2 use core::convert::TryFrom;
4 use core::{i8, i16, 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()));
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() {
56 assert!(xs.iter().eq(ys.iter().rev()));
57 assert!(xs.iter().lt(xs.iter().skip(2)));
61 fn test_counter_from_iter() {
62 let it = (0..).step_by(5).take(10);
63 let xs: Vec<isize> = FromIterator::from_iter(it);
64 assert_eq!(xs, [0, 5, 10, 15, 20, 25, 30, 35, 40, 45]);
68 fn test_iterator_chain() {
69 let xs = [0, 1, 2, 3, 4, 5];
70 let ys = [30, 40, 50, 60];
71 let expected = [0, 1, 2, 3, 4, 5, 30, 40, 50, 60];
72 let it = xs.iter().chain(&ys);
75 assert_eq!(x, expected[i]);
78 assert_eq!(i, expected.len());
80 let ys = (30..).step_by(10).take(4);
81 let it = xs.iter().cloned().chain(ys);
84 assert_eq!(x, expected[i]);
87 assert_eq!(i, expected.len());
91 fn test_iterator_chain_nth() {
92 let xs = [0, 1, 2, 3, 4, 5];
93 let ys = [30, 40, 50, 60];
95 let expected = [0, 1, 2, 3, 4, 5, 30, 40, 50, 60];
96 for (i, x) in expected.iter().enumerate() {
97 assert_eq!(Some(x), xs.iter().chain(&ys).nth(i));
99 assert_eq!(zs.iter().chain(&xs).nth(0), Some(&0));
101 let mut it = xs.iter().chain(&zs);
102 assert_eq!(it.nth(5), Some(&5));
103 assert_eq!(it.next(), None);
107 fn test_iterator_chain_last() {
108 let xs = [0, 1, 2, 3, 4, 5];
109 let ys = [30, 40, 50, 60];
111 assert_eq!(xs.iter().chain(&ys).last(), Some(&60));
112 assert_eq!(zs.iter().chain(&ys).last(), Some(&60));
113 assert_eq!(ys.iter().chain(&zs).last(), Some(&60));
114 assert_eq!(zs.iter().chain(&zs).last(), None);
118 fn test_iterator_chain_count() {
119 let xs = [0, 1, 2, 3, 4, 5];
120 let ys = [30, 40, 50, 60];
122 assert_eq!(xs.iter().chain(&ys).count(), 10);
123 assert_eq!(zs.iter().chain(&ys).count(), 4);
127 fn test_iterator_chain_find() {
128 let xs = [0, 1, 2, 3, 4, 5];
129 let ys = [30, 40, 50, 60];
130 let mut iter = xs.iter().chain(&ys);
131 assert_eq!(iter.find(|&&i| i == 4), Some(&4));
132 assert_eq!(iter.next(), Some(&5));
133 assert_eq!(iter.find(|&&i| i == 40), Some(&40));
134 assert_eq!(iter.next(), Some(&50));
135 assert_eq!(iter.find(|&&i| i == 100), None);
136 assert_eq!(iter.next(), None);
141 let xs = [0, 1, 2, 4, 5];
142 let ys = [10, 11, 12];
144 let mut it = xs.iter().zip(&ys);
145 assert_eq!(it.nth(0), Some((&0, &10)));
146 assert_eq!(it.nth(1), Some((&2, &12)));
147 assert_eq!(it.nth(0), None);
149 let mut it = xs.iter().zip(&ys);
150 assert_eq!(it.nth(3), None);
152 let mut it = ys.iter().zip(&xs);
153 assert_eq!(it.nth(3), None);
157 fn test_zip_nth_side_effects() {
158 let mut a = Vec::new();
159 let mut b = Vec::new();
160 let value = [1, 2, 3, 4, 5, 6].iter().cloned()
165 .zip([2, 3, 4, 5, 6, 7, 8].iter().cloned().map(|n| {
171 assert_eq!(value, Some((50, 6000)));
172 assert_eq!(a, vec![1, 2, 3, 4, 5]);
173 assert_eq!(b, vec![200, 300, 400, 500, 600]);
177 fn test_iterator_step_by() {
179 let mut it = (0..).step_by(1).take(3);
180 assert_eq!(it.next(), Some(0));
181 assert_eq!(it.next(), Some(1));
182 assert_eq!(it.next(), Some(2));
183 assert_eq!(it.next(), None);
185 let mut it = (0..).step_by(3).take(4);
186 assert_eq!(it.next(), Some(0));
187 assert_eq!(it.next(), Some(3));
188 assert_eq!(it.next(), Some(6));
189 assert_eq!(it.next(), Some(9));
190 assert_eq!(it.next(), None);
194 fn test_iterator_step_by_nth() {
195 let mut it = (0..16).step_by(5);
196 assert_eq!(it.nth(0), Some(0));
197 assert_eq!(it.nth(0), Some(5));
198 assert_eq!(it.nth(0), Some(10));
199 assert_eq!(it.nth(0), Some(15));
200 assert_eq!(it.nth(0), None);
202 let it = (0..18).step_by(5);
203 assert_eq!(it.clone().nth(0), Some(0));
204 assert_eq!(it.clone().nth(1), Some(5));
205 assert_eq!(it.clone().nth(2), Some(10));
206 assert_eq!(it.clone().nth(3), Some(15));
207 assert_eq!(it.clone().nth(4), None);
208 assert_eq!(it.clone().nth(42), None);
212 fn test_iterator_step_by_nth_overflow() {
213 #[cfg(target_pointer_width = "8")]
215 #[cfg(target_pointer_width = "16")]
217 #[cfg(target_pointer_width = "32")]
219 #[cfg(target_pointer_width = "64")]
224 impl Iterator for &mut Test {
226 fn next(&mut self) -> Option<Self::Item> { Some(21) }
227 fn nth(&mut self, n: usize) -> Option<Self::Item> {
228 self.0 += n as Bigger + 1;
233 let mut it = Test(0);
234 let root = usize::MAX >> (::std::mem::size_of::<usize>() * 8 / 2);
236 (&mut it).step_by(n).nth(n);
237 assert_eq!(it.0, n as Bigger * n as Bigger);
240 let mut it = Test(0);
241 (&mut it).step_by(usize::MAX).nth(5);
242 assert_eq!(it.0, (usize::MAX as Bigger) * 5);
245 let mut it = Test(0);
246 (&mut it).step_by(2).nth(usize::MAX);
247 assert_eq!(it.0, (usize::MAX as Bigger) * 2);
250 let mut it = Test(0);
251 (&mut it).step_by(1).nth(usize::MAX);
252 assert_eq!(it.0, (usize::MAX as Bigger) * 1);
257 fn test_iterator_step_by_zero() {
258 let mut it = (0..).step_by(0);
263 fn test_iterator_step_by_size_hint() {
264 struct StubSizeHint(usize, Option<usize>);
265 impl Iterator for StubSizeHint {
267 fn next(&mut self) -> Option<()> {
269 if let Some(ref mut upper) = self.1 {
274 fn size_hint(&self) -> (usize, Option<usize>) {
279 // The two checks in each case are needed because the logic
280 // is different before the first call to `next()`.
282 let mut it = StubSizeHint(10, Some(10)).step_by(1);
283 assert_eq!(it.size_hint(), (10, Some(10)));
285 assert_eq!(it.size_hint(), (9, Some(9)));
288 let mut it = StubSizeHint(10, Some(10)).step_by(3);
289 assert_eq!(it.size_hint(), (4, Some(4)));
291 assert_eq!(it.size_hint(), (3, Some(3)));
293 // larger base range, but not enough to get another element
294 let mut it = StubSizeHint(12, Some(12)).step_by(3);
295 assert_eq!(it.size_hint(), (4, Some(4)));
297 assert_eq!(it.size_hint(), (3, Some(3)));
299 // smaller base range, so fewer resulting elements
300 let mut it = StubSizeHint(9, Some(9)).step_by(3);
301 assert_eq!(it.size_hint(), (3, Some(3)));
303 assert_eq!(it.size_hint(), (2, Some(2)));
305 // infinite upper bound
306 let mut it = StubSizeHint(usize::MAX, None).step_by(1);
307 assert_eq!(it.size_hint(), (usize::MAX, None));
309 assert_eq!(it.size_hint(), (usize::MAX-1, None));
311 // still infinite with larger step
312 let mut it = StubSizeHint(7, None).step_by(3);
313 assert_eq!(it.size_hint(), (3, None));
315 assert_eq!(it.size_hint(), (2, None));
317 // propagates ExactSizeIterator
319 let it = a.iter().step_by(2);
320 assert_eq!(it.len(), 3);
322 // Cannot be TrustedLen as a step greater than one makes an iterator
323 // with (usize::MAX, None) no longer meet the safety requirements
324 trait TrustedLenCheck { fn test(self) -> bool; }
325 impl<T:Iterator> TrustedLenCheck for T {
326 default fn test(self) -> bool { false }
328 impl<T:TrustedLen> TrustedLenCheck for T {
329 fn test(self) -> bool { true }
331 assert!(TrustedLenCheck::test(a.iter()));
332 assert!(!TrustedLenCheck::test(a.iter().step_by(1)));
336 fn test_filter_map() {
337 let it = (0..).step_by(1).take(10)
338 .filter_map(|x| if x % 2 == 0 { Some(x*x) } else { None });
339 assert_eq!(it.collect::<Vec<usize>>(), [0*0, 2*2, 4*4, 6*6, 8*8]);
343 fn test_filter_map_fold() {
344 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
345 let ys = [0*0, 2*2, 4*4, 6*6, 8*8];
346 let it = xs.iter().filter_map(|&x| if x % 2 == 0 { Some(x*x) } else { None });
347 let i = it.fold(0, |i, x| {
348 assert_eq!(x, ys[i]);
351 assert_eq!(i, ys.len());
353 let it = xs.iter().filter_map(|&x| if x % 2 == 0 { Some(x*x) } else { None });
354 let i = it.rfold(ys.len(), |i, x| {
355 assert_eq!(x, ys[i - 1]);
362 fn test_iterator_enumerate() {
363 let xs = [0, 1, 2, 3, 4, 5];
364 let it = xs.iter().enumerate();
371 fn test_iterator_enumerate_nth() {
372 let xs = [0, 1, 2, 3, 4, 5];
373 for (i, &x) in xs.iter().enumerate() {
377 let mut it = xs.iter().enumerate();
378 while let Some((i, &x)) = it.nth(0) {
382 let mut it = xs.iter().enumerate();
383 while let Some((i, &x)) = it.nth(1) {
387 let (i, &x) = xs.iter().enumerate().nth(3).unwrap();
393 fn test_iterator_enumerate_nth_back() {
394 let xs = [0, 1, 2, 3, 4, 5];
395 let mut it = xs.iter().enumerate();
396 while let Some((i, &x)) = it.nth_back(0) {
400 let mut it = xs.iter().enumerate();
401 while let Some((i, &x)) = it.nth_back(1) {
405 let (i, &x) = xs.iter().enumerate().nth_back(3).unwrap();
411 fn test_iterator_enumerate_count() {
412 let xs = [0, 1, 2, 3, 4, 5];
413 assert_eq!(xs.iter().enumerate().count(), 6);
417 fn test_iterator_enumerate_fold() {
418 let xs = [0, 1, 2, 3, 4, 5];
419 let mut it = xs.iter().enumerate();
420 // steal a couple to get an interesting offset
421 assert_eq!(it.next(), Some((0, &0)));
422 assert_eq!(it.next(), Some((1, &1)));
423 let i = it.fold(2, |i, (j, &x)| {
425 assert_eq!(x, xs[j]);
428 assert_eq!(i, xs.len());
430 let mut it = xs.iter().enumerate();
431 assert_eq!(it.next(), Some((0, &0)));
432 let i = it.rfold(xs.len() - 1, |i, (j, &x)| {
434 assert_eq!(x, xs[j]);
441 fn test_iterator_filter_count() {
442 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
443 assert_eq!(xs.iter().filter(|&&x| x % 2 == 0).count(), 5);
447 fn test_iterator_filter_fold() {
448 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
449 let ys = [0, 2, 4, 6, 8];
450 let it = xs.iter().filter(|&&x| x % 2 == 0);
451 let i = it.fold(0, |i, &x| {
452 assert_eq!(x, ys[i]);
455 assert_eq!(i, ys.len());
457 let it = xs.iter().filter(|&&x| x % 2 == 0);
458 let i = it.rfold(ys.len(), |i, &x| {
459 assert_eq!(x, ys[i - 1]);
466 fn test_iterator_peekable() {
467 let xs = vec![0, 1, 2, 3, 4, 5];
468 let mut it = xs.iter().cloned().peekable();
470 assert_eq!(it.len(), 6);
471 assert_eq!(it.peek().unwrap(), &0);
472 assert_eq!(it.len(), 6);
473 assert_eq!(it.next().unwrap(), 0);
