(), None);
1346 let mut it = xs.iter().skip(5);
1347 assert_eq!(it.next(), Some(&13));
1348 assert_eq!(it.last(), Some(&30));
1352 fn test_iterator_skip_fold() {
1353 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
1354 let ys = [13, 15, 16, 17, 19, 20, 30];
1356 let it = xs.iter().skip(5);
1357 let i = it.fold(0, |i, &x| {
1358 assert_eq!(x, ys[i]);
1361 assert_eq!(i, ys.len());
1363 let mut it = xs.iter().skip(5);
1364 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
1365 let i = it.fold(1, |i, &x| {
1366 assert_eq!(x, ys[i]);
1369 assert_eq!(i, ys.len());
1371 let it = xs.iter().skip(5);
1372 let i = it.rfold(ys.len(), |i, &x| {
1374 assert_eq!(x, ys[i]);
1379 let mut it = xs.iter().skip(5);
1380 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
1381 let i = it.rfold(ys.len(), |i, &x| {
1383 assert_eq!(x, ys[i]);
1390 fn test_iterator_take() {
1391 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
1392 let ys = [0, 1, 2, 3, 5];
1394 let mut it = xs.iter().take(ys.len());
1396 assert_eq!(it.len(), ys.len());
1397 while let Some(&x) = it.next() {
1398 assert_eq!(x, ys[i]);
1400 assert_eq!(it.len(), ys.len() - i);
1402 assert_eq!(i, ys.len());
1403 assert_eq!(it.len(), 0);
1405 let mut it = xs.iter().take(ys.len());
1407 assert_eq!(it.len(), ys.len());
1408 while let Some(&x) = it.next_back() {
1410 assert_eq!(x, ys[ys.len() - i]);
1411 assert_eq!(it.len(), ys.len() - i);
1413 assert_eq!(i, ys.len());
1414 assert_eq!(it.len(), 0);
1418 fn test_iterator_take_nth() {
1419 let xs = [0, 1, 2, 4, 5];
1420 let mut it = xs.iter();
1422 let mut take = it.by_ref().take(3);
1424 while let Some(&x) = take.nth(0) {
1429 assert_eq!(it.nth(1), Some(&5));
1430 assert_eq!(it.nth(0), None);
1432 let xs = [0, 1, 2, 3, 4];
1433 let mut it = xs.iter().take(7);
1435 while let Some(&x) = it.nth(1) {
1442 fn test_iterator_take_nth_back() {
1443 let xs = [0, 1, 2, 4, 5];
1444 let mut it = xs.iter();
1446 let mut take = it.by_ref().take(3);
1448 while let Some(&x) = take.nth_back(0) {
1450 assert_eq!(x, 3 - i);
1453 assert_eq!(it.nth_back(0), None);
1455 let xs = [0, 1, 2, 3, 4];
1456 let mut it = xs.iter().take(7);
1457 assert_eq!(it.nth_back(1), Some(&3));
1458 assert_eq!(it.nth_back(1), Some(&1));
1459 assert_eq!(it.nth_back(1), None);
1463 fn test_iterator_take_short() {
1464 let xs = [0, 1, 2, 3];
1466 let mut it = xs.iter().take(5);
1468 assert_eq!(it.len(), xs.len());
1469 while let Some(&x) = it.next() {
1470 assert_eq!(x, xs[i]);
1472 assert_eq!(it.len(), xs.len() - i);
1474 assert_eq!(i, xs.len());
1475 assert_eq!(it.len(), 0);
1477 let mut it = xs.iter().take(5);
1479 assert_eq!(it.len(), xs.len());
1480 while let Some(&x) = it.next_back() {
1482 assert_eq!(x, xs[xs.len() - i]);
1483 assert_eq!(it.len(), xs.len() - i);
1485 assert_eq!(i, xs.len());
1486 assert_eq!(it.len(), 0);
1490 fn test_iterator_scan() {
1491 // test the type inference
1492 fn add(old: &mut isize, new: &usize) -> Option<f64> {
1493 *old += *new as isize;
1496 let xs = [0, 1, 2, 3, 4];
1497 let ys = [0f64, 1.0, 3.0, 6.0, 10.0];
1499 let it = xs.iter().scan(0, add);
1502 assert_eq!(x, ys[i]);
1505 assert_eq!(i, ys.len());
1509 fn test_iterator_flat_map() {
1511 let ys = [0, 1, 2, 3, 4, 5, 6, 7, 8];
1512 let it = xs.iter().flat_map(|&x| (x..).step_by(1).take(3));
1515 assert_eq!(x, ys[i]);
1518 assert_eq!(i, ys.len());
1521 /// Tests `FlatMap::fold` with items already picked off the front and back,
1522 /// to make sure all parts of the `FlatMap` are folded correctly.
1524 fn test_iterator_flat_map_fold() {
1526 let ys = [1, 2, 3, 4, 5, 6, 7];
1527 let mut it = xs.iter().flat_map(|&x| x..x + 3);
1528 assert_eq!(it.next(), Some(0));
1529 assert_eq!(it.next_back(), Some(8));
1530 let i = it.fold(0, |i, x| {
1531 assert_eq!(x, ys[i]);
1534 assert_eq!(i, ys.len());
1536 let mut it = xs.iter().flat_map(|&x| x..x + 3);
1537 assert_eq!(it.next(), Some(0));
1538 assert_eq!(it.next_back(), Some(8));
1539 let i = it.rfold(ys.len(), |i, x| {
1540 assert_eq!(x, ys[i - 1]);
1547 fn test_iterator_flatten() {
1549 let ys = [0, 1, 2, 3, 4, 5, 6, 7, 8];
1550 let it = xs.iter().map(|&x| (x..).step_by(1).take(3)).flatten();
1553 assert_eq!(x, ys[i]);
1556 assert_eq!(i, ys.len());
1559 /// Tests `Flatten::fold` with items already picked off the front and back,
1560 /// to make sure all parts of the `Flatten` are folded correctly.
1562 fn test_iterator_flatten_fold() {
1564 let ys = [1, 2, 3, 4, 5, 6, 7];
1565 let mut it = xs.iter().map(|&x| x..x + 3).flatten();
1566 assert_eq!(it.next(), Some(0));
1567 assert_eq!(it.next_back(), Some(8));
1568 let i = it.fold(0, |i, x| {
1569 assert_eq!(x, ys[i]);
1572 assert_eq!(i, ys.len());
1574 let mut it = xs.iter().map(|&x| x..x + 3).flatten();
1575 assert_eq!(it.next(), Some(0));
1576 assert_eq!(it.next_back(), Some(8));
1577 let i = it.rfold(ys.len(), |i, x| {
1578 assert_eq!(x, ys[i - 1]);
1586 let xs = [1, 2, 3, 4];
1589 let ys = xs.iter().cloned().inspect(|_| n += 1).collect::<Vec<usize>>();
1591 assert_eq!(n, xs.len());
1592 assert_eq!(&xs[..], &ys[..]);
1596 fn test_inspect_fold() {
1597 let xs = [1, 2, 3, 4];
1600 let it = xs.iter().inspect(|_| n += 1);
1601 let i = it.fold(0, |i, &x| {
1602 assert_eq!(x, xs[i]);
1605 assert_eq!(i, xs.len());
1607 assert_eq!(n, xs.len());
1611 let it = xs.iter().inspect(|_| n += 1);
1612 let i = it.rfold(xs.len(), |i, &x| {
1613 assert_eq!(x, xs[i - 1]);
1618 assert_eq!(n, xs.len());
1624 let it = (0..).step_by(1).take(cycle_len).cycle();
1625 assert_eq!(it.size_hint(), (usize::MAX, None));
1626 for (i, x) in it.take(100).enumerate() {
1627 assert_eq!(i % cycle_len, x);
1630 let mut it = (0..).step_by(1).take(0).cycle();
1631 assert_eq!(it.size_hint(), (0, Some(0)));
1632 assert_eq!(it.next(), None);
1634 assert_eq!(empty::<i32>().cycle().fold(0, |acc, x| acc + x), 0);
1636 assert_eq!(once(1).cycle().skip(1).take(4).fold(0, |acc, x| acc + x), 4);
1638 assert_eq!((0..10).cycle().take(5).sum::<i32>(), 10);
1639 assert_eq!((0..10).cycle().take(15).sum::<i32>(), 55);
1640 assert_eq!((0..10).cycle().take(25).sum::<i32>(), 100);
1642 let mut iter = (0..10).cycle();
1644 assert_eq!(iter.take(8).sum::<i32>(), 38);
1646 let mut iter = (0..10).cycle();
1648 assert_eq!(iter.take(3).sum::<i32>(), 3);
1652 fn test_iterator_nth() {
1653 let v: &[_] = &[0, 1, 2, 3, 4];
1654 for i in 0..v.len() {
1655 assert_eq!(v.iter().nth(i).unwrap(), &v[i]);
1657 assert_eq!(v.iter().nth(v.len()), None);
1661 fn test_iterator_nth_back() {
1662 let v: &[_] = &[0, 1, 2, 3, 4];
1663 for i in 0..v.len() {
1664 assert_eq!(v.iter().nth_back(i).unwrap(), &v[v.len() - 1 - i]);
1666 assert_eq!(v.iter().nth_back(v.len()), None);
1670 fn test_iterator_rev_nth_back() {
1671 let v: &[_] = &[0, 1, 2, 3, 4];
1672 for i in 0..v.len() {
1673 assert_eq!(v.iter().rev().nth_back(i).unwrap(), &v[i]);
1675 assert_eq!(v.iter().rev().nth_back(v.len()), None);
1679 fn test_iterator_rev_nth() {
1680 let v: &[_] = &[0, 1, 2, 3, 4];
1681 for i in 0..v.len() {
1682 assert_eq!(v.iter().rev().nth(i).unwrap(), &v[v.len() - 1 - i]);
1684 assert_eq!(v.iter().rev().nth(v.len()), None);
1688 fn test_iterator_advance_by() {
1689 let v: &[_] = &[0, 1, 2, 3, 4];
1691 for i in 0..v.len() {
1692 let mut iter = v.iter();
1693 assert_eq!(iter.advance_by(i), Ok(()));
1694 assert_eq!(iter.next().unwrap(), &v[i]);
1695 assert_eq!(iter.advance_by(100), Err(v.len() - 1 - i));
1698 assert_eq!(v.iter().advance_by(v.len()), Ok(()));
1699 assert_eq!(v.iter().advance_by(100), Err(v.len()));
1703 fn test_iterator_advance_back_by() {
1704 let v: &[_] = &[0, 1, 2, 3, 4];
1706 for i in 0..v.len() {
1707 let mut iter = v.iter();
1708 assert_eq!(iter.advance_back_by(i), Ok(()));
1709 assert_eq!(iter.next_back().unwrap(), &v[v.len() - 1 - i]);
1710 assert_eq!(iter.advance_back_by(100), Err(v.len() - 1 - i));
1713 assert_eq!(v.iter().advance_back_by(v.len()), Ok(()));
1714 assert_eq!(v.iter().advance_back_by(100), Err(v.len()));
1718 fn test_iterator_rev_advance_by() {
1719 let v: &[_] = &[0, 1, 2, 3, 4];
1721 for i in 0..v.len() {
1722 let mut iter = v.iter().rev();
1723 assert_eq!(iter.advance_by(i), Ok(()));
1724 assert_eq!(iter.next().unwrap(), &v[v.len() - 1 - i]);
1725 assert_eq!(iter.advance_by(100), Err(v.len() - 1 - i));
1728 assert_eq!(v.iter().rev().advance_by(v.len()), Ok(()));
1729 assert_eq!(v.iter().rev().advance_by(100), Err(v.len()));
1733 fn test_iterator_rev_advance_back_by() {
1734 let v: &[_] = &[0, 1, 2, 3, 4];
