2 use core::convert::TryFrom;
5 use core::{i16, i8, isize};
9 let empty: [isize; 0] = [];
13 assert!(!xs.iter().lt(ys.iter()));
14 assert!(!xs.iter().le(ys.iter()));
15 assert!(xs.iter().gt(ys.iter()));
16 assert!(xs.iter().ge(ys.iter()));
18 assert!(ys.iter().lt(xs.iter()));
19 assert!(ys.iter().le(xs.iter()));
20 assert!(!ys.iter().gt(xs.iter()));
21 assert!(!ys.iter().ge(xs.iter()));
23 assert!(empty.iter().lt(xs.iter()));
24 assert!(empty.iter().le(xs.iter()));
25 assert!(!empty.iter().gt(xs.iter()));
26 assert!(!empty.iter().ge(xs.iter()));
29 let u = [1.0f64, 2.0];
30 let v = [0.0f64 / 0.0, 3.0];
32 assert!(!u.iter().lt(v.iter()));
33 assert!(!u.iter().le(v.iter()));
34 assert!(!u.iter().gt(v.iter()));
35 assert!(!u.iter().ge(v.iter()));
37 let a = [0.0f64 / 0.0];
41 assert!(a.iter().lt(b.iter()) == (a[0] < b[0]));
42 assert!(a.iter().le(b.iter()) == (a[0] <= b[0]));
43 assert!(a.iter().gt(b.iter()) == (a[0] > b[0]));
44 assert!(a.iter().ge(b.iter()) == (a[0] >= b[0]));
46 assert!(c.iter().lt(b.iter()) == (c[0] < b[0]));
47 assert!(c.iter().le(b.iter()) == (c[0] <= b[0]));
48 assert!(c.iter().gt(b.iter()) == (c[0] > b[0]));
49 assert!(c.iter().ge(b.iter()) == (c[0] >= b[0]));
53 fn test_multi_iter() {
54 let xs = [1, 2, 3, 4];
55 let ys = [4, 3, 2, 1];
56 assert!(xs.iter().eq(ys.iter().rev()));
57 assert!(xs.iter().lt(xs.iter().skip(2)));
62 use core::cmp::Ordering;
64 let f = |x: i32, y: i32| (x * x).cmp(&y);
65 let xs = || [1, 2, 3, 4].iter().copied();
66 let ys = || [1, 4, 16].iter().copied();
68 assert_eq!(xs().cmp_by(ys(), f), Ordering::Less);
69 assert_eq!(ys().cmp_by(xs(), f), Ordering::Greater);
70 assert_eq!(xs().cmp_by(xs().map(|x| x * x), f), Ordering::Equal);
71 assert_eq!(xs().rev().cmp_by(ys().rev(), f), Ordering::Greater);
72 assert_eq!(xs().cmp_by(ys().rev(), f), Ordering::Less);
73 assert_eq!(xs().cmp_by(ys().take(2), f), Ordering::Greater);
77 fn test_partial_cmp_by() {
78 use core::cmp::Ordering;
81 let f = |x: i32, y: i32| (x * x).partial_cmp(&y);
82 let xs = || [1, 2, 3, 4].iter().copied();
83 let ys = || [1, 4, 16].iter().copied();
85 assert_eq!(xs().partial_cmp_by(ys(), f), Some(Ordering::Less));
86 assert_eq!(ys().partial_cmp_by(xs(), f), Some(Ordering::Greater));
87 assert_eq!(xs().partial_cmp_by(xs().map(|x| x * x), f), Some(Ordering::Equal));
88 assert_eq!(xs().rev().partial_cmp_by(ys().rev(), f), Some(Ordering::Greater));
89 assert_eq!(xs().partial_cmp_by(xs().rev(), f), Some(Ordering::Less));
90 assert_eq!(xs().partial_cmp_by(ys().take(2), f), Some(Ordering::Greater));
92 let f = |x: f64, y: f64| (x * x).partial_cmp(&y);
93 let xs = || [1.0, 2.0, 3.0, 4.0].iter().copied();
94 let ys = || [1.0, 4.0, f64::NAN, 16.0].iter().copied();
96 assert_eq!(xs().partial_cmp_by(ys(), f), None);
97 assert_eq!(ys().partial_cmp_by(xs(), f), Some(Ordering::Greater));
102 let f = |x: i32, y: i32| x * x == y;
103 let xs = || [1, 2, 3, 4].iter().copied();
104 let ys = || [1, 4, 9, 16].iter().copied();
106 assert!(xs().eq_by(ys(), f));
107 assert!(!ys().eq_by(xs(), f));
108 assert!(!xs().eq_by(xs(), f));
109 assert!(!ys().eq_by(ys(), f));
111 assert!(!xs().take(3).eq_by(ys(), f));
112 assert!(!xs().eq_by(ys().take(3), f));
113 assert!(xs().take(3).eq_by(ys().take(3), f));
117 fn test_counter_from_iter() {
118 let it = (0..).step_by(5).take(10);
119 let xs: Vec<isize> = FromIterator::from_iter(it);
120 assert_eq!(xs, [0, 5, 10, 15, 20, 25, 30, 35, 40, 45]);
124 fn test_iterator_chain() {
125 let xs = [0, 1, 2, 3, 4, 5];
126 let ys = [30, 40, 50, 60];
127 let expected = [0, 1, 2, 3, 4, 5, 30, 40, 50, 60];
128 let it = xs.iter().chain(&ys);
131 assert_eq!(x, expected[i]);
134 assert_eq!(i, expected.len());
136 let ys = (30..).step_by(10).take(4);
137 let it = xs.iter().cloned().chain(ys);
140 assert_eq!(x, expected[i]);
143 assert_eq!(i, expected.len());
147 fn test_iterator_chain_nth() {
148 let xs = [0, 1, 2, 3, 4, 5];
149 let ys = [30, 40, 50, 60];
151 let expected = [0, 1, 2, 3, 4, 5, 30, 40, 50, 60];
152 for (i, x) in expected.iter().enumerate() {
153 assert_eq!(Some(x), xs.iter().chain(&ys).nth(i));
155 assert_eq!(zs.iter().chain(&xs).nth(0), Some(&0));
157 let mut it = xs.iter().chain(&zs);
158 assert_eq!(it.nth(5), Some(&5));
159 assert_eq!(it.next(), None);
163 fn test_iterator_chain_nth_back() {
164 let xs = [0, 1, 2, 3, 4, 5];
165 let ys = [30, 40, 50, 60];
167 let expected = [0, 1, 2, 3, 4, 5, 30, 40, 50, 60];
168 for (i, x) in expected.iter().rev().enumerate() {
169 assert_eq!(Some(x), xs.iter().chain(&ys).nth_back(i));
171 assert_eq!(zs.iter().chain(&xs).nth_back(0), Some(&5));
173 let mut it = xs.iter().chain(&zs);
174 assert_eq!(it.nth_back(5), Some(&0));
175 assert_eq!(it.next(), None);
179 fn test_iterator_chain_last() {
180 let xs = [0, 1, 2, 3, 4, 5];
181 let ys = [30, 40, 50, 60];
183 assert_eq!(xs.iter().chain(&ys).last(), Some(&60));
184 assert_eq!(zs.iter().chain(&ys).last(), Some(&60));
185 assert_eq!(ys.iter().chain(&zs).last(), Some(&60));
186 assert_eq!(zs.iter().chain(&zs).last(), None);
190 fn test_iterator_chain_count() {
191 let xs = [0, 1, 2, 3, 4, 5];
192 let ys = [30, 40, 50, 60];
194 assert_eq!(xs.iter().chain(&ys).count(), 10);
195 assert_eq!(zs.iter().chain(&ys).count(), 4);
199 fn test_iterator_chain_find() {
200 let xs = [0, 1, 2, 3, 4, 5];
201 let ys = [30, 40, 50, 60];
202 let mut iter = xs.iter().chain(&ys);
203 assert_eq!(iter.find(|&&i| i == 4), Some(&4));
204 assert_eq!(iter.next(), Some(&5));
205 assert_eq!(iter.find(|&&i| i == 40), Some(&40));
206 assert_eq!(iter.next(), Some(&50));
207 assert_eq!(iter.find(|&&i| i == 100), None);
208 assert_eq!(iter.next(), None);
212 fn test_iterator_chain_size_hint() {
217 impl Iterator for Iter {
220 // alternates between `None` and `Some(())`
221 fn next(&mut self) -> Option<Self::Item> {
223 self.is_empty = false;
226 self.is_empty = true;
231 fn size_hint(&self) -> (usize, Option<usize>) {
232 if self.is_empty { (0, Some(0)) } else { (1, Some(1)) }
236 impl DoubleEndedIterator for Iter {
237 fn next_back(&mut self) -> Option<Self::Item> {
242 // this chains an iterator of length 0 with an iterator of length 1,
243 // so after calling `.next()` once, the iterator is empty and the
244 // state is `ChainState::Back`. `.size_hint()` should now disregard
245 // the size hint of the left iterator
246 let mut iter = Iter { is_empty: true }.chain(once(()));
247 assert_eq!(iter.next(), Some(()));
248 assert_eq!(iter.size_hint(), (0, Some(0)));
250 let mut iter = once(()).chain(Iter { is_empty: true });
251 assert_eq!(iter.next_back(), Some(()));
252 assert_eq!(iter.size_hint(), (0, Some(0)));
257 let xs = [0, 1, 2, 4, 5];
258 let ys = [10, 11, 12];
260 let mut it = xs.iter().zip(&ys);
261 assert_eq!(it.nth(0), Some((&0, &10)));
262 assert_eq!(it.nth(1), Some((&2, &12)));
263 assert_eq!(it.nth(0), None);
265 let mut it = xs.iter().zip(&ys);
266 assert_eq!(it.nth(3), None);
268 let mut it = ys.iter().zip(&xs);
269 assert_eq!(it.nth(3), None);
273 fn test_zip_nth_side_effects() {
274 let mut a = Vec::new();
275 let mut b = Vec::new();
276 let value = [1, 2, 3, 4, 5, 6]
283 .zip([2, 3, 4, 5, 6, 7, 8].iter().cloned().map(|n| {
289 assert_eq!(value, Some((50, 6000)));
290 assert_eq!(a, vec![1, 2, 3, 4, 5]);
291 assert_eq!(b, vec![200, 300, 400, 500, 600]);
295 fn test_iterator_step_by() {
297 let mut it = (0..).step_by(1).take(3);
298 assert_eq!(it.next(), Some(0));
299 assert_eq!(it.next(), Some(1));
300 assert_eq!(it.next(), Some(2));
301 assert_eq!(it.next(), None);
303 let mut it = (0..).step_by(3).take(4);
304 assert_eq!(it.next(), Some(0));
305 assert_eq!(it.next(), Some(3));
306 assert_eq!(it.next(), Some(6));
307 assert_eq!(it.next(), Some(9));
308 assert_eq!(it.next(), None);
310 let mut it = (0..3).step_by(1);
311 assert_eq!(it.next_back(), Some(2));
312 assert_eq!(it.next_back(), Some(1));
313 assert_eq!(it.next_back(), Some(0));
314 assert_eq!(it.next_back(), None);
316 let mut it = (0..11).step_by(3);
317 assert_eq!(it.next_back(), Some(9));
318 assert_eq!(it.next_back(), Some(6));
319 assert_eq!(it.next_back(), Some(3));
320 assert_eq!(it.next_back(), Some(0));
321 assert_eq!(it.next_back(), None);
325 fn test_iterator_step_by_nth() {
326 let mut it = (0..16).step_by(5);
327 assert_eq!(it.nth(0), Some(0));
328 assert_eq!(it.nth(0), Some(5));
329 assert_eq!(it.nth(0), Some(10));
330 assert_eq!(it.nth(0), Some(15));
331 assert_eq!(it.nth(0), None);
333 let it = (0..18).step_by(5);
334 assert_eq!(it.clone().nth(0), Some(0));
335 assert_eq!(it.clone().nth(1), Some(5));
336 assert_eq!(it.clone().nth(2), Some(10));
337 assert_eq!(it.clone().nth(3), Some(15));
338 assert_eq!(it.clone().nth(4), None);
339 assert_eq!(it.clone().nth(42), None);
343 fn test_iterator_step_by_nth_overflow() {
344 #[cfg(target_pointer_width = "8")]
346 #[cfg(target_pointer_width = "16")]
348 #[cfg(target_pointer_width = "32")]
350 #[cfg(target_pointer_width = "64")]
355 impl Iterator for &mut Test {
357 fn next(&mut self) -> Option<Self::Item> {
360 fn nth(&mut self, n: usize) -> Option<Self::Item> {
361 self.0 += n as Bigger + 1;
366 let mut it = Test(0);
367 let root = usize::MAX >> (::std::mem::size_of::<usize>() * 8 / 2);
369 (&mut it).step_by(n).nth(n);
370 assert_eq!(it.0, n as Bigger * n as Bigger);
373 let mut it = Test(0);
374 (&mut it).step_by(usize::MAX).nth(5);
375 assert_eq!(it.0, (usize::MAX as Bigger) * 5);
378 let mut it = Test(0);
379 (&mut it).step_by(2).nth(usize::MAX);
380 assert_eq!(it.0, (usize::MAX as Bigger) * 2);
383 let mut it = Test(0);
384 (&mut it).step_by(1).nth(usize::MAX);
385 assert_eq!(it.0, (usize::MAX as Bigger) * 1);
389 fn test_iterator_step_by_nth_try_fold() {
390 let mut it = (0..).step_by(10);
391 assert_eq!(it.try_fold(0, i8::checked_add), None);
392 assert_eq!(it.next(), Some(60));
393 assert_eq!(it.try_fold(0, i8::checked_add), None);
394 assert_eq!(it.next(), Some(90));
396 let mut it = (100..).step_by(10);
397 assert_eq!(it.try_fold(50, i8::checked_add), None);
398 assert_eq!(it.next(), Some(110));
400 let mut it = (100..=100).step_by(10);
401 assert_eq!(it.next(), Some(100));
402 assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
406 fn test_iterator_step_by_nth_back() {
407 let mut it = (0..16).step_by(5);
408 assert_eq!(it.nth_back(0), Some(15));
409 assert_eq!(it.nth_back(0), Some(10));
410 assert_eq!(it.nth_back(0), Some(5));
411 assert_eq!(it.nth_back(0), Some(0));
412 assert_eq!(it.nth_back(0), None);
414 let mut it = (0..16).step_by(5);
415 assert_eq!(it.next(), Some(0)); // to set `first_take` to `false`
416 assert_eq!(it.nth_back(0), Some(15));
417 assert_eq!(it.nth_back(0), Some(10));
418 assert_eq!(it.nth_back(0), Some(5));
419 assert_eq!(it.nth_back(0), None);
421 let it = || (0..18).step_by(5);
422 assert_eq!(it().nth_back(0), Some(15));
423 assert_eq!(it().nth_back(1), Some(10));
424 assert_eq!(it().nth_back(2), Some(5));
425 assert_eq!(it().nth_back(3), Some(0));
426 assert_eq!(it().nth_back(4), None);
427 assert_eq!(it().nth_back(42), None);
431 fn test_iterator_step_by_nth_try_rfold() {
432 let mut it = (0..100).step_by(10);
433 assert_eq!(it.try_rfold(0, i8::checked_add), None);
434 assert_eq!(it.next_back(), Some(70));
435 assert_eq!(it.next(), Some(0));
436 assert_eq!(it.try_rfold(0, i8::checked_add), None);
437 assert_eq!(it.next_back(), Some(30));
439 let mut it = (0..100).step_by(10);
440 assert_eq!(it.try_rfold(50, i8::checked_add), None);
441 assert_eq!(it.next_back(), Some(80));
443 let mut it = (100..=100).step_by(10);
444 assert_eq!(it.next_back(), Some(100));
445 assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
450 fn test_iterator_step_by_zero() {
451 let mut it = (0..).step_by(0);
456 fn test_iterator_step_by_size_hint() {
457 struct StubSizeHint(usize, Option<usize>);
458 impl Iterator for StubSizeHint {
460 fn next(&mut self) -> Option<()> {
462 if let Some(ref mut upper) = self.1 {
467 fn size_hint(&self) -> (usize, Option<usize>) {
472 // The two checks in each case are needed because the logic
473 // is different before the first call to `next()`.