474 assert_eq!(it.len(), 5);
475 assert_eq!(it.next().unwrap(), 1);
476 assert_eq!(it.len(), 4);
477 assert_eq!(it.next().unwrap(), 2);
478 assert_eq!(it.len(), 3);
479 assert_eq!(it.peek().unwrap(), &3);
480 assert_eq!(it.len(), 3);
481 assert_eq!(it.peek().unwrap(), &3);
482 assert_eq!(it.len(), 3);
483 assert_eq!(it.next().unwrap(), 3);
484 assert_eq!(it.len(), 2);
485 assert_eq!(it.next().unwrap(), 4);
486 assert_eq!(it.len(), 1);
487 assert_eq!(it.peek().unwrap(), &5);
488 assert_eq!(it.len(), 1);
489 assert_eq!(it.next().unwrap(), 5);
490 assert_eq!(it.len(), 0);
491 assert!(it.peek().is_none());
492 assert_eq!(it.len(), 0);
493 assert!(it.next().is_none());
494 assert_eq!(it.len(), 0);
498 fn test_iterator_peekable_count() {
499 let xs = [0, 1, 2, 3, 4, 5];
501 let zs: [i32; 0] = [];
503 assert_eq!(xs.iter().peekable().count(), 6);
505 let mut it = xs.iter().peekable();
506 assert_eq!(it.peek(), Some(&&0));
507 assert_eq!(it.count(), 6);
509 assert_eq!(ys.iter().peekable().count(), 1);
511 let mut it = ys.iter().peekable();
512 assert_eq!(it.peek(), Some(&&10));
513 assert_eq!(it.count(), 1);
515 assert_eq!(zs.iter().peekable().count(), 0);
517 let mut it = zs.iter().peekable();
518 assert_eq!(it.peek(), None);
523 fn test_iterator_peekable_nth() {
524 let xs = [0, 1, 2, 3, 4, 5];
525 let mut it = xs.iter().peekable();
527 assert_eq!(it.peek(), Some(&&0));
528 assert_eq!(it.nth(0), Some(&0));
529 assert_eq!(it.peek(), Some(&&1));
530 assert_eq!(it.nth(1), Some(&2));
531 assert_eq!(it.peek(), Some(&&3));
532 assert_eq!(it.nth(2), Some(&5));
533 assert_eq!(it.next(), None);
537 fn test_iterator_peekable_last() {
538 let xs = [0, 1, 2, 3, 4, 5];
541 let mut it = xs.iter().peekable();
542 assert_eq!(it.peek(), Some(&&0));
543 assert_eq!(it.last(), Some(&5));
545 let mut it = ys.iter().peekable();
546 assert_eq!(it.peek(), Some(&&0));
547 assert_eq!(it.last(), Some(&0));
549 let mut it = ys.iter().peekable();
550 assert_eq!(it.next(), Some(&0));
551 assert_eq!(it.peek(), None);
552 assert_eq!(it.last(), None);
556 fn test_iterator_peekable_fold() {
557 let xs = [0, 1, 2, 3, 4, 5];
558 let mut it = xs.iter().peekable();
559 assert_eq!(it.peek(), Some(&&0));
560 let i = it.fold(0, |i, &x| {
561 assert_eq!(x, xs[i]);
564 assert_eq!(i, xs.len());
567 /// This is an iterator that follows the Iterator contract,
568 /// but it is not fused. After having returned None once, it will start
569 /// producing elements if .next() is called again.
570 pub struct CycleIter<'a, T> {
575 pub fn cycle<T>(data: &[T]) -> CycleIter<'_, T> {
582 impl<'a, T> Iterator for CycleIter<'a, T> {
584 fn next(&mut self) -> Option<Self::Item> {
585 let elt = self.data.get(self.index);
587 self.index %= 1 + self.data.len();
593 fn test_iterator_peekable_remember_peek_none_1() {
594 // Check that the loop using .peek() terminates
595 let data = [1, 2, 3];
596 let mut iter = cycle(&data).peekable();
599 while let Some(_) = iter.next() {
600 let is_the_last = iter.peek().is_none();
601 assert_eq!(is_the_last, n == data.len() - 1);
603 if n > data.len() { break; }
605 assert_eq!(n, data.len());
609 fn test_iterator_peekable_remember_peek_none_2() {
611 let mut iter = cycle(&data).peekable();
613 assert_eq!(iter.peek(), None);
614 assert_eq!(iter.last(), None);
618 fn test_iterator_peekable_remember_peek_none_3() {
620 let mut iter = cycle(&data).peekable();
622 assert_eq!(iter.nth(0), Some(&0));
624 let mut iter = cycle(&data).peekable();
626 assert_eq!(iter.peek(), None);
627 assert_eq!(iter.nth(0), None);
631 fn test_iterator_take_while() {
632 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
633 let ys = [0, 1, 2, 3, 5, 13];
634 let it = xs.iter().take_while(|&x| *x < 15);
637 assert_eq!(*x, ys[i]);
640 assert_eq!(i, ys.len());
644 fn test_iterator_skip_while() {
645 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
646 let ys = [15, 16, 17, 19];
647 let it = xs.iter().skip_while(|&x| *x < 15);
650 assert_eq!(*x, ys[i]);
653 assert_eq!(i, ys.len());
657 fn test_iterator_skip_while_fold() {
658 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
659 let ys = [15, 16, 17, 19];
660 let it = xs.iter().skip_while(|&x| *x < 15);
661 let i = it.fold(0, |i, &x| {
662 assert_eq!(x, ys[i]);
665 assert_eq!(i, ys.len());
667 let mut it = xs.iter().skip_while(|&x| *x < 15);
668 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
669 let i = it.fold(1, |i, &x| {
670 assert_eq!(x, ys[i]);
673 assert_eq!(i, ys.len());
677 fn test_iterator_skip() {
678 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
679 let ys = [13, 15, 16, 17, 19, 20, 30];
680 let mut it = xs.iter().skip(5);
682 while let Some(&x) = it.next() {
683 assert_eq!(x, ys[i]);
685 assert_eq!(it.len(), xs.len()-5-i);
687 assert_eq!(i, ys.len());
688 assert_eq!(it.len(), 0);
692 fn test_iterator_skip_doubleended() {
693 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
694 let mut it = xs.iter().rev().skip(5);
695 assert_eq!(it.next(), Some(&15));
696 assert_eq!(it.by_ref().rev().next(), Some(&0));
697 assert_eq!(it.next(), Some(&13));
698 assert_eq!(it.by_ref().rev().next(), Some(&1));
699 assert_eq!(it.next(), Some(&5));
700 assert_eq!(it.by_ref().rev().next(), Some(&2));
701 assert_eq!(it.next(), Some(&3));
702 assert_eq!(it.next(), None);
703 let mut it = xs.iter().rev().skip(5).rev();
704 assert_eq!(it.next(), Some(&0));
705 assert_eq!(it.rev().next(), Some(&15));
706 let mut it_base = xs.iter();
708 let mut it = it_base.by_ref().skip(5).rev();
709 assert_eq!(it.next(), Some(&30));
710 assert_eq!(it.next(), Some(&20));
711 assert_eq!(it.next(), Some(&19));
712 assert_eq!(it.next(), Some(&17));
713 assert_eq!(it.next(), Some(&16));
714 assert_eq!(it.next(), Some(&15));
715 assert_eq!(it.next(), Some(&13));
716 assert_eq!(it.next(), None);
718 // make sure the skipped parts have not been consumed
719 assert_eq!(it_base.next(), Some(&0));
720 assert_eq!(it_base.next(), Some(&1));
721 assert_eq!(it_base.next(), Some(&2));
722 assert_eq!(it_base.next(), Some(&3));
723 assert_eq!(it_base.next(), Some(&5));
724 assert_eq!(it_base.next(), None);
725 let it = xs.iter().skip(5).rev();
726 assert_eq!(it.last(), Some(&13));
730 fn test_iterator_skip_nth() {
731 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
733 let mut it = xs.iter().skip(0);
734 assert_eq!(it.nth(0), Some(&0));
735 assert_eq!(it.nth(1), Some(&2));
737 let mut it = xs.iter().skip(5);
738 assert_eq!(it.nth(0), Some(&13));
739 assert_eq!(it.nth(1), Some(&16));
741 let mut it = xs.iter().skip(12);
742 assert_eq!(it.nth(0), None);
747 fn test_iterator_skip_count() {
748 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
750 assert_eq!(xs.iter().skip(0).count(), 12);
751 assert_eq!(xs.iter().skip(1).count(), 11);
752 assert_eq!(xs.iter().skip(11).count(), 1);
753 assert_eq!(xs.iter().skip(12).count(), 0);
754 assert_eq!(xs.iter().skip(13).count(), 0);
758 fn test_iterator_skip_last() {
759 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
761 assert_eq!(xs.iter().skip(0).last(), Some(&30));
762 assert_eq!(xs.iter().skip(1).last(), Some(&30));
763 assert_eq!(xs.iter().skip(11).last(), Some(&30));
764 assert_eq!(xs.iter().skip(12).last(), None);
765 assert_eq!(xs.iter().skip(13).last(), None);
767 let mut it = xs.iter().skip(5);
768 assert_eq!(it.next(), Some(&13));
769 assert_eq!(it.last(), Some(&30));
773 fn test_iterator_skip_fold() {
774 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
775 let ys = [13, 15, 16, 17, 19, 20, 30];
777 let it = xs.iter().skip(5);
778 let i = it.fold(0, |i, &x| {
779 assert_eq!(x, ys[i]);
782 assert_eq!(i, ys.len());
784 let mut it = xs.iter().skip(5);
785 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
786 let i = it.fold(1, |i, &x| {
787 assert_eq!(x, ys[i]);
790 assert_eq!(i, ys.len());
792 let it = xs.iter().skip(5);
793 let i = it.rfold(ys.len(), |i, &x| {
795 assert_eq!(x, ys[i]);
800 let mut it = xs.iter().skip(5);
801 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
802 let i = it.rfold(ys.len(), |i, &x| {
804 assert_eq!(x, ys[i]);
812 fn test_iterator_take() {
813 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
814 let ys = [0, 1, 2, 3, 5];
815 let mut it = xs.iter().take(5);
817 assert_eq!(it.len(), 5);
818 while let Some(&x) = it.next() {
819 assert_eq!(x, ys[i]);
821 assert_eq!(it.len(), 5-i);
823 assert_eq!(i, ys.len());
824 assert_eq!(it.len(), 0);
828 fn test_iterator_take_nth() {
829 let xs = [0, 1, 2, 4, 5];
830 let mut it = xs.iter();
832 let mut take = it.by_ref().take(3);
834 while let Some(&x) = take.nth(0) {
839 assert_eq!(it.nth(1), Some(&5));
840 assert_eq!(it.nth(0), None);
842 let xs = [0, 1, 2, 3, 4];
843 let mut it = xs.iter().take(7);
845 while let Some(&x) = it.nth(1) {
852 fn test_iterator_take_short() {
853 let xs = [0, 1, 2, 3];
854 let ys = [0, 1, 2, 3];
855 let mut it = xs.iter().take(5);
857 assert_eq!(it.len(), 4);
858 while let Some(&x) = it.next() {
859 assert_eq!(x, ys[i]);
861 assert_eq!(it.len(), 4-i);
863 assert_eq!(i, ys.len());
864 assert_eq!(it.len(), 0);
868 fn test_iterator_scan() {
869 // test the type inference
870 fn add(old: &mut isize, new: &usize) -> Option<f64> {
871 *old += *new as isize;
874 let xs = [0, 1, 2, 3, 4];
875 let ys = [0f64, 1.0, 3.0, 6.0, 10.0];
877 let it = xs.iter().scan(0, add);
880 assert_eq!(x, ys[i]);
883 assert_eq!(i, ys.len());
887 fn test_iterator_flat_map() {
889 let ys = [0, 1, 2, 3, 4, 5, 6, 7, 8];
890 let it = xs.iter().flat_map(|&x| (x..).step_by(1).take(3));
893 assert_eq!(x, ys[i]);
896 assert_eq!(i, ys.len());
899 /// Tests `FlatMap::fold` with items already picked off the front and back,
900 /// to make sure all parts of the `FlatMap` are folded correctly.
