3 use core::{i8, i16, isize};
8 let empty: [isize; 0] = [];
12 assert!(!xs.iter().lt(ys.iter()));
13 assert!(!xs.iter().le(ys.iter()));
14 assert!( xs.iter().gt(ys.iter()));
15 assert!( xs.iter().ge(ys.iter()));
17 assert!( ys.iter().lt(xs.iter()));
18 assert!( ys.iter().le(xs.iter()));
19 assert!(!ys.iter().gt(xs.iter()));
20 assert!(!ys.iter().ge(xs.iter()));
22 assert!( empty.iter().lt(xs.iter()));
23 assert!( empty.iter().le(xs.iter()));
24 assert!(!empty.iter().gt(xs.iter()));
25 assert!(!empty.iter().ge(xs.iter()));
28 let u = [1.0f64, 2.0];
29 let v = [0.0f64/0.0, 3.0];
31 assert!(!u.iter().lt(v.iter()));
32 assert!(!u.iter().le(v.iter()));
33 assert!(!u.iter().gt(v.iter()));
34 assert!(!u.iter().ge(v.iter()));
40 assert!(a.iter().lt(b.iter()) == (a[0] < b[0]));
41 assert!(a.iter().le(b.iter()) == (a[0] <= b[0]));
42 assert!(a.iter().gt(b.iter()) == (a[0] > b[0]));
43 assert!(a.iter().ge(b.iter()) == (a[0] >= b[0]));
45 assert!(c.iter().lt(b.iter()) == (c[0] < b[0]));
46 assert!(c.iter().le(b.iter()) == (c[0] <= b[0]));
47 assert!(c.iter().gt(b.iter()) == (c[0] > b[0]));
48 assert!(c.iter().ge(b.iter()) == (c[0] >= b[0]));
52 fn test_multi_iter() {
55 assert!(xs.iter().eq(ys.iter().rev()));
56 assert!(xs.iter().lt(xs.iter().skip(2)));
60 fn test_counter_from_iter() {
61 let it = (0..).step_by(5).take(10);
62 let xs: Vec<isize> = FromIterator::from_iter(it);
63 assert_eq!(xs, [0, 5, 10, 15, 20, 25, 30, 35, 40, 45]);
67 fn test_iterator_chain() {
68 let xs = [0, 1, 2, 3, 4, 5];
69 let ys = [30, 40, 50, 60];
70 let expected = [0, 1, 2, 3, 4, 5, 30, 40, 50, 60];
71 let it = xs.iter().chain(&ys);
74 assert_eq!(x, expected[i]);
77 assert_eq!(i, expected.len());
79 let ys = (30..).step_by(10).take(4);
80 let it = xs.iter().cloned().chain(ys);
83 assert_eq!(x, expected[i]);
86 assert_eq!(i, expected.len());
90 fn test_iterator_chain_nth() {
91 let xs = [0, 1, 2, 3, 4, 5];
92 let ys = [30, 40, 50, 60];
94 let expected = [0, 1, 2, 3, 4, 5, 30, 40, 50, 60];
95 for (i, x) in expected.iter().enumerate() {
96 assert_eq!(Some(x), xs.iter().chain(&ys).nth(i));
98 assert_eq!(zs.iter().chain(&xs).nth(0), Some(&0));
100 let mut it = xs.iter().chain(&zs);
101 assert_eq!(it.nth(5), Some(&5));
102 assert_eq!(it.next(), None);
106 fn test_iterator_chain_last() {
107 let xs = [0, 1, 2, 3, 4, 5];
108 let ys = [30, 40, 50, 60];
110 assert_eq!(xs.iter().chain(&ys).last(), Some(&60));
111 assert_eq!(zs.iter().chain(&ys).last(), Some(&60));
112 assert_eq!(ys.iter().chain(&zs).last(), Some(&60));
113 assert_eq!(zs.iter().chain(&zs).last(), None);
117 fn test_iterator_chain_count() {
118 let xs = [0, 1, 2, 3, 4, 5];
119 let ys = [30, 40, 50, 60];
121 assert_eq!(xs.iter().chain(&ys).count(), 10);
122 assert_eq!(zs.iter().chain(&ys).count(), 4);
126 fn test_iterator_chain_find() {
127 let xs = [0, 1, 2, 3, 4, 5];
128 let ys = [30, 40, 50, 60];
129 let mut iter = xs.iter().chain(&ys);
130 assert_eq!(iter.find(|&&i| i == 4), Some(&4));
131 assert_eq!(iter.next(), Some(&5));
132 assert_eq!(iter.find(|&&i| i == 40), Some(&40));
133 assert_eq!(iter.next(), Some(&50));
134 assert_eq!(iter.find(|&&i| i == 100), None);
135 assert_eq!(iter.next(), None);
140 let xs = [0, 1, 2, 4, 5];
141 let ys = [10, 11, 12];
143 let mut it = xs.iter().zip(&ys);
144 assert_eq!(it.nth(0), Some((&0, &10)));
145 assert_eq!(it.nth(1), Some((&2, &12)));
146 assert_eq!(it.nth(0), None);
148 let mut it = xs.iter().zip(&ys);
149 assert_eq!(it.nth(3), None);
151 let mut it = ys.iter().zip(&xs);
152 assert_eq!(it.nth(3), None);
156 fn test_zip_nth_side_effects() {
157 let mut a = Vec::new();
158 let mut b = Vec::new();
159 let value = [1, 2, 3, 4, 5, 6].iter().cloned()
164 .zip([2, 3, 4, 5, 6, 7, 8].iter().cloned().map(|n| {
170 assert_eq!(value, Some((50, 6000)));
171 assert_eq!(a, vec![1, 2, 3, 4, 5]);
172 assert_eq!(b, vec![200, 300, 400, 500, 600]);
176 fn test_iterator_step_by() {
178 let mut it = (0..).step_by(1).take(3);
179 assert_eq!(it.next(), Some(0));
180 assert_eq!(it.next(), Some(1));
181 assert_eq!(it.next(), Some(2));
182 assert_eq!(it.next(), None);
184 let mut it = (0..).step_by(3).take(4);
185 assert_eq!(it.next(), Some(0));
186 assert_eq!(it.next(), Some(3));
187 assert_eq!(it.next(), Some(6));
188 assert_eq!(it.next(), Some(9));
189 assert_eq!(it.next(), None);
193 fn test_iterator_step_by_nth() {
194 let mut it = (0..16).step_by(5);
195 assert_eq!(it.nth(0), Some(0));
196 assert_eq!(it.nth(0), Some(5));
197 assert_eq!(it.nth(0), Some(10));
198 assert_eq!(it.nth(0), Some(15));
199 assert_eq!(it.nth(0), None);
201 let it = (0..18).step_by(5);
202 assert_eq!(it.clone().nth(0), Some(0));
203 assert_eq!(it.clone().nth(1), Some(5));
204 assert_eq!(it.clone().nth(2), Some(10));
205 assert_eq!(it.clone().nth(3), Some(15));
206 assert_eq!(it.clone().nth(4), None);
207 assert_eq!(it.clone().nth(42), None);
211 fn test_iterator_step_by_nth_overflow() {
212 #[cfg(target_pointer_width = "8")]
214 #[cfg(target_pointer_width = "16")]
216 #[cfg(target_pointer_width = "32")]
218 #[cfg(target_pointer_width = "64")]
223 impl Iterator for &mut Test {
225 fn next(&mut self) -> Option<Self::Item> { Some(21) }
226 fn nth(&mut self, n: usize) -> Option<Self::Item> {
227 self.0 += n as Bigger + 1;
232 let mut it = Test(0);
233 let root = usize::MAX >> (::std::mem::size_of::<usize>() * 8 / 2);
235 (&mut it).step_by(n).nth(n);
236 assert_eq!(it.0, n as Bigger * n as Bigger);
239 let mut it = Test(0);
240 (&mut it).step_by(usize::MAX).nth(5);
241 assert_eq!(it.0, (usize::MAX as Bigger) * 5);
244 let mut it = Test(0);
245 (&mut it).step_by(2).nth(usize::MAX);
246 assert_eq!(it.0, (usize::MAX as Bigger) * 2);
249 let mut it = Test(0);
250 (&mut it).step_by(1).nth(usize::MAX);
251 assert_eq!(it.0, (usize::MAX as Bigger) * 1);
256 fn test_iterator_step_by_zero() {
257 let mut it = (0..).step_by(0);
262 fn test_iterator_step_by_size_hint() {
263 struct StubSizeHint(usize, Option<usize>);
264 impl Iterator for StubSizeHint {
266 fn next(&mut self) -> Option<()> {
268 if let Some(ref mut upper) = self.1 {
273 fn size_hint(&self) -> (usize, Option<usize>) {
278 // The two checks in each case are needed because the logic
279 // is different before the first call to `next()`.
