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_count() {
394 let xs = [0, 1, 2, 3, 4, 5];
395 assert_eq!(xs.iter().enumerate().count(), 6);
399 fn test_iterator_enumerate_fold() {
400 let xs = [0, 1, 2, 3, 4, 5];
401 let mut it = xs.iter().enumerate();
402 // steal a couple to get an interesting offset
403 assert_eq!(it.next(), Some((0, &0)));
404 assert_eq!(it.next(), Some((1, &1)));
405 let i = it.fold(2, |i, (j, &x)| {
407 assert_eq!(x, xs[j]);
410 assert_eq!(i, xs.len());
412 let mut it = xs.iter().enumerate();
413 assert_eq!(it.next(), Some((0, &0)));
414 let i = it.rfold(xs.len() - 1, |i, (j, &x)| {
416 assert_eq!(x, xs[j]);
423 fn test_iterator_filter_count() {
424 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
425 assert_eq!(xs.iter().filter(|&&x| x % 2 == 0).count(), 5);
429 fn test_iterator_filter_fold() {
430 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
431 let ys = [0, 2, 4, 6, 8];
432 let it = xs.iter().filter(|&&x| x % 2 == 0);
433 let i = it.fold(0, |i, &x| {
434 assert_eq!(x, ys[i]);
437 assert_eq!(i, ys.len());
439 let it = xs.iter().filter(|&&x| x % 2 == 0);
440 let i = it.rfold(ys.len(), |i, &x| {
441 assert_eq!(x, ys[i - 1]);
448 fn test_iterator_peekable() {
449 let xs = vec![0, 1, 2, 3, 4, 5];
450 let mut it = xs.iter().cloned().peekable();
452 assert_eq!(it.len(), 6);
453 assert_eq!(it.peek().unwrap(), &0);
454 assert_eq!(it.len(), 6);
455 assert_eq!(it.next().unwrap(), 0);
456 assert_eq!(it.len(), 5);
457 assert_eq!(it.next().unwrap(), 1);
458 assert_eq!(it.len(), 4);
459 assert_eq!(it.next().unwrap(), 2);
460 assert_eq!(it.len(), 3);
461 assert_eq!(it.peek().unwrap(), &3);
462 assert_eq!(it.len(), 3);
463 assert_eq!(it.peek().unwrap(), &3);
464 assert_eq!(it.len(), 3);
465 assert_eq!(it.next().unwrap(), 3);
466 assert_eq!(it.len(), 2);
467 assert_eq!(it.next().unwrap(), 4);
468 assert_eq!(it.len(), 1);
469 assert_eq!(it.peek().unwrap(), &5);
470 assert_eq!(it.len(), 1);
471 assert_eq!(it.next().unwrap(), 5);
472 assert_eq!(it.len(), 0);
473 assert!(it.peek().is_none());
474 assert_eq!(it.len(), 0);
475 assert!(it.next().is_none());
476 assert_eq!(it.len(), 0);
480 fn test_iterator_peekable_count() {
481 let xs = [0, 1, 2, 3, 4, 5];
483 let zs: [i32; 0] = [];
485 assert_eq!(xs.iter().peekable().count(), 6);
487 let mut it = xs.iter().peekable();
488 assert_eq!(it.peek(), Some(&&0));
489 assert_eq!(it.count(), 6);
491 assert_eq!(ys.iter().peekable().count(), 1);
493 let mut it = ys.iter().peekable();
494 assert_eq!(it.peek(), Some(&&10));
495 assert_eq!(it.count(), 1);
497 assert_eq!(zs.iter().peekable().count(), 0);
499 let mut it = zs.iter().peekable();
500 assert_eq!(it.peek(), None);
505 fn test_iterator_peekable_nth() {
506 let xs = [0, 1, 2, 3, 4, 5];
507 let mut it = xs.iter().peekable();
509 assert_eq!(it.peek(), Some(&&0));
510 assert_eq!(it.nth(0), Some(&0));
511 assert_eq!(it.peek(), Some(&&1));
512 assert_eq!(it.nth(1), Some(&2));
513 assert_eq!(it.peek(), Some(&&3));
514 assert_eq!(it.nth(2), Some(&5));
515 assert_eq!(it.next(), None);
519 fn test_iterator_peekable_last() {
520 let xs = [0, 1, 2, 3, 4, 5];
523 let mut it = xs.iter().peekable();
524 assert_eq!(it.peek(), Some(&&0));
525 assert_eq!(it.last(), Some(&5));
527 let mut it = ys.iter().peekable();
528 assert_eq!(it.peek(), Some(&&0));
529 assert_eq!(it.last(), Some(&0));
531 let mut it = ys.iter().peekable();
532 assert_eq!(it.next(), Some(&0));
533 assert_eq!(it.peek(), None);
534 assert_eq!(it.last(), None);
538 fn test_iterator_peekable_fold() {
539 let xs = [0, 1, 2, 3, 4, 5];
540 let mut it = xs.iter().peekable();
541 assert_eq!(it.peek(), Some(&&0));
542 let i = it.fold(0, |i, &x| {
543 assert_eq!(x, xs[i]);
546 assert_eq!(i, xs.len());
549 /// This is an iterator that follows the Iterator contract,
550 /// but it is not fused. After having returned None once, it will start
551 /// producing elements if .next() is called again.
552 pub struct CycleIter<'a, T: 'a> {
557 pub fn cycle<T>(data: &[T]) -> CycleIter<T> {
564 impl<'a, T> Iterator for CycleIter<'a, T> {
566 fn next(&mut self) -> Option<Self::Item> {
567 let elt = self.data.get(self.index);
569 self.index %= 1 + self.data.len();
575 fn test_iterator_peekable_remember_peek_none_1() {
576 // Check that the loop using .peek() terminates
577 let data = [1, 2, 3];
578 let mut iter = cycle(&data).peekable();
581 while let Some(_) = iter.next() {
582 let is_the_last = iter.peek().is_none();
583 assert_eq!(is_the_last, n == data.len() - 1);
585 if n > data.len() { break; }
587 assert_eq!(n, data.len());
591 fn test_iterator_peekable_remember_peek_none_2() {
593 let mut iter = cycle(&data).peekable();
595 assert_eq!(iter.peek(), None);
596 assert_eq!(iter.last(), None);
600 fn test_iterator_peekable_remember_peek_none_3() {
602 let mut iter = cycle(&data).peekable();
604 assert_eq!(iter.nth(0), Some(&0));
606 let mut iter = cycle(&data).peekable();
608 assert_eq!(iter.peek(), None);
609 assert_eq!(iter.nth(0), None);
613 fn test_iterator_take_while() {
614 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
615 let ys = [0, 1, 2, 3, 5, 13];
616 let it = xs.iter().take_while(|&x| *x < 15);
619 assert_eq!(*x, ys[i]);
622 assert_eq!(i, ys.len());
626 fn test_iterator_skip_while() {
627 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
628 let ys = [15, 16, 17, 19];
629 let it = xs.iter().skip_while(|&x| *x < 15);
632 assert_eq!(*x, ys[i]);
635 assert_eq!(i, ys.len());
639 fn test_iterator_skip_while_fold() {
640 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
641 let ys = [15, 16, 17, 19];
642 let it = xs.iter().skip_while(|&x| *x < 15);
643 let i = it.fold(0, |i, &x| {
644 assert_eq!(x, ys[i]);
647 assert_eq!(i, ys.len());
649 let mut it = xs.iter().skip_while(|&x| *x < 15);
650 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
651 let i = it.fold(1, |i, &x| {
652 assert_eq!(x, ys[i]);
655 assert_eq!(i, ys.len());
659 fn test_iterator_skip() {
660 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
661 let ys = [13, 15, 16, 17, 19, 20, 30];
662 let mut it = xs.iter().skip(5);
664 while let Some(&x) = it.next() {
665 assert_eq!(x, ys[i]);
667 assert_eq!(it.len(), xs.len()-5-i);
669 assert_eq!(i, ys.len());
670 assert_eq!(it.len(), 0);
674 fn test_iterator_skip_doubleended() {
675 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
676 let mut it = xs.iter().rev().skip(5);
677 assert_eq!(it.next(), Some(&15));
678 assert_eq!(it.by_ref().rev().next(), Some(&0));
679 assert_eq!(it.next(), Some(&13));
680 assert_eq!(it.by_ref().rev().next(), Some(&1));
681 assert_eq!(it.next(), Some(&5));
682 assert_eq!(it.by_ref().rev().next(), Some(&2));
683 assert_eq!(it.next(), Some(&3));
684 assert_eq!(it.next(), None);
685 let mut it = xs.iter().rev().skip(5).rev();
686 assert_eq!(it.next(), Some(&0));
687 assert_eq!(it.rev().next(), Some(&15));
688 let mut it_base = xs.iter();
690 let mut it = it_base.by_ref().skip(5).rev();
691 assert_eq!(it.next(), Some(&30));
692 assert_eq!(it.next(), Some(&20));
693 assert_eq!(it.next(), Some(&19));
694 assert_eq!(it.next(), Some(&17));
695 assert_eq!(it.next(), Some(&16));
696 assert_eq!(it.next(), Some(&15));
697 assert_eq!(it.next(), Some(&13));
698 assert_eq!(it.next(), None);
700 // make sure the skipped parts have not been consumed
701 assert_eq!(it_base.next(), Some(&0));
702 assert_eq!(it_base.next(), Some(&1));
703 assert_eq!(it_base.next(), Some(&2));
704 assert_eq!(it_base.next(), Some(&3));
705 assert_eq!(it_base.next(), Some(&5));
706 assert_eq!(it_base.next(), None);
707 let it = xs.iter().skip(5).rev();
708 assert_eq!(it.last(), Some(&13));
712 fn test_iterator_skip_nth() {
713 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
715 let mut it = xs.iter().skip(0);
716 assert_eq!(it.nth(0), Some(&0));
717 assert_eq!(it.nth(1), Some(&2));
719 let mut it = xs.iter().skip(5);
720 assert_eq!(it.nth(0), Some(&13));
721 assert_eq!(it.nth(1), Some(&16));
723 let mut it = xs.iter().skip(12);
724 assert_eq!(it.nth(0), None);