902 fn test_iterator_flat_map_fold() {
904 let ys = [1, 2, 3, 4, 5, 6, 7];
905 let mut it = xs.iter().flat_map(|&x| x..x+3);
906 assert_eq!(it.next(), Some(0));
907 assert_eq!(it.next_back(), Some(8));
908 let i = it.fold(0, |i, x| {
909 assert_eq!(x, ys[i]);
912 assert_eq!(i, ys.len());
914 let mut it = xs.iter().flat_map(|&x| x..x+3);
915 assert_eq!(it.next(), Some(0));
916 assert_eq!(it.next_back(), Some(8));
917 let i = it.rfold(ys.len(), |i, x| {
918 assert_eq!(x, ys[i - 1]);
925 fn test_iterator_flatten() {
927 let ys = [0, 1, 2, 3, 4, 5, 6, 7, 8];
928 let it = xs.iter().map(|&x| (x..).step_by(1).take(3)).flatten();
931 assert_eq!(x, ys[i]);
934 assert_eq!(i, ys.len());
937 /// Tests `Flatten::fold` with items already picked off the front and back,
938 /// to make sure all parts of the `Flatten` are folded correctly.
940 fn test_iterator_flatten_fold() {
942 let ys = [1, 2, 3, 4, 5, 6, 7];
943 let mut it = xs.iter().map(|&x| x..x+3).flatten();
944 assert_eq!(it.next(), Some(0));
945 assert_eq!(it.next_back(), Some(8));
946 let i = it.fold(0, |i, x| {
947 assert_eq!(x, ys[i]);
950 assert_eq!(i, ys.len());
952 let mut it = xs.iter().map(|&x| x..x+3).flatten();
953 assert_eq!(it.next(), Some(0));
954 assert_eq!(it.next_back(), Some(8));
955 let i = it.rfold(ys.len(), |i, x| {
956 assert_eq!(x, ys[i - 1]);
964 let xs = [1, 2, 3, 4];
970 .collect::<Vec<usize>>();
972 assert_eq!(n, xs.len());
973 assert_eq!(&xs[..], &ys[..]);
977 fn test_inspect_fold() {
978 let xs = [1, 2, 3, 4];
981 let it = xs.iter().inspect(|_| n += 1);
982 let i = it.fold(0, |i, &x| {
983 assert_eq!(x, xs[i]);
986 assert_eq!(i, xs.len());
988 assert_eq!(n, xs.len());
992 let it = xs.iter().inspect(|_| n += 1);
993 let i = it.rfold(xs.len(), |i, &x| {
994 assert_eq!(x, xs[i - 1]);
999 assert_eq!(n, xs.len());
1005 let it = (0..).step_by(1).take(cycle_len).cycle();
1006 assert_eq!(it.size_hint(), (usize::MAX, None));
1007 for (i, x) in it.take(100).enumerate() {
1008 assert_eq!(i % cycle_len, x);
1011 let mut it = (0..).step_by(1).take(0).cycle();
1012 assert_eq!(it.size_hint(), (0, Some(0)));
1013 assert_eq!(it.next(), None);
1015 assert_eq!(empty::<i32>().cycle().fold(0, |acc, x| acc + x), 0);
1017 assert_eq!(once(1).cycle().skip(1).take(4).fold(0, |acc, x| acc + x), 4);
1021 fn test_iterator_nth() {
1022 let v: &[_] = &[0, 1, 2, 3, 4];
1023 for i in 0..v.len() {
1024 assert_eq!(v.iter().nth(i).unwrap(), &v[i]);
1026 assert_eq!(v.iter().nth(v.len()), None);
1030 fn test_iterator_nth_back() {
1031 let v: &[_] = &[0, 1, 2, 3, 4];
1032 for i in 0..v.len() {
1033 assert_eq!(v.iter().nth_back(i).unwrap(), &v[v.len() - 1 - i]);
1035 assert_eq!(v.iter().nth_back(v.len()), None);
1039 fn test_iterator_rev_nth_back() {
1040 let v: &[_] = &[0, 1, 2, 3, 4];
1041 for i in 0..v.len() {
1042 assert_eq!(v.iter().rev().nth_back(i).unwrap(), &v[i]);
1044 assert_eq!(v.iter().rev().nth_back(v.len()), None);
1048 fn test_iterator_rev_nth() {
1049 let v: &[_] = &[0, 1, 2, 3, 4];
1050 for i in 0..v.len() {
1051 assert_eq!(v.iter().rev().nth(i).unwrap(), &v[v.len() - 1 - i]);
1053 assert_eq!(v.iter().rev().nth(v.len()), None);
1057 fn test_iterator_last() {
1058 let v: &[_] = &[0, 1, 2, 3, 4];
1059 assert_eq!(v.iter().last().unwrap(), &4);
1060 assert_eq!(v[..1].iter().last().unwrap(), &0);
1064 fn test_iterator_len() {
1065 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1066 assert_eq!(v[..4].iter().count(), 4);
1067 assert_eq!(v[..10].iter().count(), 10);
1068 assert_eq!(v[..0].iter().count(), 0);
1072 fn test_iterator_sum() {
1073 let v: &[i32] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1074 assert_eq!(v[..4].iter().cloned().sum::<i32>(), 6);
1075 assert_eq!(v.iter().cloned().sum::<i32>(), 55);
1076 assert_eq!(v[..0].iter().cloned().sum::<i32>(), 0);
1080 fn test_iterator_sum_result() {
1081 let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
1082 assert_eq!(v.iter().cloned().sum::<Result<i32, _>>(), Ok(10));
1083 let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
1084 assert_eq!(v.iter().cloned().sum::<Result<i32, _>>(), Err(()));
1088 fn test_iterator_sum_option() {
1089 let v: &[Option<i32>] = &[Some(1), Some(2), Some(3), Some(4)];
1090 assert_eq!(v.iter().cloned().sum::<Option<i32>>(), Some(10));
1091 let v: &[Option<i32>] = &[Some(1), None, Some(3), Some(4)];
1092 assert_eq!(v.iter().cloned().sum::<Option<i32>>(), None);
1096 fn test_iterator_product() {
1097 let v: &[i32] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1098 assert_eq!(v[..4].iter().cloned().product::<i32>(), 0);
1099 assert_eq!(v[1..5].iter().cloned().product::<i32>(), 24);
1100 assert_eq!(v[..0].iter().cloned().product::<i32>(), 1);
1104 fn test_iterator_product_result() {
1105 let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
1106 assert_eq!(v.iter().cloned().product::<Result<i32, _>>(), Ok(24));
1107 let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
1108 assert_eq!(v.iter().cloned().product::<Result<i32, _>>(), Err(()));
1111 /// A wrapper struct that implements `Eq` and `Ord` based on the wrapped
1112 /// integer modulo 3. Used to test that `Iterator::max` and `Iterator::min`
1113 /// return the correct element if some of them are equal.