281 let mut it = StubSizeHint(10, Some(10)).step_by(1);
282 assert_eq!(it.size_hint(), (10, Some(10)));
284 assert_eq!(it.size_hint(), (9, Some(9)));
287 let mut it = StubSizeHint(10, Some(10)).step_by(3);
288 assert_eq!(it.size_hint(), (4, Some(4)));
290 assert_eq!(it.size_hint(), (3, Some(3)));
292 // larger base range, but not enough to get another element
293 let mut it = StubSizeHint(12, Some(12)).step_by(3);
294 assert_eq!(it.size_hint(), (4, Some(4)));
296 assert_eq!(it.size_hint(), (3, Some(3)));
298 // smaller base range, so fewer resulting elements
299 let mut it = StubSizeHint(9, Some(9)).step_by(3);
300 assert_eq!(it.size_hint(), (3, Some(3)));
302 assert_eq!(it.size_hint(), (2, Some(2)));
304 // infinite upper bound
305 let mut it = StubSizeHint(usize::MAX, None).step_by(1);
306 assert_eq!(it.size_hint(), (usize::MAX, None));
308 assert_eq!(it.size_hint(), (usize::MAX-1, None));
310 // still infinite with larger step
311 let mut it = StubSizeHint(7, None).step_by(3);
312 assert_eq!(it.size_hint(), (3, None));
314 assert_eq!(it.size_hint(), (2, None));
316 // propagates ExactSizeIterator
318 let it = a.iter().step_by(2);
319 assert_eq!(it.len(), 3);
321 // Cannot be TrustedLen as a step greater than one makes an iterator
322 // with (usize::MAX, None) no longer meet the safety requirements
323 trait TrustedLenCheck { fn test(self) -> bool; }
324 impl<T:Iterator> TrustedLenCheck for T {
325 default fn test(self) -> bool { false }
327 impl<T:TrustedLen> TrustedLenCheck for T {
328 fn test(self) -> bool { true }
330 assert!(TrustedLenCheck::test(a.iter()));
331 assert!(!TrustedLenCheck::test(a.iter().step_by(1)));
335 fn test_filter_map() {
336 let it = (0..).step_by(1).take(10)
337 .filter_map(|x| if x % 2 == 0 { Some(x*x) } else { None });
338 assert_eq!(it.collect::<Vec<usize>>(), [0*0, 2*2, 4*4, 6*6, 8*8]);
342 fn test_filter_map_fold() {
343 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
344 let ys = [0*0, 2*2, 4*4, 6*6, 8*8];
345 let it = xs.iter().filter_map(|&x| if x % 2 == 0 { Some(x*x) } else { None });
346 let i = it.fold(0, |i, x| {
347 assert_eq!(x, ys[i]);
350 assert_eq!(i, ys.len());
352 let it = xs.iter().filter_map(|&x| if x % 2 == 0 { Some(x*x) } else { None });
353 let i = it.rfold(ys.len(), |i, x| {
354 assert_eq!(x, ys[i - 1]);
361 fn test_iterator_enumerate() {
362 let xs = [0, 1, 2, 3, 4, 5];
363 let it = xs.iter().enumerate();
370 fn test_iterator_enumerate_nth() {
371 let xs = [0, 1, 2, 3, 4, 5];
372 for (i, &x) in xs.iter().enumerate() {
376 let mut it = xs.iter().enumerate();
377 while let Some((i, &x)) = it.nth(0) {
381 let mut it = xs.iter().enumerate();
382 while let Some((i, &x)) = it.nth(1) {
386 let (i, &x) = xs.iter().enumerate().nth(3).unwrap();
392 fn test_iterator_enumerate_count() {
393 let xs = [0, 1, 2, 3, 4, 5];
394 assert_eq!(xs.iter().enumerate().count(), 6);
398 fn test_iterator_enumerate_fold() {
399 let xs = [0, 1, 2, 3, 4, 5];
400 let mut it = xs.iter().enumerate();
401 // steal a couple to get an interesting offset
402 assert_eq!(it.next(), Some((0, &0)));
403 assert_eq!(it.next(), Some((1, &1)));
404 let i = it.fold(2, |i, (j, &x)| {
406 assert_eq!(x, xs[j]);
409 assert_eq!(i, xs.len());
411 let mut it = xs.iter().enumerate();
412 assert_eq!(it.next(), Some((0, &0)));
413 let i = it.rfold(xs.len() - 1, |i, (j, &x)| {
415 assert_eq!(x, xs[j]);
422 fn test_iterator_filter_count() {
423 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
424 assert_eq!(xs.iter().filter(|&&x| x % 2 == 0).count(), 5);
428 fn test_iterator_filter_fold() {
429 let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
430 let ys = [0, 2, 4, 6, 8];
431 let it = xs.iter().filter(|&&x| x % 2 == 0);
432 let i = it.fold(0, |i, &x| {
433 assert_eq!(x, ys[i]);
436 assert_eq!(i, ys.len());
438 let it = xs.iter().filter(|&&x| x % 2 == 0);
439 let i = it.rfold(ys.len(), |i, &x| {
440 assert_eq!(x, ys[i - 1]);
447 fn test_iterator_peekable() {
448 let xs = vec![0, 1, 2, 3, 4, 5];
449 let mut it = xs.iter().cloned().peekable();
451 assert_eq!(it.len(), 6);
452 assert_eq!(it.peek().unwrap(), &0);
453 assert_eq!(it.len(), 6);
454 assert_eq!(it.next().unwrap(), 0);
455 assert_eq!(it.len(), 5);
456 assert_eq!(it.next().unwrap(), 1);
457 assert_eq!(it.len(), 4);
458 assert_eq!(it.next().unwrap(), 2);
459 assert_eq!(it.len(), 3);
460 assert_eq!(it.peek().unwrap(), &3);
461 assert_eq!(it.len(), 3);
462 assert_eq!(it.peek().unwrap(), &3);
463 assert_eq!(it.len(), 3);
464 assert_eq!(it.next().unwrap(), 3);
465 assert_eq!(it.len(), 2);
466 assert_eq!(it.next().unwrap(), 4);
467 assert_eq!(it.len(), 1);
468 assert_eq!(it.peek().unwrap(), &5);
469 assert_eq!(it.len(), 1);
470 assert_eq!(it.next().unwrap(), 5);
471 assert_eq!(it.len(), 0);
472 assert!(it.peek().is_none());
473 assert_eq!(it.len(), 0);
474 assert!(it.next().is_none());
475 assert_eq!(it.len(), 0);
479 fn test_iterator_peekable_count() {
480 let xs = [0, 1, 2, 3, 4, 5];
482 let zs: [i32; 0] = [];
484 assert_eq!(xs.iter().peekable().count(), 6);
486 let mut it = xs.iter().peekable();
487 assert_eq!(it.peek(), Some(&&0));
488 assert_eq!(it.count(), 6);
490 assert_eq!(ys.iter().peekable().count(), 1);
492 let mut it = ys.iter().peekable();
493 assert_eq!(it.peek(), Some(&&10));
494 assert_eq!(it.count(), 1);
496 assert_eq!(zs.iter().peekable().count(), 0);
498 let mut it = zs.iter().peekable();
499 assert_eq!(it.peek(), None);
504 fn test_iterator_peekable_nth() {
505 let xs = [0, 1, 2, 3, 4, 5];
506 let mut it = xs.iter().peekable();
508 assert_eq!(it.peek(), Some(&&0));
509 assert_eq!(it.nth(0), Some(&0));
510 assert_eq!(it.peek(), Some(&&1));
511 assert_eq!(it.nth(1), Some(&2));
512 assert_eq!(it.peek(), Some(&&3));
513 assert_eq!(it.nth(2), Some(&5));
514 assert_eq!(it.next(), None);
518 fn test_iterator_peekable_last() {
519 let xs = [0, 1, 2, 3, 4, 5];
522 let mut it = xs.iter().peekable();
523 assert_eq!(it.peek(), Some(&&0));
524 assert_eq!(it.last(), Some(&5));
526 let mut it = ys.iter().peekable();
527 assert_eq!(it.peek(), Some(&&0));
528 assert_eq!(it.last(), Some(&0));
530 let mut it = ys.iter().peekable();
531 assert_eq!(it.next(), Some(&0));
532 assert_eq!(it.peek(), None);
533 assert_eq!(it.last(), None);
537 fn test_iterator_peekable_fold() {
538 let xs = [0, 1, 2, 3, 4, 5];
539 let mut it = xs.iter().peekable();
540 assert_eq!(it.peek(), Some(&&0));
541 let i = it.fold(0, |i, &x| {
542 assert_eq!(x, xs[i]);
545 assert_eq!(i, xs.len());
548 /// This is an iterator that follows the Iterator contract,
549 /// but it is not fused. After having returned None once, it will start
550 /// producing elements if .next() is called again.