1736 for i in 0..v.len() {
1737 let mut iter = v.iter().rev();
1738 assert_eq!(iter.advance_back_by(i), Ok(()));
1739 assert_eq!(iter.next_back().unwrap(), &v[i]);
1740 assert_eq!(iter.advance_back_by(100), Err(v.len() - 1 - i));
1743 assert_eq!(v.iter().rev().advance_back_by(v.len()), Ok(()));
1744 assert_eq!(v.iter().rev().advance_back_by(100), Err(v.len()));
1748 fn test_iterator_last() {
1749 let v: &[_] = &[0, 1, 2, 3, 4];
1750 assert_eq!(v.iter().last().unwrap(), &4);
1751 assert_eq!(v[..1].iter().last().unwrap(), &0);
1755 fn test_iterator_len() {
1756 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1757 assert_eq!(v[..4].iter().count(), 4);
1758 assert_eq!(v[..10].iter().count(), 10);
1759 assert_eq!(v[..0].iter().count(), 0);
1763 fn test_iterator_sum() {
1764 let v: &[i32] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1765 assert_eq!(v[..4].iter().cloned().sum::<i32>(), 6);
1766 assert_eq!(v.iter().cloned().sum::<i32>(), 55);
1767 assert_eq!(v[..0].iter().cloned().sum::<i32>(), 0);
1771 fn test_iterator_sum_result() {
1772 let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
1773 assert_eq!(v.iter().cloned().sum::<Result<i32, _>>(), Ok(10));
1774 let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
1775 assert_eq!(v.iter().cloned().sum::<Result<i32, _>>(), Err(()));
1777 #[derive(PartialEq, Debug)]
1778 struct S(Result<i32, ()>);
1780 impl Sum<Result<i32, ()>> for S {
1781 fn sum<I: Iterator<Item = Result<i32, ()>>>(mut iter: I) -> Self {
1782 // takes the sum by repeatedly calling `next` on `iter`,
1783 // thus testing that repeated calls to `ResultShunt::try_fold`
1784 // produce the expected results
1785 Self(iter.by_ref().sum())
1789 let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
1790 assert_eq!(v.iter().cloned().sum::<S>(), S(Ok(10)));
1791 let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
1792 assert_eq!(v.iter().cloned().sum::<S>(), S(Err(())));
1796 fn test_iterator_sum_option() {
1797 let v: &[Option<i32>] = &[Some(1), Some(2), Some(3), Some(4)];
1798 assert_eq!(v.iter().cloned().sum::<Option<i32>>(), Some(10));
1799 let v: &[Option<i32>] = &[Some(1), None, Some(3), Some(4)];
1800 assert_eq!(v.iter().cloned().sum::<Option<i32>>(), None);
1804 fn test_iterator_product() {
1805 let v: &[i32] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1806 assert_eq!(v[..4].iter().cloned().product::<i32>(), 0);
1807 assert_eq!(v[1..5].iter().cloned().product::<i32>(), 24);
1808 assert_eq!(v[..0].iter().cloned().product::<i32>(), 1);
1812 fn test_iterator_product_result() {
1813 let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
1814 assert_eq!(v.iter().cloned().product::<Result<i32, _>>(), Ok(24));
1815 let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
1816 assert_eq!(v.iter().cloned().product::<Result<i32, _>>(), Err(()));
1819 /// A wrapper struct that implements `Eq` and `Ord` based on the wrapped
1820 /// integer modulo 3. Used to test that `Iterator::max` and `Iterator::min`
1821 /// return the correct element if some of them are equal.
1825 impl PartialEq for Mod3 {
1826 fn eq(&self, other: &Self) -> bool {
1827 self.0 % 3 == other.0 % 3
1833 impl PartialOrd for Mod3 {
1834 fn partial_cmp(&self, other: &Self) -> Option<core::cmp::Ordering> {
1835 Some(self.cmp(other))
1840 fn cmp(&self, other: &Self) -> core::cmp::Ordering {
1841 (self.0 % 3).cmp(&(other.0 % 3))
1846 fn test_iterator_product_option() {
1847 let v: &[Option<i32>] = &[Some(1), Some(2), Some(3), Some(4)];
1848 assert_eq!(v.iter().cloned().product::<Option<i32>>(), Some(24));
1849 let v: &[Option<i32>] = &[Some(1), None, Some(3), Some(4)];
1850 assert_eq!(v.iter().cloned().product::<Option<i32>>(), None);
1854 fn test_iterator_max() {
1855 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1856 assert_eq!(v[..4].iter().cloned().max(), Some(3));
1857 assert_eq!(v.iter().cloned().max(), Some(10));
1858 assert_eq!(v[..0].iter().cloned().max(), None);
1859 assert_eq!(v.iter().cloned().map(Mod3).max().map(|x| x.0), Some(8));
1863 fn test_iterator_min() {
1864 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1865 assert_eq!(v[..4].iter().cloned().min(), Some(0));
1866 assert_eq!(v.iter().cloned().min(), Some(0));
1867 assert_eq!(v[..0].iter().cloned().min(), None);
1868 assert_eq!(v.iter().cloned().map(Mod3).min().map(|x| x.0), Some(0));
1872 fn test_iterator_size_hint() {
1873 let c = (0..).step_by(1);
1874 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
1875 let v2 = &[10, 11, 12];
1878 assert_eq!((0..).size_hint(), (usize::MAX, None));
1879 assert_eq!(c.size_hint(), (usize::MAX, None));
1880 assert_eq!(vi.clone().size_hint(), (10, Some(10)));
1882 assert_eq!(c.clone().take(5).size_hint(), (5, Some(5)));
1883 assert_eq!(c.clone().skip(5).size_hint().1, None);
1884 assert_eq!(c.clone().take_while(|_| false).size_hint(), (0, None));
1885 assert_eq!(c.clone().map_while(|_| None::<()>).size_hint(), (0, None));
1886 assert_eq!(c.clone().skip_while(|_| false).size_hint(), (0, None));
1887 assert_eq!(c.clone().enumerate().size_hint(), (usize::MAX, None));
1888 assert_eq!(c.clone().chain(vi.clone().cloned()).size_hint(), (usize::MAX, None));
1889 assert_eq!(c.clone().zip(vi.clone()).size_hint(), (10, Some(10)));
1890 assert_eq!(c.clone().scan(0, |_, _| Some(0)).size_hint(), (0, None));
1891 assert_eq!(c.clone().filter(|_| false).size_hint(), (0, None));
1892 assert_eq!(c.clone().map(|_| 0).size_hint(), (usize::MAX, None));
1893 assert_eq!(c.filter_map(|_| Some(0)).size_hint(), (0, None));
1895 assert_eq!(vi.clone().take(5).size_hint(), (5, Some(5)));
1896 assert_eq!(vi.clone().take(12).size_hint(), (10, Some(10)));
1897 assert_eq!(vi.clone().skip(3).size_hint(), (7, Some(7)));
1898 assert_eq!(vi.clone().skip(12).size_hint(), (0, Some(0)));
1899 assert_eq!(vi.clone().take_while(|_| false).size_hint(), (0, Some(10)));
1900 assert_eq!(vi.clone().map_while(|_| None::<()>).size_hint(), (0, Some(10)));
1901 assert_eq!(vi.clone().skip_while(|_| false).size_hint(), (0, Some(10)));
1902 assert_eq!(vi.clone().enumerate().size_hint(), (10, Some(10)));
1903 assert_eq!(vi.clone().chain(v2).size_hint(), (13, Some(13)));
1904 assert_eq!(vi.clone().zip(v2).size_hint(), (3, Some(3)));
1905 assert_eq!(vi.clone().scan(0, |_, _| Some(0)).size_hint(), (0, Some(10)));
1906 assert_eq!(vi.clone().filter(|_| false).size_hint(), (0, Some(10)));
1907 assert_eq!(vi.clone().map(|&i| i + 1).size_hint(), (10, Some(10)));
1908 assert_eq!(vi.filter_map(|_| Some(0)).size_hint(), (0, Some(10)));
1913 let a = vec![1, 2, 3, 4, 5];
1914 let b: Vec<isize> = a.iter().cloned().collect();
1920 let v: Box<[isize]> = Box::new([1, 2, 3, 4, 5]);
1921 assert!(v.iter().all(|&x| x < 10));
1922 assert!(!v.iter().all(|&x| x % 2 == 0));
1923 assert!(!v.iter().all(|&x| x > 100));
1924 assert!(v[..0].iter().all(|_| panic!()));
1929 let v: Box<[isize]> = Box::new([1, 2, 3, 4, 5]);
1930 assert!(v.iter().any(|&x| x < 10));
1931 assert!(v.iter().any(|&x| x % 2 == 0));
1932 assert!(!v.iter().any(|&x| x > 100));
1933 assert!(!v[..0].iter().any(|_| panic!()));
1938 let v: &[isize] = &[1, 3, 9, 27, 103, 14, 11];
1939 assert_eq!(*v.iter().find(|&&x| x & 1 == 0).unwrap(), 14);
1940 assert_eq!(*v.iter().find(|&&x| x % 3 == 0).unwrap(), 3);
1941 assert!(v.iter().find(|&&x| x % 12 == 0).is_none());
1945 fn test_find_map() {
1946 let xs: &[isize] = &[];
1947 assert_eq!(xs.iter().find_map(half_if_even), None);
1948 let xs: &[isize] = &[3, 5];
1949 assert_eq!(xs.iter().find_map(half_if_even), None);
1950 let xs: &[isize] = &[4, 5];
1951 assert_eq!(xs.iter().find_map(half_if_even), Some(2));
1952 let xs: &[isize] = &[3, 6];
1953 assert_eq!(xs.iter().find_map(half_if_even), Some(3));
1955 let xs: &[isize] = &[1, 2, 3, 4, 5, 6, 7];
1956 let mut iter = xs.iter();
1957 assert_eq!(iter.find_map(half_if_even), Some(1));
1958 assert_eq!(iter.find_map(half_if_even), Some(2));
1959 assert_eq!(iter.find_map(half_if_even), Some(3));
1960 assert_eq!(iter.next(), Some(&7));
1962 fn half_if_even(x: &isize) -> Option<isize> {
1963 if x % 2 == 0 { Some(x / 2) } else { None }
1968 fn test_try_find() {
1969 let xs: &[isize] = &[];
1970 assert_eq!(xs.iter().try_find(testfn), Ok(None));
1971 let xs: &[isize] = &[1, 2, 3, 4];
1972 assert_eq!(xs.iter().try_find(testfn), Ok(Some(&2)));
1973 let xs: &[isize] = &[1, 3, 4];
1974 assert_eq!(xs.iter().try_find(testfn), Err(()));
1976 let xs: &[isize] = &[1, 2, 3, 4, 5, 6, 7];
1977 let mut iter = xs.iter();