1117 impl PartialEq for Mod3 {
1118 fn eq(&self, other: &Self) -> bool {
1119 self.0 % 3 == other.0 % 3
1125 impl PartialOrd for Mod3 {
1126 fn partial_cmp(&self, other: &Self) -> Option<core::cmp::Ordering> {
1127 Some(self.cmp(other))
1132 fn cmp(&self, other: &Self) -> core::cmp::Ordering {
1133 (self.0 % 3).cmp(&(other.0 % 3))
1138 fn test_iterator_product_option() {
1139 let v: &[Option<i32>] = &[Some(1), Some(2), Some(3), Some(4)];
1140 assert_eq!(v.iter().cloned().product::<Option<i32>>(), Some(24));
1141 let v: &[Option<i32>] = &[Some(1), None, Some(3), Some(4)];
1142 assert_eq!(v.iter().cloned().product::<Option<i32>>(), None);
1146 fn test_iterator_max() {
1147 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1148 assert_eq!(v[..4].iter().cloned().max(), Some(3));
1149 assert_eq!(v.iter().cloned().max(), Some(10));
1150 assert_eq!(v[..0].iter().cloned().max(), None);
1151 assert_eq!(v.iter().cloned().map(Mod3).max().map(|x| x.0), Some(8));
1155 fn test_iterator_min() {
1156 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1157 assert_eq!(v[..4].iter().cloned().min(), Some(0));
1158 assert_eq!(v.iter().cloned().min(), Some(0));
1159 assert_eq!(v[..0].iter().cloned().min(), None);
1160 assert_eq!(v.iter().cloned().map(Mod3).min().map(|x| x.0), Some(0));
1164 fn test_iterator_size_hint() {
1165 let c = (0..).step_by(1);
1166 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
1167 let v2 = &[10, 11, 12];
1170 assert_eq!((0..).size_hint(), (usize::MAX, None));
1171 assert_eq!(c.size_hint(), (usize::MAX, None));
1172 assert_eq!(vi.clone().size_hint(), (10, Some(10)));
1174 assert_eq!(c.clone().take(5).size_hint(), (5, Some(5)));
1175 assert_eq!(c.clone().skip(5).size_hint().1, None);
1176 assert_eq!(c.clone().take_while(|_| false).size_hint(), (0, None));
1177 assert_eq!(c.clone().skip_while(|_| false).size_hint(), (0, None));
1178 assert_eq!(c.clone().enumerate().size_hint(), (usize::MAX, None));
1179 assert_eq!(c.clone().chain(vi.clone().cloned()).size_hint(), (usize::MAX, None));
1180 assert_eq!(c.clone().zip(vi.clone()).size_hint(), (10, Some(10)));
1181 assert_eq!(c.clone().scan(0, |_,_| Some(0)).size_hint(), (0, None));
1182 assert_eq!(c.clone().filter(|_| false).size_hint(), (0, None));
1183 assert_eq!(c.clone().map(|_| 0).size_hint(), (usize::MAX, None));
1184 assert_eq!(c.filter_map(|_| Some(0)).size_hint(), (0, None));
1186 assert_eq!(vi.clone().take(5).size_hint(), (5, Some(5)));
1187 assert_eq!(vi.clone().take(12).size_hint(), (10, Some(10)));
1188 assert_eq!(vi.clone().skip(3).size_hint(), (7, Some(7)));
1189 assert_eq!(vi.clone().skip(12).size_hint(), (0, Some(0)));
1190 assert_eq!(vi.clone().take_while(|_| false).size_hint(), (0, Some(10)));
1191 assert_eq!(vi.clone().skip_while(|_| false).size_hint(), (0, Some(10)));
1192 assert_eq!(vi.clone().enumerate().size_hint(), (10, Some(10)));
1193 assert_eq!(vi.clone().chain(v2).size_hint(), (13, Some(13)));
1194 assert_eq!(vi.clone().zip(v2).size_hint(), (3, Some(3)));
1195 assert_eq!(vi.clone().scan(0, |_,_| Some(0)).size_hint(), (0, Some(10)));
1196 assert_eq!(vi.clone().filter(|_| false).size_hint(), (0, Some(10)));
1197 assert_eq!(vi.clone().map(|&i| i+1).size_hint(), (10, Some(10)));
1198 assert_eq!(vi.filter_map(|_| Some(0)).size_hint(), (0, Some(10)));
1203 let a = vec![1, 2, 3, 4, 5];
1204 let b: Vec<isize> = a.iter().cloned().collect();
1210 let v: Box<[isize]> = Box::new([1, 2, 3, 4, 5]);
1211 assert!(v.iter().all(|&x| x < 10));
1212 assert!(!v.iter().all(|&x| x % 2 == 0));
1213 assert!(!v.iter().all(|&x| x > 100));
1214 assert!(v[..0].iter().all(|_| panic!()));
1219 let v: Box<[isize]> = Box::new([1, 2, 3, 4, 5]);
1220 assert!(v.iter().any(|&x| x < 10));
1221 assert!(v.iter().any(|&x| x % 2 == 0));
1222 assert!(!v.iter().any(|&x| x > 100));
1223 assert!(!v[..0].iter().any(|_| panic!()));
1228 let v: &[isize] = &[1, 3, 9, 27, 103, 14, 11];
1229 assert_eq!(*v.iter().find(|&&x| x & 1 == 0).unwrap(), 14);
1230 assert_eq!(*v.iter().find(|&&x| x % 3 == 0).unwrap(), 3);
1231 assert!(v.iter().find(|&&x| x % 12 == 0).is_none());
1235 fn test_find_map() {
1236 let xs: &[isize] = &[];
1237 assert_eq!(xs.iter().find_map(half_if_even), None);
1238 let xs: &[isize] = &[3, 5];
1239 assert_eq!(xs.iter().find_map(half_if_even), None);
1240 let xs: &[isize] = &[4, 5];
1241 assert_eq!(xs.iter().find_map(half_if_even), Some(2));
1242 let xs: &[isize] = &[3, 6];
1243 assert_eq!(xs.iter().find_map(half_if_even), Some(3));
1245 let xs: &[isize] = &[1, 2, 3, 4, 5, 6, 7];
1246 let mut iter = xs.iter();
1247 assert_eq!(iter.find_map(half_if_even), Some(1));
1248 assert_eq!(iter.find_map(half_if_even), Some(2));
1249 assert_eq!(iter.find_map(half_if_even), Some(3));
1250 assert_eq!(iter.next(), Some(&7));
1252 fn half_if_even(x: &isize) -> Option<isize> {
1262 fn test_position() {
1263 let v = &[1, 3, 9, 27, 103, 14, 11];
1264 assert_eq!(v.iter().position(|x| *x & 1 == 0).unwrap(), 5);
1265 assert_eq!(v.iter().position(|x| *x % 3 == 0).unwrap(), 1);
1266 assert!(v.iter().position(|x| *x % 12 == 0).is_none());
1271 let xs = &[1, 2, 2, 1, 5, 9, 0, 2];
1272 assert_eq!(xs.iter().filter(|x| **x == 2).count(), 3);
1273 assert_eq!(xs.iter().filter(|x| **x == 5).count(), 1);
1274 assert_eq!(xs.iter().filter(|x| **x == 95).count(), 0);
1278 fn test_max_by_key() {
1279 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1280 assert_eq!(*xs.iter().max_by_key(|x| x.abs()).unwrap(), -10);
1285 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1286 assert_eq!(*xs.iter().max_by(|x, y| x.abs().cmp(&y.abs())).unwrap(), -10);
1290 fn test_min_by_key() {
1291 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1292 assert_eq!(*xs.iter().min_by_key(|x| x.abs()).unwrap(), 0);
1297 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1298 assert_eq!(*xs.iter().min_by(|x, y| x.abs().cmp(&y.abs())).unwrap(), 0);
1304 // sum the first five values
1305 let partial_sum = xs.by_ref().take(5).fold(0, |a, b| a + b);
1306 assert_eq!(partial_sum, 10);
1307 assert_eq!(xs.next(), Some(5));
1312 let xs = [2, 4, 6, 8, 10, 12, 14, 16];
1313 let mut it = xs.iter();
1316 assert!(it.rev().cloned().collect::<Vec<isize>>() ==
1317 vec![16, 14, 12, 10, 8, 6]);
1322 let xs = [2, 4, 6, 8];
1324 let mut it = xs.iter().copied();
1325 assert_eq!(it.len(), 4);
1326 assert_eq!(it.next(), Some(2));
1327 assert_eq!(it.len(), 3);
1328 assert_eq!(it.next(), Some(4));
1329 assert_eq!(it.len(), 2);
1330 assert_eq!(it.next_back(), Some(8));
1331 assert_eq!(it.len(), 1);
1332 assert_eq!(it.next_back(), Some(6));
1333 assert_eq!(it.len(), 0);
1334 assert_eq!(it.next_back(), None);
1339 let xs = [2, 4, 6, 8];
1341 let mut it = xs.iter().cloned();
1342 assert_eq!(it.len(), 4);
1343 assert_eq!(it.next(), Some(2));
1344 assert_eq!(it.len(), 3);
1345 assert_eq!(it.next(), Some(4));
1346 assert_eq!(it.len(), 2);
1347 assert_eq!(it.next_back(), Some(8));
1348 assert_eq!(it.len(), 1);
1349 assert_eq!(it.next_back(), Some(6));
1350 assert_eq!(it.len(), 0);
1351 assert_eq!(it.next_back(), None);
1355 fn test_cloned_side_effects() {
1358 let iter = [1, 2, 3]
1368 assert_eq!(count, 2);
1372 fn test_double_ended_map() {
1373 let xs = [1, 2, 3, 4, 5, 6];
1374 let mut it = xs.iter().map(|&x| x * -1);
1375 assert_eq!(it.next(), Some(-1));
1376 assert_eq!(it.next(), Some(-2));
1377 assert_eq!(it.next_back(), Some(-6));
1378 assert_eq!(it.next_back(), Some(-5));
1379 assert_eq!(it.next(), Some(-3));
1380 assert_eq!(it.next_back(), Some(-4));
1381 assert_eq!(it.next(), None);
1385 fn test_double_ended_enumerate() {
1386 let xs = [1, 2, 3, 4, 5, 6];
1387 let mut it = xs.iter().cloned().enumerate();
1388 assert_eq!(it.next(), Some((0, 1)));
1389 assert_eq!(it.next(), Some((1, 2)));
1390 assert_eq!(it.next_back(), Some((5, 6)));
1391 assert_eq!(it.next_back(), Some((4, 5)));
1392 assert_eq!(it.next_back(), Some((3, 4)));
1393 assert_eq!(it.next_back(), Some((2, 3)));
1394 assert_eq!(it.next(), None);
1398 fn test_double_ended_zip() {
1399 let xs = [1, 2, 3, 4, 5, 6];
1400 let ys = [1, 2, 3, 7];
1401 let a = xs.iter().cloned();
1402 let b = ys.iter().cloned();
1403 let mut it = a.zip(b);
1404 assert_eq!(it.next(), Some((1, 1)));
1405 assert_eq!(it.next(), Some((2, 2)));
1406 assert_eq!(it.next_back(), Some((4, 7)));
1407 assert_eq!(it.next_back(), Some((3, 3)));
1408 assert_eq!(it.next(), None);
1412 fn test_double_ended_filter() {
1413 let xs = [1, 2, 3, 4, 5, 6];