475 let mut it = StubSizeHint(10, Some(10)).step_by(1);
476 assert_eq!(it.size_hint(), (10, Some(10)));
478 assert_eq!(it.size_hint(), (9, Some(9)));
481 let mut it = StubSizeHint(10, Some(10)).step_by(3);
482 assert_eq!(it.size_hint(), (4, Some(4)));
484 assert_eq!(it.size_hint(), (3, Some(3)));
486 // larger base range, but not enough to get another element
487 let mut it = StubSizeHint(12, Some(12)).step_by(3);
488 assert_eq!(it.size_hint(), (4, Some(4)));
490 assert_eq!(it.size_hint(), (3, Some(3)));
492 // smaller base range, so fewer resulting elements
493 let mut it = StubSizeHint(9, Some(9)).step_by(3);
494 assert_eq!(it.size_hint(), (3, Some(3)));
496 assert_eq!(it.size_hint(), (2, Some(2)));
498 // infinite upper bound
499 let mut it = StubSizeHint(usize::MAX, None).step_by(1);
500 assert_eq!(it.size_hint(), (usize::MAX, None));
502 assert_eq!(it.size_hint(), (usize::MAX - 1, None));
504 // still infinite with larger step
505 let mut it = StubSizeHint(7, None).step_by(3);
506 assert_eq!(it.size_hint(), (3, None));
508 assert_eq!(it.size_hint(), (2, None));
510 // propagates ExactSizeIterator
511 let a = [1, 2, 3, 4, 5];
512 let it = a.iter().step_by(2);
513 assert_eq!(it.len(), 3);
515 // Cannot be TrustedLen as a step greater than one makes an iterator
516 // with (usize::MAX, None) no longer meet the safety requirements
517 trait TrustedLenCheck {
518 fn test(self) -> bool;
520 impl<T: Iterator> TrustedLenCheck for T {
521 default fn test(self) -> bool {
525 impl<T: TrustedLen> TrustedLenCheck for T {
526 fn test(self) -> bool {
530 assert!(TrustedLenCheck::test(a.iter()));
531 assert!(!TrustedLenCheck::test(a.iter().step_by(1)));
535 fn test_filter_map() {
536 let it = (0..).step_by(1).take(10).filter_map(|x| if x % 2 == 0 { Some(x * x) } else { None });
537 assert_eq!(it.collect::<Vec<usize>>(), [0 * 0, 2 * 2, 4 * 4, 6 * 6, 8 * 8]);
541 fn test_filter_map_fold() {
542 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
543 let ys = [0 * 0, 2 * 2, 4 * 4, 6 * 6, 8 * 8];
544 let it = xs.iter().filter_map(|&x| if x % 2 == 0 { Some(x * x) } else { None });
545 let i = it.fold(0, |i, x| {
546 assert_eq!(x, ys[i]);
549 assert_eq!(i, ys.len());
551 let it = xs.iter().filter_map(|&x| if x % 2 == 0 { Some(x * x) } else { None });
552 let i = it.rfold(ys.len(), |i, x| {
553 assert_eq!(x, ys[i - 1]);
560 fn test_iterator_enumerate() {
561 let xs = [0, 1, 2, 3, 4, 5];
562 let it = xs.iter().enumerate();
569 fn test_iterator_enumerate_nth() {
570 let xs = [0, 1, 2, 3, 4, 5];
571 for (i, &x) in xs.iter().enumerate() {
575 let mut it = xs.iter().enumerate();
576 while let Some((i, &x)) = it.nth(0) {
580 let mut it = xs.iter().enumerate();
581 while let Some((i, &x)) = it.nth(1) {
585 let (i, &x) = xs.iter().enumerate().nth(3).unwrap();
591 fn test_iterator_enumerate_nth_back() {
592 let xs = [0, 1, 2, 3, 4, 5];
593 let mut it = xs.iter().enumerate();
594 while let Some((i, &x)) = it.nth_back(0) {
598 let mut it = xs.iter().enumerate();
599 while let Some((i, &x)) = it.nth_back(1) {
603 let (i, &x) = xs.iter().enumerate().nth_back(3).unwrap();
609 fn test_iterator_enumerate_count() {
610 let xs = [0, 1, 2, 3, 4, 5];
611 assert_eq!(xs.iter().enumerate().count(), 6);
615 fn test_iterator_enumerate_fold() {
616 let xs = [0, 1, 2, 3, 4, 5];
617 let mut it = xs.iter().enumerate();
618 // steal a couple to get an interesting offset
619 assert_eq!(it.next(), Some((0, &0)));
620 assert_eq!(it.next(), Some((1, &1)));
621 let i = it.fold(2, |i, (j, &x)| {
623 assert_eq!(x, xs[j]);
626 assert_eq!(i, xs.len());
628 let mut it = xs.iter().enumerate();
629 assert_eq!(it.next(), Some((0, &0)));
630 let i = it.rfold(xs.len() - 1, |i, (j, &x)| {
632 assert_eq!(x, xs[j]);
639 fn test_iterator_filter_count() {
640 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
641 assert_eq!(xs.iter().filter(|&&x| x % 2 == 0).count(), 5);
645 fn test_iterator_filter_fold() {
646 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
647 let ys = [0, 2, 4, 6, 8];
648 let it = xs.iter().filter(|&&x| x % 2 == 0);
649 let i = it.fold(0, |i, &x| {
650 assert_eq!(x, ys[i]);
653 assert_eq!(i, ys.len());
655 let it = xs.iter().filter(|&&x| x % 2 == 0);
656 let i = it.rfold(ys.len(), |i, &x| {
657 assert_eq!(x, ys[i - 1]);
664 fn test_iterator_peekable() {
665 let xs = vec![0, 1, 2, 3, 4, 5];
667 let mut it = xs.iter().cloned().peekable();
668 assert_eq!(it.len(), 6);
669 assert_eq!(it.peek().unwrap(), &0);
670 assert_eq!(it.len(), 6);
671 assert_eq!(it.next().unwrap(), 0);
672 assert_eq!(it.len(), 5);
673 assert_eq!(it.next().unwrap(), 1);
674 assert_eq!(it.len(), 4);
675 assert_eq!(it.next().unwrap(), 2);
676 assert_eq!(it.len(), 3);
677 assert_eq!(it.peek().unwrap(), &3);
678 assert_eq!(it.len(), 3);
679 assert_eq!(it.peek().unwrap(), &3);
680 assert_eq!(it.len(), 3);
681 assert_eq!(it.next().unwrap(), 3);
682 assert_eq!(it.len(), 2);
683 assert_eq!(it.next().unwrap(), 4);
684 assert_eq!(it.len(), 1);
685 assert_eq!(it.peek().unwrap(), &5);
686 assert_eq!(it.len(), 1);
687 assert_eq!(it.next().unwrap(), 5);
688 assert_eq!(it.len(), 0);
689 assert!(it.peek().is_none());
690 assert_eq!(it.len(), 0);
691 assert!(it.next().is_none());
692 assert_eq!(it.len(), 0);
694 let mut it = xs.iter().cloned().peekable();
695 assert_eq!(it.len(), 6);
696 assert_eq!(it.peek().unwrap(), &0);
697 assert_eq!(it.len(), 6);
698 assert_eq!(it.next_back().unwrap(), 5);
699 assert_eq!(it.len(), 5);
700 assert_eq!(it.next_back().unwrap(), 4);
701 assert_eq!(it.len(), 4);
702 assert_eq!(it.next_back().unwrap(), 3);
703 assert_eq!(it.len(), 3);
704 assert_eq!(it.peek().unwrap(), &0);
705 assert_eq!(it.len(), 3);
706 assert_eq!(it.peek().unwrap(), &0);
707 assert_eq!(it.len(), 3);
708 assert_eq!(it.next_back().unwrap(), 2);
709 assert_eq!(it.len(), 2);
710 assert_eq!(it.next_back().unwrap(), 1);
711 assert_eq!(it.len(), 1);
712 assert_eq!(it.peek().unwrap(), &0);
713 assert_eq!(it.len(), 1);
714 assert_eq!(it.next_back().unwrap(), 0);
715 assert_eq!(it.len(), 0);
716 assert!(it.peek().is_none());
717 assert_eq!(it.len(), 0);
718 assert!(it.next_back().is_none());
719 assert_eq!(it.len(), 0);
723 fn test_iterator_peekable_count() {
724 let xs = [0, 1, 2, 3, 4, 5];
726 let zs: [i32; 0] = [];
728 assert_eq!(xs.iter().peekable().count(), 6);
730 let mut it = xs.iter().peekable();
731 assert_eq!(it.peek(), Some(&&0));
732 assert_eq!(it.count(), 6);
734 assert_eq!(ys.iter().peekable().count(), 1);
736 let mut it = ys.iter().peekable();
737 assert_eq!(it.peek(), Some(&&10));
738 assert_eq!(it.count(), 1);
740 assert_eq!(zs.iter().peekable().count(), 0);
742 let mut it = zs.iter().peekable();
743 assert_eq!(it.peek(), None);
747 fn test_iterator_peekable_nth() {
748 let xs = [0, 1, 2, 3, 4, 5];
749 let mut it = xs.iter().peekable();
751 assert_eq!(it.peek(), Some(&&0));
752 assert_eq!(it.nth(0), Some(&0));
753 assert_eq!(it.peek(), Some(&&1));
754 assert_eq!(it.nth(1), Some(&2));
755 assert_eq!(it.peek(), Some(&&3));
756 assert_eq!(it.nth(2), Some(&5));
757 assert_eq!(it.next(), None);
761 fn test_iterator_peekable_last() {
762 let xs = [0, 1, 2, 3, 4, 5];
765 let mut it = xs.iter().peekable();
766 assert_eq!(it.peek(), Some(&&0));
767 assert_eq!(it.last(), Some(&5));
769 let mut it = ys.iter().peekable();
770 assert_eq!(it.peek(), Some(&&0));
771 assert_eq!(it.last(), Some(&0));
773 let mut it = ys.iter().peekable();
774 assert_eq!(it.next(), Some(&0));
775 assert_eq!(it.peek(), None);
776 assert_eq!(it.last(), None);
780 fn test_iterator_peekable_fold() {
781 let xs = [0, 1, 2, 3, 4, 5];
782 let mut it = xs.iter().peekable();
783 assert_eq!(it.peek(), Some(&&0));
784 let i = it.fold(0, |i, &x| {
785 assert_eq!(x, xs[i]);
788 assert_eq!(i, xs.len());
792 fn test_iterator_peekable_rfold() {
793 let xs = [0, 1, 2, 3, 4, 5];
794 let mut it = xs.iter().peekable();
795 assert_eq!(it.peek(), Some(&&0));
796 let i = it.rfold(0, |i, &x| {
797 assert_eq!(x, xs[xs.len() - 1 - i]);
800 assert_eq!(i, xs.len());
803 /// This is an iterator that follows the Iterator contract,
804 /// but it is not fused. After having returned None once, it will start
805 /// producing elements if .next() is called again.