1978 assert_eq!(iter.try_find(testfn), Ok(Some(&2)));
1979 assert_eq!(iter.try_find(testfn), Err(()));
1980 assert_eq!(iter.next(), Some(&5));
1982 fn testfn(x: &&isize) -> Result<bool, ()> {
1994 fn test_try_find_api_usability() -> Result<(), Box<dyn std::error::Error>> {
1997 let is_my_num = |s: &str, search: i32| -> Result<bool, std::num::ParseIntError> {
1998 Ok(s.parse::<i32>()? == search)
2001 let val = a.iter().try_find(|&&s| is_my_num(s, 2))?;
2002 assert_eq!(val, Some(&"2"));
2008 fn test_position() {
2009 let v = &[1, 3, 9, 27, 103, 14, 11];
2010 assert_eq!(v.iter().position(|x| *x & 1 == 0).unwrap(), 5);
2011 assert_eq!(v.iter().position(|x| *x % 3 == 0).unwrap(), 1);
2012 assert!(v.iter().position(|x| *x % 12 == 0).is_none());
2017 let xs = &[1, 2, 2, 1, 5, 9, 0, 2];
2018 assert_eq!(xs.iter().filter(|x| **x == 2).count(), 3);
2019 assert_eq!(xs.iter().filter(|x| **x == 5).count(), 1);
2020 assert_eq!(xs.iter().filter(|x| **x == 95).count(), 0);
2024 fn test_max_by_key() {
2025 let xs: &[isize] = &[-3, 0, 1, 5, -10];
2026 assert_eq!(*xs.iter().max_by_key(|x| x.abs()).unwrap(), -10);
2031 let xs: &[isize] = &[-3, 0, 1, 5, -10];
2032 assert_eq!(*xs.iter().max_by(|x, y| x.abs().cmp(&y.abs())).unwrap(), -10);
2036 fn test_min_by_key() {
2037 let xs: &[isize] = &[-3, 0, 1, 5, -10];
2038 assert_eq!(*xs.iter().min_by_key(|x| x.abs()).unwrap(), 0);
2043 let xs: &[isize] = &[-3, 0, 1, 5, -10];
2044 assert_eq!(*xs.iter().min_by(|x, y| x.abs().cmp(&y.abs())).unwrap(), 0);
2050 // sum the first five values
2051 let partial_sum = xs.by_ref().take(5).fold(0, |a, b| a + b);
2052 assert_eq!(partial_sum, 10);
2053 assert_eq!(xs.next(), Some(5));
2058 let xs = [2, 4, 6, 8, 10, 12, 14, 16];
2059 let mut it = xs.iter();
2062 assert!(it.rev().cloned().collect::<Vec<isize>>() == vec![16, 14, 12, 10, 8, 6]);
2067 let xs = [2, 4, 6, 8];
2069 let mut it = xs.iter().copied();
2070 assert_eq!(it.len(), 4);
2071 assert_eq!(it.next(), Some(2));
2072 assert_eq!(it.len(), 3);
2073 assert_eq!(it.next(), Some(4));
2074 assert_eq!(it.len(), 2);
2075 assert_eq!(it.next_back(), Some(8));
2076 assert_eq!(it.len(), 1);
2077 assert_eq!(it.next_back(), Some(6));
2078 assert_eq!(it.len(), 0);
2079 assert_eq!(it.next_back(), None);
2084 let xs = [2, 4, 6, 8];
2086 let mut it = xs.iter().cloned();
2087 assert_eq!(it.len(), 4);
2088 assert_eq!(it.next(), Some(2));
2089 assert_eq!(it.len(), 3);
2090 assert_eq!(it.next(), Some(4));
2091 assert_eq!(it.len(), 2);
2092 assert_eq!(it.next_back(), Some(8));
2093 assert_eq!(it.len(), 1);
2094 assert_eq!(it.next_back(), Some(6));
2095 assert_eq!(it.len(), 0);
2096 assert_eq!(it.next_back(), None);
2100 fn test_cloned_side_effects() {
2103 let iter = [1, 2, 3]
2113 assert_eq!(count, 2);
2117 fn test_double_ended_map() {
2118 let xs = [1, 2, 3, 4, 5, 6];
2119 let mut it = xs.iter().map(|&x| x * -1);
2120 assert_eq!(it.next(), Some(-1));
2121 assert_eq!(it.next(), Some(-2));
2122 assert_eq!(it.next_back(), Some(-6));
2123 assert_eq!(it.next_back(), Some(-5));
2124 assert_eq!(it.next(), Some(-3));
2125 assert_eq!(it.next_back(), Some(-4));
2126 assert_eq!(it.next(), None);
2130 fn test_double_ended_enumerate() {
2131 let xs = [1, 2, 3, 4, 5, 6];
2132 let mut it = xs.iter().cloned().enumerate();
2133 assert_eq!(it.next(), Some((0, 1)));
2134 assert_eq!(it.next(), Some((1, 2)));
2135 assert_eq!(it.next_back(), Some((5, 6)));
2136 assert_eq!(it.next_back(), Some((4, 5)));
2137 assert_eq!(it.next_back(), Some((3, 4)));
2138 assert_eq!(it.next_back(), Some((2, 3)));
2139 assert_eq!(it.next(), None);
2143 fn test_double_ended_zip() {
2144 let xs = [1, 2, 3, 4, 5, 6];
2145 let ys = [1, 2, 3, 7];
2146 let a = xs.iter().cloned();
2147 let b = ys.iter().cloned();
2148 let mut it = a.zip(b);
2149 assert_eq!(it.next(), Some((1, 1)));
2150 assert_eq!(it.next(), Some((2, 2)));
2151 assert_eq!(it.next_back(), Some((4, 7)));
2152 assert_eq!(it.next_back(), Some((3, 3)));
2153 assert_eq!(it.next(), None);
2157 fn test_double_ended_filter() {
2158 let xs = [1, 2, 3, 4, 5, 6];
2159 let mut it = xs.iter().filter(|&x| *x & 1 == 0);
2160 assert_eq!(it.next_back().unwrap(), &6);
2161 assert_eq!(it.next_back().unwrap(), &4);
2162 assert_eq!(it.next().unwrap(), &2);
2163 assert_eq!(it.next_back(), None);
2167 fn test_double_ended_filter_map() {
2168 let xs = [1, 2, 3, 4, 5, 6];
2169 let mut it = xs.iter().filter_map(|&x| if x & 1 == 0 { Some(x * 2) } else { None });
2170 assert_eq!(it.next_back().unwrap(), 12);
2171 assert_eq!(it.next_back().unwrap(), 8);
2172 assert_eq!(it.next().unwrap(), 4);
2173 assert_eq!(it.next_back(), None);
2177 fn test_double_ended_chain() {
2178 let xs = [1, 2, 3, 4, 5];
2179 let ys = [7, 9, 11];
2180 let mut it = xs.iter().chain(&ys).rev();
2181 assert_eq!(it.next().unwrap(), &11);
2182 assert_eq!(it.next().unwrap(), &9);
2183 assert_eq!(it.next_back().unwrap(), &1);
2184 assert_eq!(it.next_back().unwrap(), &2);
2185 assert_eq!(it.next_back().unwrap(), &3);
2186 assert_eq!(it.next_back().unwrap(), &4);
2187 assert_eq!(it.next_back().unwrap(), &5);
2188 assert_eq!(it.next_back().unwrap(), &7);
2189 assert_eq!(it.next_back(), None);
2191 // test that .chain() is well behaved with an unfused iterator
2192 struct CrazyIterator(bool);
2193 impl CrazyIterator {
2194 fn new() -> CrazyIterator {
2195 CrazyIterator(false)
2198 impl Iterator for CrazyIterator {
2200 fn next(&mut self) -> Option<i32> {
2210 impl DoubleEndedIterator for CrazyIterator {
2211 fn next_back(&mut self) -> Option<i32> {
2216 assert_eq!(CrazyIterator::new().chain(0..10).rev().last(), Some(0));
2217 assert!((0..10).chain(CrazyIterator::new()).rev().any(|i| i == 0));
2221 fn test_rposition() {
2222 fn f(xy: &(isize, char)) -> bool {
2226 fn g(xy: &(isize, char)) -> bool {
2230 let v = [(0, 'a'), (1, 'b'), (2, 'c'), (3, 'b')];
2232 assert_eq!(v.iter().rposition(f), Some(3));
2233 assert!(v.iter().rposition(g).is_none());
2237 fn test_rev_rposition() {
2238 let v = [0, 0, 1, 1];
2239 assert_eq!(v.iter().rev().rposition(|&x| x == 1), Some(1));
2244 fn test_rposition_panic() {
2245 let v: [(Box<_>, Box<_>); 4] = [(box 0, box 0), (box 0, box 0), (box 0, box 0), (box 0, box 0)];
2247 v.iter().rposition(|_elt| {
2257 fn test_double_ended_flat_map() {
2259 let v = [5, 6, 7, 8];
2260 let mut it = u.iter().flat_map(|x| &v[*x..v.len()]);
2261 assert_eq!(it.next_back().unwrap(), &8);
2262 assert_eq!(it.next().unwrap(), &5);
2263 assert_eq!(it.next_back().unwrap(), &7);
2264 assert_eq!(it.next_back().unwrap(), &6);
2265 assert_eq!(it.next_back().unwrap(), &8);
2266 assert_eq!(it.next().unwrap(), &6);
2267 assert_eq!(it.next_back().unwrap(), &7);
2268 assert_eq!(it.next_back(), None);
2269 assert_eq!(it.next(), None);
2270 assert_eq!(it.next_back(), None);
2274 fn test_double_ended_flatten() {
2276 let v = [5, 6, 7, 8];
2277 let mut it = u.iter().map(|x| &v[*x..v.len()]).flatten();
2278 assert_eq!(it.next_back().unwrap(), &8);
2279 assert_eq!(it.next().unwrap(), &5);
2280 assert_eq!(it.next_back().unwrap(), &7);
2281 assert_eq!(it.next_back().unwrap(), &6);
2282 assert_eq!(it.next_back().unwrap(), &8);
2283 assert_eq!(it.next().unwrap(), &6);
2284 assert_eq!(it.next_back().unwrap(), &7);
2285 assert_eq!(it.next_back(), None);
2286 assert_eq!(it.next(), None);
2287 assert_eq!(it.next_back(), None);
2291 fn test_double_ended_range() {
2292 assert_eq!((11..14).rev().collect::<Vec<_>>(), [13, 12, 11]);
2293 for _ in (10..0).rev() {
2294 panic!("unreachable");
2297 assert_eq!((11..14).rev().collect::<Vec<_>>(), [13, 12, 11]);
2298 for _ in (10..0).rev() {
2299 panic!("unreachable");
2305 assert_eq!((0..5).collect::<Vec<_>>(), [0, 1, 2, 3, 4]);
2306 assert_eq!((-10..-1).collect::<Vec<_>>(), [-10, -9, -8, -7, -6, -5, -4, -3, -2]);
2307 assert_eq!((0..5).rev().collect::<Vec<_>>(), [4, 3, 2, 1, 0]);
2308 assert_eq!((200..-5).count(), 0);
2309 assert_eq!((200..-5).rev().count(), 0);
2310 assert_eq!((200..200).count(), 0);
2311 assert_eq!((200..200).rev().count(), 0);
2313 assert_eq!((0..100).size_hint(), (100, Some(100)));
2314 // this test is only meaningful when sizeof usize < sizeof u64
2315 assert_eq!((usize::MAX - 1..usize::MAX).size_hint(), (1, Some(1)));
2316 assert_eq!((-10..-1).size_hint(), (9, Some(9)));
2317 assert_eq!((-1..-10).size_hint(), (0, Some(0)));
2319 assert_eq!((-70..58).size_hint(), (128, Some(128)));
2320 assert_eq!((-128..127).size_hint(), (255, Some(255)));
2322 (-2..isize::MAX).size_hint(),