729 fn test_iterator_skip_count() {
730 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
732 assert_eq!(xs.iter().skip(0).count(), 12);
733 assert_eq!(xs.iter().skip(1).count(), 11);
734 assert_eq!(xs.iter().skip(11).count(), 1);
735 assert_eq!(xs.iter().skip(12).count(), 0);
736 assert_eq!(xs.iter().skip(13).count(), 0);
740 fn test_iterator_skip_last() {
741 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
743 assert_eq!(xs.iter().skip(0).last(), Some(&30));
744 assert_eq!(xs.iter().skip(1).last(), Some(&30));
745 assert_eq!(xs.iter().skip(11).last(), Some(&30));
746 assert_eq!(xs.iter().skip(12).last(), None);
747 assert_eq!(xs.iter().skip(13).last(), None);
749 let mut it = xs.iter().skip(5);
750 assert_eq!(it.next(), Some(&13));
751 assert_eq!(it.last(), Some(&30));
755 fn test_iterator_skip_fold() {
756 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
757 let ys = [13, 15, 16, 17, 19, 20, 30];
759 let it = xs.iter().skip(5);
760 let i = it.fold(0, |i, &x| {
761 assert_eq!(x, ys[i]);
764 assert_eq!(i, ys.len());
766 let mut it = xs.iter().skip(5);
767 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
768 let i = it.fold(1, |i, &x| {
769 assert_eq!(x, ys[i]);
772 assert_eq!(i, ys.len());
774 let it = xs.iter().skip(5);
775 let i = it.rfold(ys.len(), |i, &x| {
777 assert_eq!(x, ys[i]);
782 let mut it = xs.iter().skip(5);
783 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
784 let i = it.rfold(ys.len(), |i, &x| {
786 assert_eq!(x, ys[i]);
794 fn test_iterator_take() {
795 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
796 let ys = [0, 1, 2, 3, 5];
797 let mut it = xs.iter().take(5);
799 assert_eq!(it.len(), 5);
800 while let Some(&x) = it.next() {
801 assert_eq!(x, ys[i]);
803 assert_eq!(it.len(), 5-i);
805 assert_eq!(i, ys.len());
806 assert_eq!(it.len(), 0);
810 fn test_iterator_take_nth() {
811 let xs = [0, 1, 2, 4, 5];
812 let mut it = xs.iter();
814 let mut take = it.by_ref().take(3);
816 while let Some(&x) = take.nth(0) {
821 assert_eq!(it.nth(1), Some(&5));
822 assert_eq!(it.nth(0), None);
824 let xs = [0, 1, 2, 3, 4];
825 let mut it = xs.iter().take(7);
827 while let Some(&x) = it.nth(1) {
834 fn test_iterator_take_short() {
835 let xs = [0, 1, 2, 3];
836 let ys = [0, 1, 2, 3];
837 let mut it = xs.iter().take(5);
839 assert_eq!(it.len(), 4);
840 while let Some(&x) = it.next() {
841 assert_eq!(x, ys[i]);
843 assert_eq!(it.len(), 4-i);
845 assert_eq!(i, ys.len());
846 assert_eq!(it.len(), 0);
850 fn test_iterator_scan() {
851 // test the type inference
852 fn add(old: &mut isize, new: &usize) -> Option<f64> {
853 *old += *new as isize;
856 let xs = [0, 1, 2, 3, 4];
857 let ys = [0f64, 1.0, 3.0, 6.0, 10.0];
859 let it = xs.iter().scan(0, add);
862 assert_eq!(x, ys[i]);
865 assert_eq!(i, ys.len());
869 fn test_iterator_flat_map() {
871 let ys = [0, 1, 2, 3, 4, 5, 6, 7, 8];
872 let it = xs.iter().flat_map(|&x| (x..).step_by(1).take(3));
875 assert_eq!(x, ys[i]);
878 assert_eq!(i, ys.len());
881 /// Tests `FlatMap::fold` with items already picked off the front and back,
882 /// to make sure all parts of the `FlatMap` are folded correctly.
884 fn test_iterator_flat_map_fold() {
886 let ys = [1, 2, 3, 4, 5, 6, 7];
887 let mut it = xs.iter().flat_map(|&x| x..x+3);
888 assert_eq!(it.next(), Some(0));
889 assert_eq!(it.next_back(), Some(8));
890 let i = it.fold(0, |i, x| {
891 assert_eq!(x, ys[i]);
894 assert_eq!(i, ys.len());
896 let mut it = xs.iter().flat_map(|&x| x..x+3);
897 assert_eq!(it.next(), Some(0));
898 assert_eq!(it.next_back(), Some(8));
899 let i = it.rfold(ys.len(), |i, x| {
900 assert_eq!(x, ys[i - 1]);
907 fn test_iterator_flatten() {
909 let ys = [0, 1, 2, 3, 4, 5, 6, 7, 8];
910 let it = xs.iter().map(|&x| (x..).step_by(1).take(3)).flatten();
913 assert_eq!(x, ys[i]);
916 assert_eq!(i, ys.len());
919 /// Tests `Flatten::fold` with items already picked off the front and back,
920 /// to make sure all parts of the `Flatten` are folded correctly.
922 fn test_iterator_flatten_fold() {
924 let ys = [1, 2, 3, 4, 5, 6, 7];
925 let mut it = xs.iter().map(|&x| x..x+3).flatten();
926 assert_eq!(it.next(), Some(0));
927 assert_eq!(it.next_back(), Some(8));
928 let i = it.fold(0, |i, x| {
929 assert_eq!(x, ys[i]);
932 assert_eq!(i, ys.len());
934 let mut it = xs.iter().map(|&x| x..x+3).flatten();
935 assert_eq!(it.next(), Some(0));
936 assert_eq!(it.next_back(), Some(8));
937 let i = it.rfold(ys.len(), |i, x| {
938 assert_eq!(x, ys[i - 1]);
946 let xs = [1, 2, 3, 4];
952 .collect::<Vec<usize>>();
954 assert_eq!(n, xs.len());
955 assert_eq!(&xs[..], &ys[..]);
959 fn test_inspect_fold() {
960 let xs = [1, 2, 3, 4];
963 let it = xs.iter().inspect(|_| n += 1);
964 let i = it.fold(0, |i, &x| {
965 assert_eq!(x, xs[i]);
968 assert_eq!(i, xs.len());
970 assert_eq!(n, xs.len());
974 let it = xs.iter().inspect(|_| n += 1);
975 let i = it.rfold(xs.len(), |i, &x| {
976 assert_eq!(x, xs[i - 1]);
981 assert_eq!(n, xs.len());
987 let it = (0..).step_by(1).take(cycle_len).cycle();
988 assert_eq!(it.size_hint(), (usize::MAX, None));
989 for (i, x) in it.take(100).enumerate() {
990 assert_eq!(i % cycle_len, x);
993 let mut it = (0..).step_by(1).take(0).cycle();
994 assert_eq!(it.size_hint(), (0, Some(0)));
995 assert_eq!(it.next(), None);
997 assert_eq!(empty::<i32>().cycle().fold(0, |acc, x| acc + x), 0);
999 assert_eq!(once(1).cycle().skip(1).take(4).fold(0, |acc, x| acc + x), 4);
1003 fn test_iterator_nth() {
1004 let v: &[_] = &[0, 1, 2, 3, 4];
1005 for i in 0..v.len() {
1006 assert_eq!(v.iter().nth(i).unwrap(), &v[i]);
1008 assert_eq!(v.iter().nth(v.len()), None);
1012 fn test_iterator_nth_back() {
1013 let v: &[_] = &[0, 1, 2, 3, 4];
1014 for i in 0..v.len() {
1015 assert_eq!(v.iter().nth_back(i).unwrap(), &v[v.len() - 1 - i]);
1017 assert_eq!(v.iter().nth_back(v.len()), None);
1021 fn test_iterator_rev_nth_back() {
1022 let v: &[_] = &[0, 1, 2, 3, 4];
1023 for i in 0..v.len() {
1024 assert_eq!(v.iter().rev().nth_back(i).unwrap(), &v[i]);
1026 assert_eq!(v.iter().rev().nth_back(v.len()), None);
1030 fn test_iterator_rev_nth() {
1031 let v: &[_] = &[0, 1, 2, 3, 4];
1032 for i in 0..v.len() {
1033 assert_eq!(v.iter().rev().nth(i).unwrap(), &v[v.len() - 1 - i]);
1035 assert_eq!(v.iter().rev().nth(v.len()), None);
1039 fn test_iterator_last() {
1040 let v: &[_] = &[0, 1, 2, 3, 4];
1041 assert_eq!(v.iter().last().unwrap(), &4);
1042 assert_eq!(v[..1].iter().last().unwrap(), &0);
1046 fn test_iterator_len() {
1047 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1048 assert_eq!(v[..4].iter().count(), 4);
1049 assert_eq!(v[..10].iter().count(), 10);
1050 assert_eq!(v[..0].iter().count(), 0);
1054 fn test_iterator_sum() {
1055 let v: &[i32] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1056 assert_eq!(v[..4].iter().cloned().sum::<i32>(), 6);
1057 assert_eq!(v.iter().cloned().sum::<i32>(), 55);
1058 assert_eq!(v[..0].iter().cloned().sum::<i32>(), 0);
1062 fn test_iterator_sum_result() {
1063 let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
1064 assert_eq!(v.iter().cloned().sum::<Result<i32, _>>(), Ok(10));
1065 let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
1066 assert_eq!(v.iter().cloned().sum::<Result<i32, _>>(), Err(()));
1070 fn test_iterator_product() {
1071 let v: &[i32] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1072 assert_eq!(v[..4].iter().cloned().product::<i32>(), 0);
1073 assert_eq!(v[1..5].iter().cloned().product::<i32>(), 24);
1074 assert_eq!(v[..0].iter().cloned().product::<i32>(), 1);
1078 fn test_iterator_product_result() {
1079 let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
1080 assert_eq!(v.iter().cloned().product::<Result<i32, _>>(), Ok(24));
1081 let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
1082 assert_eq!(v.iter().cloned().product::<Result<i32, _>>(), Err(()));
1085 /// A wrapper struct that implements `Eq` and `Ord` based on the wrapped
1086 /// integer modulo 3. Used to test that `Iterator::max` and `Iterator::min`
1087 /// return the correct element if some of them are equal.