806 pub struct CycleIter<'a, T> {
811 pub fn cycle<T>(data: &[T]) -> CycleIter<'_, T> {
812 CycleIter { index: 0, data }
815 impl<'a, T> Iterator for CycleIter<'a, T> {
817 fn next(&mut self) -> Option<Self::Item> {
818 let elt = self.data.get(self.index);
820 self.index %= 1 + self.data.len();
826 fn test_iterator_peekable_remember_peek_none_1() {
827 // Check that the loop using .peek() terminates
828 let data = [1, 2, 3];
829 let mut iter = cycle(&data).peekable();
832 while let Some(_) = iter.next() {
833 let is_the_last = iter.peek().is_none();
834 assert_eq!(is_the_last, n == data.len() - 1);
840 assert_eq!(n, data.len());
844 fn test_iterator_peekable_remember_peek_none_2() {
846 let mut iter = cycle(&data).peekable();
848 assert_eq!(iter.peek(), None);
849 assert_eq!(iter.last(), None);
853 fn test_iterator_peekable_remember_peek_none_3() {
855 let mut iter = cycle(&data).peekable();
857 assert_eq!(iter.nth(0), Some(&0));
859 let mut iter = cycle(&data).peekable();
861 assert_eq!(iter.peek(), None);
862 assert_eq!(iter.nth(0), None);
866 fn test_iterator_take_while() {
867 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
868 let ys = [0, 1, 2, 3, 5, 13];
869 let it = xs.iter().take_while(|&x| *x < 15);
872 assert_eq!(*x, ys[i]);
875 assert_eq!(i, ys.len());
879 fn test_iterator_skip_while() {
880 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
881 let ys = [15, 16, 17, 19];
882 let it = xs.iter().skip_while(|&x| *x < 15);
885 assert_eq!(*x, ys[i]);
888 assert_eq!(i, ys.len());
892 fn test_iterator_skip_while_fold() {
893 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
894 let ys = [15, 16, 17, 19];
895 let it = xs.iter().skip_while(|&x| *x < 15);
896 let i = it.fold(0, |i, &x| {
897 assert_eq!(x, ys[i]);
900 assert_eq!(i, ys.len());
902 let mut it = xs.iter().skip_while(|&x| *x < 15);
903 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
904 let i = it.fold(1, |i, &x| {
905 assert_eq!(x, ys[i]);
908 assert_eq!(i, ys.len());
912 fn test_iterator_skip() {
913 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
914 let ys = [13, 15, 16, 17, 19, 20, 30];
915 let mut it = xs.iter().skip(5);
917 while let Some(&x) = it.next() {
918 assert_eq!(x, ys[i]);
920 assert_eq!(it.len(), xs.len() - 5 - i);
922 assert_eq!(i, ys.len());
923 assert_eq!(it.len(), 0);
927 fn test_iterator_skip_doubleended() {
928 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
929 let mut it = xs.iter().rev().skip(5);
930 assert_eq!(it.next(), Some(&15));
931 assert_eq!(it.by_ref().rev().next(), Some(&0));
932 assert_eq!(it.next(), Some(&13));
933 assert_eq!(it.by_ref().rev().next(), Some(&1));
934 assert_eq!(it.next(), Some(&5));
935 assert_eq!(it.by_ref().rev().next(), Some(&2));
936 assert_eq!(it.next(), Some(&3));
937 assert_eq!(it.next(), None);
938 let mut it = xs.iter().rev().skip(5).rev();
939 assert_eq!(it.next(), Some(&0));
940 assert_eq!(it.rev().next(), Some(&15));
941 let mut it_base = xs.iter();
943 let mut it = it_base.by_ref().skip(5).rev();
944 assert_eq!(it.next(), Some(&30));
945 assert_eq!(it.next(), Some(&20));
946 assert_eq!(it.next(), Some(&19));
947 assert_eq!(it.next(), Some(&17));
948 assert_eq!(it.next(), Some(&16));
949 assert_eq!(it.next(), Some(&15));
950 assert_eq!(it.next(), Some(&13));
951 assert_eq!(it.next(), None);
953 // make sure the skipped parts have not been consumed
954 assert_eq!(it_base.next(), Some(&0));
955 assert_eq!(it_base.next(), Some(&1));
956 assert_eq!(it_base.next(), Some(&2));
957 assert_eq!(it_base.next(), Some(&3));
958 assert_eq!(it_base.next(), Some(&5));
959 assert_eq!(it_base.next(), None);
960 let it = xs.iter().skip(5).rev();
961 assert_eq!(it.last(), Some(&13));
965 fn test_iterator_skip_nth() {
966 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
968 let mut it = xs.iter().skip(0);
969 assert_eq!(it.nth(0), Some(&0));
970 assert_eq!(it.nth(1), Some(&2));
972 let mut it = xs.iter().skip(5);
973 assert_eq!(it.nth(0), Some(&13));
974 assert_eq!(it.nth(1), Some(&16));
976 let mut it = xs.iter().skip(12);
977 assert_eq!(it.nth(0), None);
981 fn test_iterator_skip_count() {
982 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
984 assert_eq!(xs.iter().skip(0).count(), 12);
985 assert_eq!(xs.iter().skip(1).count(), 11);
986 assert_eq!(xs.iter().skip(11).count(), 1);
987 assert_eq!(xs.iter().skip(12).count(), 0);
988 assert_eq!(xs.iter().skip(13).count(), 0);
992 fn test_iterator_skip_last() {
993 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
995 assert_eq!(xs.iter().skip(0).last(), Some(&30));
996 assert_eq!(xs.iter().skip(1).last(), Some(&30));
997 assert_eq!(xs.iter().skip(11).last(), Some(&30));
998 assert_eq!(xs.iter().skip(12).last(), None);
999 assert_eq!(xs.iter().skip(13).last(), None);
1001 let mut it = xs.iter().skip(5);
1002 assert_eq!(it.next(), Some(&13));
1003 assert_eq!(it.last(), Some(&30));
1007 fn test_iterator_skip_fold() {
1008 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
1009 let ys = [13, 15, 16, 17, 19, 20, 30];
1011 let it = xs.iter().skip(5);
1012 let i = it.fold(0, |i, &x| {
1013 assert_eq!(x, ys[i]);
1016 assert_eq!(i, ys.len());
1018 let mut it = xs.iter().skip(5);
1019 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
1020 let i = it.fold(1, |i, &x| {
1021 assert_eq!(x, ys[i]);
1024 assert_eq!(i, ys.len());
1026 let it = xs.iter().skip(5);
1027 let i = it.rfold(ys.len(), |i, &x| {
1029 assert_eq!(x, ys[i]);
1034 let mut it = xs.iter().skip(5);
1035 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
1036 let i = it.rfold(ys.len(), |i, &x| {
1038 assert_eq!(x, ys[i]);
1045 fn test_iterator_take() {
1046 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
1047 let ys = [0, 1, 2, 3, 5];
1049 let mut it = xs.iter().take(ys.len());
1051 assert_eq!(it.len(), ys.len());
1052 while let Some(&x) = it.next() {
1053 assert_eq!(x, ys[i]);
1055 assert_eq!(it.len(), ys.len() - i);
1057 assert_eq!(i, ys.len());
1058 assert_eq!(it.len(), 0);
1060 let mut it = xs.iter().take(ys.len());
1062 assert_eq!(it.len(), ys.len());
1063 while let Some(&x) = it.next_back() {
1065 assert_eq!(x, ys[ys.len() - i]);
1066 assert_eq!(it.len(), ys.len() - i);
1068 assert_eq!(i, ys.len());
1069 assert_eq!(it.len(), 0);
1073 fn test_iterator_take_nth() {
1074 let xs = [0, 1, 2, 4, 5];
1075 let mut it = xs.iter();
1077 let mut take = it.by_ref().take(3);
1079 while let Some(&x) = take.nth(0) {
1084 assert_eq!(it.nth(1), Some(&5));
1085 assert_eq!(it.nth(0), None);
1087 let xs = [0, 1, 2, 3, 4];
1088 let mut it = xs.iter().take(7);
1090 while let Some(&x) = it.nth(1) {
1097 fn test_iterator_take_nth_back() {
1098 let xs = [0, 1, 2, 4, 5];
1099 let mut it = xs.iter();
1101 let mut take = it.by_ref().take(3);
1103 while let Some(&x) = take.nth_back(0) {
1105 assert_eq!(x, 3 - i);
1108 assert_eq!(it.nth_back(0), None);
1110 let xs = [0, 1, 2, 3, 4];
1111 let mut it = xs.iter().take(7);
1112 assert_eq!(it.nth_back(1), Some(&3));
1113 assert_eq!(it.nth_back(1), Some(&1));
1114 assert_eq!(it.nth_back(1), None);
1118 fn test_iterator_take_short() {
1119 let xs = [0, 1, 2, 3];
1121 let mut it = xs.iter().take(5);
1123 assert_eq!(it.len(), xs.len());
1124 while let Some(&x) = it.next() {
1125 assert_eq!(x, xs[i]);
1127 assert_eq!(it.len(), xs.len() - i);
1129 assert_eq!(i, xs.len());
1130 assert_eq!(it.len(), 0);
1132 let mut it = xs.iter().take(5);
1134 assert_eq!(it.len(), xs.len());
1135 while let Some(&x) = it.next_back() {
1137 assert_eq!(x, xs[xs.len() - i]);
1138 assert_eq!(it.len(), xs.len() - i);
1140 assert_eq!(i, xs.len());
1141 assert_eq!(it.len(), 0);
1145 fn test_iterator_scan() {
1146 // test the type inference
1147 fn add(old: &mut isize, new: &usize) -> Option<f64> {
1148 *old += *new as isize;
1151 let xs = [0, 1, 2, 3, 4];
1152 let ys = [0f64, 1.0, 3.0, 6.0, 10.0];
1154 let it = xs.iter().scan(0, add);
1157 assert_eq!(x, ys[i]);
1160 assert_eq!(i, ys.len());
1164 fn test_iterator_flat_map() {
1166 let ys = [0, 1, 2, 3, 4, 5, 6, 7, 8];
1167 let it = xs.iter().flat_map(|&x| (x..).step_by(1).take(3));
1170 assert_eq!(x, ys[i]);
1173 assert_eq!(i, ys.len());
1176 /// Tests `FlatMap::fold` with items already picked off the front and back,
1177 /// to make sure all parts of the `FlatMap` are folded correctly.
1179 fn test_iterator_flat_map_fold() {
1181 let ys = [1, 2, 3, 4, 5, 6, 7];
1182 let mut it = xs.iter().flat_map(|&x| x..x + 3);
1183 assert_eq!(it.next(), Some(0));
1184 assert_eq!(it.next_back(), Some(8));
1185 let i = it.fold(0, |i, x| {
1186 assert_eq!(x, ys[i]);
1189 assert_eq!(i, ys.len());
1191 let mut it = xs.iter().flat_map(|&x| x..x + 3);
1192 assert_eq!(it.next(), Some(0));
1193 assert_eq!(it.next_back(), Some(8));
1194 let i = it.rfold(ys.len(), |i, x| {
1195 assert_eq!(x, ys[i - 1]);
1202 fn test_iterator_flatten() {
1204 let ys = [0, 1, 2, 3, 4, 5, 6, 7, 8];
1205 let it = xs.iter().map(|&x| (x..).step_by(1).take(3)).flatten();
1208 assert_eq!(x, ys[i]);
1211 assert_eq!(i, ys.len());
1214 /// Tests `Flatten::fold` with items already picked off the front and back,
1215 /// to make sure all parts of the `Flatten` are folded correctly.