551 pub struct CycleIter<'a, T: 'a> {
556 pub fn cycle<T>(data: &[T]) -> CycleIter<T> {
563 impl<'a, T> Iterator for CycleIter<'a, T> {
565 fn next(&mut self) -> Option<Self::Item> {
566 let elt = self.data.get(self.index);
568 self.index %= 1 + self.data.len();
574 fn test_iterator_peekable_remember_peek_none_1() {
575 // Check that the loop using .peek() terminates
576 let data = [1, 2, 3];
577 let mut iter = cycle(&data).peekable();
580 while let Some(_) = iter.next() {
581 let is_the_last = iter.peek().is_none();
582 assert_eq!(is_the_last, n == data.len() - 1);
584 if n > data.len() { break; }
586 assert_eq!(n, data.len());
590 fn test_iterator_peekable_remember_peek_none_2() {
592 let mut iter = cycle(&data).peekable();
594 assert_eq!(iter.peek(), None);
595 assert_eq!(iter.last(), None);
599 fn test_iterator_peekable_remember_peek_none_3() {
601 let mut iter = cycle(&data).peekable();
603 assert_eq!(iter.nth(0), Some(&0));
605 let mut iter = cycle(&data).peekable();
607 assert_eq!(iter.peek(), None);
608 assert_eq!(iter.nth(0), None);
612 fn test_iterator_take_while() {
613 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
614 let ys = [0, 1, 2, 3, 5, 13];
615 let it = xs.iter().take_while(|&x| *x < 15);
618 assert_eq!(*x, ys[i]);
621 assert_eq!(i, ys.len());
625 fn test_iterator_skip_while() {
626 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
627 let ys = [15, 16, 17, 19];
628 let it = xs.iter().skip_while(|&x| *x < 15);
631 assert_eq!(*x, ys[i]);
634 assert_eq!(i, ys.len());
638 fn test_iterator_skip_while_fold() {
639 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
640 let ys = [15, 16, 17, 19];
641 let it = xs.iter().skip_while(|&x| *x < 15);
642 let i = it.fold(0, |i, &x| {
643 assert_eq!(x, ys[i]);
646 assert_eq!(i, ys.len());
648 let mut it = xs.iter().skip_while(|&x| *x < 15);
649 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
650 let i = it.fold(1, |i, &x| {
651 assert_eq!(x, ys[i]);
654 assert_eq!(i, ys.len());
658 fn test_iterator_skip() {
659 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
660 let ys = [13, 15, 16, 17, 19, 20, 30];
661 let mut it = xs.iter().skip(5);
663 while let Some(&x) = it.next() {
664 assert_eq!(x, ys[i]);
666 assert_eq!(it.len(), xs.len()-5-i);
668 assert_eq!(i, ys.len());
669 assert_eq!(it.len(), 0);
673 fn test_iterator_skip_doubleended() {
674 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
675 let mut it = xs.iter().rev().skip(5);
676 assert_eq!(it.next(), Some(&15));
677 assert_eq!(it.by_ref().rev().next(), Some(&0));
678 assert_eq!(it.next(), Some(&13));
679 assert_eq!(it.by_ref().rev().next(), Some(&1));
680 assert_eq!(it.next(), Some(&5));
681 assert_eq!(it.by_ref().rev().next(), Some(&2));
682 assert_eq!(it.next(), Some(&3));
683 assert_eq!(it.next(), None);
684 let mut it = xs.iter().rev().skip(5).rev();
685 assert_eq!(it.next(), Some(&0));
686 assert_eq!(it.rev().next(), Some(&15));
687 let mut it_base = xs.iter();
689 let mut it = it_base.by_ref().skip(5).rev();
690 assert_eq!(it.next(), Some(&30));
691 assert_eq!(it.next(), Some(&20));
692 assert_eq!(it.next(), Some(&19));
693 assert_eq!(it.next(), Some(&17));
694 assert_eq!(it.next(), Some(&16));
695 assert_eq!(it.next(), Some(&15));
696 assert_eq!(it.next(), Some(&13));
697 assert_eq!(it.next(), None);
699 // make sure the skipped parts have not been consumed
700 assert_eq!(it_base.next(), Some(&0));
701 assert_eq!(it_base.next(), Some(&1));
702 assert_eq!(it_base.next(), Some(&2));
703 assert_eq!(it_base.next(), Some(&3));
704 assert_eq!(it_base.next(), Some(&5));
705 assert_eq!(it_base.next(), None);
706 let it = xs.iter().skip(5).rev();
707 assert_eq!(it.last(), Some(&13));
711 fn test_iterator_skip_nth() {
712 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
714 let mut it = xs.iter().skip(0);
715 assert_eq!(it.nth(0), Some(&0));
716 assert_eq!(it.nth(1), Some(&2));
718 let mut it = xs.iter().skip(5);
719 assert_eq!(it.nth(0), Some(&13));
720 assert_eq!(it.nth(1), Some(&16));
722 let mut it = xs.iter().skip(12);
723 assert_eq!(it.nth(0), None);
728 fn test_iterator_skip_count() {
729 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
731 assert_eq!(xs.iter().skip(0).count(), 12);
732 assert_eq!(xs.iter().skip(1).count(), 11);
733 assert_eq!(xs.iter().skip(11).count(), 1);
734 assert_eq!(xs.iter().skip(12).count(), 0);
735 assert_eq!(xs.iter().skip(13).count(), 0);
739 fn test_iterator_skip_last() {
740 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
742 assert_eq!(xs.iter().skip(0).last(), Some(&30));
743 assert_eq!(xs.iter().skip(1).last(), Some(&30));
744 assert_eq!(xs.iter().skip(11).last(), Some(&30));
745 assert_eq!(xs.iter().skip(12).last(), None);
746 assert_eq!(xs.iter().skip(13).last(), None);
748 let mut it = xs.iter().skip(5);
749 assert_eq!(it.next(), Some(&13));
750 assert_eq!(it.last(), Some(&30));
754 fn test_iterator_skip_fold() {
755 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
756 let ys = [13, 15, 16, 17, 19, 20, 30];
758 let it = xs.iter().skip(5);
759 let i = it.fold(0, |i, &x| {
760 assert_eq!(x, ys[i]);
763 assert_eq!(i, ys.len());
765 let mut it = xs.iter().skip(5);
766 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
767 let i = it.fold(1, |i, &x| {
768 assert_eq!(x, ys[i]);
771 assert_eq!(i, ys.len());
773 let it = xs.iter().skip(5);
774 let i = it.rfold(ys.len(), |i, &x| {
776 assert_eq!(x, ys[i]);
781 let mut it = xs.iter().skip(5);
782 assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
783 let i = it.rfold(ys.len(), |i, &x| {
785 assert_eq!(x, ys[i]);
793 fn test_iterator_take() {
794 let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
795 let ys = [0, 1, 2, 3, 5];
796 let mut it = xs.iter().take(5);
798 assert_eq!(it.len(), 5);
799 while let Some(&x) = it.next() {
800 assert_eq!(x, ys[i]);
802 assert_eq!(it.len(), 5-i);
804 assert_eq!(i, ys.len());
805 assert_eq!(it.len(), 0);
809 fn test_iterator_take_nth() {
810 let xs = [0, 1, 2, 4, 5];
811 let mut it = xs.iter();
813 let mut take = it.by_ref().take(3);
815 while let Some(&x) = take.nth(0) {
820 assert_eq!(it.nth(1), Some(&5));
821 assert_eq!(it.nth(0), None);
823 let xs = [0, 1, 2, 3, 4];
824 let mut it = xs.iter().take(7);
826 while let Some(&x) = it.nth(1) {
833 fn test_iterator_take_short() {
834 let xs = [0, 1, 2, 3];
835 let ys = [0, 1, 2, 3];
836 let mut it = xs.iter().take(5);
838 assert_eq!(it.len(), 4);
839 while let Some(&x) = it.next() {
840 assert_eq!(x, ys[i]);
842 assert_eq!(it.len(), 4-i);
844 assert_eq!(i, ys.len());
845 assert_eq!(it.len(), 0);
849 fn test_iterator_scan() {
850 // test the type inference
851 fn add(old: &mut isize, new: &usize) -> Option<f64> {
852 *old += *new as isize;
855 let xs = [0, 1, 2, 3, 4];
856 let ys = [0f64, 1.0, 3.0, 6.0, 10.0];
858 let it = xs.iter().scan(0, add);
861 assert_eq!(x, ys[i]);
864 assert_eq!(i, ys.len());
868 fn test_iterator_flat_map() {
870 let ys = [0, 1, 2, 3, 4, 5, 6, 7, 8];
871 let it = xs.iter().flat_map(|&x| (x..).step_by(1).take(3));
874 assert_eq!(x, ys[i]);
877 assert_eq!(i, ys.len());
880 /// Test `FlatMap::fold` with items already picked off the front and back,
881 /// to make sure all parts of the `FlatMap` are folded correctly.
883 fn test_iterator_flat_map_fold() {
885 let ys = [1, 2, 3, 4, 5, 6, 7];
886 let mut it = xs.iter().flat_map(|&x| x..x+3);
887 assert_eq!(it.next(), Some(0));
888 assert_eq!(it.next_back(), Some(8));
889 let i = it.fold(0, |i, x| {
890 assert_eq!(x, ys[i]);
893 assert_eq!(i, ys.len());
895 let mut it = xs.iter().flat_map(|&x| x..x+3);
896 assert_eq!(it.next(), Some(0));
897 assert_eq!(it.next_back(), Some(8));
898 let i = it.rfold(ys.len(), |i, x| {
899 assert_eq!(x, ys[i - 1]);
906 fn test_iterator_flatten() {
908 let ys = [0, 1, 2, 3, 4, 5, 6, 7, 8];
909 let it = xs.iter().map(|&x| (x..).step_by(1).take(3)).flatten();
912 assert_eq!(x, ys[i]);
915 assert_eq!(i, ys.len());
918 /// Test `Flatten::fold` with items already picked off the front and back,
919 /// to make sure all parts of the `Flatten` are folded correctly.