2323 (isize::MAX as usize + 2, Some(isize::MAX as usize + 2))
2328 fn test_char_range() {
2331 let from = if cfg!(miri) { char::from_u32(0xD800 - 10).unwrap() } else { '\0' };
2332 let to = if cfg!(miri) { char::from_u32(0xDFFF + 10).unwrap() } else { char::MAX };
2333 assert!((from..=to).eq((from as u32..=to as u32).filter_map(char::from_u32)));
2334 assert!((from..=to).rev().eq((from as u32..=to as u32).filter_map(char::from_u32).rev()));
2336 assert_eq!(('\u{D7FF}'..='\u{E000}').count(), 2);
2337 assert_eq!(('\u{D7FF}'..='\u{E000}').size_hint(), (2, Some(2)));
2338 assert_eq!(('\u{D7FF}'..'\u{E000}').count(), 1);
2339 assert_eq!(('\u{D7FF}'..'\u{E000}').size_hint(), (1, Some(1)));
2343 fn test_range_exhaustion() {
2345 assert!(r.is_empty());
2346 assert_eq!(r.next(), None);
2347 assert_eq!(r.next_back(), None);
2348 assert_eq!(r, 10..10);
2351 assert_eq!(r.next(), Some(10));
2352 assert_eq!(r.next(), Some(11));
2353 assert!(r.is_empty());
2354 assert_eq!(r, 12..12);
2355 assert_eq!(r.next(), None);
2358 assert_eq!(r.next_back(), Some(11));
2359 assert_eq!(r.next_back(), Some(10));
2360 assert!(r.is_empty());
2361 assert_eq!(r, 10..10);
2362 assert_eq!(r.next_back(), None);
2364 let mut r = 100..10;
2365 assert!(r.is_empty());
2366 assert_eq!(r.next(), None);
2367 assert_eq!(r.next_back(), None);
2368 assert_eq!(r, 100..10);
2372 fn test_range_inclusive_exhaustion() {
2373 let mut r = 10..=10;
2374 assert_eq!(r.next(), Some(10));
2375 assert!(r.is_empty());
2376 assert_eq!(r.next(), None);
2377 assert_eq!(r.next(), None);
2379 assert_eq!(*r.start(), 10);
2380 assert_eq!(*r.end(), 10);
2381 assert_ne!(r, 10..=10);
2383 let mut r = 10..=10;
2384 assert_eq!(r.next_back(), Some(10));
2385 assert!(r.is_empty());
2386 assert_eq!(r.next_back(), None);
2388 assert_eq!(*r.start(), 10);
2389 assert_eq!(*r.end(), 10);
2390 assert_ne!(r, 10..=10);
2392 let mut r = 10..=12;
2393 assert_eq!(r.next(), Some(10));
2394 assert_eq!(r.next(), Some(11));
2395 assert_eq!(r.next(), Some(12));
2396 assert!(r.is_empty());
2397 assert_eq!(r.next(), None);
2399 let mut r = 10..=12;
2400 assert_eq!(r.next_back(), Some(12));
2401 assert_eq!(r.next_back(), Some(11));
2402 assert_eq!(r.next_back(), Some(10));
2403 assert!(r.is_empty());
2404 assert_eq!(r.next_back(), None);
2406 let mut r = 10..=12;
2407 assert_eq!(r.nth(2), Some(12));
2408 assert!(r.is_empty());
2409 assert_eq!(r.next(), None);
2411 let mut r = 10..=12;
2412 assert_eq!(r.nth(5), None);
2413 assert!(r.is_empty());
2414 assert_eq!(r.next(), None);
2416 let mut r = 100..=10;
2417 assert_eq!(r.next(), None);
2418 assert!(r.is_empty());
2419 assert_eq!(r.next(), None);
2420 assert_eq!(r.next(), None);
2421 assert_eq!(r, 100..=10);
2423 let mut r = 100..=10;
2424 assert_eq!(r.next_back(), None);
2425 assert!(r.is_empty());
2426 assert_eq!(r.next_back(), None);
2427 assert_eq!(r.next_back(), None);
2428 assert_eq!(r, 100..=10);
2432 fn test_range_nth() {
2433 assert_eq!((10..15).nth(0), Some(10));
2434 assert_eq!((10..15).nth(1), Some(11));
2435 assert_eq!((10..15).nth(4), Some(14));
2436 assert_eq!((10..15).nth(5), None);
2439 assert_eq!(r.nth(2), Some(12));
2440 assert_eq!(r, 13..20);
2441 assert_eq!(r.nth(2), Some(15));
2442 assert_eq!(r, 16..20);
2443 assert_eq!(r.nth(10), None);
2444 assert_eq!(r, 20..20);
2448 fn test_range_nth_back() {
2449 assert_eq!((10..15).nth_back(0), Some(14));
2450 assert_eq!((10..15).nth_back(1), Some(13));
2451 assert_eq!((10..15).nth_back(4), Some(10));
2452 assert_eq!((10..15).nth_back(5), None);
2453 assert_eq!((-120..80_i8).nth_back(199), Some(-120));
2456 assert_eq!(r.nth_back(2), Some(17));
2457 assert_eq!(r, 10..17);
2458 assert_eq!(r.nth_back(2), Some(14));
2459 assert_eq!(r, 10..14);
2460 assert_eq!(r.nth_back(10), None);
2461 assert_eq!(r, 10..10);
2465 fn test_range_from_nth() {
2466 assert_eq!((10..).nth(0), Some(10));
2467 assert_eq!((10..).nth(1), Some(11));
2468 assert_eq!((10..).nth(4), Some(14));
2471 assert_eq!(r.nth(2), Some(12));
2472 assert_eq!(r, 13..);
2473 assert_eq!(r.nth(2), Some(15));
2474 assert_eq!(r, 16..);
2475 assert_eq!(r.nth(10), Some(26));
2476 assert_eq!(r, 27..);
2478 assert_eq!((0..).size_hint(), (usize::MAX, None));
2481 fn is_trusted_len<I: TrustedLen>(_: I) {}
2484 fn test_range_from_take() {
2485 let mut it = (0..).take(3);
2486 assert_eq!(it.next(), Some(0));
2487 assert_eq!(it.next(), Some(1));
2488 assert_eq!(it.next(), Some(2));
2489 assert_eq!(it.next(), None);
2490 is_trusted_len((0..).take(3));
2491 assert_eq!((0..).take(3).size_hint(), (3, Some(3)));
2492 assert_eq!((0..).take(0).size_hint(), (0, Some(0)));
2493 assert_eq!((0..).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
2497 fn test_range_from_take_collect() {
2498 let v: Vec<_> = (0..).take(3).collect();
2499 assert_eq!(v, vec![0, 1, 2]);
2503 fn test_range_inclusive_nth() {
2504 assert_eq!((10..=15).nth(0), Some(10));
2505 assert_eq!((10..=15).nth(1), Some(11));
2506 assert_eq!((10..=15).nth(5), Some(15));
2507 assert_eq!((10..=15).nth(6), None);
2509 let mut exhausted_via_next = 10_u8..=20;
2510 while exhausted_via_next.next().is_some() {}
2512 let mut r = 10_u8..=20;
2513 assert_eq!(r.nth(2), Some(12));
2514 assert_eq!(r, 13..=20);
2515 assert_eq!(r.nth(2), Some(15));
2516 assert_eq!(r, 16..=20);
2517 assert_eq!(r.is_empty(), false);
2518 assert_eq!(ExactSizeIterator::is_empty(&r), false);
2519 assert_eq!(r.nth(10), None);
2520 assert_eq!(r.is_empty(), true);
2521 assert_eq!(r, exhausted_via_next);
2522 assert_eq!(ExactSizeIterator::is_empty(&r), true);
2526 fn test_range_inclusive_nth_back() {
2527 assert_eq!((10..=15).nth_back(0), Some(15));
2528 assert_eq!((10..=15).nth_back(1), Some(14));
2529 assert_eq!((10..=15).nth_back(5), Some(10));
2530 assert_eq!((10..=15).nth_back(6), None);
2531 assert_eq!((-120..=80_i8).nth_back(200), Some(-120));
2533 let mut exhausted_via_next_back = 10_u8..=20;
2534 while exhausted_via_next_back.next_back().is_some() {}
2536 let mut r = 10_u8..=20;
2537 assert_eq!(r.nth_back(2), Some(18));
2538 assert_eq!(r, 10..=17);
2539 assert_eq!(r.nth_back(2), Some(15));
2540 assert_eq!(r, 10..=14);
2541 assert_eq!(r.is_empty(), false);
2542 assert_eq!(ExactSizeIterator::is_empty(&r), false);
2543 assert_eq!(r.nth_back(10), None);
2544 assert_eq!(r.is_empty(), true);
2545 assert_eq!(r, exhausted_via_next_back);
2546 assert_eq!(ExactSizeIterator::is_empty(&r), true);
2550 fn test_range_len() {
2551 assert_eq!((0..10_u8).len(), 10);
2552 assert_eq!((9..10_u8).len(), 1);
2553 assert_eq!((10..10_u8).len(), 0);
2554 assert_eq!((11..10_u8).len(), 0);
2555 assert_eq!((100..10_u8).len(), 0);
2559 fn test_range_inclusive_len() {
2560 assert_eq!((0..=10_u8).len(), 11);
2561 assert_eq!((9..=10_u8).len(), 2);
2562 assert_eq!((10..=10_u8).len(), 1);
2563 assert_eq!((11..=10_u8).len(), 0);
2564 assert_eq!((100..=10_u8).len(), 0);
2568 fn test_range_step() {
2569 #![allow(deprecated)]
2571 assert_eq!((0..20).step_by(5).collect::<Vec<isize>>(), [0, 5, 10, 15]);
2572 assert_eq!((1..21).rev().step_by(5).collect::<Vec<isize>>(), [20, 15, 10, 5]);
2573 assert_eq!((1..21).rev().step_by(6).collect::<Vec<isize>>(), [20, 14, 8, 2]);
2574 assert_eq!((200..255).step_by(50).collect::<Vec<u8>>(), [200, 250]);
2575 assert_eq!((200..-5).step_by(1).collect::<Vec<isize>>(), []);
2576 assert_eq!((200..200).step_by(1).collect::<Vec<isize>>(), []);
2578 assert_eq!((0..20).step_by(1).size_hint(), (20, Some(20)));
2579 assert_eq!((0..20).step_by(21).size_hint(), (1, Some(1)));
2580 assert_eq!((0..20).step_by(5).size_hint(), (4, Some(4)));
2581 assert_eq!((1..21).rev().step_by(5).size_hint(), (4, Some(4)));
2582 assert_eq!((1..21).rev().step_by(6).size_hint(), (4, Some(4)));
2583 assert_eq!((20..-5).step_by(1).size_hint(), (0, Some(0)));
2584 assert_eq!((20..20).step_by(1).size_hint(), (0, Some(0)));
2585 assert_eq!((i8::MIN..i8::MAX).step_by(-(i8::MIN as i32) as usize).size_hint(), (2, Some(2)));
2586 assert_eq!((i16::MIN..i16::MAX).step_by(i16::MAX as usize).size_hint(), (3, Some(3)));
2587 assert_eq!((isize::MIN..isize::MAX).step_by(1).size_hint(), (usize::MAX, Some(usize::MAX)));
2591 fn test_step_by_skip() {
2592 assert_eq!((0..640).step_by(128).skip(1).collect::<Vec<_>>(), [128, 256, 384, 512]);
2593 assert_eq!((0..=50).step_by(10).nth(3), Some(30));
2594 assert_eq!((200..=255u8).step_by(10).nth(3), Some(230));
2598 fn test_range_inclusive_step() {
2599 assert_eq!((0..=50).step_by(10).collect::<Vec<_>>(), [0, 10, 20, 30, 40, 50]);