1217 fn test_iterator_flatten_fold() {
1219 let ys = [1, 2, 3, 4, 5, 6, 7];
1220 let mut it = xs.iter().map(|&x| x..x + 3).flatten();
1221 assert_eq!(it.next(), Some(0));
1222 assert_eq!(it.next_back(), Some(8));
1223 let i = it.fold(0, |i, x| {
1224 assert_eq!(x, ys[i]);
1227 assert_eq!(i, ys.len());
1229 let mut it = xs.iter().map(|&x| x..x + 3).flatten();
1230 assert_eq!(it.next(), Some(0));
1231 assert_eq!(it.next_back(), Some(8));
1232 let i = it.rfold(ys.len(), |i, x| {
1233 assert_eq!(x, ys[i - 1]);
1241 let xs = [1, 2, 3, 4];
1244 let ys = xs.iter().cloned().inspect(|_| n += 1).collect::<Vec<usize>>();
1246 assert_eq!(n, xs.len());
1247 assert_eq!(&xs[..], &ys[..]);
1251 fn test_inspect_fold() {
1252 let xs = [1, 2, 3, 4];
1255 let it = xs.iter().inspect(|_| n += 1);
1256 let i = it.fold(0, |i, &x| {
1257 assert_eq!(x, xs[i]);
1260 assert_eq!(i, xs.len());
1262 assert_eq!(n, xs.len());
1266 let it = xs.iter().inspect(|_| n += 1);
1267 let i = it.rfold(xs.len(), |i, &x| {
1268 assert_eq!(x, xs[i - 1]);
1273 assert_eq!(n, xs.len());
1279 let it = (0..).step_by(1).take(cycle_len).cycle();
1280 assert_eq!(it.size_hint(), (usize::MAX, None));
1281 for (i, x) in it.take(100).enumerate() {
1282 assert_eq!(i % cycle_len, x);
1285 let mut it = (0..).step_by(1).take(0).cycle();
1286 assert_eq!(it.size_hint(), (0, Some(0)));
1287 assert_eq!(it.next(), None);
1289 assert_eq!(empty::<i32>().cycle().fold(0, |acc, x| acc + x), 0);
1291 assert_eq!(once(1).cycle().skip(1).take(4).fold(0, |acc, x| acc + x), 4);
1293 assert_eq!((0..10).cycle().take(5).sum::<i32>(), 10);
1294 assert_eq!((0..10).cycle().take(15).sum::<i32>(), 55);
1295 assert_eq!((0..10).cycle().take(25).sum::<i32>(), 100);
1297 let mut iter = (0..10).cycle();
1299 assert_eq!(iter.take(8).sum::<i32>(), 38);
1301 let mut iter = (0..10).cycle();
1303 assert_eq!(iter.take(3).sum::<i32>(), 3);
1307 fn test_iterator_nth() {
1308 let v: &[_] = &[0, 1, 2, 3, 4];
1309 for i in 0..v.len() {
1310 assert_eq!(v.iter().nth(i).unwrap(), &v[i]);
1312 assert_eq!(v.iter().nth(v.len()), None);
1316 fn test_iterator_nth_back() {
1317 let v: &[_] = &[0, 1, 2, 3, 4];
1318 for i in 0..v.len() {
1319 assert_eq!(v.iter().nth_back(i).unwrap(), &v[v.len() - 1 - i]);
1321 assert_eq!(v.iter().nth_back(v.len()), None);
1325 fn test_iterator_rev_nth_back() {
1326 let v: &[_] = &[0, 1, 2, 3, 4];
1327 for i in 0..v.len() {
1328 assert_eq!(v.iter().rev().nth_back(i).unwrap(), &v[i]);
1330 assert_eq!(v.iter().rev().nth_back(v.len()), None);
1334 fn test_iterator_rev_nth() {
1335 let v: &[_] = &[0, 1, 2, 3, 4];
1336 for i in 0..v.len() {
1337 assert_eq!(v.iter().rev().nth(i).unwrap(), &v[v.len() - 1 - i]);
1339 assert_eq!(v.iter().rev().nth(v.len()), None);
1343 fn test_iterator_last() {
1344 let v: &[_] = &[0, 1, 2, 3, 4];
1345 assert_eq!(v.iter().last().unwrap(), &4);
1346 assert_eq!(v[..1].iter().last().unwrap(), &0);
1350 fn test_iterator_len() {
1351 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1352 assert_eq!(v[..4].iter().count(), 4);
1353 assert_eq!(v[..10].iter().count(), 10);
1354 assert_eq!(v[..0].iter().count(), 0);
1358 fn test_iterator_sum() {
1359 let v: &[i32] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1360 assert_eq!(v[..4].iter().cloned().sum::<i32>(), 6);
1361 assert_eq!(v.iter().cloned().sum::<i32>(), 55);
1362 assert_eq!(v[..0].iter().cloned().sum::<i32>(), 0);
1366 fn test_iterator_sum_result() {
1367 let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
1368 assert_eq!(v.iter().cloned().sum::<Result<i32, _>>(), Ok(10));
1369 let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
1370 assert_eq!(v.iter().cloned().sum::<Result<i32, _>>(), Err(()));
1372 #[derive(PartialEq, Debug)]
1373 struct S(Result<i32, ()>);
1375 impl Sum<Result<i32, ()>> for S {
1376 fn sum<I: Iterator<Item = Result<i32, ()>>>(mut iter: I) -> Self {
1377 // takes the sum by repeatedly calling `next` on `iter`,
1378 // thus testing that repeated calls to `ResultShunt::try_fold`
1379 // produce the expected results
1380 Self(iter.by_ref().sum())
1384 let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
1385 assert_eq!(v.iter().cloned().sum::<S>(), S(Ok(10)));
1386 let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
1387 assert_eq!(v.iter().cloned().sum::<S>(), S(Err(())));
1391 fn test_iterator_sum_option() {
1392 let v: &[Option<i32>] = &[Some(1), Some(2), Some(3), Some(4)];
1393 assert_eq!(v.iter().cloned().sum::<Option<i32>>(), Some(10));
1394 let v: &[Option<i32>] = &[Some(1), None, Some(3), Some(4)];
1395 assert_eq!(v.iter().cloned().sum::<Option<i32>>(), None);
1399 fn test_iterator_product() {
1400 let v: &[i32] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1401 assert_eq!(v[..4].iter().cloned().product::<i32>(), 0);
1402 assert_eq!(v[1..5].iter().cloned().product::<i32>(), 24);
1403 assert_eq!(v[..0].iter().cloned().product::<i32>(), 1);
1407 fn test_iterator_product_result() {
1408 let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
1409 assert_eq!(v.iter().cloned().product::<Result<i32, _>>(), Ok(24));
1410 let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
1411 assert_eq!(v.iter().cloned().product::<Result<i32, _>>(), Err(()));
1414 /// A wrapper struct that implements `Eq` and `Ord` based on the wrapped
1415 /// integer modulo 3. Used to test that `Iterator::max` and `Iterator::min`
1416 /// return the correct element if some of them are equal.
1420 impl PartialEq for Mod3 {
1421 fn eq(&self, other: &Self) -> bool {
1422 self.0 % 3 == other.0 % 3
1428 impl PartialOrd for Mod3 {
1429 fn partial_cmp(&self, other: &Self) -> Option<core::cmp::Ordering> {
1430 Some(self.cmp(other))
1435 fn cmp(&self, other: &Self) -> core::cmp::Ordering {
1436 (self.0 % 3).cmp(&(other.0 % 3))
1441 fn test_iterator_product_option() {
1442 let v: &[Option<i32>] = &[Some(1), Some(2), Some(3), Some(4)];
1443 assert_eq!(v.iter().cloned().product::<Option<i32>>(), Some(24));
1444 let v: &[Option<i32>] = &[Some(1), None, Some(3), Some(4)];
1445 assert_eq!(v.iter().cloned().product::<Option<i32>>(), None);
1449 fn test_iterator_max() {
1450 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1451 assert_eq!(v[..4].iter().cloned().max(), Some(3));
1452 assert_eq!(v.iter().cloned().max(), Some(10));
1453 assert_eq!(v[..0].iter().cloned().max(), None);
1454 assert_eq!(v.iter().cloned().map(Mod3).max().map(|x| x.0), Some(8));
1458 fn test_iterator_min() {
1459 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1460 assert_eq!(v[..4].iter().cloned().min(), Some(0));
1461 assert_eq!(v.iter().cloned().min(), Some(0));
1462 assert_eq!(v[..0].iter().cloned().min(), None);
1463 assert_eq!(v.iter().cloned().map(Mod3).min().map(|x| x.0), Some(0));
1467 fn test_iterator_size_hint() {
1468 let c = (0..).step_by(1);
1469 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
1470 let v2 = &[10, 11, 12];
1473 assert_eq!((0..).size_hint(), (usize::MAX, None));
1474 assert_eq!(c.size_hint(), (usize::MAX, None));
1475 assert_eq!(vi.clone().size_hint(), (10, Some(10)));
1477 assert_eq!(c.clone().take(5).size_hint(), (5, Some(5)));
1478 assert_eq!(c.clone().skip(5).size_hint().1, None);
1479 assert_eq!(c.clone().take_while(|_| false).size_hint(), (0, None));
1480 assert_eq!(c.clone().skip_while(|_| false).size_hint(), (0, None));
1481 assert_eq!(c.clone().enumerate().size_hint(), (usize::MAX, None));
1482 assert_eq!(c.clone().chain(vi.clone().cloned()).size_hint(), (usize::MAX, None));
1483 assert_eq!(c.clone().zip(vi.clone()).size_hint(), (10, Some(10)));
1484 assert_eq!(c.clone().scan(0, |_, _| Some(0)).size_hint(), (0, None));
1485 assert_eq!(c.clone().filter(|_| false).size_hint(), (0, None));
1486 assert_eq!(c.clone().map(|_| 0).size_hint(), (usize::MAX, None));
1487 assert_eq!(c.filter_map(|_| Some(0)).size_hint(), (0, None));
1489 assert_eq!(vi.clone().take(5).size_hint(), (5, Some(5)));
1490 assert_eq!(vi.clone().take(12).size_hint(), (10, Some(10)));
1491 assert_eq!(vi.clone().skip(3).size_hint(), (7, Some(7)));
1492 assert_eq!(vi.clone().skip(12).size_hint(), (0, Some(0)));
1493 assert_eq!(vi.clone().take_while(|_| false).size_hint(), (0, Some(10)));
1494 assert_eq!(vi.clone().skip_while(|_| false).size_hint(), (0, Some(10)));
1495 assert_eq!(vi.clone().enumerate().size_hint(), (10, Some(10)));
1496 assert_eq!(vi.clone().chain(v2).size_hint(), (13, Some(13)));
1497 assert_eq!(vi.clone().zip(v2).size_hint(), (3, Some(3)));
1498 assert_eq!(vi.clone().scan(0, |_, _| Some(0)).size_hint(), (0, Some(10)));
1499 assert_eq!(vi.clone().filter(|_| false).size_hint(), (0, Some(10)));
1500 assert_eq!(vi.clone().map(|&i| i + 1).size_hint(), (10, Some(10)));
1501 assert_eq!(vi.filter_map(|_| Some(0)).size_hint(), (0, Some(10)));
1506 let a = vec![1, 2, 3, 4, 5];
1507 let b: Vec<isize> = a.iter().cloned().collect();
1513 let v: Box<[isize]> = Box::new([1, 2, 3, 4, 5]);
1514 assert!(v.iter().all(|&x| x < 10));
1515 assert!(!v.iter().all(|&x| x % 2 == 0));
1516 assert!(!v.iter().all(|&x| x > 100));
1517 assert!(v[..0].iter().all(|_| panic!()));
1522 let v: Box<[isize]> = Box::new([1, 2, 3, 4, 5]);
1523 assert!(v.iter().any(|&x| x < 10));
1524 assert!(v.iter().any(|&x| x % 2 == 0));
1525 assert!(!v.iter().any(|&x| x > 100));
1526 assert!(!v[..0].iter().any(|_| panic!()));
1531 let v: &[isize] = &[1, 3, 9, 27, 103, 14, 11];
1532 assert_eq!(*v.iter().find(|&&x| x & 1 == 0).unwrap(), 14);
1533 assert_eq!(*v.iter().find(|&&x| x % 3 == 0).unwrap(), 3);
1534 assert!(v.iter().find(|&&x| x % 12 == 0).is_none());
1538 fn test_find_map() {
1539 let xs: &[isize] = &[];
1540 assert_eq!(xs.iter().find_map(half_if_even), None);
1541 let xs: &[isize] = &[3, 5];
1542 assert_eq!(xs.iter().find_map(half_if_even), None);
1543 let xs: &[isize] = &[4, 5];
1544 assert_eq!(xs.iter().find_map(half_if_even), Some(2));
1545 let xs: &[isize] = &[3, 6];
1546 assert_eq!(xs.iter().find_map(half_if_even), Some(3));
1548 let xs: &[isize] = &[1, 2, 3, 4, 5, 6, 7];
1549 let mut iter = xs.iter();
1550 assert_eq!(iter.find_map(half_if_even), Some(1));