921 fn test_iterator_flatten_fold() {
923 let ys = [1, 2, 3, 4, 5, 6, 7];
924 let mut it = xs.iter().map(|&x| x..x+3).flatten();
925 assert_eq!(it.next(), Some(0));
926 assert_eq!(it.next_back(), Some(8));
927 let i = it.fold(0, |i, x| {
928 assert_eq!(x, ys[i]);
931 assert_eq!(i, ys.len());
933 let mut it = xs.iter().map(|&x| x..x+3).flatten();
934 assert_eq!(it.next(), Some(0));
935 assert_eq!(it.next_back(), Some(8));
936 let i = it.rfold(ys.len(), |i, x| {
937 assert_eq!(x, ys[i - 1]);
945 let xs = [1, 2, 3, 4];
951 .collect::<Vec<usize>>();
953 assert_eq!(n, xs.len());
954 assert_eq!(&xs[..], &ys[..]);
958 fn test_inspect_fold() {
959 let xs = [1, 2, 3, 4];
962 let it = xs.iter().inspect(|_| n += 1);
963 let i = it.fold(0, |i, &x| {
964 assert_eq!(x, xs[i]);
967 assert_eq!(i, xs.len());
969 assert_eq!(n, xs.len());
973 let it = xs.iter().inspect(|_| n += 1);
974 let i = it.rfold(xs.len(), |i, &x| {
975 assert_eq!(x, xs[i - 1]);
980 assert_eq!(n, xs.len());
986 let it = (0..).step_by(1).take(cycle_len).cycle();
987 assert_eq!(it.size_hint(), (usize::MAX, None));
988 for (i, x) in it.take(100).enumerate() {
989 assert_eq!(i % cycle_len, x);
992 let mut it = (0..).step_by(1).take(0).cycle();
993 assert_eq!(it.size_hint(), (0, Some(0)));
994 assert_eq!(it.next(), None);
996 assert_eq!(empty::<i32>().cycle().fold(0, |acc, x| acc + x), 0);
998 assert_eq!(once(1).cycle().skip(1).take(4).fold(0, |acc, x| acc + x), 4);
1002 fn test_iterator_nth() {
1003 let v: &[_] = &[0, 1, 2, 3, 4];
1004 for i in 0..v.len() {
1005 assert_eq!(v.iter().nth(i).unwrap(), &v[i]);
1007 assert_eq!(v.iter().nth(v.len()), None);
1011 fn test_iterator_nth_back() {
1012 let v: &[_] = &[0, 1, 2, 3, 4];
1013 for i in 0..v.len() {
1014 assert_eq!(v.iter().nth_back(i).unwrap(), &v[v.len() - 1 - i]);
1016 assert_eq!(v.iter().nth_back(v.len()), None);
1020 fn test_iterator_rev_nth_back() {
1021 let v: &[_] = &[0, 1, 2, 3, 4];
1022 for i in 0..v.len() {
1023 assert_eq!(v.iter().rev().nth_back(i).unwrap(), &v[i]);
1025 assert_eq!(v.iter().rev().nth_back(v.len()), None);
1029 fn test_iterator_rev_nth() {
1030 let v: &[_] = &[0, 1, 2, 3, 4];
1031 for i in 0..v.len() {
1032 assert_eq!(v.iter().rev().nth(i).unwrap(), &v[v.len() - 1 - i]);
1034 assert_eq!(v.iter().rev().nth(v.len()), None);
1038 fn test_iterator_last() {
1039 let v: &[_] = &[0, 1, 2, 3, 4];
1040 assert_eq!(v.iter().last().unwrap(), &4);
1041 assert_eq!(v[..1].iter().last().unwrap(), &0);
1045 fn test_iterator_len() {
1046 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1047 assert_eq!(v[..4].iter().count(), 4);
1048 assert_eq!(v[..10].iter().count(), 10);
1049 assert_eq!(v[..0].iter().count(), 0);
1053 fn test_iterator_sum() {
1054 let v: &[i32] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1055 assert_eq!(v[..4].iter().cloned().sum::<i32>(), 6);
1056 assert_eq!(v.iter().cloned().sum::<i32>(), 55);
1057 assert_eq!(v[..0].iter().cloned().sum::<i32>(), 0);
1061 fn test_iterator_sum_result() {
1062 let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
1063 assert_eq!(v.iter().cloned().sum::<Result<i32, _>>(), Ok(10));
1064 let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
1065 assert_eq!(v.iter().cloned().sum::<Result<i32, _>>(), Err(()));
1069 fn test_iterator_product() {
1070 let v: &[i32] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1071 assert_eq!(v[..4].iter().cloned().product::<i32>(), 0);
1072 assert_eq!(v[1..5].iter().cloned().product::<i32>(), 24);
1073 assert_eq!(v[..0].iter().cloned().product::<i32>(), 1);
1077 fn test_iterator_product_result() {
1078 let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
1079 assert_eq!(v.iter().cloned().product::<Result<i32, _>>(), Ok(24));
1080 let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
1081 assert_eq!(v.iter().cloned().product::<Result<i32, _>>(), Err(()));
1085 fn test_iterator_max() {
1086 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1087 assert_eq!(v[..4].iter().cloned().max(), Some(3));
1088 assert_eq!(v.iter().cloned().max(), Some(10));
1089 assert_eq!(v[..0].iter().cloned().max(), None);
1093 fn test_iterator_min() {
1094 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
1095 assert_eq!(v[..4].iter().cloned().min(), Some(0));
1096 assert_eq!(v.iter().cloned().min(), Some(0));
1097 assert_eq!(v[..0].iter().cloned().min(), None);
1101 fn test_iterator_size_hint() {
1102 let c = (0..).step_by(1);
1103 let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
1104 let v2 = &[10, 11, 12];
1107 assert_eq!((0..).size_hint(), (usize::MAX, None));
1108 assert_eq!(c.size_hint(), (usize::MAX, None));
1109 assert_eq!(vi.clone().size_hint(), (10, Some(10)));
1111 assert_eq!(c.clone().take(5).size_hint(), (5, Some(5)));
1112 assert_eq!(c.clone().skip(5).size_hint().1, None);
1113 assert_eq!(c.clone().take_while(|_| false).size_hint(), (0, None));
1114 assert_eq!(c.clone().skip_while(|_| false).size_hint(), (0, None));
1115 assert_eq!(c.clone().enumerate().size_hint(), (usize::MAX, None));
1116 assert_eq!(c.clone().chain(vi.clone().cloned()).size_hint(), (usize::MAX, None));
1117 assert_eq!(c.clone().zip(vi.clone()).size_hint(), (10, Some(10)));
1118 assert_eq!(c.clone().scan(0, |_,_| Some(0)).size_hint(), (0, None));
1119 assert_eq!(c.clone().filter(|_| false).size_hint(), (0, None));
1120 assert_eq!(c.clone().map(|_| 0).size_hint(), (usize::MAX, None));
1121 assert_eq!(c.filter_map(|_| Some(0)).size_hint(), (0, None));
1123 assert_eq!(vi.clone().take(5).size_hint(), (5, Some(5)));
1124 assert_eq!(vi.clone().take(12).size_hint(), (10, Some(10)));
1125 assert_eq!(vi.clone().skip(3).size_hint(), (7, Some(7)));
1126 assert_eq!(vi.clone().skip(12).size_hint(), (0, Some(0)));
1127 assert_eq!(vi.clone().take_while(|_| false).size_hint(), (0, Some(10)));
1128 assert_eq!(vi.clone().skip_while(|_| false).size_hint(), (0, Some(10)));
1129 assert_eq!(vi.clone().enumerate().size_hint(), (10, Some(10)));
1130 assert_eq!(vi.clone().chain(v2).size_hint(), (13, Some(13)));
1131 assert_eq!(vi.clone().zip(v2).size_hint(), (3, Some(3)));
1132 assert_eq!(vi.clone().scan(0, |_,_| Some(0)).size_hint(), (0, Some(10)));
1133 assert_eq!(vi.clone().filter(|_| false).size_hint(), (0, Some(10)));
1134 assert_eq!(vi.clone().map(|&i| i+1).size_hint(), (10, Some(10)));
1135 assert_eq!(vi.filter_map(|_| Some(0)).size_hint(), (0, Some(10)));
1140 let a = vec![1, 2, 3, 4, 5];
1141 let b: Vec<isize> = a.iter().cloned().collect();
1147 let v: Box<[isize]> = Box::new([1, 2, 3, 4, 5]);
1148 assert!(v.iter().all(|&x| x < 10));
1149 assert!(!v.iter().all(|&x| x % 2 == 0));
1150 assert!(!v.iter().all(|&x| x > 100));
1151 assert!(v[..0].iter().all(|_| panic!()));
1156 let v: Box<[isize]> = Box::new([1, 2, 3, 4, 5]);
1157 assert!(v.iter().any(|&x| x < 10));
1158 assert!(v.iter().any(|&x| x % 2 == 0));
1159 assert!(!v.iter().any(|&x| x > 100));
1160 assert!(!v[..0].iter().any(|_| panic!()));
1165 let v: &[isize] = &[1, 3, 9, 27, 103, 14, 11];
1166 assert_eq!(*v.iter().find(|&&x| x & 1 == 0).unwrap(), 14);
1167 assert_eq!(*v.iter().find(|&&x| x % 3 == 0).unwrap(), 3);
1168 assert!(v.iter().find(|&&x| x % 12 == 0).is_none());
1172 fn test_find_map() {
1173 let xs: &[isize] = &[];
1174 assert_eq!(xs.iter().find_map(half_if_even), None);
1175 let xs: &[isize] = &[3, 5];
1176 assert_eq!(xs.iter().find_map(half_if_even), None);
1177 let xs: &[isize] = &[4, 5];
1178 assert_eq!(xs.iter().find_map(half_if_even), Some(2));
1179 let xs: &[isize] = &[3, 6];
1180 assert_eq!(xs.iter().find_map(half_if_even), Some(3));
1182 let xs: &[isize] = &[1, 2, 3, 4, 5, 6, 7];
1183 let mut iter = xs.iter();
1184 assert_eq!(iter.find_map(half_if_even), Some(1));