2600 assert_eq!((0..=5).step_by(1).collect::<Vec<_>>(), [0, 1, 2, 3, 4, 5]);
2601 assert_eq!((200..=255u8).step_by(10).collect::<Vec<_>>(), [200, 210, 220, 230, 240, 250]);
2602 assert_eq!((250..=255u8).step_by(1).collect::<Vec<_>>(), [250, 251, 252, 253, 254, 255]);
2606 fn test_range_last_max() {
2607 assert_eq!((0..20).last(), Some(19));
2608 assert_eq!((-20..0).last(), Some(-1));
2609 assert_eq!((5..5).last(), None);
2611 assert_eq!((0..20).max(), Some(19));
2612 assert_eq!((-20..0).max(), Some(-1));
2613 assert_eq!((5..5).max(), None);
2617 fn test_range_inclusive_last_max() {
2618 assert_eq!((0..=20).last(), Some(20));
2619 assert_eq!((-20..=0).last(), Some(0));
2620 assert_eq!((5..=5).last(), Some(5));
2621 let mut r = 10..=10;
2623 assert_eq!(r.last(), None);
2625 assert_eq!((0..=20).max(), Some(20));
2626 assert_eq!((-20..=0).max(), Some(0));
2627 assert_eq!((5..=5).max(), Some(5));
2628 let mut r = 10..=10;
2630 assert_eq!(r.max(), None);
2634 fn test_range_min() {
2635 assert_eq!((0..20).min(), Some(0));
2636 assert_eq!((-20..0).min(), Some(-20));
2637 assert_eq!((5..5).min(), None);
2641 fn test_range_inclusive_min() {
2642 assert_eq!((0..=20).min(), Some(0));
2643 assert_eq!((-20..=0).min(), Some(-20));
2644 assert_eq!((5..=5).min(), Some(5));
2645 let mut r = 10..=10;
2647 assert_eq!(r.min(), None);
2651 fn test_range_inclusive_folds() {
2652 assert_eq!((1..=10).sum::<i32>(), 55);
2653 assert_eq!((1..=10).rev().sum::<i32>(), 55);
2655 let mut it = 44..=50;
2656 assert_eq!(it.try_fold(0, i8::checked_add), None);
2657 assert_eq!(it, 47..=50);
2658 assert_eq!(it.try_fold(0, i8::checked_add), None);
2659 assert_eq!(it, 50..=50);
2660 assert_eq!(it.try_fold(0, i8::checked_add), Some(50));
2661 assert!(it.is_empty());
2662 assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
2663 assert!(it.is_empty());
2665 let mut it = 40..=47;
2666 assert_eq!(it.try_rfold(0, i8::checked_add), None);
2667 assert_eq!(it, 40..=44);
2668 assert_eq!(it.try_rfold(0, i8::checked_add), None);
2669 assert_eq!(it, 40..=41);
2670 assert_eq!(it.try_rfold(0, i8::checked_add), Some(81));
2671 assert!(it.is_empty());
2672 assert_eq!(it.try_rfold(0, i8::checked_add), Some(0));
2673 assert!(it.is_empty());
2675 let mut it = 10..=20;
2676 assert_eq!(it.try_fold(0, |a, b| Some(a + b)), Some(165));
2677 assert!(it.is_empty());
2678 assert_eq!(it.try_fold(0, |a, b| Some(a + b)), Some(0));
2679 assert!(it.is_empty());
2681 let mut it = 10..=20;
2682 assert_eq!(it.try_rfold(0, |a, b| Some(a + b)), Some(165));
2683 assert!(it.is_empty());
2684 assert_eq!(it.try_rfold(0, |a, b| Some(a + b)), Some(0));
2685 assert!(it.is_empty());
2689 fn test_range_size_hint() {
2690 assert_eq!((0..0usize).size_hint(), (0, Some(0)));
2691 assert_eq!((0..100usize).size_hint(), (100, Some(100)));
2692 assert_eq!((0..usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
2694 let umax = u128::try_from(usize::MAX).unwrap();
2695 assert_eq!((0..0u128).size_hint(), (0, Some(0)));
2696 assert_eq!((0..100u128).size_hint(), (100, Some(100)));
2697 assert_eq!((0..umax).size_hint(), (usize::MAX, Some(usize::MAX)));
2698 assert_eq!((0..umax + 1).size_hint(), (usize::MAX, None));
2700 assert_eq!((0..0isize).size_hint(), (0, Some(0)));
2701 assert_eq!((-100..100isize).size_hint(), (200, Some(200)));
2702 assert_eq!((isize::MIN..isize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
2704 let imin = i128::try_from(isize::MIN).unwrap();
2705 let imax = i128::try_from(isize::MAX).unwrap();
2706 assert_eq!((0..0i128).size_hint(), (0, Some(0)));
2707 assert_eq!((-100..100i128).size_hint(), (200, Some(200)));
2708 assert_eq!((imin..imax).size_hint(), (usize::MAX, Some(usize::MAX)));
2709 assert_eq!((imin..imax + 1).size_hint(), (usize::MAX, None));
2713 fn test_range_inclusive_size_hint() {
2714 assert_eq!((1..=0usize).size_hint(), (0, Some(0)));
2715 assert_eq!((0..=0usize).size_hint(), (1, Some(1)));
2716 assert_eq!((0..=100usize).size_hint(), (101, Some(101)));
2717 assert_eq!((0..=usize::MAX - 1).size_hint(), (usize::MAX, Some(usize::MAX)));
2718 assert_eq!((0..=usize::MAX).size_hint(), (usize::MAX, None));
2720 let umax = u128::try_from(usize::MAX).unwrap();
2721 assert_eq!((1..=0u128).size_hint(), (0, Some(0)));
2722 assert_eq!((0..=0u128).size_hint(), (1, Some(1)));
2723 assert_eq!((0..=100u128).size_hint(), (101, Some(101)));
2724 assert_eq!((0..=umax - 1).size_hint(), (usize::MAX, Some(usize::MAX)));
2725 assert_eq!((0..=umax).size_hint(), (usize::MAX, None));
2726 assert_eq!((0..=umax + 1).size_hint(), (usize::MAX, None));
2728 assert_eq!((0..=-1isize).size_hint(), (0, Some(0)));
2729 assert_eq!((0..=0isize).size_hint(), (1, Some(1)));
2730 assert_eq!((-100..=100isize).size_hint(), (201, Some(201)));
2731 assert_eq!((isize::MIN..=isize::MAX - 1).size_hint(), (usize::MAX, Some(usize::MAX)));
2732 assert_eq!((isize::MIN..=isize::MAX).size_hint(), (usize::MAX, None));
2734 let imin = i128::try_from(isize::MIN).unwrap();
2735 let imax = i128::try_from(isize::MAX).unwrap();
2736 assert_eq!((0..=-1i128).size_hint(), (0, Some(0)));
2737 assert_eq!((0..=0i128).size_hint(), (1, Some(1)));
2738 assert_eq!((-100..=100i128).size_hint(), (201, Some(201)));
2739 assert_eq!((imin..=imax - 1).size_hint(), (usize::MAX, Some(usize::MAX)));
2740 assert_eq!((imin..=imax).size_hint(), (usize::MAX, None));
2741 assert_eq!((imin..=imax + 1).size_hint(), (usize::MAX, None));
2746 let mut it = repeat(42);
2747 assert_eq!(it.next(), Some(42));
2748 assert_eq!(it.next(), Some(42));
2749 assert_eq!(it.next(), Some(42));
2750 assert_eq!(repeat(42).size_hint(), (usize::MAX, None));
2754 fn test_repeat_take() {
2755 let mut it = repeat(42).take(3);
2756 assert_eq!(it.next(), Some(42));
2757 assert_eq!(it.next(), Some(42));
2758 assert_eq!(it.next(), Some(42));
2759 assert_eq!(it.next(), None);
2760 is_trusted_len(repeat(42).take(3));
2761 assert_eq!(repeat(42).take(3).size_hint(), (3, Some(3)));
2762 assert_eq!(repeat(42).take(0).size_hint(), (0, Some(0)));
2763 assert_eq!(repeat(42).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
2767 fn test_repeat_take_collect() {
2768 let v: Vec<_> = repeat(42).take(3).collect();
2769 assert_eq!(v, vec![42, 42, 42]);
2773 fn test_repeat_with() {
2774 #[derive(PartialEq, Debug)]
2775 struct NotClone(usize);
2776 let mut it = repeat_with(|| NotClone(42));
2777 assert_eq!(it.next(), Some(NotClone(42)));
2778 assert_eq!(it.next(), Some(NotClone(42)));
2779 assert_eq!(it.next(), Some(NotClone(42)));
2780 assert_eq!(repeat_with(|| NotClone(42)).size_hint(), (usize::MAX, None));
2784 fn test_repeat_with_take() {
2785 let mut it = repeat_with(|| 42).take(3);
2786 assert_eq!(it.next(), Some(42));
2787 assert_eq!(it.next(), Some(42));
2788 assert_eq!(it.next(), Some(42));
2789 assert_eq!(it.next(), None);
2790 is_trusted_len(repeat_with(|| 42).take(3));
2791 assert_eq!(repeat_with(|| 42).take(3).size_hint(), (3, Some(3)));
2792 assert_eq!(repeat_with(|| 42).take(0).size_hint(), (0, Some(0)));
2793 assert_eq!(repeat_with(|| 42).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
2797 fn test_repeat_with_take_collect() {
2799 let v: Vec<_> = repeat_with(|| {
2806 assert_eq!(v, vec![1, 2, 4, 8, 16]);
2810 fn test_successors() {
2811 let mut powers_of_10 = successors(Some(1_u16), |n| n.checked_mul(10));
2812 assert_eq!(powers_of_10.by_ref().collect::<Vec<_>>(), &[1, 10, 100, 1_000, 10_000]);
2813 assert_eq!(powers_of_10.next(), None);
2815 let mut empty = successors(None::<u32>, |_| unimplemented!());
2816 assert_eq!(empty.next(), None);
2817 assert_eq!(empty.next(), None);
2823 assert_eq!(it.len(), 3);
2824 assert_eq!(it.next(), Some(0));
2825 assert_eq!(it.len(), 2);
2826 assert_eq!(it.next(), Some(1));
2827 assert_eq!(it.len(), 1);
2828 assert_eq!(it.next(), Some(2));
2829 assert_eq!(it.len(), 0);
2830 assert_eq!(it.next(), None);
2831 assert_eq!(it.len(), 0);
2832 assert_eq!(it.next(), None);
2833 assert_eq!(it.len(), 0);
2834 assert_eq!(it.next(), None);
2835 assert_eq!(it.len(), 0);
2839 fn test_fuse_nth() {
2841 let mut it = xs.iter();
2843 assert_eq!(it.len(), 3);
2844 assert_eq!(it.nth(2), Some(&2));
2845 assert_eq!(it.len(), 0);
2846 assert_eq!(it.nth(2), None);
2847 assert_eq!(it.len(), 0);
2851 fn test_fuse_last() {
2855 assert_eq!(it.len(), 3);
2856 assert_eq!(it.last(), Some(&2));
2860 fn test_fuse_count() {
2864 assert_eq!(it.len(), 3);
2865 assert_eq!(it.count(), 3);
2866 // Can't check len now because count consumes.