1551 assert_eq!(iter.find_map(half_if_even), Some(2));
1552 assert_eq!(iter.find_map(half_if_even), Some(3));
1553 assert_eq!(iter.next(), Some(&7));
1555 fn half_if_even(x: &isize) -> Option<isize> {
1556 if x % 2 == 0 { Some(x / 2) } else { None }
1561 fn test_try_find() {
1562 let xs: &[isize] = &[];
1563 assert_eq!(xs.iter().try_find(testfn), Ok(None));
1564 let xs: &[isize] = &[1, 2, 3, 4];
1565 assert_eq!(xs.iter().try_find(testfn), Ok(Some(&2)));
1566 let xs: &[isize] = &[1, 3, 4];
1567 assert_eq!(xs.iter().try_find(testfn), Err(()));
1569 let xs: &[isize] = &[1, 2, 3, 4, 5, 6, 7];
1570 let mut iter = xs.iter();
1571 assert_eq!(iter.try_find(testfn), Ok(Some(&2)));
1572 assert_eq!(iter.try_find(testfn), Err(()));
1573 assert_eq!(iter.next(), Some(&5));
1575 fn testfn(x: &&isize) -> Result<bool, ()> {
1587 fn test_try_find_api_usability() -> Result<(), Box<dyn std::error::Error>> {
1590 let is_my_num = |s: &str, search: i32| -> Result<bool, std::num::ParseIntError> {
1591 Ok(s.parse::<i32>()? == search)
1594 let val = a.iter().try_find(|&&s| is_my_num(s, 2))?;
1595 assert_eq!(val, Some(&"2"));
1601 fn test_position() {
1602 let v = &[1, 3, 9, 27, 103, 14, 11];
1603 assert_eq!(v.iter().position(|x| *x & 1 == 0).unwrap(), 5);
1604 assert_eq!(v.iter().position(|x| *x % 3 == 0).unwrap(), 1);
1605 assert!(v.iter().position(|x| *x % 12 == 0).is_none());
1610 let xs = &[1, 2, 2, 1, 5, 9, 0, 2];
1611 assert_eq!(xs.iter().filter(|x| **x == 2).count(), 3);
1612 assert_eq!(xs.iter().filter(|x| **x == 5).count(), 1);
1613 assert_eq!(xs.iter().filter(|x| **x == 95).count(), 0);
1617 fn test_max_by_key() {
1618 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1619 assert_eq!(*xs.iter().max_by_key(|x| x.abs()).unwrap(), -10);
1624 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1625 assert_eq!(*xs.iter().max_by(|x, y| x.abs().cmp(&y.abs())).unwrap(), -10);
1629 fn test_min_by_key() {
1630 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1631 assert_eq!(*xs.iter().min_by_key(|x| x.abs()).unwrap(), 0);
1636 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1637 assert_eq!(*xs.iter().min_by(|x, y| x.abs().cmp(&y.abs())).unwrap(), 0);
1643 // sum the first five values
1644 let partial_sum = xs.by_ref().take(5).fold(0, |a, b| a + b);
1645 assert_eq!(partial_sum, 10);
1646 assert_eq!(xs.next(), Some(5));
1651 let xs = [2, 4, 6, 8, 10, 12, 14, 16];
1652 let mut it = xs.iter();
1655 assert!(it.rev().cloned().collect::<Vec<isize>>() == vec![16, 14, 12, 10, 8, 6]);
1660 let xs = [2, 4, 6, 8];
1662 let mut it = xs.iter().copied();
1663 assert_eq!(it.len(), 4);
1664 assert_eq!(it.next(), Some(2));
1665 assert_eq!(it.len(), 3);
1666 assert_eq!(it.next(), Some(4));
1667 assert_eq!(it.len(), 2);
1668 assert_eq!(it.next_back(), Some(8));
1669 assert_eq!(it.len(), 1);
1670 assert_eq!(it.next_back(), Some(6));
1671 assert_eq!(it.len(), 0);
1672 assert_eq!(it.next_back(), None);
1677 let xs = [2, 4, 6, 8];
1679 let mut it = xs.iter().cloned();
1680 assert_eq!(it.len(), 4);
1681 assert_eq!(it.next(), Some(2));
1682 assert_eq!(it.len(), 3);
1683 assert_eq!(it.next(), Some(4));
1684 assert_eq!(it.len(), 2);
1685 assert_eq!(it.next_back(), Some(8));
1686 assert_eq!(it.len(), 1);
1687 assert_eq!(it.next_back(), Some(6));
1688 assert_eq!(it.len(), 0);
1689 assert_eq!(it.next_back(), None);
1693 fn test_cloned_side_effects() {
1696 let iter = [1, 2, 3]
1706 assert_eq!(count, 2);
1710 fn test_double_ended_map() {
1711 let xs = [1, 2, 3, 4, 5, 6];
1712 let mut it = xs.iter().map(|&x| x * -1);
1713 assert_eq!(it.next(), Some(-1));
1714 assert_eq!(it.next(), Some(-2));
1715 assert_eq!(it.next_back(), Some(-6));
1716 assert_eq!(it.next_back(), Some(-5));
1717 assert_eq!(it.next(), Some(-3));
1718 assert_eq!(it.next_back(), Some(-4));
1719 assert_eq!(it.next(), None);
1723 fn test_double_ended_enumerate() {
1724 let xs = [1, 2, 3, 4, 5, 6];
1725 let mut it = xs.iter().cloned().enumerate();
1726 assert_eq!(it.next(), Some((0, 1)));
1727 assert_eq!(it.next(), Some((1, 2)));
1728 assert_eq!(it.next_back(), Some((5, 6)));
1729 assert_eq!(it.next_back(), Some((4, 5)));
1730 assert_eq!(it.next_back(), Some((3, 4)));
1731 assert_eq!(it.next_back(), Some((2, 3)));
1732 assert_eq!(it.next(), None);
1736 fn test_double_ended_zip() {
1737 let xs = [1, 2, 3, 4, 5, 6];
1738 let ys = [1, 2, 3, 7];
1739 let a = xs.iter().cloned();
1740 let b = ys.iter().cloned();
1741 let mut it = a.zip(b);
1742 assert_eq!(it.next(), Some((1, 1)));
1743 assert_eq!(it.next(), Some((2, 2)));
1744 assert_eq!(it.next_back(), Some((4, 7)));
1745 assert_eq!(it.next_back(), Some((3, 3)));
1746 assert_eq!(it.next(), None);
1750 fn test_double_ended_filter() {
1751 let xs = [1, 2, 3, 4, 5, 6];
1752 let mut it = xs.iter().filter(|&x| *x & 1 == 0);
1753 assert_eq!(it.next_back().unwrap(), &6);
1754 assert_eq!(it.next_back().unwrap(), &4);
1755 assert_eq!(it.next().unwrap(), &2);
1756 assert_eq!(it.next_back(), None);
1760 fn test_double_ended_filter_map() {
1761 let xs = [1, 2, 3, 4, 5, 6];
1762 let mut it = xs.iter().filter_map(|&x| if x & 1 == 0 { Some(x * 2) } else { None });
1763 assert_eq!(it.next_back().unwrap(), 12);
1764 assert_eq!(it.next_back().unwrap(), 8);
1765 assert_eq!(it.next().unwrap(), 4);
1766 assert_eq!(it.next_back(), None);
1770 fn test_double_ended_chain() {
1771 let xs = [1, 2, 3, 4, 5];
1772 let ys = [7, 9, 11];
1773 let mut it = xs.iter().chain(&ys).rev();
1774 assert_eq!(it.next().unwrap(), &11);
1775 assert_eq!(it.next().unwrap(), &9);
1776 assert_eq!(it.next_back().unwrap(), &1);
1777 assert_eq!(it.next_back().unwrap(), &2);
1778 assert_eq!(it.next_back().unwrap(), &3);
1779 assert_eq!(it.next_back().unwrap(), &4);
1780 assert_eq!(it.next_back().unwrap(), &5);
1781 assert_eq!(it.next_back().unwrap(), &7);
1782 assert_eq!(it.next_back(), None);
1784 // test that .chain() is well behaved with an unfused iterator
1785 struct CrazyIterator(bool);
1786 impl CrazyIterator {
1787 fn new() -> CrazyIterator {
1788 CrazyIterator(false)
1791 impl Iterator for CrazyIterator {
1793 fn next(&mut self) -> Option<i32> {
1803 impl DoubleEndedIterator for CrazyIterator {
1804 fn next_back(&mut self) -> Option<i32> {
1809 assert_eq!(CrazyIterator::new().chain(0..10).rev().last(), Some(0));
1810 assert!((0..10).chain(CrazyIterator::new()).rev().any(|i| i == 0));
1814 fn test_rposition() {
1815 fn f(xy: &(isize, char)) -> bool {
1819 fn g(xy: &(isize, char)) -> bool {
1823 let v = [(0, 'a'), (1, 'b'), (2, 'c'), (3, 'b')];
1825 assert_eq!(v.iter().rposition(f), Some(3));
1826 assert!(v.iter().rposition(g).is_none());
1830 fn test_rev_rposition() {
1831 let v = [0, 0, 1, 1];
1832 assert_eq!(v.iter().rev().rposition(|&x| x == 1), Some(1));
1837 fn test_rposition_panic() {
1838 let v: [(Box<_>, Box<_>); 4] = [(box 0, box 0), (box 0, box 0), (box 0, box 0), (box 0, box 0)];
1840 v.iter().rposition(|_elt| {
1850 fn test_double_ended_flat_map() {
1852 let v = [5, 6, 7, 8];
1853 let mut it = u.iter().flat_map(|x| &v[*x..v.len()]);
1854 assert_eq!(it.next_back().unwrap(), &8);
1855 assert_eq!(it.next().unwrap(), &5);
1856 assert_eq!(it.next_back().unwrap(), &7);
1857 assert_eq!(it.next_back().unwrap(), &6);
1858 assert_eq!(it.next_back().unwrap(), &8);
1859 assert_eq!(it.next().unwrap(), &6);
1860 assert_eq!(it.next_back().unwrap(), &7);
1861 assert_eq!(it.next_back(), None);
1862 assert_eq!(it.next(), None);
1863 assert_eq!(it.next_back(), None);
1867 fn test_double_ended_flatten() {
1869 let v = [5, 6, 7, 8];
1870 let mut it = u.iter().map(|x| &v[*x..v.len()]).flatten();
1871 assert_eq!(it.next_back().unwrap(), &8);
1872 assert_eq!(it.next().unwrap(), &5);
1873 assert_eq!(it.next_back().unwrap(), &7);
1874 assert_eq!(it.next_back().unwrap(), &6);
1875 assert_eq!(it.next_back().unwrap(), &8);
1876 assert_eq!(it.next().unwrap(), &6);
1877 assert_eq!(it.next_back().unwrap(), &7);
1878 assert_eq!(it.next_back(), None);
1879 assert_eq!(it.next(), None);
1880 assert_eq!(it.next_back(), None);
1884 fn test_double_ended_range() {
1885 assert_eq!((11..14).rev().collect::<Vec<_>>(), [13, 12, 11]);
1886 for _ in (10..0).rev() {
1887 panic!("unreachable");
1890 assert_eq!((11..14).rev().collect::<Vec<_>>(), [13, 12, 11]);
1891 for _ in (10..0).rev() {
1892 panic!("unreachable");
1898 assert_eq!((0..5).collect::<Vec<_>>(), [0, 1, 2, 3, 4]);
1899 assert_eq!((-10..-1).collect::<Vec<_>>(), [-10, -9, -8, -7, -6, -5, -4, -3, -2]);
1900 assert_eq!((0..5).rev().collect::<Vec<_>>(), [4, 3, 2, 1, 0]);
1901 assert_eq!((200..-5).count(), 0);
1902 assert_eq!((200..-5).rev().count(), 0);
1903 assert_eq!((200..200).count(), 0);
1904 assert_eq!((200..200).rev().count(), 0);
1906 assert_eq!((0..100).size_hint(), (100, Some(100)));
1907 // this test is only meaningful when sizeof usize < sizeof u64
1908 assert_eq!((usize::MAX - 1..usize::MAX).size_hint(), (1, Some(1)));
1909 assert_eq!((-10..-1).size_hint(), (9, Some(9)));
1910 assert_eq!((-1..-10).size_hint(), (0, Some(0)));
1912 assert_eq!((-70..58).size_hint(), (128, Some(128)));
1913 assert_eq!((-128..127).size_hint(), (255, Some(255)));
1915 (-2..isize::MAX).size_hint(),
1916 (isize::MAX as usize + 2, Some(isize::MAX as usize + 2))
1921 fn test_range_exhaustion() {
1923 assert!(r.is_empty());
1924 assert_eq!(r.next(), None);
1925 assert_eq!(r.next_back(), None);
1926 assert_eq!(r, 10..10);
1929 assert_eq!(r.next(), Some(10));
1930 assert_eq!(r.next(), Some(11));
1931 assert!(r.is_empty());
1932 assert_eq!(r, 12..12);
1933 assert_eq!(r.next(), None);
1936 assert_eq!(r.next_back(), Some(11));
1937 assert_eq!(r.next_back(), Some(10));
1938 assert!(r.is_empty());
1939 assert_eq!(r, 10..10);
1940 assert_eq!(r.next_back(), None);
1942 let mut r = 100..10;
1943 assert!(r.is_empty());
1944 assert_eq!(r.next(), None);
1945 assert_eq!(r.next_back(), None);
1946 assert_eq!(r, 100..10);
1950 fn test_range_inclusive_exhaustion() {
1951 let mut r = 10..=10;
1952 assert_eq!(r.next(), Some(10));
1953 assert!(r.is_empty());
1954 assert_eq!(r.next(), None);
1955 assert_eq!(r.next(), None);
1957 let mut r = 10..=10;
1958 assert_eq!(r.next_back(), Some(10));