1185 assert_eq!(iter.find_map(half_if_even), Some(2));
1186 assert_eq!(iter.find_map(half_if_even), Some(3));
1187 assert_eq!(iter.next(), Some(&7));
1189 fn half_if_even(x: &isize) -> Option<isize> {
1199 fn test_position() {
1200 let v = &[1, 3, 9, 27, 103, 14, 11];
1201 assert_eq!(v.iter().position(|x| *x & 1 == 0).unwrap(), 5);
1202 assert_eq!(v.iter().position(|x| *x % 3 == 0).unwrap(), 1);
1203 assert!(v.iter().position(|x| *x % 12 == 0).is_none());
1208 let xs = &[1, 2, 2, 1, 5, 9, 0, 2];
1209 assert_eq!(xs.iter().filter(|x| **x == 2).count(), 3);
1210 assert_eq!(xs.iter().filter(|x| **x == 5).count(), 1);
1211 assert_eq!(xs.iter().filter(|x| **x == 95).count(), 0);
1215 fn test_max_by_key() {
1216 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1217 assert_eq!(*xs.iter().max_by_key(|x| x.abs()).unwrap(), -10);
1222 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1223 assert_eq!(*xs.iter().max_by(|x, y| x.abs().cmp(&y.abs())).unwrap(), -10);
1227 fn test_min_by_key() {
1228 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1229 assert_eq!(*xs.iter().min_by_key(|x| x.abs()).unwrap(), 0);
1234 let xs: &[isize] = &[-3, 0, 1, 5, -10];
1235 assert_eq!(*xs.iter().min_by(|x, y| x.abs().cmp(&y.abs())).unwrap(), 0);
1241 // sum the first five values
1242 let partial_sum = xs.by_ref().take(5).fold(0, |a, b| a + b);
1243 assert_eq!(partial_sum, 10);
1244 assert_eq!(xs.next(), Some(5));
1249 let xs = [2, 4, 6, 8, 10, 12, 14, 16];
1250 let mut it = xs.iter();
1253 assert!(it.rev().cloned().collect::<Vec<isize>>() ==
1254 vec![16, 14, 12, 10, 8, 6]);
1259 let xs = [2, 4, 6, 8];
1261 let mut it = xs.iter().copied();
1262 assert_eq!(it.len(), 4);
1263 assert_eq!(it.next(), Some(2));
1264 assert_eq!(it.len(), 3);
1265 assert_eq!(it.next(), Some(4));
1266 assert_eq!(it.len(), 2);
1267 assert_eq!(it.next_back(), Some(8));
1268 assert_eq!(it.len(), 1);
1269 assert_eq!(it.next_back(), Some(6));
1270 assert_eq!(it.len(), 0);
1271 assert_eq!(it.next_back(), None);
1276 let xs = [2, 4, 6, 8];
1278 let mut it = xs.iter().cloned();
1279 assert_eq!(it.len(), 4);
1280 assert_eq!(it.next(), Some(2));
1281 assert_eq!(it.len(), 3);
1282 assert_eq!(it.next(), Some(4));
1283 assert_eq!(it.len(), 2);
1284 assert_eq!(it.next_back(), Some(8));
1285 assert_eq!(it.len(), 1);
1286 assert_eq!(it.next_back(), Some(6));
1287 assert_eq!(it.len(), 0);
1288 assert_eq!(it.next_back(), None);
1292 fn test_cloned_side_effects() {
1295 let iter = [1, 2, 3]
1305 assert_eq!(count, 2);
1309 fn test_double_ended_map() {
1310 let xs = [1, 2, 3, 4, 5, 6];
1311 let mut it = xs.iter().map(|&x| x * -1);
1312 assert_eq!(it.next(), Some(-1));
1313 assert_eq!(it.next(), Some(-2));
1314 assert_eq!(it.next_back(), Some(-6));
1315 assert_eq!(it.next_back(), Some(-5));
1316 assert_eq!(it.next(), Some(-3));
1317 assert_eq!(it.next_back(), Some(-4));
1318 assert_eq!(it.next(), None);
1322 fn test_double_ended_enumerate() {
1323 let xs = [1, 2, 3, 4, 5, 6];
1324 let mut it = xs.iter().cloned().enumerate();
1325 assert_eq!(it.next(), Some((0, 1)));
1326 assert_eq!(it.next(), Some((1, 2)));
1327 assert_eq!(it.next_back(), Some((5, 6)));
1328 assert_eq!(it.next_back(), Some((4, 5)));
1329 assert_eq!(it.next_back(), Some((3, 4)));
1330 assert_eq!(it.next_back(), Some((2, 3)));
1331 assert_eq!(it.next(), None);
1335 fn test_double_ended_zip() {
1336 let xs = [1, 2, 3, 4, 5, 6];
1337 let ys = [1, 2, 3, 7];
1338 let a = xs.iter().cloned();
1339 let b = ys.iter().cloned();
1340 let mut it = a.zip(b);
1341 assert_eq!(it.next(), Some((1, 1)));
1342 assert_eq!(it.next(), Some((2, 2)));
1343 assert_eq!(it.next_back(), Some((4, 7)));
1344 assert_eq!(it.next_back(), Some((3, 3)));
1345 assert_eq!(it.next(), None);
1349 fn test_double_ended_filter() {
1350 let xs = [1, 2, 3, 4, 5, 6];
1351 let mut it = xs.iter().filter(|&x| *x & 1 == 0);
1352 assert_eq!(it.next_back().unwrap(), &6);
1353 assert_eq!(it.next_back().unwrap(), &4);
1354 assert_eq!(it.next().unwrap(), &2);
1355 assert_eq!(it.next_back(), None);
1359 fn test_double_ended_filter_map() {
1360 let xs = [1, 2, 3, 4, 5, 6];
1361 let mut it = xs.iter().filter_map(|&x| if x & 1 == 0 { Some(x * 2) } else { None });
1362 assert_eq!(it.next_back().unwrap(), 12);
1363 assert_eq!(it.next_back().unwrap(), 8);
1364 assert_eq!(it.next().unwrap(), 4);
1365 assert_eq!(it.next_back(), None);
1369 fn test_double_ended_chain() {
1370 let xs = [1, 2, 3, 4, 5];
1371 let ys = [7, 9, 11];
1372 let mut it = xs.iter().chain(&ys).rev();
1373 assert_eq!(it.next().unwrap(), &11);
1374 assert_eq!(it.next().unwrap(), &9);
1375 assert_eq!(it.next_back().unwrap(), &1);
1376 assert_eq!(it.next_back().unwrap(), &2);
1377 assert_eq!(it.next_back().unwrap(), &3);
1378 assert_eq!(it.next_back().unwrap(), &4);
1379 assert_eq!(it.next_back().unwrap(), &5);
1380 assert_eq!(it.next_back().unwrap(), &7);
1381 assert_eq!(it.next_back(), None);
1384 // test that .chain() is well behaved with an unfused iterator
1385 struct CrazyIterator(bool);
1386 impl CrazyIterator { fn new() -> CrazyIterator { CrazyIterator(false) } }
1387 impl Iterator for CrazyIterator {
1389 fn next(&mut self) -> Option<i32> {
1390 if self.0 { Some(99) } else { self.0 = true; None }
1394 impl DoubleEndedIterator for CrazyIterator {
1395 fn next_back(&mut self) -> Option<i32> {
1400 assert_eq!(CrazyIterator::new().chain(0..10).rev().last(), Some(0));
1401 assert!((0..10).chain(CrazyIterator::new()).rev().any(|i| i == 0));
1405 fn test_rposition() {
1406 fn f(xy: &(isize, char)) -> bool { let (_x, y) = *xy; y == 'b' }
1407 fn g(xy: &(isize, char)) -> bool { let (_x, y) = *xy; y == 'd' }
1408 let v = [(0, 'a'), (1, 'b'), (2, 'c'), (3, 'b')];
1410 assert_eq!(v.iter().rposition(f), Some(3));
1411 assert!(v.iter().rposition(g).is_none());
1416 fn test_rposition_panic() {
1417 let v: [(Box<_>, Box<_>); 4] =
1418 [(box 0, box 0), (box 0, box 0),
1419 (box 0, box 0), (box 0, box 0)];
1421 v.iter().rposition(|_elt| {
1432 fn test_double_ended_flat_map() {
1435 let mut it = u.iter().flat_map(|x| &v[*x..v.len()]);
1436 assert_eq!(it.next_back().unwrap(), &8);
1437 assert_eq!(it.next().unwrap(), &5);
1438 assert_eq!(it.next_back().unwrap(), &7);
1439 assert_eq!(it.next_back().unwrap(), &6);
1440 assert_eq!(it.next_back().unwrap(), &8);
1441 assert_eq!(it.next().unwrap(), &6);
1442 assert_eq!(it.next_back().unwrap(), &7);
1443 assert_eq!(it.next_back(), None);
1444 assert_eq!(it.next(), None);
1445 assert_eq!(it.next_back(), None);
1449 fn test_double_ended_flatten() {
1452 let mut it = u.iter().map(|x| &v[*x..v.len()]).flatten();
1453 assert_eq!(it.next_back().unwrap(), &8);
1454 assert_eq!(it.next().unwrap(), &5);
1455 assert_eq!(it.next_back().unwrap(), &7);
1456 assert_eq!(it.next_back().unwrap(), &6);
1457 assert_eq!(it.next_back().unwrap(), &8);
1458 assert_eq!(it.next().unwrap(), &6);
1459 assert_eq!(it.next_back().unwrap(), &7);
1460 assert_eq!(it.next_back(), None);
1461 assert_eq!(it.next(), None);
1462 assert_eq!(it.next_back(), None);
1466 fn test_double_ended_range() {
1467 assert_eq!((11..14).rev().collect::<Vec<_>>(), [13, 12, 11]);
1468 for _ in (10..0).rev() {
1469 panic!("unreachable");
1472 assert_eq!((11..14).rev().collect::<Vec<_>>(), [13, 12, 11]);
1473 for _ in (10..0).rev() {
1474 panic!("unreachable");
1480 assert_eq!((0..5).collect::<Vec<_>>(), [0, 1, 2, 3, 4]);
1481 assert_eq!((-10..-1).collect::<Vec<_>>(), [-10, -9, -8, -7, -6, -5, -4, -3, -2]);
1482 assert_eq!((0..5).rev().collect::<Vec<_>>(), [4, 3, 2, 1, 0]);
1483 assert_eq!((200..-5).count(), 0);
1484 assert_eq!((200..-5).rev().count(), 0);
1485 assert_eq!((200..200).count(), 0);
1486 assert_eq!((200..200).rev().count(), 0);