1414 let mut it = xs.iter().filter(|&x| *x & 1 == 0);
1415 assert_eq!(it.next_back().unwrap(), &6);
1416 assert_eq!(it.next_back().unwrap(), &4);
1417 assert_eq!(it.next().unwrap(), &2);
1418 assert_eq!(it.next_back(), None);
1422 fn test_double_ended_filter_map() {
1423 let xs = [1, 2, 3, 4, 5, 6];
1424 let mut it = xs.iter().filter_map(|&x| if x & 1 == 0 { Some(x * 2) } else { None });
1425 assert_eq!(it.next_back().unwrap(), 12);
1426 assert_eq!(it.next_back().unwrap(), 8);
1427 assert_eq!(it.next().unwrap(), 4);
1428 assert_eq!(it.next_back(), None);
1432 fn test_double_ended_chain() {
1433 let xs = [1, 2, 3, 4, 5];
1434 let ys = [7, 9, 11];
1435 let mut it = xs.iter().chain(&ys).rev();
1436 assert_eq!(it.next().unwrap(), &11);
1437 assert_eq!(it.next().unwrap(), &9);
1438 assert_eq!(it.next_back().unwrap(), &1);
1439 assert_eq!(it.next_back().unwrap(), &2);
1440 assert_eq!(it.next_back().unwrap(), &3);
1441 assert_eq!(it.next_back().unwrap(), &4);
1442 assert_eq!(it.next_back().unwrap(), &5);
1443 assert_eq!(it.next_back().unwrap(), &7);
1444 assert_eq!(it.next_back(), None);
1447 // test that .chain() is well behaved with an unfused iterator
1448 struct CrazyIterator(bool);
1449 impl CrazyIterator { fn new() -> CrazyIterator { CrazyIterator(false) } }
1450 impl Iterator for CrazyIterator {
1452 fn next(&mut self) -> Option<i32> {
1453 if self.0 { Some(99) } else { self.0 = true; None }
1457 impl DoubleEndedIterator for CrazyIterator {
1458 fn next_back(&mut self) -> Option<i32> {
1463 assert_eq!(CrazyIterator::new().chain(0..10).rev().last(), Some(0));
1464 assert!((0..10).chain(CrazyIterator::new()).rev().any(|i| i == 0));
1468 fn test_rposition() {
1469 fn f(xy: &(isize, char)) -> bool { let (_x, y) = *xy; y == 'b' }
1470 fn g(xy: &(isize, char)) -> bool { let (_x, y) = *xy; y == 'd' }
1471 let v = [(0, 'a'), (1, 'b'), (2, 'c'), (3, 'b')];
1473 assert_eq!(v.iter().rposition(f), Some(3));
1474 assert!(v.iter().rposition(g).is_none());
1479 fn test_rposition_panic() {
1480 let v: [(Box<_>, Box<_>); 4] =
1481 [(box 0, box 0), (box 0, box 0),
1482 (box 0, box 0), (box 0, box 0)];
1484 v.iter().rposition(|_elt| {
1495 fn test_double_ended_flat_map() {
1498 let mut it = u.iter().flat_map(|x| &v[*x..v.len()]);
1499 assert_eq!(it.next_back().unwrap(), &8);
1500 assert_eq!(it.next().unwrap(), &5);
1501 assert_eq!(it.next_back().unwrap(), &7);
1502 assert_eq!(it.next_back().unwrap(), &6);
1503 assert_eq!(it.next_back().unwrap(), &8);
1504 assert_eq!(it.next().unwrap(), &6);
1505 assert_eq!(it.next_back().unwrap(), &7);
1506 assert_eq!(it.next_back(), None);
1507 assert_eq!(it.next(), None);
1508 assert_eq!(it.next_back(), None);
1512 fn test_double_ended_flatten() {
1515 let mut it = u.iter().map(|x| &v[*x..v.len()]).flatten();
1516 assert_eq!(it.next_back().unwrap(), &8);
1517 assert_eq!(it.next().unwrap(), &5);
1518 assert_eq!(it.next_back().unwrap(), &7);
1519 assert_eq!(it.next_back().unwrap(), &6);
1520 assert_eq!(it.next_back().unwrap(), &8);
1521 assert_eq!(it.next().unwrap(), &6);
1522 assert_eq!(it.next_back().unwrap(), &7);
1523 assert_eq!(it.next_back(), None);
1524 assert_eq!(it.next(), None);
1525 assert_eq!(it.next_back(), None);
1529 fn test_double_ended_range() {
1530 assert_eq!((11..14).rev().collect::<Vec<_>>(), [13, 12, 11]);
1531 for _ in (10..0).rev() {
1532 panic!("unreachable");
1535 assert_eq!((11..14).rev().collect::<Vec<_>>(), [13, 12, 11]);
1536 for _ in (10..0).rev() {
1537 panic!("unreachable");
1543 assert_eq!((0..5).collect::<Vec<_>>(), [0, 1, 2, 3, 4]);
1544 assert_eq!((-10..-1).collect::<Vec<_>>(), [-10, -9, -8, -7, -6, -5, -4, -3, -2]);
1545 assert_eq!((0..5).rev().collect::<Vec<_>>(), [4, 3, 2, 1, 0]);
1546 assert_eq!((200..-5).count(), 0);
1547 assert_eq!((200..-5).rev().count(), 0);
1548 assert_eq!((200..200).count(), 0);
1549 assert_eq!((200..200).rev().count(), 0);
1551 assert_eq!((0..100).size_hint(), (100, Some(100)));
1552 // this test is only meaningful when sizeof usize < sizeof u64
1553 assert_eq!((usize::MAX - 1..usize::MAX).size_hint(), (1, Some(1)));
1554 assert_eq!((-10..-1).size_hint(), (9, Some(9)));
1555 assert_eq!((-1..-10).size_hint(), (0, Some(0)));
1557 assert_eq!((-70..58).size_hint(), (128, Some(128)));
1558 assert_eq!((-128..127).size_hint(), (255, Some(255)));
1559 assert_eq!((-2..isize::MAX).size_hint(),
1560 (isize::MAX as usize + 2, Some(isize::MAX as usize + 2)));
1564 fn test_range_exhaustion() {
1566 assert!(r.is_empty());
1567 assert_eq!(r.next(), None);
1568 assert_eq!(r.next_back(), None);
1569 assert_eq!(r, 10..10);
1572 assert_eq!(r.next(), Some(10));
1573 assert_eq!(r.next(), Some(11));
1574 assert!(r.is_empty());
1575 assert_eq!(r, 12..12);
1576 assert_eq!(r.next(), None);
1579 assert_eq!(r.next_back(), Some(11));
1580 assert_eq!(r.next_back(), Some(10));
1581 assert!(r.is_empty());
1582 assert_eq!(r, 10..10);
1583 assert_eq!(r.next_back(), None);
1585 let mut r = 100..10;
1586 assert!(r.is_empty());
1587 assert_eq!(r.next(), None);
1588 assert_eq!(r.next_back(), None);
1589 assert_eq!(r, 100..10);
1593 fn test_range_inclusive_exhaustion() {
1594 let mut r = 10..=10;
1595 assert_eq!(r.next(), Some(10));
1596 assert!(r.is_empty());
1597 assert_eq!(r.next(), None);
1598 assert_eq!(r.next(), None);
1600 let mut r = 10..=10;
1601 assert_eq!(r.next_back(), Some(10));
1602 assert!(r.is_empty());
1603 assert_eq!(r.next_back(), None);
1605 let mut r = 10..=12;
1606 assert_eq!(r.next(), Some(10));
1607 assert_eq!(r.next(), Some(11));
1608 assert_eq!(r.next(), Some(12));
1609 assert!(r.is_empty());
1610 assert_eq!(r.next(), None);
1612 let mut r = 10..=12;
1613 assert_eq!(r.next_back(), Some(12));
1614 assert_eq!(r.next_back(), Some(11));
1615 assert_eq!(r.next_back(), Some(10));
1616 assert!(r.is_empty());
1617 assert_eq!(r.next_back(), None);
1619 let mut r = 10..=12;
1620 assert_eq!(r.nth(2), Some(12));
1621 assert!(r.is_empty());
1622 assert_eq!(r.next(), None);
1624 let mut r = 10..=12;
1625 assert_eq!(r.nth(5), None);
1626 assert!(r.is_empty());
1627 assert_eq!(r.next(), None);
1629 let mut r = 100..=10;
1630 assert_eq!(r.next(), None);
1631 assert!(r.is_empty());
1632 assert_eq!(r.next(), None);
1633 assert_eq!(r.next(), None);
1634 assert_eq!(r, 100..=10);
1636 let mut r = 100..=10;
1637 assert_eq!(r.next_back(), None);
1638 assert!(r.is_empty());
1639 assert_eq!(r.next_back(), None);
1640 assert_eq!(r.next_back(), None);
1641 assert_eq!(r, 100..=10);
1645 fn test_range_nth() {
1646 assert_eq!((10..15).nth(0), Some(10));
1647 assert_eq!((10..15).nth(1), Some(11));
1648 assert_eq!((10..15).nth(4), Some(14));
1649 assert_eq!((10..15).nth(5), None);
1652 assert_eq!(r.nth(2), Some(12));
1653 assert_eq!(r, 13..20);
1654 assert_eq!(r.nth(2), Some(15));
1655 assert_eq!(r, 16..20);
1656 assert_eq!(r.nth(10), None);
1657 assert_eq!(r, 20..20);
1661 fn test_range_nth_back() {
1662 assert_eq!((10..15).nth_back(0), Some(14));
1663 assert_eq!((10..15).nth_back(1), Some(13));
1664 assert_eq!((10..15).nth_back(4), Some(10));
1665 assert_eq!((10..15).nth_back(5), None);
1666 assert_eq!((-120..80_i8).nth_back(199), Some(-120));
1669 assert_eq!(r.nth_back(2), Some(17));
1670 assert_eq!(r, 10..17);
1671 assert_eq!(r.nth_back(2), Some(14));
1672 assert_eq!(r, 10..14);
1673 assert_eq!(r.nth_back(10), None);
1674 assert_eq!(r, 10..10);
1678 fn test_range_from_nth() {
1679 assert_eq!((10..).nth(0), Some(10));
1680 assert_eq!((10..).nth(1), Some(11));
1681 assert_eq!((10..).nth(4), Some(14));
1684 assert_eq!(r.nth(2), Some(12));
1685 assert_eq!(r, 13..);
1686 assert_eq!(r.nth(2), Some(15));
1687 assert_eq!(r, 16..);
1688 assert_eq!(r.nth(10), Some(26));
1689 assert_eq!(r, 27..);
1691 assert_eq!((0..).size_hint(), (usize::MAX, None));
1694 fn is_trusted_len<I: TrustedLen>(_: I) {}
1697 fn test_range_from_take() {
1698 let mut it = (0..).take(3);
1699 assert_eq!(it.next(), Some(0));
1700 assert_eq!(it.next(), Some(1));
1701 assert_eq!(it.next(), Some(2));
1702 assert_eq!(it.next(), None);
1703 is_trusted_len((0..).take(3));
1704 assert_eq!((0..).take(3).size_hint(), (3, Some(3)));
1705 assert_eq!((0..).take(0).size_hint(), (0, Some(0)));
1706 assert_eq!((0..).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
1710 fn test_range_from_take_collect() {
1711 let v: Vec<_> = (0..).take(3).collect();
1712 assert_eq!(v, vec![0, 1, 2]);
1716 fn test_range_inclusive_nth() {
1717 assert_eq!((10..=15).nth(0), Some(10));
1718 assert_eq!((10..=15).nth(1), Some(11));