2870 fn test_fuse_fold() {
2872 let it = xs.iter(); // `FusedIterator`
2873 let i = it.fuse().fold(0, |i, &x| {
2874 assert_eq!(x, xs[i]);
2877 assert_eq!(i, xs.len());
2879 let it = xs.iter(); // `FusedIterator`
2880 let i = it.fuse().rfold(xs.len(), |i, &x| {
2881 assert_eq!(x, xs[i - 1]);
2886 let it = xs.iter().scan((), |_, &x| Some(x)); // `!FusedIterator`
2887 let i = it.fuse().fold(0, |i, x| {
2888 assert_eq!(x, xs[i]);
2891 assert_eq!(i, xs.len());
2896 let mut it = once(42);
2897 assert_eq!(it.next(), Some(42));
2898 assert_eq!(it.next(), None);
2902 fn test_once_with() {
2903 let count = Cell::new(0);
2904 let mut it = once_with(|| {
2905 count.set(count.get() + 1);
2909 assert_eq!(count.get(), 0);
2910 assert_eq!(it.next(), Some(42));
2911 assert_eq!(count.get(), 1);
2912 assert_eq!(it.next(), None);
2913 assert_eq!(count.get(), 1);
2914 assert_eq!(it.next(), None);
2915 assert_eq!(count.get(), 1);
2920 let mut it = empty::<i32>();
2921 assert_eq!(it.next(), None);
2925 fn test_chain_fold() {
2929 let mut iter = xs.iter().chain(&ys);
2931 let mut result = Vec::new();
2932 iter.fold((), |(), &elt| result.push(elt));
2933 assert_eq!(&[2, 3, 1, 2, 0], &result[..]);
2937 fn test_steps_between() {
2938 assert_eq!(Step::steps_between(&20_u8, &200_u8), Some(180_usize));
2939 assert_eq!(Step::steps_between(&-20_i8, &80_i8), Some(100_usize));
2940 assert_eq!(Step::steps_between(&-120_i8, &80_i8), Some(200_usize));
2941 assert_eq!(Step::steps_between(&20_u32, &4_000_100_u32), Some(4_000_080_usize));
2942 assert_eq!(Step::steps_between(&-20_i32, &80_i32), Some(100_usize));
2943 assert_eq!(Step::steps_between(&-2_000_030_i32, &2_000_050_i32), Some(4_000_080_usize));
2945 // Skip u64/i64 to avoid differences with 32-bit vs 64-bit platforms
2947 assert_eq!(Step::steps_between(&20_u128, &200_u128), Some(180_usize));
2948 assert_eq!(Step::steps_between(&-20_i128, &80_i128), Some(100_usize));
2949 if cfg!(target_pointer_width = "64") {
2950 assert_eq!(Step::steps_between(&10_u128, &0x1_0000_0000_0000_0009_u128), Some(usize::MAX));
2952 assert_eq!(Step::steps_between(&10_u128, &0x1_0000_0000_0000_000a_u128), None);
2953 assert_eq!(Step::steps_between(&10_i128, &0x1_0000_0000_0000_000a_i128), None);
2955 Step::steps_between(&-0x1_0000_0000_0000_0000_i128, &0x1_0000_0000_0000_0000_i128,),
2961 fn test_step_forward() {
2962 assert_eq!(Step::forward_checked(55_u8, 200_usize), Some(255_u8));
2963 assert_eq!(Step::forward_checked(252_u8, 200_usize), None);
2964 assert_eq!(Step::forward_checked(0_u8, 256_usize), None);
2965 assert_eq!(Step::forward_checked(-110_i8, 200_usize), Some(90_i8));
2966 assert_eq!(Step::forward_checked(-110_i8, 248_usize), None);
2967 assert_eq!(Step::forward_checked(-126_i8, 256_usize), None);
2969 assert_eq!(Step::forward_checked(35_u16, 100_usize), Some(135_u16));
2970 assert_eq!(Step::forward_checked(35_u16, 65500_usize), Some(u16::MAX));
2971 assert_eq!(Step::forward_checked(36_u16, 65500_usize), None);
2972 assert_eq!(Step::forward_checked(-110_i16, 200_usize), Some(90_i16));
2973 assert_eq!(Step::forward_checked(-20_030_i16, 50_050_usize), Some(30_020_i16));
2974 assert_eq!(Step::forward_checked(-10_i16, 40_000_usize), None);
2975 assert_eq!(Step::forward_checked(-10_i16, 70_000_usize), None);
2977 assert_eq!(Step::forward_checked(10_u128, 70_000_usize), Some(70_010_u128));
2978 assert_eq!(Step::forward_checked(10_i128, 70_030_usize), Some(70_040_i128));
2980 Step::forward_checked(0xffff_ffff_ffff_ffff__ffff_ffff_ffff_ff00_u128, 0xff_usize),
2984 Step::forward_checked(0xffff_ffff_ffff_ffff__ffff_ffff_ffff_ff00_u128, 0x100_usize),
2988 Step::forward_checked(0x7fff_ffff_ffff_ffff__ffff_ffff_ffff_ff00_i128, 0xff_usize),
2992 Step::forward_checked(0x7fff_ffff_ffff_ffff__ffff_ffff_ffff_ff00_i128, 0x100_usize),
2998 fn test_step_backward() {
2999 assert_eq!(Step::backward_checked(255_u8, 200_usize), Some(55_u8));
3000 assert_eq!(Step::backward_checked(100_u8, 200_usize), None);
3001 assert_eq!(Step::backward_checked(255_u8, 256_usize), None);
3002 assert_eq!(Step::backward_checked(90_i8, 200_usize), Some(-110_i8));
3003 assert_eq!(Step::backward_checked(110_i8, 248_usize), None);
3004 assert_eq!(Step::backward_checked(127_i8, 256_usize), None);
3006 assert_eq!(Step::backward_checked(135_u16, 100_usize), Some(35_u16));
3007 assert_eq!(Step::backward_checked(u16::MAX, 65500_usize), Some(35_u16));
3008 assert_eq!(Step::backward_checked(10_u16, 11_usize), None);
3009 assert_eq!(Step::backward_checked(90_i16, 200_usize), Some(-110_i16));
3010 assert_eq!(Step::backward_checked(30_020_i16, 50_050_usize), Some(-20_030_i16));
3011 assert_eq!(Step::backward_checked(-10_i16, 40_000_usize), None);
3012 assert_eq!(Step::backward_checked(-10_i16, 70_000_usize), None);
3014 assert_eq!(Step::backward_checked(70_010_u128, 70_000_usize), Some(10_u128));
3015 assert_eq!(Step::backward_checked(70_020_i128, 70_030_usize), Some(-10_i128));
3016 assert_eq!(Step::backward_checked(10_u128, 7_usize), Some(3_u128));
3017 assert_eq!(Step::backward_checked(10_u128, 11_usize), None);
3019 Step::backward_checked(-0x7fff_ffff_ffff_ffff__ffff_ffff_ffff_ff00_i128, 0x100_usize),
3025 fn test_rev_try_folds() {
3026 let f = &|acc, x| i32::checked_add(2 * acc, x);
3027 assert_eq!((1..10).rev().try_fold(7, f), (1..10).try_rfold(7, f));
3028 assert_eq!((1..10).rev().try_rfold(7, f), (1..10).try_fold(7, f));
3030 let a = [10, 20, 30, 40, 100, 60, 70, 80, 90];
3031 let mut iter = a.iter().rev();
3032 assert_eq!(iter.try_fold(0_i8, |acc, &x| acc.checked_add(x)), None);
3033 assert_eq!(iter.next(), Some(&70));
3034 let mut iter = a.iter().rev();
3035 assert_eq!(iter.try_rfold(0_i8, |acc, &x| acc.checked_add(x)), None);
3036 assert_eq!(iter.next_back(), Some(&60));
3040 fn test_cloned_try_folds() {
3041 let a = [1, 2, 3, 4, 5, 6, 7, 8, 9];
3042 let f = &|acc, x| i32::checked_add(2 * acc, x);
3043 let f_ref = &|acc, &x| i32::checked_add(2 * acc, x);
3044 assert_eq!(a.iter().cloned().try_fold(7, f), a.iter().try_fold(7, f_ref));
3045 assert_eq!(a.iter().cloned().try_rfold(7, f), a.iter().try_rfold(7, f_ref));
3047 let a = [10, 20, 30, 40, 100, 60, 70, 80, 90];
3048 let mut iter = a.iter().cloned();
3049 assert_eq!(iter.try_fold(0_i8, |acc, x| acc.checked_add(x)), None);
3050 assert_eq!(iter.next(), Some(60));
3051 let mut iter = a.iter().cloned();
3052 assert_eq!(iter.try_rfold(0_i8, |acc, x| acc.checked_add(x)), None);
3053 assert_eq!(iter.next_back(), Some(70));
3057 fn test_chain_try_folds() {
3058 let c = || (0..10).chain(10..20);
3060 let f = &|acc, x| i32::checked_add(2 * acc, x);
3061 assert_eq!(c().try_fold(7, f), (0..20).try_fold(7, f));
3062 assert_eq!(c().try_rfold(7, f), (0..20).rev().try_fold(7, f));
3065 assert_eq!(iter.position(|x| x == 5), Some(5));
3066 assert_eq!(iter.next(), Some(6), "stopped in front, state Both");
3067 assert_eq!(iter.position(|x| x == 13), Some(6));
3068 assert_eq!(iter.next(), Some(14), "stopped in back, state Back");
3069 assert_eq!(iter.try_fold(0, |acc, x| Some(acc + x)), Some((15..20).sum()));
3071 let mut iter = c().rev(); // use rev to access try_rfold
3072 assert_eq!(iter.position(|x| x == 15), Some(4));
3073 assert_eq!(iter.next(), Some(14), "stopped in back, state Both");
3074 assert_eq!(iter.position(|x| x == 5), Some(8));
3075 assert_eq!(iter.next(), Some(4), "stopped in front, state Front");
3076 assert_eq!(iter.try_fold(0, |acc, x| Some(acc + x)), Some((0..4).sum()));
3079 iter.by_ref().rev().nth(14); // skip the last 15, ending in state Front
3080 assert_eq!(iter.try_fold(7, f), (0..5).try_fold(7, f));
3083 iter.nth(14); // skip the first 15, ending in state Back
3084 assert_eq!(iter.try_rfold(7, f), (15..20).try_rfold(7, f));
3088 fn test_map_try_folds() {
3089 let f = &|acc, x| i32::checked_add(2 * acc, x);