1488 assert_eq!((0..100).size_hint(), (100, Some(100)));
1489 // this test is only meaningful when sizeof usize < sizeof u64
1490 assert_eq!((usize::MAX - 1..usize::MAX).size_hint(), (1, Some(1)));
1491 assert_eq!((-10..-1).size_hint(), (9, Some(9)));
1492 assert_eq!((-1..-10).size_hint(), (0, Some(0)));
1494 assert_eq!((-70..58).size_hint(), (128, Some(128)));
1495 assert_eq!((-128..127).size_hint(), (255, Some(255)));
1496 assert_eq!((-2..isize::MAX).size_hint(),
1497 (isize::MAX as usize + 2, Some(isize::MAX as usize + 2)));
1501 fn test_range_exhaustion() {
1503 assert!(r.is_empty());
1504 assert_eq!(r.next(), None);
1505 assert_eq!(r.next_back(), None);
1506 assert_eq!(r, 10..10);
1509 assert_eq!(r.next(), Some(10));
1510 assert_eq!(r.next(), Some(11));
1511 assert!(r.is_empty());
1512 assert_eq!(r, 12..12);
1513 assert_eq!(r.next(), None);
1516 assert_eq!(r.next_back(), Some(11));
1517 assert_eq!(r.next_back(), Some(10));
1518 assert!(r.is_empty());
1519 assert_eq!(r, 10..10);
1520 assert_eq!(r.next_back(), None);
1522 let mut r = 100..10;
1523 assert!(r.is_empty());
1524 assert_eq!(r.next(), None);
1525 assert_eq!(r.next_back(), None);
1526 assert_eq!(r, 100..10);
1530 fn test_range_inclusive_exhaustion() {
1531 let mut r = 10..=10;
1532 assert_eq!(r.next(), Some(10));
1533 assert!(r.is_empty());
1534 assert_eq!(r.next(), None);
1535 assert_eq!(r.next(), None);
1537 let mut r = 10..=10;
1538 assert_eq!(r.next_back(), Some(10));
1539 assert!(r.is_empty());
1540 assert_eq!(r.next_back(), None);
1542 let mut r = 10..=12;
1543 assert_eq!(r.next(), Some(10));
1544 assert_eq!(r.next(), Some(11));
1545 assert_eq!(r.next(), Some(12));
1546 assert!(r.is_empty());
1547 assert_eq!(r.next(), None);
1549 let mut r = 10..=12;
1550 assert_eq!(r.next_back(), Some(12));
1551 assert_eq!(r.next_back(), Some(11));
1552 assert_eq!(r.next_back(), Some(10));
1553 assert!(r.is_empty());
1554 assert_eq!(r.next_back(), None);
1556 let mut r = 10..=12;
1557 assert_eq!(r.nth(2), Some(12));
1558 assert!(r.is_empty());
1559 assert_eq!(r.next(), None);
1561 let mut r = 10..=12;
1562 assert_eq!(r.nth(5), None);
1563 assert!(r.is_empty());
1564 assert_eq!(r.next(), None);
1566 let mut r = 100..=10;
1567 assert_eq!(r.next(), None);
1568 assert!(r.is_empty());
1569 assert_eq!(r.next(), None);
1570 assert_eq!(r.next(), None);
1571 assert_eq!(r, 100..=10);
1573 let mut r = 100..=10;
1574 assert_eq!(r.next_back(), None);
1575 assert!(r.is_empty());
1576 assert_eq!(r.next_back(), None);
1577 assert_eq!(r.next_back(), None);
1578 assert_eq!(r, 100..=10);
1582 fn test_range_nth() {
1583 assert_eq!((10..15).nth(0), Some(10));
1584 assert_eq!((10..15).nth(1), Some(11));
1585 assert_eq!((10..15).nth(4), Some(14));
1586 assert_eq!((10..15).nth(5), None);
1589 assert_eq!(r.nth(2), Some(12));
1590 assert_eq!(r, 13..20);
1591 assert_eq!(r.nth(2), Some(15));
1592 assert_eq!(r, 16..20);
1593 assert_eq!(r.nth(10), None);
1594 assert_eq!(r, 20..20);
1598 fn test_range_from_nth() {
1599 assert_eq!((10..).nth(0), Some(10));
1600 assert_eq!((10..).nth(1), Some(11));
1601 assert_eq!((10..).nth(4), Some(14));
1604 assert_eq!(r.nth(2), Some(12));
1605 assert_eq!(r, 13..);
1606 assert_eq!(r.nth(2), Some(15));
1607 assert_eq!(r, 16..);
1608 assert_eq!(r.nth(10), Some(26));
1609 assert_eq!(r, 27..);
1611 assert_eq!((0..).size_hint(), (usize::MAX, None));
1614 fn is_trusted_len<I: TrustedLen>(_: I) {}
1617 fn test_range_from_take() {
1618 let mut it = (0..).take(3);
1619 assert_eq!(it.next(), Some(0));
1620 assert_eq!(it.next(), Some(1));
1621 assert_eq!(it.next(), Some(2));
1622 assert_eq!(it.next(), None);
1623 is_trusted_len((0..).take(3));
1624 assert_eq!((0..).take(3).size_hint(), (3, Some(3)));
1625 assert_eq!((0..).take(0).size_hint(), (0, Some(0)));
1626 assert_eq!((0..).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
1630 fn test_range_from_take_collect() {
1631 let v: Vec<_> = (0..).take(3).collect();
1632 assert_eq!(v, vec![0, 1, 2]);
1636 fn test_range_inclusive_nth() {
1637 assert_eq!((10..=15).nth(0), Some(10));
1638 assert_eq!((10..=15).nth(1), Some(11));
1639 assert_eq!((10..=15).nth(5), Some(15));
1640 assert_eq!((10..=15).nth(6), None);
1642 let mut r = 10_u8..=20;
1643 assert_eq!(r.nth(2), Some(12));
1644 assert_eq!(r, 13..=20);
1645 assert_eq!(r.nth(2), Some(15));
1646 assert_eq!(r, 16..=20);
1647 assert_eq!(r.is_empty(), false);
1648 assert_eq!(ExactSizeIterator::is_empty(&r), false);
1649 assert_eq!(r.nth(10), None);
1650 assert_eq!(r.is_empty(), true);
1651 assert_eq!(ExactSizeIterator::is_empty(&r), true);
1655 fn test_range_step() {
1656 #![allow(deprecated)]
1658 assert_eq!((0..20).step_by(5).collect::<Vec<isize>>(), [0, 5, 10, 15]);
1659 assert_eq!((1..21).rev().step_by(5).collect::<Vec<isize>>(), [20, 15, 10, 5]);
1660 assert_eq!((1..21).rev().step_by(6).collect::<Vec<isize>>(), [20, 14, 8, 2]);
1661 assert_eq!((200..255).step_by(50).collect::<Vec<u8>>(), [200, 250]);
1662 assert_eq!((200..-5).step_by(1).collect::<Vec<isize>>(), []);
1663 assert_eq!((200..200).step_by(1).collect::<Vec<isize>>(), []);
1665 assert_eq!((0..20).step_by(1).size_hint(), (20, Some(20)));
1666 assert_eq!((0..20).step_by(21).size_hint(), (1, Some(1)));
1667 assert_eq!((0..20).step_by(5).size_hint(), (4, Some(4)));
1668 assert_eq!((1..21).rev().step_by(5).size_hint(), (4, Some(4)));
1669 assert_eq!((1..21).rev().step_by(6).size_hint(), (4, Some(4)));
1670 assert_eq!((20..-5).step_by(1).size_hint(), (0, Some(0)));
1671 assert_eq!((20..20).step_by(1).size_hint(), (0, Some(0)));
1672 assert_eq!((i8::MIN..i8::MAX).step_by(-(i8::MIN as i32) as usize).size_hint(), (2, Some(2)));
1673 assert_eq!((i16::MIN..i16::MAX).step_by(i16::MAX as usize).size_hint(), (3, Some(3)));
1674 assert_eq!((isize::MIN..isize::MAX).step_by(1).size_hint(), (usize::MAX, Some(usize::MAX)));
1678 fn test_step_by_skip() {
1679 assert_eq!((0..640).step_by(128).skip(1).collect::<Vec<_>>(), [128, 256, 384, 512]);
1680 assert_eq!((0..=50).step_by(10).nth(3), Some(30));
1681 assert_eq!((200..=255u8).step_by(10).nth(3), Some(230));
1685 fn test_range_inclusive_step() {
1686 assert_eq!((0..=50).step_by(10).collect::<Vec<_>>(), [0, 10, 20, 30, 40, 50]);
1687 assert_eq!((0..=5).step_by(1).collect::<Vec<_>>(), [0, 1, 2, 3, 4, 5]);
1688 assert_eq!((200..=255u8).step_by(10).collect::<Vec<_>>(), [200, 210, 220, 230, 240, 250]);
1689 assert_eq!((250..=255u8).step_by(1).collect::<Vec<_>>(), [250, 251, 252, 253, 254, 255]);
1693 fn test_range_last_max() {
1694 assert_eq!((0..20).last(), Some(19));
1695 assert_eq!((-20..0).last(), Some(-1));
1696 assert_eq!((5..5).last(), None);
1698 assert_eq!((0..20).max(), Some(19));
1699 assert_eq!((-20..0).max(), Some(-1));
1700 assert_eq!((5..5).max(), None);
1704 fn test_range_inclusive_last_max() {
1705 assert_eq!((0..=20).last(), Some(20));
1706 assert_eq!((-20..=0).last(), Some(0));
1707 assert_eq!((5..=5).last(), Some(5));
1708 let mut r = 10..=10;
1710 assert_eq!(r.last(), None);
1712 assert_eq!((0..=20).max(), Some(20));
1713 assert_eq!((-20..=0).max(), Some(0));
1714 assert_eq!((5..=5).max(), Some(5));
1715 let mut r = 10..=10;
1717 assert_eq!(r.max(), None);
1721 fn test_range_min() {
1722 assert_eq!((0..20).min(), Some(0));
1723 assert_eq!((-20..0).min(), Some(-20));
1724 assert_eq!((5..5).min(), None);
1728 fn test_range_inclusive_min() {
1729 assert_eq!((0..=20).min(), Some(0));
1730 assert_eq!((-20..=0).min(), Some(-20));
1731 assert_eq!((5..=5).min(), Some(5));
1732 let mut r = 10..=10;
1734 assert_eq!(r.min(), None);
1738 fn test_range_inclusive_folds() {
1739 assert_eq!((1..=10).sum::<i32>(), 55);
1740 assert_eq!((1..=10).rev().sum::<i32>(), 55);
1742 let mut it = 40..=50;