1719 assert_eq!((10..=15).nth(5), Some(15));
1720 assert_eq!((10..=15).nth(6), None);
1722 let mut r = 10_u8..=20;
1723 assert_eq!(r.nth(2), Some(12));
1724 assert_eq!(r, 13..=20);
1725 assert_eq!(r.nth(2), Some(15));
1726 assert_eq!(r, 16..=20);
1727 assert_eq!(r.is_empty(), false);
1728 assert_eq!(ExactSizeIterator::is_empty(&r), false);
1729 assert_eq!(r.nth(10), None);
1730 assert_eq!(r.is_empty(), true);
1731 assert_eq!(ExactSizeIterator::is_empty(&r), true);
1735 fn test_range_inclusive_nth_back() {
1736 assert_eq!((10..=15).nth_back(0), Some(15));
1737 assert_eq!((10..=15).nth_back(1), Some(14));
1738 assert_eq!((10..=15).nth_back(5), Some(10));
1739 assert_eq!((10..=15).nth_back(6), None);
1740 assert_eq!((-120..=80_i8).nth_back(200), Some(-120));
1742 let mut r = 10_u8..=20;
1743 assert_eq!(r.nth_back(2), Some(18));
1744 assert_eq!(r, 10..=17);
1745 assert_eq!(r.nth_back(2), Some(15));
1746 assert_eq!(r, 10..=14);
1747 assert_eq!(r.is_empty(), false);
1748 assert_eq!(ExactSizeIterator::is_empty(&r), false);
1749 assert_eq!(r.nth_back(10), None);
1750 assert_eq!(r.is_empty(), true);
1751 assert_eq!(ExactSizeIterator::is_empty(&r), true);
1755 fn test_range_step() {
1756 #![allow(deprecated)]
1758 assert_eq!((0..20).step_by(5).collect::<Vec<isize>>(), [0, 5, 10, 15]);
1759 assert_eq!((1..21).rev().step_by(5).collect::<Vec<isize>>(), [20, 15, 10, 5]);
1760 assert_eq!((1..21).rev().step_by(6).collect::<Vec<isize>>(), [20, 14, 8, 2]);
1761 assert_eq!((200..255).step_by(50).collect::<Vec<u8>>(), [200, 250]);
1762 assert_eq!((200..-5).step_by(1).collect::<Vec<isize>>(), []);
1763 assert_eq!((200..200).step_by(1).collect::<Vec<isize>>(), []);
1765 assert_eq!((0..20).step_by(1).size_hint(), (20, Some(20)));
1766 assert_eq!((0..20).step_by(21).size_hint(), (1, Some(1)));
1767 assert_eq!((0..20).step_by(5).size_hint(), (4, Some(4)));
1768 assert_eq!((1..21).rev().step_by(5).size_hint(), (4, Some(4)));
1769 assert_eq!((1..21).rev().step_by(6).size_hint(), (4, Some(4)));
1770 assert_eq!((20..-5).step_by(1).size_hint(), (0, Some(0)));
1771 assert_eq!((20..20).step_by(1).size_hint(), (0, Some(0)));
1772 assert_eq!((i8::MIN..i8::MAX).step_by(-(i8::MIN as i32) as usize).size_hint(), (2, Some(2)));
1773 assert_eq!((i16::MIN..i16::MAX).step_by(i16::MAX as usize).size_hint(), (3, Some(3)));
1774 assert_eq!((isize::MIN..isize::MAX).step_by(1).size_hint(), (usize::MAX, Some(usize::MAX)));
1778 fn test_step_by_skip() {
1779 assert_eq!((0..640).step_by(128).skip(1).collect::<Vec<_>>(), [128, 256, 384, 512]);
1780 assert_eq!((0..=50).step_by(10).nth(3), Some(30));
1781 assert_eq!((200..=255u8).step_by(10).nth(3), Some(230));
1785 fn test_range_inclusive_step() {
1786 assert_eq!((0..=50).step_by(10).collect::<Vec<_>>(), [0, 10, 20, 30, 40, 50]);
1787 assert_eq!((0..=5).step_by(1).collect::<Vec<_>>(), [0, 1, 2, 3, 4, 5]);
1788 assert_eq!((200..=255u8).step_by(10).collect::<Vec<_>>(), [200, 210, 220, 230, 240, 250]);
1789 assert_eq!((250..=255u8).step_by(1).collect::<Vec<_>>(), [250, 251, 252, 253, 254, 255]);
1793 fn test_range_last_max() {
1794 assert_eq!((0..20).last(), Some(19));
1795 assert_eq!((-20..0).last(), Some(-1));
1796 assert_eq!((5..5).last(), None);
1798 assert_eq!((0..20).max(), Some(19));
1799 assert_eq!((-20..0).max(), Some(-1));
1800 assert_eq!((5..5).max(), None);
1804 fn test_range_inclusive_last_max() {
1805 assert_eq!((0..=20).last(), Some(20));
1806 assert_eq!((-20..=0).last(), Some(0));
1807 assert_eq!((5..=5).last(), Some(5));
1808 let mut r = 10..=10;
1810 assert_eq!(r.last(), None);
1812 assert_eq!((0..=20).max(), Some(20));
1813 assert_eq!((-20..=0).max(), Some(0));
1814 assert_eq!((5..=5).max(), Some(5));
1815 let mut r = 10..=10;
1817 assert_eq!(r.max(), None);
1821 fn test_range_min() {
1822 assert_eq!((0..20).min(), Some(0));
1823 assert_eq!((-20..0).min(), Some(-20));
1824 assert_eq!((5..5).min(), None);
1828 fn test_range_inclusive_min() {
1829 assert_eq!((0..=20).min(), Some(0));
1830 assert_eq!((-20..=0).min(), Some(-20));
1831 assert_eq!((5..=5).min(), Some(5));
1832 let mut r = 10..=10;
1834 assert_eq!(r.min(), None);
1838 fn test_range_inclusive_folds() {
1839 assert_eq!((1..=10).sum::<i32>(), 55);
1840 assert_eq!((1..=10).rev().sum::<i32>(), 55);
1842 let mut it = 44..=50;
1843 assert_eq!(it.try_fold(0, i8::checked_add), None);
1844 assert_eq!(it, 47..=50);
1845 assert_eq!(it.try_fold(0, i8::checked_add), None);
1846 assert_eq!(it, 50..=50);
1847 assert_eq!(it.try_fold(0, i8::checked_add), Some(50));
1848 assert!(it.is_empty());
1849 assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
1850 assert!(it.is_empty());
1852 let mut it = 40..=47;
1853 assert_eq!(it.try_rfold(0, i8::checked_add), None);
1854 assert_eq!(it, 40..=44);
1855 assert_eq!(it.try_rfold(0, i8::checked_add), None);
1856 assert_eq!(it, 40..=41);
1857 assert_eq!(it.try_rfold(0, i8::checked_add), Some(81));
1858 assert!(it.is_empty());
1859 assert_eq!(it.try_rfold(0, i8::checked_add), Some(0));
1860 assert!(it.is_empty());
1862 let mut it = 10..=20;
1863 assert_eq!(it.try_fold(0, |a,b| Some(a+b)), Some(165));
1864 assert!(it.is_empty());
1865 assert_eq!(it.try_fold(0, |a,b| Some(a+b)), Some(0));
1866 assert!(it.is_empty());
1868 let mut it = 10..=20;
1869 assert_eq!(it.try_rfold(0, |a,b| Some(a+b)), Some(165));
1870 assert!(it.is_empty());
1871 assert_eq!(it.try_rfold(0, |a,b| Some(a+b)), Some(0));
1872 assert!(it.is_empty());
1876 fn test_range_size_hint() {
1877 use core::usize::MAX as UMAX;
1878 assert_eq!((0..0usize).size_hint(), (0, Some(0)));
1879 assert_eq!((0..100usize).size_hint(), (100, Some(100)));
1880 assert_eq!((0..UMAX).size_hint(), (UMAX, Some(UMAX)));
1882 let umax = u128::try_from(UMAX).unwrap();
1883 assert_eq!((0..0u128).size_hint(), (0, Some(0)));
1884 assert_eq!((0..100u128).size_hint(), (100, Some(100)));
1885 assert_eq!((0..umax).size_hint(), (UMAX, Some(UMAX)));
1886 assert_eq!((0..umax + 1).size_hint(), (UMAX, None));
1888 use core::isize::{MAX as IMAX, MIN as IMIN};
1889 assert_eq!((0..0isize).size_hint(), (0, Some(0)));
1890 assert_eq!((-100..100isize).size_hint(), (200, Some(200)));
1891 assert_eq!((IMIN..IMAX).size_hint(), (UMAX, Some(UMAX)));
1893 let imin = i128::try_from(IMIN).unwrap();
1894 let imax = i128::try_from(IMAX).unwrap();
1895 assert_eq!((0..0i128).size_hint(), (0, Some(0)));
1896 assert_eq!((-100..100i128).size_hint(), (200, Some(200)));
1897 assert_eq!((imin..imax).size_hint(), (UMAX, Some(UMAX)));
1898 assert_eq!((imin..imax + 1).size_hint(), (UMAX, None));
1902 fn test_range_inclusive_size_hint() {
1903 use core::usize::MAX as UMAX;
1904 assert_eq!((1..=0usize).size_hint(), (0, Some(0)));
1905 assert_eq!((0..=0usize).size_hint(), (1, Some(1)));
1906 assert_eq!((0..=100usize).size_hint(), (101, Some(101)));
1907 assert_eq!((0..=UMAX - 1).size_hint(), (UMAX, Some(UMAX)));
1908 assert_eq!((0..=UMAX).size_hint(), (UMAX, None));
1910 let umax = u128::try_from(UMAX).unwrap();
1911 assert_eq!((1..=0u128).size_hint(), (0, Some(0)));
1912 assert_eq!((0..=0u128).size_hint(), (1, Some(1)));
1913 assert_eq!((0..=100u128).size_hint(), (101, Some(101)));
1914 assert_eq!((0..=umax - 1).size_hint(), (UMAX, Some(UMAX)));
1915 assert_eq!((0..=umax).size_hint(), (UMAX, None));
1916 assert_eq!((0..=umax + 1).size_hint(), (UMAX, None));
1918 use core::isize::{MAX as IMAX, MIN as IMIN};
1919 assert_eq!((0..=-1isize).size_hint(), (0, Some(0)));
1920 assert_eq!((0..=0isize).size_hint(), (1, Some(1)));
1921 assert_eq!((-100..=100isize).size_hint(), (201, Some(201)));
1922 assert_eq!((IMIN..=IMAX - 1).size_hint(), (UMAX, Some(UMAX)));
1923 assert_eq!((IMIN..=IMAX).size_hint(), (UMAX, None));
1925 let imin = i128::try_from(IMIN).unwrap();
1926 let imax = i128::try_from(IMAX).unwrap();
1927 assert_eq!((0..=-1i128).size_hint(), (0, Some(0)));
1928 assert_eq!((0..=0i128).size_hint(), (1, Some(1)));
1929 assert_eq!((-100..=100i128).size_hint(), (201, Some(201)));
1930 assert_eq!((imin..=imax - 1).size_hint(), (UMAX, Some(UMAX)));
1931 assert_eq!((imin..=imax).size_hint(), (UMAX, None));
1932 assert_eq!((imin..=imax + 1).size_hint(), (UMAX, None));
1937 let mut it = repeat(42);
1938 assert_eq!(it.next(), Some(42));
1939 assert_eq!(it.next(), Some(42));
1940 assert_eq!(it.next(), Some(42));
1941 assert_eq!(repeat(42).size_hint(), (usize::MAX, None));
1945 fn test_repeat_take() {
1946 let mut it = repeat(42).take(3);
1947 assert_eq!(it.next(), Some(42));