3090 assert_eq!((0..10).map(|x| x + 3).try_fold(7, f), (3..13).try_fold(7, f));
3091 assert_eq!((0..10).map(|x| x + 3).try_rfold(7, f), (3..13).try_rfold(7, f));
3093 let mut iter = (0..40).map(|x| x + 10);
3094 assert_eq!(iter.try_fold(0, i8::checked_add), None);
3095 assert_eq!(iter.next(), Some(20));
3096 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
3097 assert_eq!(iter.next_back(), Some(46));
3101 fn test_filter_try_folds() {
3102 fn p(&x: &i32) -> bool {
3105 let f = &|acc, x| i32::checked_add(2 * acc, x);
3106 assert_eq!((-10..20).filter(p).try_fold(7, f), (0..10).try_fold(7, f));
3107 assert_eq!((-10..20).filter(p).try_rfold(7, f), (0..10).try_rfold(7, f));
3109 let mut iter = (0..40).filter(|&x| x % 2 == 1);
3110 assert_eq!(iter.try_fold(0, i8::checked_add), None);
3111 assert_eq!(iter.next(), Some(25));
3112 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
3113 assert_eq!(iter.next_back(), Some(31));
3117 fn test_filter_map_try_folds() {
3118 let mp = &|x| if 0 <= x && x < 10 { Some(x * 2) } else { None };
3119 let f = &|acc, x| i32::checked_add(2 * acc, x);
3120 assert_eq!((-9..20).filter_map(mp).try_fold(7, f), (0..10).map(|x| 2 * x).try_fold(7, f));
3121 assert_eq!((-9..20).filter_map(mp).try_rfold(7, f), (0..10).map(|x| 2 * x).try_rfold(7, f));
3123 let mut iter = (0..40).filter_map(|x| if x % 2 == 1 { None } else { Some(x * 2 + 10) });
3124 assert_eq!(iter.try_fold(0, i8::checked_add), None);
3125 assert_eq!(iter.next(), Some(38));
3126 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
3127 assert_eq!(iter.next_back(), Some(78));
3131 fn test_enumerate_try_folds() {
3132 let f = &|acc, (i, x)| usize::checked_add(2 * acc, x / (i + 1) + i);
3133 assert_eq!((9..18).enumerate().try_fold(7, f), (0..9).map(|i| (i, i + 9)).try_fold(7, f));
3134 assert_eq!((9..18).enumerate().try_rfold(7, f), (0..9).map(|i| (i, i + 9)).try_rfold(7, f));
3136 let mut iter = (100..200).enumerate();
3137 let f = &|acc, (i, x)| u8::checked_add(acc, u8::checked_div(x, i as u8 + 1)?);
3138 assert_eq!(iter.try_fold(0, f), None);
3139 assert_eq!(iter.next(), Some((7, 107)));
3140 assert_eq!(iter.try_rfold(0, f), None);
3141 assert_eq!(iter.next_back(), Some((11, 111)));
3145 fn test_peek_try_folds() {
3146 let f = &|acc, x| i32::checked_add(2 * acc, x);
3148 assert_eq!((1..20).peekable().try_fold(7, f), (1..20).try_fold(7, f));
3149 assert_eq!((1..20).peekable().try_rfold(7, f), (1..20).try_rfold(7, f));
3151 let mut iter = (1..20).peekable();
3152 assert_eq!(iter.peek(), Some(&1));
3153 assert_eq!(iter.try_fold(7, f), (1..20).try_fold(7, f));
3155 let mut iter = (1..20).peekable();
3156 assert_eq!(iter.peek(), Some(&1));
3157 assert_eq!(iter.try_rfold(7, f), (1..20).try_rfold(7, f));
3159 let mut iter = [100, 20, 30, 40, 50, 60, 70].iter().cloned().peekable();
3160 assert_eq!(iter.peek(), Some(&100));
3161 assert_eq!(iter.try_fold(0, i8::checked_add), None);
3162 assert_eq!(iter.peek(), Some(&40));
3164 let mut iter = [100, 20, 30, 40, 50, 60, 70].iter().cloned().peekable();
3165 assert_eq!(iter.peek(), Some(&100));
3166 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
3167 assert_eq!(iter.peek(), Some(&100));
3168 assert_eq!(iter.next_back(), Some(50));
3170 let mut iter = (2..5).peekable();
3171 assert_eq!(iter.peek(), Some(&2));
3172 assert_eq!(iter.try_for_each(Err), Err(2));
3173 assert_eq!(iter.peek(), Some(&3));
3174 assert_eq!(iter.try_for_each(Err), Err(3));
3175 assert_eq!(iter.peek(), Some(&4));
3176 assert_eq!(iter.try_for_each(Err), Err(4));
3177 assert_eq!(iter.peek(), None);
3178 assert_eq!(iter.try_for_each(Err), Ok(()));
3180 let mut iter = (2..5).peekable();
3181 assert_eq!(iter.peek(), Some(&2));
3182 assert_eq!(iter.try_rfold((), |(), x| Err(x)), Err(4));
3183 assert_eq!(iter.peek(), Some(&2));
3184 assert_eq!(iter.try_rfold((), |(), x| Err(x)), Err(3));
3185 assert_eq!(iter.peek(), Some(&2));
3186 assert_eq!(iter.try_rfold((), |(), x| Err(x)), Err(2));
3187 assert_eq!(iter.peek(), None);
3188 assert_eq!(iter.try_rfold((), |(), x| Err(x)), Ok(()));
3192 fn test_skip_while_try_fold() {
3193 let f = &|acc, x| i32::checked_add(2 * acc, x);
3194 fn p(&x: &i32) -> bool {
3197 assert_eq!((1..20).skip_while(p).try_fold(7, f), (6..20).try_fold(7, f));
3198 let mut iter = (1..20).skip_while(p);
3199 assert_eq!(iter.nth(5), Some(11));
3200 assert_eq!(iter.try_fold(7, f), (12..20).try_fold(7, f));
3202 let mut iter = (0..50).skip_while(|&x| (x % 20) < 15);
3203 assert_eq!(iter.try_fold(0, i8::checked_add), None);
3204 assert_eq!(iter.next(), Some(23));
3208 fn test_take_while_folds() {
3209 let f = &|acc, x| i32::checked_add(2 * acc, x);
3210 assert_eq!((1..20).take_while(|&x| x != 10).try_fold(7, f), (1..10).try_fold(7, f));
3211 let mut iter = (1..20).take_while(|&x| x != 10);
3212 assert_eq!(iter.try_fold(0, |x, y| Some(x + y)), Some((1..10).sum()));
3213 assert_eq!(iter.next(), None, "flag should be set");
3214 let iter = (1..20).take_while(|&x| x != 10);
3215 assert_eq!(iter.fold(0, |x, y| x + y), (1..10).sum());
3217 let mut iter = (10..50).take_while(|&x| x != 40);
3218 assert_eq!(iter.try_fold(0, i8::checked_add), None);
3219 assert_eq!(iter.next(), Some(20));
3223 fn test_skip_try_folds() {
3224 let f = &|acc, x| i32::checked_add(2 * acc, x);
3225 assert_eq!((1..20).skip(9).try_fold(7, f), (10..20).try_fold(7, f));
3226 assert_eq!((1..20).skip(9).try_rfold(7, f), (10..20).try_rfold(7, f));
3228 let mut iter = (0..30).skip(10);
3229 assert_eq!(iter.try_fold(0, i8::checked_add), None);
3230 assert_eq!(iter.next(), Some(20));
3231 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
3232 assert_eq!(iter.next_back(), Some(24));
3236 fn test_skip_nth_back() {
3237 let xs = [0, 1, 2, 3, 4, 5];
3238 let mut it = xs.iter().skip(2);
3239 assert_eq!(it.nth_back(0), Some(&5));
3240 assert_eq!(it.nth_back(1), Some(&3));
3241 assert_eq!(it.nth_back(0), Some(&2));
3242 assert_eq!(it.nth_back(0), None);
3244 let ys = [2, 3, 4, 5];
3245 let mut ity = ys.iter();
3246 let mut it = xs.iter().skip(2);
3247 assert_eq!(it.nth_back(1), ity.nth_back(1));
3248 assert_eq!(it.clone().nth(0), ity.clone().nth(0));
3249 assert_eq!(it.nth_back(0), ity.nth_back(0));
3250 assert_eq!(it.clone().nth(0), ity.clone().nth(0));
3251 assert_eq!(it.nth_back(0), ity.nth_back(0));
3252 assert_eq!(it.clone().nth(0), ity.clone().nth(0));
3253 assert_eq!(it.nth_back(0), ity.nth_back(0));
3254 assert_eq!(it.clone().nth(0), ity.clone().nth(0));
3256 let mut it = xs.iter().skip(2);
3257 assert_eq!(it.nth_back(4), None);
3258 assert_eq!(it.nth_back(0), None);
3260 let mut it = xs.iter();
3261 it.by_ref().skip(2).nth_back(3);
3262 assert_eq!(it.next_back(), Some(&1));
3264 let mut it = xs.iter();
3265 it.by_ref().skip(2).nth_back(10);
3266 assert_eq!(it.next_back(), Some(&1));
3270 fn test_take_try_folds() {
3271 let f = &|acc, x| i32::checked_add(2 * acc, x);
3272 assert_eq!((10..30).take(10).try_fold(7, f), (10..20).try_fold(7, f));
3273 assert_eq!((10..30).take(10).try_rfold(7, f), (10..20).try_rfold(7, f));
3275 let mut iter = (10..30).take(20);
3276 assert_eq!(iter.try_fold(0, i8::checked_add), None);
3277 assert_eq!(iter.next(), Some(20));
3278 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
3279 assert_eq!(iter.next_back(), Some(24));
3281 let mut iter = (2..20).take(3);
3282 assert_eq!(iter.try_for_each(Err), Err(2));
3283 assert_eq!(iter.try_for_each(Err), Err(3));
3284 assert_eq!(iter.try_for_each(Err), Err(4));
3285 assert_eq!(iter.try_for_each(Err), Ok(()));
3287 let mut iter = (2..20).take(3).rev();
3288 assert_eq!(iter.try_for_each(Err), Err(4));
3289 assert_eq!(iter.try_for_each(Err), Err(3));
3290 assert_eq!(iter.try_for_each(Err), Err(2));
3291 assert_eq!(iter.try_for_each(Err), Ok(()));
3295 fn test_flat_map_try_folds() {
3296 let f = &|acc, x| i32::checked_add(acc * 2 / 3, x);
3297 let mr = &|x| (5 * x)..(5 * x + 5);