1091 impl PartialEq for Mod3 {
1092 fn eq(&self, other: &Self) -> bool {
1093 self.0 % 3 == other.0 % 3
1099 impl PartialOrd for Mod3 {
1100 fn partial_cmp(&self, other: &Self) -> Option<core::cmp::Ordering> {
1101 Some(self.cmp(other))
1106 fn cmp(&self, other: &Self) -> core::cmp::Ordering {
1107 (self.0 % 3).cmp(&(other.0 % 3))
1112 fn test_iterator_max() {
1113 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1114 assert_eq!(v[..4].iter().cloned().max(), Some(3));
1115 assert_eq!(v.iter().cloned().max(), Some(10));
1116 assert_eq!(v[..0].iter().cloned().max(), None);
1117 assert_eq!(v.iter().cloned().map(Mod3).max().map(|x| x.0), Some(8));
1121 fn test_iterator_min() {
1122 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1123 assert_eq!(v[..4].iter().cloned().min(), Some(0));
1124 assert_eq!(v.iter().cloned().min(), Some(0));
1125 assert_eq!(v[..0].iter().cloned().min(), None);
1126 assert_eq!(v.iter().cloned().map(Mod3).min().map(|x| x.0), Some(0));
1130 fn test_iterator_size_hint() {
1131 let c = (0..).step_by(1);
1132 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
1133 let v2 = &[10, 11, 12];
1136 assert_eq!((0..).size_hint(), (usize::MAX, None));
1137 assert_eq!(c.size_hint(), (usize::MAX, None));
1138 assert_eq!(vi.clone().size_hint(), (10, Some(10)));
1140 assert_eq!(c.clone().take(5).size_hint(), (5, Some(5)));
1141 assert_eq!(c.clone().skip(5).size_hint().1, None);
1142 assert_eq!(c.clone().take_while(|_| false).size_hint(), (0, None));
1143 assert_eq!(c.clone().skip_while(|_| false).size_hint(), (0, None));
1144 assert_eq!(c.clone().enumerate().size_hint(), (usize::MAX, None));
1145 assert_eq!(c.clone().chain(vi.clone().cloned()).size_hint(), (usize::MAX, None));
1146 assert_eq!(c.clone().zip(vi.clone()).size_hint(), (10, Some(10)));
1147 assert_eq!(c.clone().scan(0, |_,_| Some(0)).size_hint(), (0, None));
1148 assert_eq!(c.clone().filter(|_| false).size_hint(), (0, None));
1149 assert_eq!(c.clone().map(|_| 0).size_hint(), (usize::MAX, None));
1150 assert_eq!(c.filter_map(|_| Some(0)).size_hint(), (0, None));
1152 assert_eq!(vi.clone().take(5).size_hint(), (5, Some(5)));
1153 assert_eq!(vi.clone().take(12).size_hint(), (10, Some(10)));
1154 assert_eq!(vi.clone().skip(3).size_hint(), (7, Some(7)));
1155 assert_eq!(vi.clone().skip(12).size_hint(), (0, Some(0)));
1156 assert_eq!(vi.clone().take_while(|_| false).size_hint(), (0, Some(10)));
1157 assert_eq!(vi.clone().skip_while(|_| false).size_hint(), (0, Some(10)));
1158 assert_eq!(vi.clone().enumerate().size_hint(), (10, Some(10)));
1159 assert_eq!(vi.clone().chain(v2).size_hint(), (13, Some(13)));
1160 assert_eq!(vi.clone().zip(v2).size_hint(), (3, Some(3)));
1161 assert_eq!(vi.clone().scan(0, |_,_| Some(0)).size_hint(), (0, Some(10)));
1162 assert_eq!(vi.clone().filter(|_| false).size_hint(), (0, Some(10)));
1163 assert_eq!(vi.clone().map(|&i| i+1).size_hint(), (10, Some(10)));
1164 assert_eq!(vi.filter_map(|_| Some(0)).size_hint(), (0, Some(10)));
1169 let a = vec![1, 2, 3, 4, 5];
1170 let b: Vec<isize> = a.iter().cloned().collect();
1176 let v: Box<[isize]> = Box::new([1, 2, 3, 4, 5]);
1177 assert!(v.iter().all(|&x| x < 10));
1178 assert!(!v.iter().all(|&x| x % 2 == 0));
1179 assert!(!v.iter().all(|&x| x > 100));
1180 assert!(v[..0].iter().all(|_| panic!()));
1185 let v: Box<[isize]> = Box::new([1, 2, 3, 4, 5]);
1186 assert!(v.iter().any(|&x| x < 10));
1187 assert!(v.iter().any(|&x| x % 2 == 0));
1188 assert!(!v.iter().any(|&x| x > 100));
1189 assert!(!v[..0].iter().any(|_| panic!()));
1194 let v: &[isize] = &[1, 3, 9, 27, 103, 14, 11];
1195 assert_eq!(*v.iter().find(|&&x| x & 1 == 0).unwrap(), 14);
1196 assert_eq!(*v.iter().find(|&&x| x % 3 == 0).unwrap(), 3);
1197 assert!(v.iter().find(|&&x| x % 12 == 0).is_none());
1201 fn test_find_map() {
1202 let xs: &[isize] = &[];
1203 assert_eq!(xs.iter().find_map(half_if_even), None);
1204 let xs: &[isize] = &[3, 5];
1205 assert_eq!(xs.iter().find_map(half_if_even), None);
1206 let xs: &[isize] = &[4, 5];
1207 assert_eq!(xs.iter().find_map(half_if_even), Some(2));
1208 let xs: &[isize] = &[3, 6];
1209 assert_eq!(xs.iter().find_map(half_if_even), Some(3));
1211 let xs: &[isize] = &[1, 2, 3, 4, 5, 6, 7];
1212 let mut iter = xs.iter();
1213 assert_eq!(iter.find_map(half_if_even), Some(1));
1214 assert_eq!(iter.find_map(half_if_even), Some(2));
1215 assert_eq!(iter.find_map(half_if_even), Some(3));
1216 assert_eq!(iter.next(), Some(&7));
1218 fn half_if_even(x: &isize) -> Option<isize> {
1228 fn test_position() {
1229 let v = &[1, 3, 9, 27, 103, 14, 11];
1230 assert_eq!(v.iter().position(|x| *x & 1 == 0).unwrap(), 5);
1231 assert_eq!(v.iter().position(|x| *x % 3 == 0).unwrap(), 1);
1232 assert!(v.iter().position(|x| *x % 12 == 0).is_none());
1237 let xs = &[1, 2, 2, 1, 5, 9, 0, 2];
1238 assert_eq!(xs.iter().filter(|x| **x == 2).count(), 3);
1239 assert_eq!(xs.iter().filter(|x| **x == 5).count(), 1);
1240 assert_eq!(xs.iter().filter(|x| **x == 95).count(), 0);
1244 fn test_max_by_key() {
1245 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1246 assert_eq!(*xs.iter().max_by_key(|x| x.abs()).unwrap(), -10);
1251 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1252 assert_eq!(*xs.iter().max_by(|x, y| x.abs().cmp(&y.abs())).unwrap(), -10);
1256 fn test_min_by_key() {
1257 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1258 assert_eq!(*xs.iter().min_by_key(|x| x.abs()).unwrap(), 0);
1263 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1264 assert_eq!(*xs.iter().min_by(|x, y| x.abs().cmp(&y.abs())).unwrap(), 0);
1270 // sum the first five values
1271 let partial_sum = xs.by_ref().take(5).fold(0, |a, b| a + b);
1272 assert_eq!(partial_sum, 10);
1273 assert_eq!(xs.next(), Some(5));
1278 let xs = [2, 4, 6, 8, 10, 12, 14, 16];
1279 let mut it = xs.iter();
1282 assert!(it.rev().cloned().collect::<Vec<isize>>() ==
1283 vec![16, 14, 12, 10, 8, 6]);
1288 let xs = [2, 4, 6, 8];
1290 let mut it = xs.iter().copied();
1291 assert_eq!(it.len(), 4);
1292 assert_eq!(it.next(), Some(2));
1293 assert_eq!(it.len(), 3);
1294 assert_eq!(it.next(), Some(4));
1295 assert_eq!(it.len(), 2);
1296 assert_eq!(it.next_back(), Some(8));
1297 assert_eq!(it.len(), 1);
1298 assert_eq!(it.next_back(), Some(6));
1299 assert_eq!(it.len(), 0);
1300 assert_eq!(it.next_back(), None);
1305 let xs = [2, 4, 6, 8];
1307 let mut it = xs.iter().cloned();
1308 assert_eq!(it.len(), 4);