1948 assert_eq!(it.next(), Some(42));
1949 assert_eq!(it.next(), Some(42));
1950 assert_eq!(it.next(), None);
1951 is_trusted_len(repeat(42).take(3));
1952 assert_eq!(repeat(42).take(3).size_hint(), (3, Some(3)));
1953 assert_eq!(repeat(42).take(0).size_hint(), (0, Some(0)));
1954 assert_eq!(repeat(42).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
1958 fn test_repeat_take_collect() {
1959 let v: Vec<_> = repeat(42).take(3).collect();
1960 assert_eq!(v, vec![42, 42, 42]);
1964 fn test_repeat_with() {
1965 #[derive(PartialEq, Debug)]
1966 struct NotClone(usize);
1967 let mut it = repeat_with(|| NotClone(42));
1968 assert_eq!(it.next(), Some(NotClone(42)));
1969 assert_eq!(it.next(), Some(NotClone(42)));
1970 assert_eq!(it.next(), Some(NotClone(42)));
1971 assert_eq!(repeat_with(|| NotClone(42)).size_hint(), (usize::MAX, None));
1975 fn test_repeat_with_take() {
1976 let mut it = repeat_with(|| 42).take(3);
1977 assert_eq!(it.next(), Some(42));
1978 assert_eq!(it.next(), Some(42));
1979 assert_eq!(it.next(), Some(42));
1980 assert_eq!(it.next(), None);
1981 is_trusted_len(repeat_with(|| 42).take(3));
1982 assert_eq!(repeat_with(|| 42).take(3).size_hint(), (3, Some(3)));
1983 assert_eq!(repeat_with(|| 42).take(0).size_hint(), (0, Some(0)));
1984 assert_eq!(repeat_with(|| 42).take(usize::MAX).size_hint(),
1985 (usize::MAX, Some(usize::MAX)));
1989 fn test_repeat_with_take_collect() {
1991 let v: Vec<_> = repeat_with(|| { let tmp = curr; curr *= 2; tmp })
1993 assert_eq!(v, vec![1, 2, 4, 8, 16]);
1997 fn test_successors() {
1998 let mut powers_of_10 = successors(Some(1_u16), |n| n.checked_mul(10));
1999 assert_eq!(powers_of_10.by_ref().collect::<Vec<_>>(), &[1, 10, 100, 1_000, 10_000]);
2000 assert_eq!(powers_of_10.next(), None);
2002 let mut empty = successors(None::<u32>, |_| unimplemented!());
2003 assert_eq!(empty.next(), None);
2004 assert_eq!(empty.next(), None);
2010 assert_eq!(it.len(), 3);
2011 assert_eq!(it.next(), Some(0));
2012 assert_eq!(it.len(), 2);
2013 assert_eq!(it.next(), Some(1));
2014 assert_eq!(it.len(), 1);
2015 assert_eq!(it.next(), Some(2));
2016 assert_eq!(it.len(), 0);
2017 assert_eq!(it.next(), None);
2018 assert_eq!(it.len(), 0);
2019 assert_eq!(it.next(), None);
2020 assert_eq!(it.len(), 0);
2021 assert_eq!(it.next(), None);
2022 assert_eq!(it.len(), 0);
2026 fn test_fuse_nth() {
2028 let mut it = xs.iter();
2030 assert_eq!(it.len(), 3);
2031 assert_eq!(it.nth(2), Some(&2));
2032 assert_eq!(it.len(), 0);
2033 assert_eq!(it.nth(2), None);
2034 assert_eq!(it.len(), 0);
2038 fn test_fuse_last() {
2042 assert_eq!(it.len(), 3);
2043 assert_eq!(it.last(), Some(&2));
2047 fn test_fuse_count() {
2051 assert_eq!(it.len(), 3);
2052 assert_eq!(it.count(), 3);
2053 // Can't check len now because count consumes.
2057 fn test_fuse_fold() {
2059 let it = xs.iter(); // `FusedIterator`
2060 let i = it.fuse().fold(0, |i, &x| {
2061 assert_eq!(x, xs[i]);
2064 assert_eq!(i, xs.len());
2066 let it = xs.iter(); // `FusedIterator`
2067 let i = it.fuse().rfold(xs.len(), |i, &x| {
2068 assert_eq!(x, xs[i - 1]);
2073 let it = xs.iter().scan((), |_, &x| Some(x)); // `!FusedIterator`
2074 let i = it.fuse().fold(0, |i, x| {
2075 assert_eq!(x, xs[i]);
2078 assert_eq!(i, xs.len());
2083 let mut it = once(42);
2084 assert_eq!(it.next(), Some(42));
2085 assert_eq!(it.next(), None);
2089 fn test_once_with() {
2090 let count = Cell::new(0);
2091 let mut it = once_with(|| {
2092 count.set(count.get() + 1);
2096 assert_eq!(count.get(), 0);
2097 assert_eq!(it.next(), Some(42));
2098 assert_eq!(count.get(), 1);
2099 assert_eq!(it.next(), None);
2100 assert_eq!(count.get(), 1);
2101 assert_eq!(it.next(), None);
2102 assert_eq!(count.get(), 1);
2107 let mut it = empty::<i32>();
2108 assert_eq!(it.next(), None);
2112 fn test_chain_fold() {
2116 let mut iter = xs.iter().chain(&ys);
2118 let mut result = Vec::new();
2119 iter.fold((), |(), &elt| result.push(elt));
2120 assert_eq!(&[2, 3, 1, 2, 0], &result[..]);
2124 fn test_step_replace_unsigned() {
2126 let y = x.replace_zero();
2131 let y = x.replace_one();
2137 fn test_step_replace_signed() {
2139 let y = x.replace_zero();
2144 let y = x.replace_one();
2150 fn test_step_replace_no_between() {
2152 let y = x.replace_zero();
2157 let y = x.replace_one();
2163 fn test_rev_try_folds() {
2164 let f = &|acc, x| i32::checked_add(2*acc, x);
2165 assert_eq!((1..10).rev().try_fold(7, f), (1..10).try_rfold(7, f));
2166 assert_eq!((1..10).rev().try_rfold(7, f), (1..10).try_fold(7, f));
2168 let a = [10, 20, 30, 40, 100, 60, 70, 80, 90];
2169 let mut iter = a.iter().rev();
2170 assert_eq!(iter.try_fold(0_i8, |acc, &x| acc.checked_add(x)), None);
2171 assert_eq!(iter.next(), Some(&70));
2172 let mut iter = a.iter().rev();
2173 assert_eq!(iter.try_rfold(0_i8, |acc, &x| acc.checked_add(x)), None);
2174 assert_eq!(iter.next_back(), Some(&60));
2178 fn test_cloned_try_folds() {
2179 let a = [1, 2, 3, 4, 5, 6, 7, 8, 9];
2180 let f = &|acc, x| i32::checked_add(2*acc, x);
2181 let f_ref = &|acc, &x| i32::checked_add(2*acc, x);
2182 assert_eq!(a.iter().cloned().try_fold(7, f), a.iter().try_fold(7, f_ref));
2183 assert_eq!(a.iter().cloned().try_rfold(7, f), a.iter().try_rfold(7, f_ref));
2185 let a = [10, 20, 30, 40, 100, 60, 70, 80, 90];
2186 let mut iter = a.iter().cloned();
2187 assert_eq!(iter.try_fold(0_i8, |acc, x| acc.checked_add(x)), None);
2188 assert_eq!(iter.next(), Some(60));
2189 let mut iter = a.iter().cloned();
2190 assert_eq!(iter.try_rfold(0_i8, |acc, x| acc.checked_add(x)), None);
2191 assert_eq!(iter.next_back(), Some(70));
2195 fn test_chain_try_folds() {
2196 let c = || (0..10).chain(10..20);
2198 let f = &|acc, x| i32::checked_add(2*acc, x);
2199 assert_eq!(c().try_fold(7, f), (0..20).try_fold(7, f));
2200 assert_eq!(c().try_rfold(7, f), (0..20).rev().try_fold(7, f));
2203 assert_eq!(iter.position(|x| x == 5), Some(5));
2204 assert_eq!(iter.next(), Some(6), "stopped in front, state Both");
2205 assert_eq!(iter.position(|x| x == 13), Some(6));
2206 assert_eq!(iter.next(), Some(14), "stopped in back, state Back");
2207 assert_eq!(iter.try_fold(0, |acc, x| Some(acc+x)), Some((15..20).sum()));
2209 let mut iter = c().rev(); // use rev to access try_rfold
2210 assert_eq!(iter.position(|x| x == 15), Some(4));
2211 assert_eq!(iter.next(), Some(14), "stopped in back, state Both");
2212 assert_eq!(iter.position(|x| x == 5), Some(8));
2213 assert_eq!(iter.next(), Some(4), "stopped in front, state Front");
2214 assert_eq!(iter.try_fold(0, |acc, x| Some(acc+x)), Some((0..4).sum()));
2217 iter.by_ref().rev().nth(14); // skip the last 15, ending in state Front
2218 assert_eq!(iter.try_fold(7, f), (0..5).try_fold(7, f));
2221 iter.nth(14); // skip the first 15, ending in state Back
2222 assert_eq!(iter.try_rfold(7, f), (15..20).try_rfold(7, f));
2226 fn test_map_try_folds() {
2227 let f = &|acc, x| i32::checked_add(2*acc, x);
2228 assert_eq!((0..10).map(|x| x+3).try_fold(7, f), (3..13).try_fold(7, f));
2229 assert_eq!((0..10).map(|x| x+3).try_rfold(7, f), (3..13).try_rfold(7, f));
2231 let mut iter = (0..40).map(|x| x+10);
2232 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2233 assert_eq!(iter.next(), Some(20));
2234 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2235 assert_eq!(iter.next_back(), Some(46));
2239 fn test_filter_try_folds() {
2240 fn p(&x: &i32) -> bool { 0 <= x && x < 10 }
2241 let f = &|acc, x| i32::checked_add(2*acc, x);
2242 assert_eq!((-10..20).filter(p).try_fold(7, f), (0..10).try_fold(7, f));
2243 assert_eq!((-10..20).filter(p).try_rfold(7, f), (0..10).try_rfold(7, f));
2245 let mut iter = (0..40).filter(|&x| x % 2 == 1);
2246 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2247 assert_eq!(iter.next(), Some(25));
2248 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2249 assert_eq!(iter.next_back(), Some(31));
2253 fn test_filter_map_try_folds() {
2254 let mp = &|x| if 0 <= x && x < 10 { Some(x*2) } else { None };
2255 let f = &|acc, x| i32::checked_add(2*acc, x);
2256 assert_eq!((-9..20).filter_map(mp).try_fold(7, f), (0..10).map(|x| 2*x).try_fold(7, f));
2257 assert_eq!((-9..20).filter_map(mp).try_rfold(7, f), (0..10).map(|x| 2*x).try_rfold(7, f));
2259 let mut iter = (0..40).filter_map(|x| if x%2 == 1 { None } else { Some(x*2 + 10) });
2260 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2261 assert_eq!(iter.next(), Some(38));
2262 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2263 assert_eq!(iter.next_back(), Some(78));