1743 assert_eq!(it.try_fold(0, i8::checked_add), None);
1744 assert_eq!(it, 44..=50);
1745 assert_eq!(it.try_rfold(0, i8::checked_add), None);
1746 assert_eq!(it, 44..=47);
1748 let mut it = 10..=20;
1749 assert_eq!(it.try_fold(0, |a,b| Some(a+b)), Some(165));
1750 assert!(it.is_empty());
1752 let mut it = 10..=20;
1753 assert_eq!(it.try_rfold(0, |a,b| Some(a+b)), Some(165));
1754 assert!(it.is_empty());
1759 let mut it = repeat(42);
1760 assert_eq!(it.next(), Some(42));
1761 assert_eq!(it.next(), Some(42));
1762 assert_eq!(it.next(), Some(42));
1763 assert_eq!(repeat(42).size_hint(), (usize::MAX, None));
1767 fn test_repeat_take() {
1768 let mut it = repeat(42).take(3);
1769 assert_eq!(it.next(), Some(42));
1770 assert_eq!(it.next(), Some(42));
1771 assert_eq!(it.next(), Some(42));
1772 assert_eq!(it.next(), None);
1773 is_trusted_len(repeat(42).take(3));
1774 assert_eq!(repeat(42).take(3).size_hint(), (3, Some(3)));
1775 assert_eq!(repeat(42).take(0).size_hint(), (0, Some(0)));
1776 assert_eq!(repeat(42).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
1780 fn test_repeat_take_collect() {
1781 let v: Vec<_> = repeat(42).take(3).collect();
1782 assert_eq!(v, vec![42, 42, 42]);
1786 fn test_repeat_with() {
1787 #[derive(PartialEq, Debug)]
1788 struct NotClone(usize);
1789 let mut it = repeat_with(|| NotClone(42));
1790 assert_eq!(it.next(), Some(NotClone(42)));
1791 assert_eq!(it.next(), Some(NotClone(42)));
1792 assert_eq!(it.next(), Some(NotClone(42)));
1793 assert_eq!(repeat_with(|| NotClone(42)).size_hint(), (usize::MAX, None));
1797 fn test_repeat_with_take() {
1798 let mut it = repeat_with(|| 42).take(3);
1799 assert_eq!(it.next(), Some(42));
1800 assert_eq!(it.next(), Some(42));
1801 assert_eq!(it.next(), Some(42));
1802 assert_eq!(it.next(), None);
1803 is_trusted_len(repeat_with(|| 42).take(3));
1804 assert_eq!(repeat_with(|| 42).take(3).size_hint(), (3, Some(3)));
1805 assert_eq!(repeat_with(|| 42).take(0).size_hint(), (0, Some(0)));
1806 assert_eq!(repeat_with(|| 42).take(usize::MAX).size_hint(),
1807 (usize::MAX, Some(usize::MAX)));
1811 fn test_repeat_with_take_collect() {
1813 let v: Vec<_> = repeat_with(|| { let tmp = curr; curr *= 2; tmp })
1815 assert_eq!(v, vec![1, 2, 4, 8, 16]);
1819 fn test_successors() {
1820 let mut powers_of_10 = successors(Some(1_u16), |n| n.checked_mul(10));
1821 assert_eq!(powers_of_10.by_ref().collect::<Vec<_>>(), &[1, 10, 100, 1_000, 10_000]);
1822 assert_eq!(powers_of_10.next(), None);
1824 let mut empty = successors(None::<u32>, |_| unimplemented!());
1825 assert_eq!(empty.next(), None);
1826 assert_eq!(empty.next(), None);
1832 assert_eq!(it.len(), 3);
1833 assert_eq!(it.next(), Some(0));
1834 assert_eq!(it.len(), 2);
1835 assert_eq!(it.next(), Some(1));
1836 assert_eq!(it.len(), 1);
1837 assert_eq!(it.next(), Some(2));
1838 assert_eq!(it.len(), 0);
1839 assert_eq!(it.next(), None);
1840 assert_eq!(it.len(), 0);
1841 assert_eq!(it.next(), None);
1842 assert_eq!(it.len(), 0);
1843 assert_eq!(it.next(), None);
1844 assert_eq!(it.len(), 0);
1848 fn test_fuse_nth() {
1850 let mut it = xs.iter();
1852 assert_eq!(it.len(), 3);
1853 assert_eq!(it.nth(2), Some(&2));
1854 assert_eq!(it.len(), 0);
1855 assert_eq!(it.nth(2), None);
1856 assert_eq!(it.len(), 0);
1860 fn test_fuse_last() {
1864 assert_eq!(it.len(), 3);
1865 assert_eq!(it.last(), Some(&2));
1869 fn test_fuse_count() {
1873 assert_eq!(it.len(), 3);
1874 assert_eq!(it.count(), 3);
1875 // Can't check len now because count consumes.
1879 fn test_fuse_fold() {
1881 let it = xs.iter(); // `FusedIterator`
1882 let i = it.fuse().fold(0, |i, &x| {
1883 assert_eq!(x, xs[i]);
1886 assert_eq!(i, xs.len());
1888 let it = xs.iter(); // `FusedIterator`
1889 let i = it.fuse().rfold(xs.len(), |i, &x| {
1890 assert_eq!(x, xs[i - 1]);
1895 let it = xs.iter().scan((), |_, &x| Some(x)); // `!FusedIterator`
1896 let i = it.fuse().fold(0, |i, x| {
1897 assert_eq!(x, xs[i]);
1900 assert_eq!(i, xs.len());
1905 let mut it = once(42);
1906 assert_eq!(it.next(), Some(42));
1907 assert_eq!(it.next(), None);
1911 fn test_once_with() {
1912 let count = Cell::new(0);
1913 let mut it = once_with(|| {
1914 count.set(count.get() + 1);
1918 assert_eq!(count.get(), 0);
1919 assert_eq!(it.next(), Some(42));
1920 assert_eq!(count.get(), 1);
1921 assert_eq!(it.next(), None);
1922 assert_eq!(count.get(), 1);
1923 assert_eq!(it.next(), None);
1924 assert_eq!(count.get(), 1);
1929 let mut it = empty::<i32>();
1930 assert_eq!(it.next(), None);
1934 fn test_chain_fold() {
1938 let mut iter = xs.iter().chain(&ys);
1940 let mut result = Vec::new();
1941 iter.fold((), |(), &elt| result.push(elt));
1942 assert_eq!(&[2, 3, 1, 2, 0], &result[..]);
1946 fn test_step_replace_unsigned() {
1948 let y = x.replace_zero();
1953 let y = x.replace_one();
1959 fn test_step_replace_signed() {
1961 let y = x.replace_zero();
1966 let y = x.replace_one();
1972 fn test_step_replace_no_between() {
1974 let y = x.replace_zero();
1979 let y = x.replace_one();
1985 fn test_rev_try_folds() {
1986 let f = &|acc, x| i32::checked_add(2*acc, x);
1987 assert_eq!((1..10).rev().try_fold(7, f), (1..10).try_rfold(7, f));
1988 assert_eq!((1..10).rev().try_rfold(7, f), (1..10).try_fold(7, f));
1990 let a = [10, 20, 30, 40, 100, 60, 70, 80, 90];
1991 let mut iter = a.iter().rev();
1992 assert_eq!(iter.try_fold(0_i8, |acc, &x| acc.checked_add(x)), None);
1993 assert_eq!(iter.next(), Some(&70));
1994 let mut iter = a.iter().rev();
1995 assert_eq!(iter.try_rfold(0_i8, |acc, &x| acc.checked_add(x)), None);
1996 assert_eq!(iter.next_back(), Some(&60));
2000 fn test_cloned_try_folds() {
2001 let a = [1, 2, 3, 4, 5, 6, 7, 8, 9];
2002 let f = &|acc, x| i32::checked_add(2*acc, x);
2003 let f_ref = &|acc, &x| i32::checked_add(2*acc, x);
2004 assert_eq!(a.iter().cloned().try_fold(7, f), a.iter().try_fold(7, f_ref));
2005 assert_eq!(a.iter().cloned().try_rfold(7, f), a.iter().try_rfold(7, f_ref));
2007 let a = [10, 20, 30, 40, 100, 60, 70, 80, 90];
2008 let mut iter = a.iter().cloned();
2009 assert_eq!(iter.try_fold(0_i8, |acc, x| acc.checked_add(x)), None);
2010 assert_eq!(iter.next(), Some(60));
2011 let mut iter = a.iter().cloned();
2012 assert_eq!(iter.try_rfold(0_i8, |acc, x| acc.checked_add(x)), None);
2013 assert_eq!(iter.next_back(), Some(70));
2017 fn test_chain_try_folds() {
2018 let c = || (0..10).chain(10..20);
2020 let f = &|acc, x| i32::checked_add(2*acc, x);
2021 assert_eq!(c().try_fold(7, f), (0..20).try_fold(7, f));
2022 assert_eq!(c().try_rfold(7, f), (0..20).rev().try_fold(7, f));
2025 assert_eq!(iter.position(|x| x == 5), Some(5));
2026 assert_eq!(iter.next(), Some(6), "stopped in front, state Both");
2027 assert_eq!(iter.position(|x| x == 13), Some(6));
2028 assert_eq!(iter.next(), Some(14), "stopped in back, state Back");
2029 assert_eq!(iter.try_fold(0, |acc, x| Some(acc+x)), Some((15..20).sum()));
2031 let mut iter = c().rev(); // use rev to access try_rfold
2032 assert_eq!(iter.position(|x| x == 15), Some(4));
2033 assert_eq!(iter.next(), Some(14), "stopped in back, state Both");
2034 assert_eq!(iter.position(|x| x == 5), Some(8));
2035 assert_eq!(iter.next(), Some(4), "stopped in front, state Front");
2036 assert_eq!(iter.try_fold(0, |acc, x| Some(acc+x)), Some((0..4).sum()));
2039 iter.by_ref().rev().nth(14); // skip the last 15, ending in state Front
2040 assert_eq!(iter.try_fold(7, f), (0..5).try_fold(7, f));
2043 iter.nth(14); // skip the first 15, ending in state Back
2044 assert_eq!(iter.try_rfold(7, f), (15..20).try_rfold(7, f));
2048 fn test_map_try_folds() {
2049 let f = &|acc, x| i32::checked_add(2*acc, x);
2050 assert_eq!((0..10).map(|x| x+3).try_fold(7, f), (3..13).try_fold(7, f));