1309 assert_eq!(it.next(), Some(2));
1310 assert_eq!(it.len(), 3);
1311 assert_eq!(it.next(), Some(4));
1312 assert_eq!(it.len(), 2);
1313 assert_eq!(it.next_back(), Some(8));
1314 assert_eq!(it.len(), 1);
1315 assert_eq!(it.next_back(), Some(6));
1316 assert_eq!(it.len(), 0);
1317 assert_eq!(it.next_back(), None);
1321 fn test_cloned_side_effects() {
1324 let iter = [1, 2, 3]
1334 assert_eq!(count, 2);
1338 fn test_double_ended_map() {
1339 let xs = [1, 2, 3, 4, 5, 6];
1340 let mut it = xs.iter().map(|&x| x * -1);
1341 assert_eq!(it.next(), Some(-1));
1342 assert_eq!(it.next(), Some(-2));
1343 assert_eq!(it.next_back(), Some(-6));
1344 assert_eq!(it.next_back(), Some(-5));
1345 assert_eq!(it.next(), Some(-3));
1346 assert_eq!(it.next_back(), Some(-4));
1347 assert_eq!(it.next(), None);
1351 fn test_double_ended_enumerate() {
1352 let xs = [1, 2, 3, 4, 5, 6];
1353 let mut it = xs.iter().cloned().enumerate();
1354 assert_eq!(it.next(), Some((0, 1)));
1355 assert_eq!(it.next(), Some((1, 2)));
1356 assert_eq!(it.next_back(), Some((5, 6)));
1357 assert_eq!(it.next_back(), Some((4, 5)));
1358 assert_eq!(it.next_back(), Some((3, 4)));
1359 assert_eq!(it.next_back(), Some((2, 3)));
1360 assert_eq!(it.next(), None);
1364 fn test_double_ended_zip() {
1365 let xs = [1, 2, 3, 4, 5, 6];
1366 let ys = [1, 2, 3, 7];
1367 let a = xs.iter().cloned();
1368 let b = ys.iter().cloned();
1369 let mut it = a.zip(b);
1370 assert_eq!(it.next(), Some((1, 1)));
1371 assert_eq!(it.next(), Some((2, 2)));
1372 assert_eq!(it.next_back(), Some((4, 7)));
1373 assert_eq!(it.next_back(), Some((3, 3)));
1374 assert_eq!(it.next(), None);
1378 fn test_double_ended_filter() {
1379 let xs = [1, 2, 3, 4, 5, 6];
1380 let mut it = xs.iter().filter(|&x| *x & 1 == 0);
1381 assert_eq!(it.next_back().unwrap(), &6);
1382 assert_eq!(it.next_back().unwrap(), &4);
1383 assert_eq!(it.next().unwrap(), &2);
1384 assert_eq!(it.next_back(), None);
1388 fn test_double_ended_filter_map() {
1389 let xs = [1, 2, 3, 4, 5, 6];
1390 let mut it = xs.iter().filter_map(|&x| if x & 1 == 0 { Some(x * 2) } else { None });
1391 assert_eq!(it.next_back().unwrap(), 12);
1392 assert_eq!(it.next_back().unwrap(), 8);
1393 assert_eq!(it.next().unwrap(), 4);
1394 assert_eq!(it.next_back(), None);
1398 fn test_double_ended_chain() {
1399 let xs = [1, 2, 3, 4, 5];
1400 let ys = [7, 9, 11];
1401 let mut it = xs.iter().chain(&ys).rev();
1402 assert_eq!(it.next().unwrap(), &11);
1403 assert_eq!(it.next().unwrap(), &9);
1404 assert_eq!(it.next_back().unwrap(), &1);
1405 assert_eq!(it.next_back().unwrap(), &2);
1406 assert_eq!(it.next_back().unwrap(), &3);
1407 assert_eq!(it.next_back().unwrap(), &4);
1408 assert_eq!(it.next_back().unwrap(), &5);
1409 assert_eq!(it.next_back().unwrap(), &7);
1410 assert_eq!(it.next_back(), None);
1413 // test that .chain() is well behaved with an unfused iterator
1414 struct CrazyIterator(bool);
1415 impl CrazyIterator { fn new() -> CrazyIterator { CrazyIterator(false) } }
1416 impl Iterator for CrazyIterator {
1418 fn next(&mut self) -> Option<i32> {
1419 if self.0 { Some(99) } else { self.0 = true; None }
1423 impl DoubleEndedIterator for CrazyIterator {
1424 fn next_back(&mut self) -> Option<i32> {
1429 assert_eq!(CrazyIterator::new().chain(0..10).rev().last(), Some(0));
1430 assert!((0..10).chain(CrazyIterator::new()).rev().any(|i| i == 0));
1434 fn test_rposition() {
1435 fn f(xy: &(isize, char)) -> bool { let (_x, y) = *xy; y == 'b' }
1436 fn g(xy: &(isize, char)) -> bool { let (_x, y) = *xy; y == 'd' }
1437 let v = [(0, 'a'), (1, 'b'), (2, 'c'), (3, 'b')];
1439 assert_eq!(v.iter().rposition(f), Some(3));
1440 assert!(v.iter().rposition(g).is_none());
1445 fn test_rposition_panic() {
1446 let v: [(Box<_>, Box<_>); 4] =
1447 [(box 0, box 0), (box 0, box 0),
1448 (box 0, box 0), (box 0, box 0)];
1450 v.iter().rposition(|_elt| {
1461 fn test_double_ended_flat_map() {
1464 let mut it = u.iter().flat_map(|x| &v[*x..v.len()]);
1465 assert_eq!(it.next_back().unwrap(), &8);
1466 assert_eq!(it.next().unwrap(), &5);
1467 assert_eq!(it.next_back().unwrap(), &7);
1468 assert_eq!(it.next_back().unwrap(), &6);
1469 assert_eq!(it.next_back().unwrap(), &8);
1470 assert_eq!(it.next().unwrap(), &6);
1471 assert_eq!(it.next_back().unwrap(), &7);
1472 assert_eq!(it.next_back(), None);
1473 assert_eq!(it.next(), None);
1474 assert_eq!(it.next_back(), None);
1478 fn test_double_ended_flatten() {
1481 let mut it = u.iter().map(|x| &v[*x..v.len()]).flatten();
1482 assert_eq!(it.next_back().unwrap(), &8);
1483 assert_eq!(it.next().unwrap(), &5);
1484 assert_eq!(it.next_back().unwrap(), &7);
1485 assert_eq!(it.next_back().unwrap(), &6);
1486 assert_eq!(it.next_back().unwrap(), &8);
1487 assert_eq!(it.next().unwrap(), &6);
1488 assert_eq!(it.next_back().unwrap(), &7);
1489 assert_eq!(it.next_back(), None);
1490 assert_eq!(it.next(), None);
1491 assert_eq!(it.next_back(), None);
1495 fn test_double_ended_range() {
1496 assert_eq!((11..14).rev().collect::<Vec<_>>(), [13, 12, 11]);
1497 for _ in (10..0).rev() {
1498 panic!("unreachable");
1501 assert_eq!((11..14).rev().collect::<Vec<_>>(), [13, 12, 11]);
1502 for _ in (10..0).rev() {
1503 panic!("unreachable");
1509 assert_eq!((0..5).collect::<Vec<_>>(), [0, 1, 2, 3, 4]);
1510 assert_eq!((-10..-1).collect::<Vec<_>>(), [-10, -9, -8, -7, -6, -5, -4, -3, -2]);
1511 assert_eq!((0..5).rev().collect::<Vec<_>>(), [4, 3, 2, 1, 0]);
1512 assert_eq!((200..-5).count(), 0);
1513 assert_eq!((200..-5).rev().count(), 0);
1514 assert_eq!((200..200).count(), 0);
1515 assert_eq!((200..200).rev().count(), 0);
1517 assert_eq!((0..100).size_hint(), (100, Some(100)));
1518 // this test is only meaningful when sizeof usize < sizeof u64
1519 assert_eq!((usize::MAX - 1..usize::MAX).size_hint(), (1, Some(1)));
1520 assert_eq!((-10..-1).size_hint(), (9, Some(9)));
1521 assert_eq!((-1..-10).size_hint(), (0, Some(0)));
1523 assert_eq!((-70..58).size_hint(), (128, Some(128)));
1524 assert_eq!((-128..127).size_hint(), (255, Some(255)));
1525 assert_eq!((-2..isize::MAX).size_hint(),
1526 (isize::MAX as usize + 2, Some(isize::MAX as usize + 2)));
1530 fn test_range_exhaustion() {
1532 assert!(r.is_empty());
1533 assert_eq!(r.next(), None);
1534 assert_eq!(r.next_back(), None);
1535 assert_eq!(r, 10..10);
1538 assert_eq!(r.next(), Some(10));
1539 assert_eq!(r.next(), Some(11));
1540 assert!(r.is_empty());
1541 assert_eq!(r, 12..12);