2267 fn test_enumerate_try_folds() {
2268 let f = &|acc, (i, x)| usize::checked_add(2*acc, x/(i+1) + i);
2269 assert_eq!((9..18).enumerate().try_fold(7, f), (0..9).map(|i| (i, i+9)).try_fold(7, f));
2270 assert_eq!((9..18).enumerate().try_rfold(7, f), (0..9).map(|i| (i, i+9)).try_rfold(7, f));
2272 let mut iter = (100..200).enumerate();
2273 let f = &|acc, (i, x)| u8::checked_add(acc, u8::checked_div(x, i as u8 + 1)?);
2274 assert_eq!(iter.try_fold(0, f), None);
2275 assert_eq!(iter.next(), Some((7, 107)));
2276 assert_eq!(iter.try_rfold(0, f), None);
2277 assert_eq!(iter.next_back(), Some((11, 111)));
2281 fn test_peek_try_fold() {
2282 let f = &|acc, x| i32::checked_add(2*acc, x);
2283 assert_eq!((1..20).peekable().try_fold(7, f), (1..20).try_fold(7, f));
2284 let mut iter = (1..20).peekable();
2285 assert_eq!(iter.peek(), Some(&1));
2286 assert_eq!(iter.try_fold(7, f), (1..20).try_fold(7, f));
2288 let mut iter = [100, 20, 30, 40, 50, 60, 70].iter().cloned().peekable();
2289 assert_eq!(iter.peek(), Some(&100));
2290 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2291 assert_eq!(iter.peek(), Some(&40));
2295 fn test_skip_while_try_fold() {
2296 let f = &|acc, x| i32::checked_add(2*acc, x);
2297 fn p(&x: &i32) -> bool { (x % 10) <= 5 }
2298 assert_eq!((1..20).skip_while(p).try_fold(7, f), (6..20).try_fold(7, f));
2299 let mut iter = (1..20).skip_while(p);
2300 assert_eq!(iter.nth(5), Some(11));
2301 assert_eq!(iter.try_fold(7, f), (12..20).try_fold(7, f));
2303 let mut iter = (0..50).skip_while(|&x| (x % 20) < 15);
2304 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2305 assert_eq!(iter.next(), Some(23));
2309 fn test_take_while_folds() {
2310 let f = &|acc, x| i32::checked_add(2*acc, x);
2311 assert_eq!((1..20).take_while(|&x| x != 10).try_fold(7, f), (1..10).try_fold(7, f));
2312 let mut iter = (1..20).take_while(|&x| x != 10);
2313 assert_eq!(iter.try_fold(0, |x, y| Some(x+y)), Some((1..10).sum()));
2314 assert_eq!(iter.next(), None, "flag should be set");
2315 let iter = (1..20).take_while(|&x| x != 10);
2316 assert_eq!(iter.fold(0, |x, y| x+y), (1..10).sum());
2318 let mut iter = (10..50).take_while(|&x| x != 40);
2319 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2320 assert_eq!(iter.next(), Some(20));
2324 fn test_skip_try_folds() {
2325 let f = &|acc, x| i32::checked_add(2*acc, x);
2326 assert_eq!((1..20).skip(9).try_fold(7, f), (10..20).try_fold(7, f));
2327 assert_eq!((1..20).skip(9).try_rfold(7, f), (10..20).try_rfold(7, f));
2329 let mut iter = (0..30).skip(10);
2330 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2331 assert_eq!(iter.next(), Some(20));
2332 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2333 assert_eq!(iter.next_back(), Some(24));
2337 fn test_skip_nth_back() {
2338 let xs = [0, 1, 2, 3, 4, 5];
2339 let mut it = xs.iter().skip(2);
2340 assert_eq!(it.nth_back(0), Some(&5));
2341 assert_eq!(it.nth_back(1), Some(&3));
2342 assert_eq!(it.nth_back(0), Some(&2));
2343 assert_eq!(it.nth_back(0), None);
2345 let ys = [2, 3, 4, 5];
2346 let mut ity = ys.iter();
2347 let mut it = xs.iter().skip(2);
2348 assert_eq!(it.nth_back(1), ity.nth_back(1));
2349 assert_eq!(it.clone().nth(0), ity.clone().nth(0));
2350 assert_eq!(it.nth_back(0), ity.nth_back(0));
2351 assert_eq!(it.clone().nth(0), ity.clone().nth(0));
2352 assert_eq!(it.nth_back(0), ity.nth_back(0));
2353 assert_eq!(it.clone().nth(0), ity.clone().nth(0));
2354 assert_eq!(it.nth_back(0), ity.nth_back(0));
2355 assert_eq!(it.clone().nth(0), ity.clone().nth(0));
2357 let mut it = xs.iter().skip(2);
2358 assert_eq!(it.nth_back(4), None);
2359 assert_eq!(it.nth_back(0), None);
2361 let mut it = xs.iter();
2362 it.by_ref().skip(2).nth_back(3);
2363 assert_eq!(it.next_back(), Some(&1));
2365 let mut it = xs.iter();
2366 it.by_ref().skip(2).nth_back(10);
2367 assert_eq!(it.next_back(), Some(&1));
2371 fn test_take_try_folds() {
2372 let f = &|acc, x| i32::checked_add(2*acc, x);
2373 assert_eq!((10..30).take(10).try_fold(7, f), (10..20).try_fold(7, f));
2374 //assert_eq!((10..30).take(10).try_rfold(7, f), (10..20).try_rfold(7, f));
2376 let mut iter = (10..30).take(20);
2377 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2378 assert_eq!(iter.next(), Some(20));
2379 //assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2380 //assert_eq!(iter.next_back(), Some(24));
2384 fn test_flat_map_try_folds() {
2385 let f = &|acc, x| i32::checked_add(acc*2/3, x);
2386 let mr = &|x| (5*x)..(5*x + 5);
2387 assert_eq!((0..10).flat_map(mr).try_fold(7, f), (0..50).try_fold(7, f));
2388 assert_eq!((0..10).flat_map(mr).try_rfold(7, f), (0..50).try_rfold(7, f));
2389 let mut iter = (0..10).flat_map(mr);
2390 iter.next(); iter.next_back(); // have front and back iters in progress
2391 assert_eq!(iter.try_rfold(7, f), (1..49).try_rfold(7, f));
2393 let mut iter = (0..10).flat_map(|x| (4*x)..(4*x + 4));
2394 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2395 assert_eq!(iter.next(), Some(17));
2396 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2397 assert_eq!(iter.next_back(), Some(35));
2401 fn test_flatten_try_folds() {
2402 let f = &|acc, x| i32::checked_add(acc*2/3, x);
2403 let mr = &|x| (5*x)..(5*x + 5);
2404 assert_eq!((0..10).map(mr).flatten().try_fold(7, f), (0..50).try_fold(7, f));
2405 assert_eq!((0..10).map(mr).flatten().try_rfold(7, f), (0..50).try_rfold(7, f));
2406 let mut iter = (0..10).map(mr).flatten();
2407 iter.next(); iter.next_back(); // have front and back iters in progress
2408 assert_eq!(iter.try_rfold(7, f), (1..49).try_rfold(7, f));
2410 let mut iter = (0..10).map(|x| (4*x)..(4*x + 4)).flatten();
2411 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2412 assert_eq!(iter.next(), Some(17));
2413 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2414 assert_eq!(iter.next_back(), Some(35));
2418 fn test_functor_laws() {
2420 fn identity<T>(x: T) -> T { x }
2421 assert_eq!((0..10).map(identity).sum::<usize>(), (0..10).sum());
2424 fn f(x: usize) -> usize { x + 3 }
2425 fn g(x: usize) -> usize { x * 2 }
2426 fn h(x: usize) -> usize { g(f(x)) }
2427 assert_eq!((0..10).map(f).map(g).sum::<usize>(), (0..10).map(h).sum());
2431 fn test_monad_laws_left_identity() {
2432 fn f(x: usize) -> impl Iterator<Item = usize> {
2433 (0..10).map(move |y| x * y)
2435 assert_eq!(once(42).flat_map(f.clone()).sum::<usize>(), f(42).sum());
2439 fn test_monad_laws_right_identity() {
2440 assert_eq!((0..10).flat_map(|x| once(x)).sum::<usize>(), (0..10).sum());
2444 fn test_monad_laws_associativity() {
2445 fn f(x: usize) -> impl Iterator<Item = usize> { 0..x }
2446 fn g(x: usize) -> impl Iterator<Item = usize> { (0..x).rev() }
2447 assert_eq!((0..10).flat_map(f).flat_map(g).sum::<usize>(),
2448 (0..10).flat_map(|x| f(x).flat_map(g)).sum::<usize>());
2452 fn test_is_sorted() {
2453 assert!([1, 2, 2, 9].iter().is_sorted());
2454 assert!(![1, 3, 2].iter().is_sorted());
2455 assert!([0].iter().is_sorted());
2456 assert!(std::iter::empty::<i32>().is_sorted());
2457 assert!(![0.0, 1.0, std::f32::NAN].iter().is_sorted());
2458 assert!([-2, -1, 0, 3].iter().is_sorted());
2459 assert!(![-2i32, -1, 0, 3].iter().is_sorted_by_key(|n| n.abs()));
2460 assert!(!["c", "bb", "aaa"].iter().is_sorted());
2461 assert!(["c", "bb", "aaa"].iter().is_sorted_by_key(|s| s.len()));
2465 fn test_partition() {
2466 fn check(xs: &mut [i32], ref p: impl Fn(&i32) -> bool, expected: usize) {
2467 let i = xs.iter_mut().partition_in_place(p);
2468 assert_eq!(expected, i);
2469 assert!(xs[..i].iter().all(p));
2470 assert!(!xs[i..].iter().any(p));
2471 assert!(xs.iter().is_partitioned(p));
2472 if i == 0 || i == xs.len() {
2473 assert!(xs.iter().rev().is_partitioned(p));
2475 assert!(!xs.iter().rev().is_partitioned(p));
2479 check(&mut [], |_| true, 0);
2480 check(&mut [], |_| false, 0);
2482 check(&mut [0], |_| true, 1);
2483 check(&mut [0], |_| false, 0);
2485 check(&mut [-1, 1], |&x| x > 0, 1);
2486 check(&mut [-1, 1], |&x| x < 0, 1);
2488 let ref mut xs = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
2489 check(xs, |_| true, 10);
2490 check(xs, |_| false, 0);
2491 check(xs, |&x| x % 2 == 0, 5); // evens
2492 check(xs, |&x| x % 2 == 1, 5); // odds
2493 check(xs, |&x| x % 3 == 0, 4); // multiple of 3
2494 check(xs, |&x| x % 4 == 0, 3); // multiple of 4
2495 check(xs, |&x| x % 5 == 0, 2); // multiple of 5
2496 check(xs, |&x| x < 3, 3); // small
2497 check(xs, |&x| x > 6, 3); // large