1959 assert!(r.is_empty());
1960 assert_eq!(r.next_back(), None);
1962 let mut r = 10..=12;
1963 assert_eq!(r.next(), Some(10));
1964 assert_eq!(r.next(), Some(11));
1965 assert_eq!(r.next(), Some(12));
1966 assert!(r.is_empty());
1967 assert_eq!(r.next(), None);
1969 let mut r = 10..=12;
1970 assert_eq!(r.next_back(), Some(12));
1971 assert_eq!(r.next_back(), Some(11));
1972 assert_eq!(r.next_back(), Some(10));
1973 assert!(r.is_empty());
1974 assert_eq!(r.next_back(), None);
1976 let mut r = 10..=12;
1977 assert_eq!(r.nth(2), Some(12));
1978 assert!(r.is_empty());
1979 assert_eq!(r.next(), None);
1981 let mut r = 10..=12;
1982 assert_eq!(r.nth(5), None);
1983 assert!(r.is_empty());
1984 assert_eq!(r.next(), None);
1986 let mut r = 100..=10;
1987 assert_eq!(r.next(), None);
1988 assert!(r.is_empty());
1989 assert_eq!(r.next(), None);
1990 assert_eq!(r.next(), None);
1991 assert_eq!(r, 100..=10);
1993 let mut r = 100..=10;
1994 assert_eq!(r.next_back(), None);
1995 assert!(r.is_empty());
1996 assert_eq!(r.next_back(), None);
1997 assert_eq!(r.next_back(), None);
1998 assert_eq!(r, 100..=10);
2002 fn test_range_nth() {
2003 assert_eq!((10..15).nth(0), Some(10));
2004 assert_eq!((10..15).nth(1), Some(11));
2005 assert_eq!((10..15).nth(4), Some(14));
2006 assert_eq!((10..15).nth(5), None);
2009 assert_eq!(r.nth(2), Some(12));
2010 assert_eq!(r, 13..20);
2011 assert_eq!(r.nth(2), Some(15));
2012 assert_eq!(r, 16..20);
2013 assert_eq!(r.nth(10), None);
2014 assert_eq!(r, 20..20);
2018 fn test_range_nth_back() {
2019 assert_eq!((10..15).nth_back(0), Some(14));
2020 assert_eq!((10..15).nth_back(1), Some(13));
2021 assert_eq!((10..15).nth_back(4), Some(10));
2022 assert_eq!((10..15).nth_back(5), None);
2023 assert_eq!((-120..80_i8).nth_back(199), Some(-120));
2026 assert_eq!(r.nth_back(2), Some(17));
2027 assert_eq!(r, 10..17);
2028 assert_eq!(r.nth_back(2), Some(14));
2029 assert_eq!(r, 10..14);
2030 assert_eq!(r.nth_back(10), None);
2031 assert_eq!(r, 10..10);
2035 fn test_range_from_nth() {
2036 assert_eq!((10..).nth(0), Some(10));
2037 assert_eq!((10..).nth(1), Some(11));
2038 assert_eq!((10..).nth(4), Some(14));
2041 assert_eq!(r.nth(2), Some(12));
2042 assert_eq!(r, 13..);
2043 assert_eq!(r.nth(2), Some(15));
2044 assert_eq!(r, 16..);
2045 assert_eq!(r.nth(10), Some(26));
2046 assert_eq!(r, 27..);
2048 assert_eq!((0..).size_hint(), (usize::MAX, None));
2051 fn is_trusted_len<I: TrustedLen>(_: I) {}
2054 fn test_range_from_take() {
2055 let mut it = (0..).take(3);
2056 assert_eq!(it.next(), Some(0));
2057 assert_eq!(it.next(), Some(1));
2058 assert_eq!(it.next(), Some(2));
2059 assert_eq!(it.next(), None);
2060 is_trusted_len((0..).take(3));
2061 assert_eq!((0..).take(3).size_hint(), (3, Some(3)));
2062 assert_eq!((0..).take(0).size_hint(), (0, Some(0)));
2063 assert_eq!((0..).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
2067 fn test_range_from_take_collect() {
2068 let v: Vec<_> = (0..).take(3).collect();
2069 assert_eq!(v, vec![0, 1, 2]);
2073 fn test_range_inclusive_nth() {
2074 assert_eq!((10..=15).nth(0), Some(10));
2075 assert_eq!((10..=15).nth(1), Some(11));
2076 assert_eq!((10..=15).nth(5), Some(15));
2077 assert_eq!((10..=15).nth(6), None);
2079 let mut r = 10_u8..=20;
2080 assert_eq!(r.nth(2), Some(12));
2081 assert_eq!(r, 13..=20);
2082 assert_eq!(r.nth(2), Some(15));
2083 assert_eq!(r, 16..=20);
2084 assert_eq!(r.is_empty(), false);
2085 assert_eq!(ExactSizeIterator::is_empty(&r), false);
2086 assert_eq!(r.nth(10), None);
2087 assert_eq!(r.is_empty(), true);
2088 assert_eq!(ExactSizeIterator::is_empty(&r), true);
2092 fn test_range_inclusive_nth_back() {
2093 assert_eq!((10..=15).nth_back(0), Some(15));
2094 assert_eq!((10..=15).nth_back(1), Some(14));
2095 assert_eq!((10..=15).nth_back(5), Some(10));
2096 assert_eq!((10..=15).nth_back(6), None);
2097 assert_eq!((-120..=80_i8).nth_back(200), Some(-120));
2099 let mut r = 10_u8..=20;
2100 assert_eq!(r.nth_back(2), Some(18));
2101 assert_eq!(r, 10..=17);
2102 assert_eq!(r.nth_back(2), Some(15));
2103 assert_eq!(r, 10..=14);
2104 assert_eq!(r.is_empty(), false);
2105 assert_eq!(ExactSizeIterator::is_empty(&r), false);
2106 assert_eq!(r.nth_back(10), None);
2107 assert_eq!(r.is_empty(), true);
2108 assert_eq!(ExactSizeIterator::is_empty(&r), true);
2112 fn test_range_step() {
2113 #![allow(deprecated)]
2115 assert_eq!((0..20).step_by(5).collect::<Vec<isize>>(), [0, 5, 10, 15]);
2116 assert_eq!((1..21).rev().step_by(5).collect::<Vec<isize>>(), [20, 15, 10, 5]);
2117 assert_eq!((1..21).rev().step_by(6).collect::<Vec<isize>>(), [20, 14, 8, 2]);
2118 assert_eq!((200..255).step_by(50).collect::<Vec<u8>>(), [200, 250]);
2119 assert_eq!((200..-5).step_by(1).collect::<Vec<isize>>(), []);
2120 assert_eq!((200..200).step_by(1).collect::<Vec<isize>>(), []);
2122 assert_eq!((0..20).step_by(1).size_hint(), (20, Some(20)));
2123 assert_eq!((0..20).step_by(21).size_hint(), (1, Some(1)));
2124 assert_eq!((0..20).step_by(5).size_hint(), (4, Some(4)));
2125 assert_eq!((1..21).rev().step_by(5).size_hint(), (4, Some(4)));
2126 assert_eq!((1..21).rev().step_by(6).size_hint(), (4, Some(4)));
2127 assert_eq!((20..-5).step_by(1).size_hint(), (0, Some(0)));
2128 assert_eq!((20..20).step_by(1).size_hint(), (0, Some(0)));
2129 assert_eq!((i8::MIN..i8::MAX).step_by(-(i8::MIN as i32) as usize).size_hint(), (2, Some(2)));
2130 assert_eq!((i16::MIN..i16::MAX).step_by(i16::MAX as usize).size_hint(), (3, Some(3)));
2131 assert_eq!((isize::MIN..isize::MAX).step_by(1).size_hint(), (usize::MAX, Some(usize::MAX)));
2135 fn test_step_by_skip() {
2136 assert_eq!((0..640).step_by(128).skip(1).collect::<Vec<_>>(), [128, 256, 384, 512]);
2137 assert_eq!((0..=50).step_by(10).nth(3), Some(30));
2138 assert_eq!((200..=255u8).step_by(10).nth(3), Some(230));
2142 fn test_range_inclusive_step() {
2143 assert_eq!((0..=50).step_by(10).collect::<Vec<_>>(), [0, 10, 20, 30, 40, 50]);
2144 assert_eq!((0..=5).step_by(1).collect::<Vec<_>>(), [0, 1, 2, 3, 4, 5]);
2145 assert_eq!((200..=255u8).step_by(10).collect::<Vec<_>>(), [200, 210, 220, 230, 240, 250]);
2146 assert_eq!((250..=255u8).step_by(1).collect::<Vec<_>>(), [250, 251, 252, 253, 254, 255]);
2150 fn test_range_last_max() {
2151 assert_eq!((0..20).last(), Some(19));
2152 assert_eq!((-20..0).last(), Some(-1));
2153 assert_eq!((5..5).last(), None);
2155 assert_eq!((0..20).max(), Some(19));
2156 assert_eq!((-20..0).max(), Some(-1));
2157 assert_eq!((5..5).max(), None);
2161 fn test_range_inclusive_last_max() {
2162 assert_eq!((0..=20).last(), Some(20));
2163 assert_eq!((-20..=0).last(), Some(0));
2164 assert_eq!((5..=5).last(), Some(5));
2165 let mut r = 10..=10;
2167 assert_eq!(r.last(), None);
2169 assert_eq!((0..=20).max(), Some(20));
2170 assert_eq!((-20..=0).max(), Some(0));
2171 assert_eq!((5..=5).max(), Some(5));
2172 let mut r = 10..=10;
2174 assert_eq!(r.max(), None);
2178 fn test_range_min() {
2179 assert_eq!((0..20).min(), Some(0));
2180 assert_eq!((-20..0).min(), Some(-20));
2181 assert_eq!((5..5).min(), None);
2185 fn test_range_inclusive_min() {
2186 assert_eq!((0..=20).min(), Some(0));
2187 assert_eq!((-20..=0).min(), Some(-20));
2188 assert_eq!((5..=5).min(), Some(5));
2189 let mut r = 10..=10;
2191 assert_eq!(r.min(), None);
2195 fn test_range_inclusive_folds() {
2196 assert_eq!((1..=10).sum::<i32>(), 55);
2197 assert_eq!((1..=10).rev().sum::<i32>(), 55);
2199 let mut it = 44..=50;
2200 assert_eq!(it.try_fold(0, i8::checked_add), None);
2201 assert_eq!(it, 47..=50);
2202 assert_eq!(it.try_fold(0, i8::checked_add), None);
2203 assert_eq!(it, 50..=50);
2204 assert_eq!(it.try_fold(0, i8::checked_add), Some(50));
2205 assert!(it.is_empty());
2206 assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
2207 assert!(it.is_empty());
2209 let mut it = 40..=47;
2210 assert_eq!(it.try_rfold(0, i8::checked_add), None);
2211 assert_eq!(it, 40..=44);
2212 assert_eq!(it.try_rfold(0, i8::checked_add), None);
2213 assert_eq!(it, 40..=41);
2214 assert_eq!(it.try_rfold(0, i8::checked_add), Some(81));
2215 assert!(it.is_empty());
2216 assert_eq!(it.try_rfold(0, i8::checked_add), Some(0));
2217 assert!(it.is_empty());
2219 let mut it = 10..=20;
2220 assert_eq!(it.try_fold(0, |a, b| Some(a + b)), Some(165));
2221 assert!(it.is_empty());
2222 assert_eq!(it.try_fold(0, |a, b| Some(a + b)), Some(0));
2223 assert!(it.is_empty());
2225 let mut it = 10..=20;
2226 assert_eq!(it.try_rfold(0, |a, b| Some(a + b)), Some(165));
2227 assert!(it.is_empty());
2228 assert_eq!(it.try_rfold(0, |a, b| Some(a + b)), Some(0));
2229 assert!(it.is_empty());
2233 fn test_range_size_hint() {
2234 use core::usize::MAX as UMAX;
2235 assert_eq!((0..0usize).size_hint(), (0, Some(0)));
2236 assert_eq!((0..100usize).size_hint(), (100, Some(100)));
2237 assert_eq!((0..UMAX).size_hint(), (UMAX, Some(UMAX)));
2239 let umax = u128::try_from(UMAX).unwrap();
2240 assert_eq!((0..0u128).size_hint(), (0, Some(0)));
2241 assert_eq!((0..100u128).size_hint(), (100, Some(100)));
2242 assert_eq!((0..umax).size_hint(), (UMAX, Some(UMAX)));
2243 assert_eq!((0..umax + 1).size_hint(), (UMAX, None));
2245 use core::isize::{MAX as IMAX, MIN as IMIN};
2246 assert_eq!((0..0isize).size_hint(), (0, Some(0)));
2247 assert_eq!((-100..100isize).size_hint(), (200, Some(200)));
2248 assert_eq!((IMIN..IMAX).size_hint(), (UMAX, Some(UMAX)));
2250 let imin = i128::try_from(IMIN).unwrap();
2251 let imax = i128::try_from(IMAX).unwrap();
2252 assert_eq!((0..0i128).size_hint(), (0, Some(0)));
2253 assert_eq!((-100..100i128).size_hint(), (200, Some(200)));
2254 assert_eq!((imin..imax).size_hint(), (UMAX, Some(UMAX)));
2255 assert_eq!((imin..imax + 1).size_hint(), (UMAX, None));
2259 fn test_range_inclusive_size_hint() {
2260 use core::usize::MAX as UMAX;
2261 assert_eq!((1..=0usize).size_hint(), (0, Some(0)));
2262 assert_eq!((0..=0usize).size_hint(), (1, Some(1)));
2263 assert_eq!((0..=100usize).size_hint(), (101, Some(101)));
2264 assert_eq!((0..=UMAX - 1).size_hint(), (UMAX, Some(UMAX)));
2265 assert_eq!((0..=UMAX).size_hint(), (UMAX, None));