1542 assert_eq!(r.next(), None);
1545 assert_eq!(r.next_back(), Some(11));
1546 assert_eq!(r.next_back(), Some(10));
1547 assert!(r.is_empty());
1548 assert_eq!(r, 10..10);
1549 assert_eq!(r.next_back(), None);
1551 let mut r = 100..10;
1552 assert!(r.is_empty());
1553 assert_eq!(r.next(), None);
1554 assert_eq!(r.next_back(), None);
1555 assert_eq!(r, 100..10);
1559 fn test_range_inclusive_exhaustion() {
1560 let mut r = 10..=10;
1561 assert_eq!(r.next(), Some(10));
1562 assert!(r.is_empty());
1563 assert_eq!(r.next(), None);
1564 assert_eq!(r.next(), None);
1566 let mut r = 10..=10;
1567 assert_eq!(r.next_back(), Some(10));
1568 assert!(r.is_empty());
1569 assert_eq!(r.next_back(), None);
1571 let mut r = 10..=12;
1572 assert_eq!(r.next(), Some(10));
1573 assert_eq!(r.next(), Some(11));
1574 assert_eq!(r.next(), Some(12));
1575 assert!(r.is_empty());
1576 assert_eq!(r.next(), None);
1578 let mut r = 10..=12;
1579 assert_eq!(r.next_back(), Some(12));
1580 assert_eq!(r.next_back(), Some(11));
1581 assert_eq!(r.next_back(), Some(10));
1582 assert!(r.is_empty());
1583 assert_eq!(r.next_back(), None);
1585 let mut r = 10..=12;
1586 assert_eq!(r.nth(2), Some(12));
1587 assert!(r.is_empty());
1588 assert_eq!(r.next(), None);
1590 let mut r = 10..=12;
1591 assert_eq!(r.nth(5), None);
1592 assert!(r.is_empty());
1593 assert_eq!(r.next(), None);
1595 let mut r = 100..=10;
1596 assert_eq!(r.next(), None);
1597 assert!(r.is_empty());
1598 assert_eq!(r.next(), None);
1599 assert_eq!(r.next(), None);
1600 assert_eq!(r, 100..=10);
1602 let mut r = 100..=10;
1603 assert_eq!(r.next_back(), None);
1604 assert!(r.is_empty());
1605 assert_eq!(r.next_back(), None);
1606 assert_eq!(r.next_back(), None);
1607 assert_eq!(r, 100..=10);
1611 fn test_range_nth() {
1612 assert_eq!((10..15).nth(0), Some(10));
1613 assert_eq!((10..15).nth(1), Some(11));
1614 assert_eq!((10..15).nth(4), Some(14));
1615 assert_eq!((10..15).nth(5), None);
1618 assert_eq!(r.nth(2), Some(12));
1619 assert_eq!(r, 13..20);
1620 assert_eq!(r.nth(2), Some(15));
1621 assert_eq!(r, 16..20);
1622 assert_eq!(r.nth(10), None);
1623 assert_eq!(r, 20..20);
1627 fn test_range_from_nth() {
1628 assert_eq!((10..).nth(0), Some(10));
1629 assert_eq!((10..).nth(1), Some(11));
1630 assert_eq!((10..).nth(4), Some(14));
1633 assert_eq!(r.nth(2), Some(12));
1634 assert_eq!(r, 13..);
1635 assert_eq!(r.nth(2), Some(15));
1636 assert_eq!(r, 16..);
1637 assert_eq!(r.nth(10), Some(26));
1638 assert_eq!(r, 27..);
1640 assert_eq!((0..).size_hint(), (usize::MAX, None));
1643 fn is_trusted_len<I: TrustedLen>(_: I) {}
1646 fn test_range_from_take() {
1647 let mut it = (0..).take(3);
1648 assert_eq!(it.next(), Some(0));
1649 assert_eq!(it.next(), Some(1));
1650 assert_eq!(it.next(), Some(2));
1651 assert_eq!(it.next(), None);
1652 is_trusted_len((0..).take(3));
1653 assert_eq!((0..).take(3).size_hint(), (3, Some(3)));
1654 assert_eq!((0..).take(0).size_hint(), (0, Some(0)));
1655 assert_eq!((0..).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
1659 fn test_range_from_take_collect() {
1660 let v: Vec<_> = (0..).take(3).collect();
1661 assert_eq!(v, vec![0, 1, 2]);
1665 fn test_range_inclusive_nth() {
1666 assert_eq!((10..=15).nth(0), Some(10));
1667 assert_eq!((10..=15).nth(1), Some(11));
1668 assert_eq!((10..=15).nth(5), Some(15));
1669 assert_eq!((10..=15).nth(6), None);
1671 let mut r = 10_u8..=20;
1672 assert_eq!(r.nth(2), Some(12));
1673 assert_eq!(r, 13..=20);
1674 assert_eq!(r.nth(2), Some(15));
1675 assert_eq!(r, 16..=20);
1676 assert_eq!(r.is_empty(), false);
1677 assert_eq!(ExactSizeIterator::is_empty(&r), false);
1678 assert_eq!(r.nth(10), None);
1679 assert_eq!(r.is_empty(), true);
1680 assert_eq!(ExactSizeIterator::is_empty(&r), true);
1684 fn test_range_step() {
1685 #![allow(deprecated)]
1687 assert_eq!((0..20).step_by(5).collect::<Vec<isize>>(), [0, 5, 10, 15]);
1688 assert_eq!((1..21).rev().step_by(5).collect::<Vec<isize>>(), [20, 15, 10, 5]);
1689 assert_eq!((1..21).rev().step_by(6).collect::<Vec<isize>>(), [20, 14, 8, 2]);
1690 assert_eq!((200..255).step_by(50).collect::<Vec<u8>>(), [200, 250]);
1691 assert_eq!((200..-5).step_by(1).collect::<Vec<isize>>(), []);
1692 assert_eq!((200..200).step_by(1).collect::<Vec<isize>>(), []);
1694 assert_eq!((0..20).step_by(1).size_hint(), (20, Some(20)));
1695 assert_eq!((0..20).step_by(21).size_hint(), (1, Some(1)));
1696 assert_eq!((0..20).step_by(5).size_hint(), (4, Some(4)));
1697 assert_eq!((1..21).rev().step_by(5).size_hint(), (4, Some(4)));
1698 assert_eq!((1..21).rev().step_by(6).size_hint(), (4, Some(4)));
1699 assert_eq!((20..-5).step_by(1).size_hint(), (0, Some(0)));
1700 assert_eq!((20..20).step_by(1).size_hint(), (0, Some(0)));
1701 assert_eq!((i8::MIN..i8::MAX).step_by(-(i8::MIN as i32) as usize).size_hint(), (2, Some(2)));
1702 assert_eq!((i16::MIN..i16::MAX).step_by(i16::MAX as usize).size_hint(), (3, Some(3)));
1703 assert_eq!((isize::MIN..isize::MAX).step_by(1).size_hint(), (usize::MAX, Some(usize::MAX)));
1707 fn test_step_by_skip() {
1708 assert_eq!((0..640).step_by(128).skip(1).collect::<Vec<_>>(), [128, 256, 384, 512]);
1709 assert_eq!((0..=50).step_by(10).nth(3), Some(30));
1710 assert_eq!((200..=255u8).step_by(10).nth(3), Some(230));
1714 fn test_range_inclusive_step() {
1715 assert_eq!((0..=50).step_by(10).collect::<Vec<_>>(), [0, 10, 20, 30, 40, 50]);
1716 assert_eq!((0..=5).step_by(1).collect::<Vec<_>>(), [0, 1, 2, 3, 4, 5]);
1717 assert_eq!((200..=255u8).step_by(10).collect::<Vec<_>>(), [200, 210, 220, 230, 240, 250]);
1718 assert_eq!((250..=255u8).step_by(1).collect::<Vec<_>>(), [250, 251, 252, 253, 254, 255]);
1722 fn test_range_last_max() {
1723 assert_eq!((0..20).last(), Some(19));
1724 assert_eq!((-20..0).last(), Some(-1));
1725 assert_eq!((5..5).last(), None);
1727 assert_eq!((0..20).max(), Some(19));
1728 assert_eq!((-20..0).max(), Some(-1));
1729 assert_eq!((5..5).max(), None);
1733 fn test_range_inclusive_last_max() {
1734 assert_eq!((0..=20).last(), Some(20));
1735 assert_eq!((-20..=0).last(), Some(0));
1736 assert_eq!((5..=5).last(), Some(5));
1737 let mut r = 10..=10;
1739 assert_eq!(r.last(), None);
1741 assert_eq!((0..=20).max(), Some(20));
1742 assert_eq!((-20..=0).max(), Some(0));
1743 assert_eq!((5..=5).max(), Some(5));
1744 let mut r = 10..=10;
1746 assert_eq!(r.max(), None);
1750 fn test_range_min() {
1751 assert_eq!((0..20).min(), Some(0));
1752 assert_eq!((-20..0).min(), Some(-20));