2051 assert_eq!((0..10).map(|x| x+3).try_rfold(7, f), (3..13).try_rfold(7, f));
2053 let mut iter = (0..40).map(|x| x+10);
2054 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2055 assert_eq!(iter.next(), Some(20));
2056 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2057 assert_eq!(iter.next_back(), Some(46));
2061 fn test_filter_try_folds() {
2062 fn p(&x: &i32) -> bool { 0 <= x && x < 10 }
2063 let f = &|acc, x| i32::checked_add(2*acc, x);
2064 assert_eq!((-10..20).filter(p).try_fold(7, f), (0..10).try_fold(7, f));
2065 assert_eq!((-10..20).filter(p).try_rfold(7, f), (0..10).try_rfold(7, f));
2067 let mut iter = (0..40).filter(|&x| x % 2 == 1);
2068 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2069 assert_eq!(iter.next(), Some(25));
2070 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2071 assert_eq!(iter.next_back(), Some(31));
2075 fn test_filter_map_try_folds() {
2076 let mp = &|x| if 0 <= x && x < 10 { Some(x*2) } else { None };
2077 let f = &|acc, x| i32::checked_add(2*acc, x);
2078 assert_eq!((-9..20).filter_map(mp).try_fold(7, f), (0..10).map(|x| 2*x).try_fold(7, f));
2079 assert_eq!((-9..20).filter_map(mp).try_rfold(7, f), (0..10).map(|x| 2*x).try_rfold(7, f));
2081 let mut iter = (0..40).filter_map(|x| if x%2 == 1 { None } else { Some(x*2 + 10) });
2082 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2083 assert_eq!(iter.next(), Some(38));
2084 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2085 assert_eq!(iter.next_back(), Some(78));
2089 fn test_enumerate_try_folds() {
2090 let f = &|acc, (i, x)| usize::checked_add(2*acc, x/(i+1) + i);
2091 assert_eq!((9..18).enumerate().try_fold(7, f), (0..9).map(|i| (i, i+9)).try_fold(7, f));
2092 assert_eq!((9..18).enumerate().try_rfold(7, f), (0..9).map(|i| (i, i+9)).try_rfold(7, f));
2094 let mut iter = (100..200).enumerate();
2095 let f = &|acc, (i, x)| u8::checked_add(acc, u8::checked_div(x, i as u8 + 1)?);
2096 assert_eq!(iter.try_fold(0, f), None);
2097 assert_eq!(iter.next(), Some((7, 107)));
2098 assert_eq!(iter.try_rfold(0, f), None);
2099 assert_eq!(iter.next_back(), Some((11, 111)));
2103 fn test_peek_try_fold() {
2104 let f = &|acc, x| i32::checked_add(2*acc, x);
2105 assert_eq!((1..20).peekable().try_fold(7, f), (1..20).try_fold(7, f));
2106 let mut iter = (1..20).peekable();
2107 assert_eq!(iter.peek(), Some(&1));
2108 assert_eq!(iter.try_fold(7, f), (1..20).try_fold(7, f));
2110 let mut iter = [100, 20, 30, 40, 50, 60, 70].iter().cloned().peekable();
2111 assert_eq!(iter.peek(), Some(&100));
2112 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2113 assert_eq!(iter.peek(), Some(&40));
2117 fn test_skip_while_try_fold() {
2118 let f = &|acc, x| i32::checked_add(2*acc, x);
2119 fn p(&x: &i32) -> bool { (x % 10) <= 5 }
2120 assert_eq!((1..20).skip_while(p).try_fold(7, f), (6..20).try_fold(7, f));
2121 let mut iter = (1..20).skip_while(p);
2122 assert_eq!(iter.nth(5), Some(11));
2123 assert_eq!(iter.try_fold(7, f), (12..20).try_fold(7, f));
2125 let mut iter = (0..50).skip_while(|&x| (x % 20) < 15);
2126 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2127 assert_eq!(iter.next(), Some(23));
2131 fn test_take_while_folds() {
2132 let f = &|acc, x| i32::checked_add(2*acc, x);
2133 assert_eq!((1..20).take_while(|&x| x != 10).try_fold(7, f), (1..10).try_fold(7, f));
2134 let mut iter = (1..20).take_while(|&x| x != 10);
2135 assert_eq!(iter.try_fold(0, |x, y| Some(x+y)), Some((1..10).sum()));
2136 assert_eq!(iter.next(), None, "flag should be set");
2137 let iter = (1..20).take_while(|&x| x != 10);
2138 assert_eq!(iter.fold(0, |x, y| x+y), (1..10).sum());
2140 let mut iter = (10..50).take_while(|&x| x != 40);
2141 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2142 assert_eq!(iter.next(), Some(20));
2146 fn test_skip_try_folds() {
2147 let f = &|acc, x| i32::checked_add(2*acc, x);
2148 assert_eq!((1..20).skip(9).try_fold(7, f), (10..20).try_fold(7, f));
2149 assert_eq!((1..20).skip(9).try_rfold(7, f), (10..20).try_rfold(7, f));
2151 let mut iter = (0..30).skip(10);
2152 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2153 assert_eq!(iter.next(), Some(20));
2154 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2155 assert_eq!(iter.next_back(), Some(24));
2159 fn test_take_try_folds() {
2160 let f = &|acc, x| i32::checked_add(2*acc, x);
2161 assert_eq!((10..30).take(10).try_fold(7, f), (10..20).try_fold(7, f));
2162 //assert_eq!((10..30).take(10).try_rfold(7, f), (10..20).try_rfold(7, f));
2164 let mut iter = (10..30).take(20);
2165 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2166 assert_eq!(iter.next(), Some(20));
2167 //assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2168 //assert_eq!(iter.next_back(), Some(24));
2172 fn test_flat_map_try_folds() {
2173 let f = &|acc, x| i32::checked_add(acc*2/3, x);
2174 let mr = &|x| (5*x)..(5*x + 5);
2175 assert_eq!((0..10).flat_map(mr).try_fold(7, f), (0..50).try_fold(7, f));
2176 assert_eq!((0..10).flat_map(mr).try_rfold(7, f), (0..50).try_rfold(7, f));
2177 let mut iter = (0..10).flat_map(mr);
2178 iter.next(); iter.next_back(); // have front and back iters in progress
2179 assert_eq!(iter.try_rfold(7, f), (1..49).try_rfold(7, f));
2181 let mut iter = (0..10).flat_map(|x| (4*x)..(4*x + 4));
2182 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2183 assert_eq!(iter.next(), Some(17));
2184 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2185 assert_eq!(iter.next_back(), Some(35));
2189 fn test_flatten_try_folds() {
2190 let f = &|acc, x| i32::checked_add(acc*2/3, x);
2191 let mr = &|x| (5*x)..(5*x + 5);
2192 assert_eq!((0..10).map(mr).flatten().try_fold(7, f), (0..50).try_fold(7, f));
2193 assert_eq!((0..10).map(mr).flatten().try_rfold(7, f), (0..50).try_rfold(7, f));
2194 let mut iter = (0..10).map(mr).flatten();
2195 iter.next(); iter.next_back(); // have front and back iters in progress
2196 assert_eq!(iter.try_rfold(7, f), (1..49).try_rfold(7, f));
2198 let mut iter = (0..10).map(|x| (4*x)..(4*x + 4)).flatten();
2199 assert_eq!(iter.try_fold(0, i8::checked_add), None);
2200 assert_eq!(iter.next(), Some(17));
2201 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
2202 assert_eq!(iter.next_back(), Some(35));
2206 fn test_functor_laws() {
2208 fn identity<T>(x: T) -> T { x }
2209 assert_eq!((0..10).map(identity).sum::<usize>(), (0..10).sum());
2212 fn f(x: usize) -> usize { x + 3 }
2213 fn g(x: usize) -> usize { x * 2 }
2214 fn h(x: usize) -> usize { g(f(x)) }
2215 assert_eq!((0..10).map(f).map(g).sum::<usize>(), (0..10).map(h).sum());
2219 fn test_monad_laws_left_identity() {
2220 fn f(x: usize) -> impl Iterator<Item = usize> {
2221 (0..10).map(move |y| x * y)
2223 assert_eq!(once(42).flat_map(f.clone()).sum::<usize>(), f(42).sum());
2227 fn test_monad_laws_right_identity() {
2228 assert_eq!((0..10).flat_map(|x| once(x)).sum::<usize>(), (0..10).sum());
2232 fn test_monad_laws_associativity() {
2233 fn f(x: usize) -> impl Iterator<Item = usize> { 0..x }
2234 fn g(x: usize) -> impl Iterator<Item = usize> { (0..x).rev() }
2235 assert_eq!((0..10).flat_map(f).flat_map(g).sum::<usize>(),
2236 (0..10).flat_map(|x| f(x).flat_map(g)).sum::<usize>());
2240 fn test_is_sorted() {
2241 assert!([1, 2, 2, 9].iter().is_sorted());
2242 assert!(![1, 3, 2].iter().is_sorted());
2243 assert!([0].iter().is_sorted());
2244 assert!(std::iter::empty::<i32>().is_sorted());
2245 assert!(![0.0, 1.0, std::f32::NAN].iter().is_sorted());
2246 assert!([-2, -1, 0, 3].iter().is_sorted());
2247 assert!(![-2i32, -1, 0, 3].iter().is_sorted_by_key(|n| n.abs()));
2248 assert!(!["c", "bb", "aaa"].iter().is_sorted());
2249 assert!(["c", "bb", "aaa"].iter().is_sorted_by_key(|s| s.len()));