2267 let umax = u128::try_from(UMAX).unwrap();
2268 assert_eq!((1..=0u128).size_hint(), (0, Some(0)));
2269 assert_eq!((0..=0u128).size_hint(), (1, Some(1)));
2270 assert_eq!((0..=100u128).size_hint(), (101, Some(101)));
2271 assert_eq!((0..=umax - 1).size_hint(), (UMAX, Some(UMAX)));
2272 assert_eq!((0..=umax).size_hint(), (UMAX, None));
2273 assert_eq!((0..=umax + 1).size_hint(), (UMAX, None));
2275 use core::isize::{MAX as IMAX, MIN as IMIN};
2276 assert_eq!((0..=-1isize).size_hint(), (0, Some(0)));
2277 assert_eq!((0..=0isize).size_hint(), (1, Some(1)));
2278 assert_eq!((-100..=100isize).size_hint(), (201, Some(201)));
2279 assert_eq!((IMIN..=IMAX - 1).size_hint(), (UMAX, Some(UMAX)));
2280 assert_eq!((IMIN..=IMAX).size_hint(), (UMAX, None));
2282 let imin = i128::try_from(IMIN).unwrap();
2283 let imax = i128::try_from(IMAX).unwrap();
2284 assert_eq!((0..=-1i128).size_hint(), (0, Some(0)));
2285 assert_eq!((0..=0i128).size_hint(), (1, Some(1)));
2286 assert_eq!((-100..=100i128).size_hint(), (201, Some(201)));
2287 assert_eq!((imin..=imax - 1).size_hint(), (UMAX, Some(UMAX)));
2288 assert_eq!((imin..=imax).size_hint(), (UMAX, None));
2289 assert_eq!((imin..=imax + 1).size_hint(), (UMAX, None));
2294 let mut it = repeat(42);
2295 assert_eq!(it.next(), Some(42));
2296 assert_eq!(it.next(), Some(42));
2297 assert_eq!(it.next(), Some(42));
2298 assert_eq!(repeat(42).size_hint(), (usize::MAX, None));
2302 fn test_repeat_take() {
2303 let mut it = repeat(42).take(3);
2304 assert_eq!(it.next(), Some(42));
2305 assert_eq!(it.next(), Some(42));
2306 assert_eq!(it.next(), Some(42));
2307 assert_eq!(it.next(), None);
2308 is_trusted_len(repeat(42).take(3));
2309 assert_eq!(repeat(42).take(3).size_hint(), (3, Some(3)));
2310 assert_eq!(repeat(42).take(0).size_hint(), (0, Some(0)));
2311 assert_eq!(repeat(42).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
2315 fn test_repeat_take_collect() {
2316 let v: Vec<_> = repeat(42).take(3).collect();
2317 assert_eq!(v, vec![42, 42, 42]);
2321 fn test_repeat_with() {
2322 #[derive(PartialEq, Debug)]
2323 struct NotClone(usize);
2324 let mut it = repeat_with(|| NotClone(42));
2325 assert_eq!(it.next(), Some(NotClone(42)));
2326 assert_eq!(it.next(), Some(NotClone(42)));
2327 assert_eq!(it.next(), Some(NotClone(42)));
2328 assert_eq!(repeat_with(|| NotClone(42)).size_hint(), (usize::MAX, None));
2332 fn test_repeat_with_take() {
2333 let mut it = repeat_with(|| 42).take(3);
2334 assert_eq!(it.next(), Some(42));
2335 assert_eq!(it.next(), Some(42));
2336 assert_eq!(it.next(), Some(42));
2337 assert_eq!(it.next(), None);
2338 is_trusted_len(repeat_with(|| 42).take(3));
2339 assert_eq!(repeat_with(|| 42).take(3).size_hint(), (3, Some(3)));
2340 assert_eq!(repeat_with(|| 42).take(0).size_hint(), (0, Some(0)));
2341 assert_eq!(repeat_with(|| 42).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
2345 fn test_repeat_with_take_collect() {
2347 let v: Vec<_> = repeat_with(|| {
2354 assert_eq!(v, vec![1, 2, 4, 8, 16]);
2358 fn test_successors() {
2359 let mut powers_of_10 = successors(Some(1_u16), |n| n.checked_mul(10));
2360 assert_eq!(powers_of_10.by_ref().collect::<Vec<_>>(), &[1, 10, 100, 1_000, 10_000]);
2361 assert_eq!(powers_of_10.next(), None);
2363 let mut empty = successors(None::<u32>, |_| unimplemented!());
2364 assert_eq!(empty.next(), None);
2365 assert_eq!(empty.next(), None);
2371 assert_eq!(it.len(), 3);
2372 assert_eq!(it.next(), Some(0));
2373 assert_eq!(it.len(), 2);
2374 assert_eq!(it.next(), Some(1));
2375 assert_eq!(it.len(), 1);
2376 assert_eq!(it.next(), Some(2));
2377 assert_eq!(it.len(), 0);
2378 assert_eq!(it.next(), None);
2379 assert_eq!(it.len(), 0);
2380 assert_eq!(it.next(), None);
2381 assert_eq!(it.len(), 0);
2382 assert_eq!(it.next(), None);
2383 assert_eq!(it.len(), 0);
2387 fn test_fuse_nth() {
2389 let mut it = xs.iter();
2391 assert_eq!(it.len(), 3);
2392 assert_eq!(it.nth(2), Some(&2));
2393 assert_eq!(it.len(), 0);
2394 assert_eq!(it.nth(2), None);
2395 assert_eq!(it.len(), 0);
2399 fn test_fuse_last() {
2403 assert_eq!(it.len(), 3);
2404 assert_eq!(it.last(), Some(&2));
2408 fn test_fuse_count() {
2412 assert_eq!(it.len(), 3);
2413 assert_eq!(it.count(), 3);
2414 // Can't check len now because count consumes.
2418 fn test_fuse_fold() {
2420 let it = xs.iter(); // `FusedIterator`
2421 let i = it.fuse().fold(0, |i, &x| {
2422 assert_eq!(x, xs[i]);
2425 assert_eq!(i, xs.len());
2427 let it = xs.iter(); // `FusedIterator`
2428 let i = it.fuse().rfold(xs.len(), |i, &x| {
2429 assert_eq!(x, xs[i - 1]);
2434 let it = xs.iter().scan((), |_, &x| Some(x)); // `!FusedIterator`
2435 let i = it.fuse().fold(0, |i, x| {
2436 assert_eq!(x, xs[i]);
2439 assert_eq!(i, xs.len());
2444 let mut it = once(42);
2445 assert_eq!(it.next(), Some(42));
2446 assert_eq!(it.next(), None);
2450 fn test_once_with() {
2451 let count = Cell::new(0);
2452 let mut it = once_with(|| {
2453 count.set(count.get() + 1);
2457 assert_eq!(count.get(), 0);
2458 assert_eq!(it.next(), Some(42));
2459 assert_eq!(count.get(), 1);
2460 assert_eq!(it.next(), None);
2461 assert_eq!(count.get(), 1);
2462 assert_eq!(it.next(), None);
2463 assert_eq!(count.get(), 1);
2468 let mut it = empty::<i32>();
2469 assert_eq!(it.next(), None);
2473 fn test_chain_fold() {
2477 let mut iter = xs.iter().chain(&ys);
2479 let mut result = Vec::new();
2480 iter.fold((), |(), &elt| result.push(elt));
2481 assert_eq!(&[2, 3, 1, 2, 0], &result[..]);
2485 fn test_step_replace_unsigned() {
2487 let y = x.replace_zero();
2492 let y = x.replace_one();
2498 fn test_step_replace_signed() {
2500 let y = x.replace_zero();
2505 let y = x.replace_one();
2511 fn test_step_replace_no_between() {
2513 let y = x.replace_zero();
2518 let y = x.replace_one();
2524 fn test_rev_try_folds() {
2525 let f = &|acc, x| i32::checked_add(2 * acc, x);
2526 assert_eq!((1..10).rev().try_fold(7, f), (1..10).try_rfold(7, f));
2527 assert_eq!((1..10).rev().try_rfold(7, f), (1..10).try_fold(7, f));
2529 let a = [10, 20, 30, 40, 100, 60, 70, 80, 90];
2530 let mut iter = a.iter().rev();
2531 assert_eq!(iter.try_fold(0_i8, |acc, &x| acc.checked_add(x)), None);
2532 assert_eq!(iter.next(), Some(&70));
2533 let mut iter = a.iter().rev();
2534 assert_eq!(iter.try_rfold(0_i8, |acc, &x| acc.checked_add(x)), None);
2535 assert_eq!(iter.next_back(), Some(&60));
2539 fn test_cloned_try_folds() {
2540 let a = [1, 2, 3, 4, 5, 6, 7, 8, 9];
2541 let f = &|acc, x| i32::checked_add(2 * acc, x);
2542 let f_ref = &|acc, &x| i32::checked_add(2 * acc, x);
2543 assert_eq!(a.iter().cloned().try_fold(7, f), a.iter().try_fold(7, f_ref));
2544 assert_eq!(a.iter().cloned().try_rfold(7, f), a.iter().try_rfold(7, f_ref));
2546 let a = [10, 20, 30, 40, 100, 60, 70, 80, 90];
2547 let mut iter = a.iter().cloned();
2548 assert_eq!(iter.try_fold(0_i8, |acc, x| acc.checked_add(x)), None);
2549 assert_eq!(iter.next(), Some(60));
2550 let mut iter = a.iter().cloned();
2551 assert_eq!(iter.try_rfold(0_i8, |acc, x| acc.checked_add(x)), None);
2552 assert_eq!(iter.next_back(), Some(70));
2556 fn test_chain_try_folds() {
2557 let c = || (0..10).chain(10..20);
2559 let f = &|acc, x| i32::checked_add(2 * acc, x);
2560 assert_eq!(c().try_fold(7, f), (0..20).try_fold(7, f));
2561 assert_eq!(c().try_rfold(7, f), (0..20).rev().try_fold(7, f));
2564 assert_eq!(iter.position(|x| x == 5), Some(5));
2565 assert_eq!(iter.next(), Some(6), "stopped in front, state Both");
2566 assert_eq!(iter.position(|x| x == 13), Some(6));
2567 assert_eq!(iter.next(), Some(14), "stopped in back, state Back");
2568 assert_eq!(iter.try_fold(0, |acc, x| Some(acc + x)), Some((15..20).sum()));
2570 let mut iter = c().rev(); // use rev to access try_rfold
2571 assert_eq!(iter.position(|x| x == 15), Some(4));
2572 assert_eq!(iter.next(), Some(14), "stopped in back, state Both");
2573 assert_eq!(iter.position(|x| x == 5), Some(8));
2574 assert_eq!(iter.next(), Some(4), "stopped in front, state Front");
2575 assert_eq!(iter.try_fold(0, |acc, x| Some(acc + x)), Some((0..4).sum()));
2578 iter.by_ref().rev().nth(14); // skip the last 15, ending in state Front
2579 assert_eq!(iter.try_fold(7, f), (0..5).try_fold(7, f));
2582 iter.nth(14); // skip the first 15, ending in state Back
2583 assert_eq!(iter.try_rfold(7, f), (15..20).try_rfold(7, f));
2587 fn test_map_try_folds() {
2588 let f = &|acc, x| i32::checked_add(2 * acc, x);
2589 assert_eq!((0..10).map(|x| x + 3).try_fold(7, f), (3..13).try_fold(7, f));
2590 assert_eq!((0..10).map(|x| x + 3).try_rfold(7, f), (3..13).try_rfold(7, f));
2592 let mut iter = (0..40).map(|x| x + 10);
2593 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2594 assert_eq!(iter.next(), Some(20));
2595 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2596 assert_eq!(iter.next_back(), Some(46));
2600 fn test_filter_try_folds() {
2601 fn p(&x: &i32) -> bool {
2604 let f = &|acc, x| i32::checked_add(2 * acc, x);
2605 assert_eq!((-10..20).filter(p).try_fold(7, f), (0..10).try_fold(7, f));
2606 assert_eq!((-10..20).filter(p).try_rfold(7, f), (0..10).try_rfold(7, f));
2608 let mut iter = (0..40).filter(|&x| x % 2 == 1);
2609 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2610 assert_eq!(iter.next(), Some(25));
2611 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2612 assert_eq!(iter.next_back(), Some(31));
2616 fn test_filter_map_try_folds() {
2617 let mp = &|x| if 0 <= x && x < 10 { Some(x * 2) } else { None };
2618 let f = &|acc, x| i32::checked_add(2 * acc, x);
2619 assert_eq!((-9..20).filter_map(mp).try_fold(7, f), (0..10).map(|x| 2 * x).try_fold(7, f));
2620 assert_eq!((-9..20).filter_map(mp).try_rfold(7, f), (0..10).map(|x| 2 * x).try_rfold(7, f));
2622 let mut iter = (0..40).filter_map(|x| if x % 2 == 1 { None } else { Some(x * 2 + 10) });
2623 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2624 assert_eq!(iter.next(), Some(38));
2625 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2626 assert_eq!(iter.next_back(), Some(78));
2630 fn test_enumerate_try_folds() {
2631 let f = &|acc, (i, x)| usize::checked_add(2 * acc, x / (i + 1) + i);