1753 assert_eq!((5..5).min(), None);
1757 fn test_range_inclusive_min() {
1758 assert_eq!((0..=20).min(), Some(0));
1759 assert_eq!((-20..=0).min(), Some(-20));
1760 assert_eq!((5..=5).min(), Some(5));
1761 let mut r = 10..=10;
1763 assert_eq!(r.min(), None);
1767 fn test_range_inclusive_folds() {
1768 assert_eq!((1..=10).sum::<i32>(), 55);
1769 assert_eq!((1..=10).rev().sum::<i32>(), 55);
1771 let mut it = 44..=50;
1772 assert_eq!(it.try_fold(0, i8::checked_add), None);
1773 assert_eq!(it, 47..=50);
1774 assert_eq!(it.try_fold(0, i8::checked_add), None);
1775 assert_eq!(it, 50..=50);
1776 assert_eq!(it.try_fold(0, i8::checked_add), Some(50));
1777 assert!(it.is_empty());
1778 assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
1779 assert!(it.is_empty());
1781 let mut it = 40..=47;
1782 assert_eq!(it.try_rfold(0, i8::checked_add), None);
1783 assert_eq!(it, 40..=44);
1784 assert_eq!(it.try_rfold(0, i8::checked_add), None);
1785 assert_eq!(it, 40..=41);
1786 assert_eq!(it.try_rfold(0, i8::checked_add), Some(81));
1787 assert!(it.is_empty());
1788 assert_eq!(it.try_rfold(0, i8::checked_add), Some(0));
1789 assert!(it.is_empty());
1791 let mut it = 10..=20;
1792 assert_eq!(it.try_fold(0, |a,b| Some(a+b)), Some(165));
1793 assert!(it.is_empty());
1794 assert_eq!(it.try_fold(0, |a,b| Some(a+b)), Some(0));
1795 assert!(it.is_empty());
1797 let mut it = 10..=20;
1798 assert_eq!(it.try_rfold(0, |a,b| Some(a+b)), Some(165));
1799 assert!(it.is_empty());
1800 assert_eq!(it.try_rfold(0, |a,b| Some(a+b)), Some(0));
1801 assert!(it.is_empty());
1805 fn test_range_size_hint() {
1806 use core::usize::MAX as UMAX;
1807 assert_eq!((0..0usize).size_hint(), (0, Some(0)));
1808 assert_eq!((0..100usize).size_hint(), (100, Some(100)));
1809 assert_eq!((0..UMAX).size_hint(), (UMAX, Some(UMAX)));
1811 let umax = u128::try_from(UMAX).unwrap();
1812 assert_eq!((0..0u128).size_hint(), (0, Some(0)));
1813 assert_eq!((0..100u128).size_hint(), (100, Some(100)));
1814 assert_eq!((0..umax).size_hint(), (UMAX, Some(UMAX)));
1815 assert_eq!((0..umax + 1).size_hint(), (UMAX, None));
1817 use core::isize::{MAX as IMAX, MIN as IMIN};
1818 assert_eq!((0..0isize).size_hint(), (0, Some(0)));
1819 assert_eq!((-100..100isize).size_hint(), (200, Some(200)));
1820 assert_eq!((IMIN..IMAX).size_hint(), (UMAX, Some(UMAX)));
1822 let imin = i128::try_from(IMIN).unwrap();
1823 let imax = i128::try_from(IMAX).unwrap();
1824 assert_eq!((0..0i128).size_hint(), (0, Some(0)));
1825 assert_eq!((-100..100i128).size_hint(), (200, Some(200)));
1826 assert_eq!((imin..imax).size_hint(), (UMAX, Some(UMAX)));
1827 assert_eq!((imin..imax + 1).size_hint(), (UMAX, None));
1831 fn test_range_inclusive_size_hint() {
1832 use core::usize::MAX as UMAX;
1833 assert_eq!((1..=0usize).size_hint(), (0, Some(0)));
1834 assert_eq!((0..=0usize).size_hint(), (1, Some(1)));
1835 assert_eq!((0..=100usize).size_hint(), (101, Some(101)));
1836 assert_eq!((0..=UMAX - 1).size_hint(), (UMAX, Some(UMAX)));
1837 assert_eq!((0..=UMAX).size_hint(), (UMAX, None));
1839 let umax = u128::try_from(UMAX).unwrap();
1840 assert_eq!((1..=0u128).size_hint(), (0, Some(0)));
1841 assert_eq!((0..=0u128).size_hint(), (1, Some(1)));
1842 assert_eq!((0..=100u128).size_hint(), (101, Some(101)));
1843 assert_eq!((0..=umax - 1).size_hint(), (UMAX, Some(UMAX)));
1844 assert_eq!((0..=umax).size_hint(), (UMAX, None));
1845 assert_eq!((0..=umax + 1).size_hint(), (UMAX, None));
1847 use core::isize::{MAX as IMAX, MIN as IMIN};
1848 assert_eq!((0..=-1isize).size_hint(), (0, Some(0)));
1849 assert_eq!((0..=0isize).size_hint(), (1, Some(1)));
1850 assert_eq!((-100..=100isize).size_hint(), (201, Some(201)));
1851 assert_eq!((IMIN..=IMAX - 1).size_hint(), (UMAX, Some(UMAX)));
1852 assert_eq!((IMIN..=IMAX).size_hint(), (UMAX, None));
1854 let imin = i128::try_from(IMIN).unwrap();
1855 let imax = i128::try_from(IMAX).unwrap();
1856 assert_eq!((0..=-1i128).size_hint(), (0, Some(0)));
1857 assert_eq!((0..=0i128).size_hint(), (1, Some(1)));
1858 assert_eq!((-100..=100i128).size_hint(), (201, Some(201)));
1859 assert_eq!((imin..=imax - 1).size_hint(), (UMAX, Some(UMAX)));
1860 assert_eq!((imin..=imax).size_hint(), (UMAX, None));
1861 assert_eq!((imin..=imax + 1).size_hint(), (UMAX, None));
1866 let mut it = repeat(42);
1867 assert_eq!(it.next(), Some(42));
1868 assert_eq!(it.next(), Some(42));
1869 assert_eq!(it.next(), Some(42));
1870 assert_eq!(repeat(42).size_hint(), (usize::MAX, None));
1874 fn test_repeat_take() {
1875 let mut it = repeat(42).take(3);
1876 assert_eq!(it.next(), Some(42));
1877 assert_eq!(it.next(), Some(42));
1878 assert_eq!(it.next(), Some(42));
1879 assert_eq!(it.next(), None);
1880 is_trusted_len(repeat(42).take(3));
1881 assert_eq!(repeat(42).take(3).size_hint(), (3, Some(3)));
1882 assert_eq!(repeat(42).take(0).size_hint(), (0, Some(0)));
1883 assert_eq!(repeat(42).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
1887 fn test_repeat_take_collect() {
1888 let v: Vec<_> = repeat(42).take(3).collect();
1889 assert_eq!(v, vec![42, 42, 42]);
1893 fn test_repeat_with() {
1894 #[derive(PartialEq, Debug)]
1895 struct NotClone(usize);
1896 let mut it = repeat_with(|| NotClone(42));
1897 assert_eq!(it.next(), Some(NotClone(42)));
1898 assert_eq!(it.next(), Some(NotClone(42)));
1899 assert_eq!(it.next(), Some(NotClone(42)));
1900 assert_eq!(repeat_with(|| NotClone(42)).size_hint(), (usize::MAX, None));
1904 fn test_repeat_with_take() {
1905 let mut it = repeat_with(|| 42).take(3);
1906 assert_eq!(it.next(), Some(42));
1907 assert_eq!(it.next(), Some(42));
1908 assert_eq!(it.next(), Some(42));
1909 assert_eq!(it.next(), None);
1910 is_trusted_len(repeat_with(|| 42).take(3));
1911 assert_eq!(repeat_with(|| 42).take(3).size_hint(), (3, Some(3)));
1912 assert_eq!(repeat_with(|| 42).take(0).size_hint(), (0, Some(0)));
1913 assert_eq!(repeat_with(|| 42).take(usize::MAX).size_hint(),
1914 (usize::MAX, Some(usize::MAX)));
1918 fn test_repeat_with_take_collect() {
1920 let v: Vec<_> = repeat_with(|| { let tmp = curr; curr *= 2; tmp })
1922 assert_eq!(v, vec![1, 2, 4, 8, 16]);
1926 fn test_successors() {
1927 let mut powers_of_10 = successors(Some(1_u16), |n| n.checked_mul(10));
1928 assert_eq!(powers_of_10.by_ref().collect::<Vec<_>>(), &[1, 10, 100, 1_000, 10_000]);
1929 assert_eq!(powers_of_10.next(), None);
1931 let mut empty = successors(None::<u32>, |_| unimplemented!());