3298 assert_eq!((0..10).flat_map(mr).try_fold(7, f), (0..50).try_fold(7, f));
3299 assert_eq!((0..10).flat_map(mr).try_rfold(7, f), (0..50).try_rfold(7, f));
3300 let mut iter = (0..10).flat_map(mr);
3302 iter.next_back(); // have front and back iters in progress
3303 assert_eq!(iter.try_rfold(7, f), (1..49).try_rfold(7, f));
3305 let mut iter = (0..10).flat_map(|x| (4 * x)..(4 * x + 4));
3306 assert_eq!(iter.try_fold(0, i8::checked_add), None);
3307 assert_eq!(iter.next(), Some(17));
3308 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
3309 assert_eq!(iter.next_back(), Some(35));
3313 fn test_flatten_try_folds() {
3314 let f = &|acc, x| i32::checked_add(acc * 2 / 3, x);
3315 let mr = &|x| (5 * x)..(5 * x + 5);
3316 assert_eq!((0..10).map(mr).flatten().try_fold(7, f), (0..50).try_fold(7, f));
3317 assert_eq!((0..10).map(mr).flatten().try_rfold(7, f), (0..50).try_rfold(7, f));
3318 let mut iter = (0..10).map(mr).flatten();
3320 iter.next_back(); // have front and back iters in progress
3321 assert_eq!(iter.try_rfold(7, f), (1..49).try_rfold(7, f));
3323 let mut iter = (0..10).map(|x| (4 * x)..(4 * x + 4)).flatten();
3324 assert_eq!(iter.try_fold(0, i8::checked_add), None);
3325 assert_eq!(iter.next(), Some(17));
3326 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
3327 assert_eq!(iter.next_back(), Some(35));
3331 fn test_functor_laws() {
3333 fn identity<T>(x: T) -> T {
3336 assert_eq!((0..10).map(identity).sum::<usize>(), (0..10).sum());
3339 fn f(x: usize) -> usize {
3342 fn g(x: usize) -> usize {
3345 fn h(x: usize) -> usize {
3348 assert_eq!((0..10).map(f).map(g).sum::<usize>(), (0..10).map(h).sum());
3352 fn test_monad_laws_left_identity() {
3353 fn f(x: usize) -> impl Iterator<Item = usize> {
3354 (0..10).map(move |y| x * y)
3356 assert_eq!(once(42).flat_map(f.clone()).sum::<usize>(), f(42).sum());
3360 fn test_monad_laws_right_identity() {
3361 assert_eq!((0..10).flat_map(|x| once(x)).sum::<usize>(), (0..10).sum());
3365 fn test_monad_laws_associativity() {
3366 fn f(x: usize) -> impl Iterator<Item = usize> {
3369 fn g(x: usize) -> impl Iterator<Item = usize> {
3373 (0..10).flat_map(f).flat_map(g).sum::<usize>(),
3374 (0..10).flat_map(|x| f(x).flat_map(g)).sum::<usize>()
3379 fn test_is_sorted() {
3380 assert!([1, 2, 2, 9].iter().is_sorted());
3381 assert!(![1, 3, 2].iter().is_sorted());
3382 assert!([0].iter().is_sorted());
3383 assert!(std::iter::empty::<i32>().is_sorted());
3384 assert!(![0.0, 1.0, f32::NAN].iter().is_sorted());
3385 assert!([-2, -1, 0, 3].iter().is_sorted());
3386 assert!(![-2i32, -1, 0, 3].iter().is_sorted_by_key(|n| n.abs()));
3387 assert!(!["c", "bb", "aaa"].iter().is_sorted());
3388 assert!(["c", "bb", "aaa"].iter().is_sorted_by_key(|s| s.len()));
3392 fn test_partition() {
3393 fn check(xs: &mut [i32], ref p: impl Fn(&i32) -> bool, expected: usize) {
3394 let i = xs.iter_mut().partition_in_place(p);
3395 assert_eq!(expected, i);
3396 assert!(xs[..i].iter().all(p));
3397 assert!(!xs[i..].iter().any(p));
3398 assert!(xs.iter().is_partitioned(p));
3399 if i == 0 || i == xs.len() {
3400 assert!(xs.iter().rev().is_partitioned(p));
3402 assert!(!xs.iter().rev().is_partitioned(p));
3406 check(&mut [], |_| true, 0);
3407 check(&mut [], |_| false, 0);
3409 check(&mut [0], |_| true, 1);
3410 check(&mut [0], |_| false, 0);
3412 check(&mut [-1, 1], |&x| x > 0, 1);
3413 check(&mut [-1, 1], |&x| x < 0, 1);
3415 let ref mut xs = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
3416 check(xs, |_| true, 10);
3417 check(xs, |_| false, 0);
3418 check(xs, |&x| x % 2 == 0, 5); // evens
3419 check(xs, |&x| x % 2 == 1, 5); // odds
3420 check(xs, |&x| x % 3 == 0, 4); // multiple of 3
3421 check(xs, |&x| x % 4 == 0, 3); // multiple of 4
3422 check(xs, |&x| x % 5 == 0, 2); // multiple of 5
3423 check(xs, |&x| x < 3, 3); // small
3424 check(xs, |&x| x > 6, 3); // large
3427 /// An iterator that panics whenever `next` or next_back` is called
3428 /// after `None` has already been returned. This does not violate
3429 /// `Iterator`'s contract. Used to test that iterator adaptors don't
3430 /// poll their inner iterators after exhausting them.
3431 struct NonFused<I> {
3436 impl<I> NonFused<I> {
3437 fn new(iter: I) -> Self {
3438 Self { iter, done: false }
3442 impl<I> Iterator for NonFused<I>
3446 type Item = I::Item;
3448 fn next(&mut self) -> Option<Self::Item> {
3449 assert!(!self.done, "this iterator has already returned None");
3450 self.iter.next().or_else(|| {
3457 impl<I> DoubleEndedIterator for NonFused<I>
3459 I: DoubleEndedIterator,
3461 fn next_back(&mut self) -> Option<Self::Item> {
3462 assert!(!self.done, "this iterator has already returned None");
3463 self.iter.next_back().or_else(|| {
3471 fn test_peekable_non_fused() {
3472 let mut iter = NonFused::new(empty::<i32>()).peekable();
3474 assert_eq!(iter.peek(), None);
3475 assert_eq!(iter.next_back(), None);
3479 fn test_flatten_non_fused_outer() {
3480 let mut iter = NonFused::new(once(0..2)).flatten();
3482 assert_eq!(iter.next_back(), Some(1));
3483 assert_eq!(iter.next(), Some(0));
3484 assert_eq!(iter.next(), None);
3488 fn test_flatten_non_fused_inner() {
3489 let mut iter = once(0..1).chain(once(1..3)).flat_map(NonFused::new);
3491 assert_eq!(iter.next_back(), Some(2));
3492 assert_eq!(iter.next(), Some(0));
3493 assert_eq!(iter.next(), Some(1));
3494 assert_eq!(iter.next(), None);
3498 pub fn extend_for_unit() {
3501 let iter = (0..5).map(|_| {
3510 fn test_intersperse() {
3511 let xs = ["a", "", "b", "c"];
3512 let v: Vec<&str> = xs.iter().map(|x| x.clone()).intersperse(", ").collect();
3513 let text: String = v.concat();
3514 assert_eq!(text, "a, , b, c".to_string());
3516 let ys = [0, 1, 2, 3];
3517 let mut it = ys[..0].iter().map(|x| *x).intersperse(1);
3518 assert!(it.next() == None);
3522 fn test_intersperse_size_hint() {
3523 let xs = ["a", "", "b", "c"];
3524 let mut iter = xs.iter().map(|x| x.clone()).intersperse(", ");
3525 assert_eq!(iter.size_hint(), (7, Some(7)));
3527 assert_eq!(iter.next(), Some("a"));
3528 assert_eq!(iter.size_hint(), (6, Some(6)));
3529 assert_eq!(iter.next(), Some(", "));
3530 assert_eq!(iter.size_hint(), (5, Some(5)));
3532 assert_eq!([].iter().intersperse(&()).size_hint(), (0, Some(0)));
3536 fn test_fold_specialization_intersperse() {
3537 let mut iter = (1..2).intersperse(0);
3538 iter.clone().for_each(|x| assert_eq!(Some(x), iter.next()));
3540 let mut iter = (1..3).intersperse(0);
3541 iter.clone().for_each(|x| assert_eq!(Some(x), iter.next()));
3543 let mut iter = (1..4).intersperse(0);
3544 iter.clone().for_each(|x| assert_eq!(Some(x), iter.next()));
3548 fn test_try_fold_specialization_intersperse_ok() {
3549 let mut iter = (1..2).intersperse(0);
3550 iter.clone().try_for_each(|x| {
3551 assert_eq!(Some(x), iter.next());
3555 let mut iter = (1..3).intersperse(0);
3556 iter.clone().try_for_each(|x| {
3557 assert_eq!(Some(x), iter.next());
3561 let mut iter = (1..4).intersperse(0);
3562 iter.clone().try_for_each(|x| {
3563 assert_eq!(Some(x), iter.next());
3569 fn test_try_fold_specialization_intersperse_err() {
3570 let orig_iter = ["a", "b"].iter().copied().intersperse("-");
3572 // Abort after the first item.
3573 let mut iter = orig_iter.clone();
3574 iter.try_for_each(|_| None::<()>);
3575 assert_eq!(iter.next(), Some("-"));
3576 assert_eq!(iter.next(), Some("b"));
3577 assert_eq!(iter.next(), None);
3579 // Abort after the second item.
3580 let mut iter = orig_iter.clone();
3581 iter.try_for_each(|item| if item == "-" { None } else { Some(()) });
3582 assert_eq!(iter.next(), Some("b"));
3583 assert_eq!(iter.next(), None);
3585 // Abort after the third item.
3586 let mut iter = orig_iter.clone();
3587 iter.try_for_each(|item| if item == "b" { None } else { Some(()) });
3588 assert_eq!(iter.next(), None);