2632 assert_eq!((9..18).enumerate().try_fold(7, f), (0..9).map(|i| (i, i + 9)).try_fold(7, f));
2633 assert_eq!((9..18).enumerate().try_rfold(7, f), (0..9).map(|i| (i, i + 9)).try_rfold(7, f));
2635 let mut iter = (100..200).enumerate();
2636 let f = &|acc, (i, x)| u8::checked_add(acc, u8::checked_div(x, i as u8 + 1)?);
2637 assert_eq!(iter.try_fold(0, f), None);
2638 assert_eq!(iter.next(), Some((7, 107)));
2639 assert_eq!(iter.try_rfold(0, f), None);
2640 assert_eq!(iter.next_back(), Some((11, 111)));
2644 fn test_peek_try_folds() {
2645 let f = &|acc, x| i32::checked_add(2 * acc, x);
2647 assert_eq!((1..20).peekable().try_fold(7, f), (1..20).try_fold(7, f));
2648 assert_eq!((1..20).peekable().try_rfold(7, f), (1..20).try_rfold(7, f));
2650 let mut iter = (1..20).peekable();
2651 assert_eq!(iter.peek(), Some(&1));
2652 assert_eq!(iter.try_fold(7, f), (1..20).try_fold(7, f));
2654 let mut iter = (1..20).peekable();
2655 assert_eq!(iter.peek(), Some(&1));
2656 assert_eq!(iter.try_rfold(7, f), (1..20).try_rfold(7, f));
2658 let mut iter = [100, 20, 30, 40, 50, 60, 70].iter().cloned().peekable();
2659 assert_eq!(iter.peek(), Some(&100));
2660 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2661 assert_eq!(iter.peek(), Some(&40));
2663 let mut iter = [100, 20, 30, 40, 50, 60, 70].iter().cloned().peekable();
2664 assert_eq!(iter.peek(), Some(&100));
2665 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2666 assert_eq!(iter.peek(), Some(&100));
2667 assert_eq!(iter.next_back(), Some(50));
2669 let mut iter = (2..5).peekable();
2670 assert_eq!(iter.peek(), Some(&2));
2671 assert_eq!(iter.try_for_each(Err), Err(2));
2672 assert_eq!(iter.peek(), Some(&3));
2673 assert_eq!(iter.try_for_each(Err), Err(3));
2674 assert_eq!(iter.peek(), Some(&4));
2675 assert_eq!(iter.try_for_each(Err), Err(4));
2676 assert_eq!(iter.peek(), None);
2677 assert_eq!(iter.try_for_each(Err), Ok(()));
2679 let mut iter = (2..5).peekable();
2680 assert_eq!(iter.peek(), Some(&2));
2681 assert_eq!(iter.try_rfold((), |(), x| Err(x)), Err(4));
2682 assert_eq!(iter.peek(), Some(&2));
2683 assert_eq!(iter.try_rfold((), |(), x| Err(x)), Err(3));
2684 assert_eq!(iter.peek(), Some(&2));
2685 assert_eq!(iter.try_rfold((), |(), x| Err(x)), Err(2));
2686 assert_eq!(iter.peek(), None);
2687 assert_eq!(iter.try_rfold((), |(), x| Err(x)), Ok(()));
2691 fn test_skip_while_try_fold() {
2692 let f = &|acc, x| i32::checked_add(2 * acc, x);
2693 fn p(&x: &i32) -> bool {
2696 assert_eq!((1..20).skip_while(p).try_fold(7, f), (6..20).try_fold(7, f));
2697 let mut iter = (1..20).skip_while(p);
2698 assert_eq!(iter.nth(5), Some(11));
2699 assert_eq!(iter.try_fold(7, f), (12..20).try_fold(7, f));
2701 let mut iter = (0..50).skip_while(|&x| (x % 20) < 15);
2702 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2703 assert_eq!(iter.next(), Some(23));
2707 fn test_take_while_folds() {
2708 let f = &|acc, x| i32::checked_add(2 * acc, x);
2709 assert_eq!((1..20).take_while(|&x| x != 10).try_fold(7, f), (1..10).try_fold(7, f));
2710 let mut iter = (1..20).take_while(|&x| x != 10);
2711 assert_eq!(iter.try_fold(0, |x, y| Some(x + y)), Some((1..10).sum()));
2712 assert_eq!(iter.next(), None, "flag should be set");
2713 let iter = (1..20).take_while(|&x| x != 10);
2714 assert_eq!(iter.fold(0, |x, y| x + y), (1..10).sum());
2716 let mut iter = (10..50).take_while(|&x| x != 40);
2717 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2718 assert_eq!(iter.next(), Some(20));
2722 fn test_skip_try_folds() {
2723 let f = &|acc, x| i32::checked_add(2 * acc, x);
2724 assert_eq!((1..20).skip(9).try_fold(7, f), (10..20).try_fold(7, f));
2725 assert_eq!((1..20).skip(9).try_rfold(7, f), (10..20).try_rfold(7, f));
2727 let mut iter = (0..30).skip(10);
2728 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2729 assert_eq!(iter.next(), Some(20));
2730 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2731 assert_eq!(iter.next_back(), Some(24));
2735 fn test_skip_nth_back() {
2736 let xs = [0, 1, 2, 3, 4, 5];
2737 let mut it = xs.iter().skip(2);
2738 assert_eq!(it.nth_back(0), Some(&5));
2739 assert_eq!(it.nth_back(1), Some(&3));
2740 assert_eq!(it.nth_back(0), Some(&2));
2741 assert_eq!(it.nth_back(0), None);
2743 let ys = [2, 3, 4, 5];
2744 let mut ity = ys.iter();
2745 let mut it = xs.iter().skip(2);
2746 assert_eq!(it.nth_back(1), ity.nth_back(1));
2747 assert_eq!(it.clone().nth(0), ity.clone().nth(0));
2748 assert_eq!(it.nth_back(0), ity.nth_back(0));
2749 assert_eq!(it.clone().nth(0), ity.clone().nth(0));
2750 assert_eq!(it.nth_back(0), ity.nth_back(0));
2751 assert_eq!(it.clone().nth(0), ity.clone().nth(0));
2752 assert_eq!(it.nth_back(0), ity.nth_back(0));
2753 assert_eq!(it.clone().nth(0), ity.clone().nth(0));
2755 let mut it = xs.iter().skip(2);
2756 assert_eq!(it.nth_back(4), None);
2757 assert_eq!(it.nth_back(0), None);
2759 let mut it = xs.iter();
2760 it.by_ref().skip(2).nth_back(3);
2761 assert_eq!(it.next_back(), Some(&1));
2763 let mut it = xs.iter();
2764 it.by_ref().skip(2).nth_back(10);
2765 assert_eq!(it.next_back(), Some(&1));
2769 fn test_take_try_folds() {
2770 let f = &|acc, x| i32::checked_add(2 * acc, x);
2771 assert_eq!((10..30).take(10).try_fold(7, f), (10..20).try_fold(7, f));
2772 assert_eq!((10..30).take(10).try_rfold(7, f), (10..20).try_rfold(7, f));
2774 let mut iter = (10..30).take(20);
2775 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2776 assert_eq!(iter.next(), Some(20));
2777 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2778 assert_eq!(iter.next_back(), Some(24));
2780 let mut iter = (2..20).take(3);
2781 assert_eq!(iter.try_for_each(Err), Err(2));
2782 assert_eq!(iter.try_for_each(Err), Err(3));
2783 assert_eq!(iter.try_for_each(Err), Err(4));
2784 assert_eq!(iter.try_for_each(Err), Ok(()));
2786 let mut iter = (2..20).take(3).rev();
2787 assert_eq!(iter.try_for_each(Err), Err(4));
2788 assert_eq!(iter.try_for_each(Err), Err(3));
2789 assert_eq!(iter.try_for_each(Err), Err(2));
2790 assert_eq!(iter.try_for_each(Err), Ok(()));
2794 fn test_flat_map_try_folds() {
2795 let f = &|acc, x| i32::checked_add(acc * 2 / 3, x);
2796 let mr = &|x| (5 * x)..(5 * x + 5);
2797 assert_eq!((0..10).flat_map(mr).try_fold(7, f), (0..50).try_fold(7, f));
2798 assert_eq!((0..10).flat_map(mr).try_rfold(7, f), (0..50).try_rfold(7, f));
2799 let mut iter = (0..10).flat_map(mr);
2801 iter.next_back(); // have front and back iters in progress
2802 assert_eq!(iter.try_rfold(7, f), (1..49).try_rfold(7, f));
2804 let mut iter = (0..10).flat_map(|x| (4 * x)..(4 * x + 4));
2805 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2806 assert_eq!(iter.next(), Some(17));
2807 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2808 assert_eq!(iter.next_back(), Some(35));
2812 fn test_flatten_try_folds() {
2813 let f = &|acc, x| i32::checked_add(acc * 2 / 3, x);
2814 let mr = &|x| (5 * x)..(5 * x + 5);
2815 assert_eq!((0..10).map(mr).flatten().try_fold(7, f), (0..50).try_fold(7, f));
2816 assert_eq!((0..10).map(mr).flatten().try_rfold(7, f), (0..50).try_rfold(7, f));
2817 let mut iter = (0..10).map(mr).flatten();
2819 iter.next_back(); // have front and back iters in progress
2820 assert_eq!(iter.try_rfold(7, f), (1..49).try_rfold(7, f));
2822 let mut iter = (0..10).map(|x| (4 * x)..(4 * x + 4)).flatten();
2823 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2824 assert_eq!(iter.next(), Some(17));
2825 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2826 assert_eq!(iter.next_back(), Some(35));
2830 fn test_functor_laws() {
2832 fn identity<T>(x: T) -> T {
2835 assert_eq!((0..10).map(identity).sum::<usize>(), (0..10).sum());
2838 fn f(x: usize) -> usize {
2841 fn g(x: usize) -> usize {
2844 fn h(x: usize) -> usize {
2847 assert_eq!((0..10).map(f).map(g).sum::<usize>(), (0..10).map(h).sum());
2851 fn test_monad_laws_left_identity() {
2852 fn f(x: usize) -> impl Iterator<Item = usize> {
2853 (0..10).map(move |y| x * y)
2855 assert_eq!(once(42).flat_map(f.clone()).sum::<usize>(), f(42).sum());
2859 fn test_monad_laws_right_identity() {
2860 assert_eq!((0..10).flat_map(|x| once(x)).sum::<usize>(), (0..10).sum());
2864 fn test_monad_laws_associativity() {
2865 fn f(x: usize) -> impl Iterator<Item = usize> {
2868 fn g(x: usize) -> impl Iterator<Item = usize> {
2872 (0..10).flat_map(f).flat_map(g).sum::<usize>(),
2873 (0..10).flat_map(|x| f(x).flat_map(g)).sum::<usize>()
2878 fn test_is_sorted() {
2879 assert!([1, 2, 2, 9].iter().is_sorted());
2880 assert!(![1, 3, 2].iter().is_sorted());
2881 assert!([0].iter().is_sorted());
2882 assert!(std::iter::empty::<i32>().is_sorted());
2883 assert!(![0.0, 1.0, std::f32::NAN].iter().is_sorted());
2884 assert!([-2, -1, 0, 3].iter().is_sorted());
2885 assert!(![-2i32, -1, 0, 3].iter().is_sorted_by_key(|n| n.abs()));
2886 assert!(!["c", "bb", "aaa"].iter().is_sorted());
2887 assert!(["c", "bb", "aaa"].iter().is_sorted_by_key(|s| s.len()));
2891 fn test_partition() {
2892 fn check(xs: &mut [i32], ref p: impl Fn(&i32) -> bool, expected: usize) {
2893 let i = xs.iter_mut().partition_in_place(p);
2894 assert_eq!(expected, i);
2895 assert!(xs[..i].iter().all(p));
2896 assert!(!xs[i..].iter().any(p));
2897 assert!(xs.iter().is_partitioned(p));
2898 if i == 0 || i == xs.len() {
2899 assert!(xs.iter().rev().is_partitioned(p));
2901 assert!(!xs.iter().rev().is_partitioned(p));
2905 check(&mut [], |_| true, 0);
2906 check(&mut [], |_| false, 0);
2908 check(&mut [0], |_| true, 1);
2909 check(&mut [0], |_| false, 0);
2911 check(&mut [-1, 1], |&x| x > 0, 1);
2912 check(&mut [-1, 1], |&x| x < 0, 1);
2914 let ref mut xs = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
2915 check(xs, |_| true, 10);
2916 check(xs, |_| false, 0);
2917 check(xs, |&x| x % 2 == 0, 5); // evens
2918 check(xs, |&x| x % 2 == 1, 5); // odds
2919 check(xs, |&x| x % 3 == 0, 4); // multiple of 3
2920 check(xs, |&x| x % 4 == 0, 3); // multiple of 4
2921 check(xs, |&x| x % 5 == 0, 2); // multiple of 5
2922 check(xs, |&x| x < 3, 3); // small
2923 check(xs, |&x| x > 6, 3); // large