1932 assert_eq!(empty.next(), None);
1933 assert_eq!(empty.next(), None);
1939 assert_eq!(it.len(), 3);
1940 assert_eq!(it.next(), Some(0));
1941 assert_eq!(it.len(), 2);
1942 assert_eq!(it.next(), Some(1));
1943 assert_eq!(it.len(), 1);
1944 assert_eq!(it.next(), Some(2));
1945 assert_eq!(it.len(), 0);
1946 assert_eq!(it.next(), None);
1947 assert_eq!(it.len(), 0);
1948 assert_eq!(it.next(), None);
1949 assert_eq!(it.len(), 0);
1950 assert_eq!(it.next(), None);
1951 assert_eq!(it.len(), 0);
1955 fn test_fuse_nth() {
1957 let mut it = xs.iter();
1959 assert_eq!(it.len(), 3);
1960 assert_eq!(it.nth(2), Some(&2));
1961 assert_eq!(it.len(), 0);
1962 assert_eq!(it.nth(2), None);
1963 assert_eq!(it.len(), 0);
1967 fn test_fuse_last() {
1971 assert_eq!(it.len(), 3);
1972 assert_eq!(it.last(), Some(&2));
1976 fn test_fuse_count() {
1980 assert_eq!(it.len(), 3);
1981 assert_eq!(it.count(), 3);
1982 // Can't check len now because count consumes.
1986 fn test_fuse_fold() {
1988 let it = xs.iter(); // `FusedIterator`
1989 let i = it.fuse().fold(0, |i, &x| {
1990 assert_eq!(x, xs[i]);
1993 assert_eq!(i, xs.len());
1995 let it = xs.iter(); // `FusedIterator`
1996 let i = it.fuse().rfold(xs.len(), |i, &x| {
1997 assert_eq!(x, xs[i - 1]);
2002 let it = xs.iter().scan((), |_, &x| Some(x)); // `!FusedIterator`
2003 let i = it.fuse().fold(0, |i, x| {
2004 assert_eq!(x, xs[i]);
2007 assert_eq!(i, xs.len());
2012 let mut it = once(42);
2013 assert_eq!(it.next(), Some(42));
2014 assert_eq!(it.next(), None);
2018 fn test_once_with() {
2019 let count = Cell::new(0);
2020 let mut it = once_with(|| {
2021 count.set(count.get() + 1);
2025 assert_eq!(count.get(), 0);
2026 assert_eq!(it.next(), Some(42));
2027 assert_eq!(count.get(), 1);
2028 assert_eq!(it.next(), None);
2029 assert_eq!(count.get(), 1);
2030 assert_eq!(it.next(), None);
2031 assert_eq!(count.get(), 1);
2036 let mut it = empty::<i32>();
2037 assert_eq!(it.next(), None);
2041 fn test_chain_fold() {
2045 let mut iter = xs.iter().chain(&ys);
2047 let mut result = Vec::new();
2048 iter.fold((), |(), &elt| result.push(elt));
2049 assert_eq!(&[2, 3, 1, 2, 0], &result[..]);
2053 fn test_step_replace_unsigned() {
2055 let y = x.replace_zero();
2060 let y = x.replace_one();
2066 fn test_step_replace_signed() {
2068 let y = x.replace_zero();
2073 let y = x.replace_one();
2079 fn test_step_replace_no_between() {
2081 let y = x.replace_zero();
2086 let y = x.replace_one();
2092 fn test_rev_try_folds() {
2093 let f = &|acc, x| i32::checked_add(2*acc, x);
2094 assert_eq!((1..10).rev().try_fold(7, f), (1..10).try_rfold(7, f));
2095 assert_eq!((1..10).rev().try_rfold(7, f), (1..10).try_fold(7, f));
2097 let a = [10, 20, 30, 40, 100, 60, 70, 80, 90];
2098 let mut iter = a.iter().rev();
2099 assert_eq!(iter.try_fold(0_i8, |acc, &x| acc.checked_add(x)), None);
2100 assert_eq!(iter.next(), Some(&70));
2101 let mut iter = a.iter().rev();
2102 assert_eq!(iter.try_rfold(0_i8, |acc, &x| acc.checked_add(x)), None);
2103 assert_eq!(iter.next_back(), Some(&60));
2107 fn test_cloned_try_folds() {
2108 let a = [1, 2, 3, 4, 5, 6, 7, 8, 9];
2109 let f = &|acc, x| i32::checked_add(2*acc, x);
2110 let f_ref = &|acc, &x| i32::checked_add(2*acc, x);
2111 assert_eq!(a.iter().cloned().try_fold(7, f), a.iter().try_fold(7, f_ref));
2112 assert_eq!(a.iter().cloned().try_rfold(7, f), a.iter().try_rfold(7, f_ref));
2114 let a = [10, 20, 30, 40, 100, 60, 70, 80, 90];
2115 let mut iter = a.iter().cloned();
2116 assert_eq!(iter.try_fold(0_i8, |acc, x| acc.checked_add(x)), None);
2117 assert_eq!(iter.next(), Some(60));
2118 let mut iter = a.iter().cloned();
2119 assert_eq!(iter.try_rfold(0_i8, |acc, x| acc.checked_add(x)), None);
2120 assert_eq!(iter.next_back(), Some(70));
2124 fn test_chain_try_folds() {
2125 let c = || (0..10).chain(10..20);
2127 let f = &|acc, x| i32::checked_add(2*acc, x);
2128 assert_eq!(c().try_fold(7, f), (0..20).try_fold(7, f));
2129 assert_eq!(c().try_rfold(7, f), (0..20).rev().try_fold(7, f));
2132 assert_eq!(iter.position(|x| x == 5), Some(5));
2133 assert_eq!(iter.next(), Some(6), "stopped in front, state Both");
2134 assert_eq!(iter.position(|x| x == 13), Some(6));
2135 assert_eq!(iter.next(), Some(14), "stopped in back, state Back");
2136 assert_eq!(iter.try_fold(0, |acc, x| Some(acc+x)), Some((15..20).sum()));
2138 let mut iter = c().rev(); // use rev to access try_rfold
2139 assert_eq!(iter.position(|x| x == 15), Some(4));
2140 assert_eq!(iter.next(), Some(14), "stopped in back, state Both");
2141 assert_eq!(iter.position(|x| x == 5), Some(8));
2142 assert_eq!(iter.next(), Some(4), "stopped in front, state Front");
2143 assert_eq!(iter.try_fold(0, |acc, x| Some(acc+x)), Some((0..4).sum()));
2146 iter.by_ref().rev().nth(14); // skip the last 15, ending in state Front
2147 assert_eq!(iter.try_fold(7, f), (0..5).try_fold(7, f));
2150 iter.nth(14); // skip the first 15, ending in state Back
2151 assert_eq!(iter.try_rfold(7, f), (15..20).try_rfold(7, f));
2155 fn test_map_try_folds() {
2156 let f = &|acc, x| i32::checked_add(2*acc, x);
2157 assert_eq!((0..10).map(|x| x+3).try_fold(7, f), (3..13).try_fold(7, f));
2158 assert_eq!((0..10).map(|x| x+3).try_rfold(7, f), (3..13).try_rfold(7, f));
2160 let mut iter = (0..40).map(|x| x+10);
2161 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2162 assert_eq!(iter.next(), Some(20));
2163 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2164 assert_eq!(iter.next_back(), Some(46));
2168 fn test_filter_try_folds() {
2169 fn p(&x: &i32) -> bool { 0 <= x && x < 10 }
2170 let f = &|acc, x| i32::checked_add(2*acc, x);
2171 assert_eq!((-10..20).filter(p).try_fold(7, f), (0..10).try_fold(7, f));
2172 assert_eq!((-10..20).filter(p).try_rfold(7, f), (0..10).try_rfold(7, f));
2174 let mut iter = (0..40).filter(|&x| x % 2 == 1);
2175 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2176 assert_eq!(iter.next(), Some(25));
2177 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2178 assert_eq!(iter.next_back(), Some(31));
2182 fn test_filter_map_try_folds() {
2183 let mp = &|x| if 0 <= x && x < 10 { Some(x*2) } else { None };
2184 let f = &|acc, x| i32::checked_add(2*acc, x);
2185 assert_eq!((-9..20).filter_map(mp).try_fold(7, f), (0..10).map(|x| 2*x).try_fold(7, f));
2186 assert_eq!((-9..20).filter_map(mp).try_rfold(7, f), (0..10).map(|x| 2*x).try_rfold(7, f));
2188 let mut iter = (0..40).filter_map(|x| if x%2 == 1 { None } else { Some(x*2 + 10) });
2189 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2190 assert_eq!(iter.next(), Some(38));
2191 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2192 assert_eq!(iter.next_back(), Some(78));
2196 fn test_enumerate_try_folds() {
2197 let f = &|acc, (i, x)| usize::checked_add(2*acc, x/(i+1) + i);
2198 assert_eq!((9..18).enumerate().try_fold(7, f), (0..9).map(|i| (i, i+9)).try_fold(7, f));
2199 assert_eq!((9..18).enumerate().try_rfold(7, f), (0..9).map(|i| (i, i+9)).try_rfold(7, f));
2201 let mut iter = (100..200).enumerate();
2202 let f = &|acc, (i, x)| u8::checked_add(acc, u8::checked_div(x, i as u8 + 1)?);
2203 assert_eq!(iter.try_fold(0, f), None);
2204 assert_eq!(iter.next(), Some((7, 107)));
2205 assert_eq!(iter.try_rfold(0, f), None);
2206 assert_eq!(iter.next_back(), Some((11, 111)));
2210 fn test_peek_try_fold() {
2211 let f = &|acc, x| i32::checked_add(2*acc, x);
2212 assert_eq!((1..20).peekable().try_fold(7, f), (1..20).try_fold(7, f));
2213 let mut iter = (1..20).peekable();
2214 assert_eq!(iter.peek(), Some(&1));
2215 assert_eq!(iter.try_fold(7, f), (1..20).try_fold(7, f));
2217 let mut iter = [100, 20, 30, 40, 50, 60, 70].iter().cloned().peekable();
2218 assert_eq!(iter.peek(), Some(&100));
2219 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2220 assert_eq!(iter.peek(), Some(&40));
2224 fn test_skip_while_try_fold() {
2225 let f = &|acc, x| i32::checked_add(2*acc, x);
2226 fn p(&x: &i32) -> bool { (x % 10) <= 5 }
2227 assert_eq!((1..20).skip_while(p).try_fold(7, f), (6..20).try_fold(7, f));
2228 let mut iter = (1..20).skip_while(p);
2229 assert_eq!(iter.nth(5), Some(11));
2230 assert_eq!(iter.try_fold(7, f), (12..20).try_fold(7, f));
2232 let mut iter = (0..50).skip_while(|&x| (x % 20) < 15);
2233 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2234 assert_eq!(iter.next(), Some(23));
2238 fn test_take_while_folds() {
2239 let f = &|acc, x| i32::checked_add(2*acc, x);
2240 assert_eq!((1..20).take_while(|&x| x != 10).try_fold(7, f), (1..10).try_fold(7, f));
2241 let mut iter = (1..20).take_while(|&x| x != 10);
2242 assert_eq!(iter.try_fold(0, |x, y| Some(x+y)), Some((1..10).sum()));
2243 assert_eq!(iter.next(), None, "flag should be set");
2244 let iter = (1..20).take_while(|&x| x != 10);
2245 assert_eq!(iter.fold(0, |x, y| x+y), (1..10).sum());
2247 let mut iter = (10..50).take_while(|&x| x != 40);
2248 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2249 assert_eq!(iter.next(), Some(20));
2253 fn test_skip_try_folds() {
2254 let f = &|acc, x| i32::checked_add(2*acc, x);
2255 assert_eq!((1..20).skip(9).try_fold(7, f), (10..20).try_fold(7, f));
2256 assert_eq!((1..20).skip(9).try_rfold(7, f), (10..20).try_rfold(7, f));
2258 let mut iter = (0..30).skip(10);
2259 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2260 assert_eq!(iter.next(), Some(20));
2261 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2262 assert_eq!(iter.next_back(), Some(24));
2266 fn test_take_try_folds() {
2267 let f = &|acc, x| i32::checked_add(2*acc, x);
2268 assert_eq!((10..30).take(10).try_fold(7, f), (10..20).try_fold(7, f));
2269 //assert_eq!((10..30).take(10).try_rfold(7, f), (10..20).try_rfold(7, f));
2271 let mut iter = (10..30).take(20);
2272 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2273 assert_eq!(iter.next(), Some(20));
2274 //assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2275 //assert_eq!(iter.next_back(), Some(24));
2279 fn test_flat_map_try_folds() {
2280 let f = &|acc, x| i32::checked_add(acc*2/3, x);
2281 let mr = &|x| (5*x)..(5*x + 5);
2282 assert_eq!((0..10).flat_map(mr).try_fold(7, f), (0..50).try_fold(7, f));
2283 assert_eq!((0..10).flat_map(mr).try_rfold(7, f), (0..50).try_rfold(7, f));
2284 let mut iter = (0..10).flat_map(mr);
2285 iter.next(); iter.next_back(); // have front and back iters in progress
2286 assert_eq!(iter.try_rfold(7, f), (1..49).try_rfold(7, f));
2288 let mut iter = (0..10).flat_map(|x| (4*x)..(4*x + 4));
2289 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2290 assert_eq!(iter.next(), Some(17));
2291 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2292 assert_eq!(iter.next_back(), Some(35));
2296 fn test_flatten_try_folds() {
2297 let f = &|acc, x| i32::checked_add(acc*2/3, x);
2298 let mr = &|x| (5*x)..(5*x + 5);
2299 assert_eq!((0..10).map(mr).flatten().try_fold(7, f), (0..50).try_fold(7, f));
2300 assert_eq!((0..10).map(mr).flatten().try_rfold(7, f), (0..50).try_rfold(7, f));
2301 let mut iter = (0..10).map(mr).flatten();
2302 iter.next(); iter.next_back(); // have front and back iters in progress
2303 assert_eq!(iter.try_rfold(7, f), (1..49).try_rfold(7, f));
2305 let mut iter = (0..10).map(|x| (4*x)..(4*x + 4)).flatten();
2306 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2307 assert_eq!(iter.next(), Some(17));
2308 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2309 assert_eq!(iter.next_back(), Some(35));
2313 fn test_functor_laws() {
2315 fn identity<T>(x: T) -> T { x }
2316 assert_eq!((0..10).map(identity).sum::<usize>(), (0..10).sum());
2319 fn f(x: usize) -> usize { x + 3 }
2320 fn g(x: usize) -> usize { x * 2 }
2321 fn h(x: usize) -> usize { g(f(x)) }
2322 assert_eq!((0..10).map(f).map(g).sum::<usize>(), (0..10).map(h).sum());
2326 fn test_monad_laws_left_identity() {
2327 fn f(x: usize) -> impl Iterator<Item = usize> {
2328 (0..10).map(move |y| x * y)
2330 assert_eq!(once(42).flat_map(f.clone()).sum::<usize>(), f(42).sum());
2334 fn test_monad_laws_right_identity() {
2335 assert_eq!((0..10).flat_map(|x| once(x)).sum::<usize>(), (0..10).sum());
2339 fn test_monad_laws_associativity() {
2340 fn f(x: usize) -> impl Iterator<Item = usize> { 0..x }
2341 fn g(x: usize) -> impl Iterator<Item = usize> { (0..x).rev() }
2342 assert_eq!((0..10).flat_map(f).flat_map(g).sum::<usize>(),
2343 (0..10).flat_map(|x| f(x).flat_map(g)).sum::<usize>());
2347 fn test_is_sorted() {
2348 assert!([1, 2, 2, 9].iter().is_sorted());
2349 assert!(![1, 3, 2].iter().is_sorted());
2350 assert!([0].iter().is_sorted());
2351 assert!(std::iter::empty::<i32>().is_sorted());
2352 assert!(![0.0, 1.0, std::f32::NAN].iter().is_sorted());
2353 assert!([-2, -1, 0, 3].iter().is_sorted());
2354 assert!(![-2i32, -1, 0, 3].iter().is_sorted_by_key(|n| n.abs()));
2355 assert!(!["c", "bb", "aaa"].iter().is_sorted());
2356 assert!(["c", "bb", "aaa"].iter().is_sorted_by_key(|s| s.len()));