5 fn test_iterator_peekable() {
6 let xs = vec![0, 1, 2, 3, 4, 5];
8 let mut it = xs.iter().cloned().peekable();
9 assert_eq!(it.len(), 6);
10 assert_eq!(it.peek().unwrap(), &0);
11 assert_eq!(it.len(), 6);
12 assert_eq!(it.next().unwrap(), 0);
13 assert_eq!(it.len(), 5);
14 assert_eq!(it.next().unwrap(), 1);
15 assert_eq!(it.len(), 4);
16 assert_eq!(it.next().unwrap(), 2);
17 assert_eq!(it.len(), 3);
18 assert_eq!(it.peek().unwrap(), &3);
19 assert_eq!(it.len(), 3);
20 assert_eq!(it.peek().unwrap(), &3);
21 assert_eq!(it.len(), 3);
22 assert_eq!(it.next().unwrap(), 3);
23 assert_eq!(it.len(), 2);
24 assert_eq!(it.next().unwrap(), 4);
25 assert_eq!(it.len(), 1);
26 assert_eq!(it.peek().unwrap(), &5);
27 assert_eq!(it.len(), 1);
28 assert_eq!(it.next().unwrap(), 5);
29 assert_eq!(it.len(), 0);
30 assert!(it.peek().is_none());
31 assert_eq!(it.len(), 0);
32 assert!(it.next().is_none());
33 assert_eq!(it.len(), 0);
35 let mut it = xs.iter().cloned().peekable();
36 assert_eq!(it.len(), 6);
37 assert_eq!(it.peek().unwrap(), &0);
38 assert_eq!(it.len(), 6);
39 assert_eq!(it.next_back().unwrap(), 5);
40 assert_eq!(it.len(), 5);
41 assert_eq!(it.next_back().unwrap(), 4);
42 assert_eq!(it.len(), 4);
43 assert_eq!(it.next_back().unwrap(), 3);
44 assert_eq!(it.len(), 3);
45 assert_eq!(it.peek().unwrap(), &0);
46 assert_eq!(it.len(), 3);
47 assert_eq!(it.peek().unwrap(), &0);
48 assert_eq!(it.len(), 3);
49 assert_eq!(it.next_back().unwrap(), 2);
50 assert_eq!(it.len(), 2);
51 assert_eq!(it.next_back().unwrap(), 1);
52 assert_eq!(it.len(), 1);
53 assert_eq!(it.peek().unwrap(), &0);
54 assert_eq!(it.len(), 1);
55 assert_eq!(it.next_back().unwrap(), 0);
56 assert_eq!(it.len(), 0);
57 assert!(it.peek().is_none());
58 assert_eq!(it.len(), 0);
59 assert!(it.next_back().is_none());
60 assert_eq!(it.len(), 0);
64 fn test_iterator_peekable_count() {
65 let xs = [0, 1, 2, 3, 4, 5];
67 let zs: [i32; 0] = [];
69 assert_eq!(xs.iter().peekable().count(), 6);
71 let mut it = xs.iter().peekable();
72 assert_eq!(it.peek(), Some(&&0));
73 assert_eq!(it.count(), 6);
75 assert_eq!(ys.iter().peekable().count(), 1);
77 let mut it = ys.iter().peekable();
78 assert_eq!(it.peek(), Some(&&10));
79 assert_eq!(it.count(), 1);
81 assert_eq!(zs.iter().peekable().count(), 0);
83 let mut it = zs.iter().peekable();
84 assert_eq!(it.peek(), None);
88 fn test_iterator_peekable_nth() {
89 let xs = [0, 1, 2, 3, 4, 5];
90 let mut it = xs.iter().peekable();
92 assert_eq!(it.peek(), Some(&&0));
93 assert_eq!(it.nth(0), Some(&0));
94 assert_eq!(it.peek(), Some(&&1));
95 assert_eq!(it.nth(1), Some(&2));
96 assert_eq!(it.peek(), Some(&&3));
97 assert_eq!(it.nth(2), Some(&5));
98 assert_eq!(it.next(), None);
102 fn test_iterator_peekable_last() {
103 let xs = [0, 1, 2, 3, 4, 5];
106 let mut it = xs.iter().peekable();
107 assert_eq!(it.peek(), Some(&&0));
108 assert_eq!(it.last(), Some(&5));
110 let mut it = ys.iter().peekable();
111 assert_eq!(it.peek(), Some(&&0));
112 assert_eq!(it.last(), Some(&0));
114 let mut it = ys.iter().peekable();
115 assert_eq!(it.next(), Some(&0));
116 assert_eq!(it.peek(), None);
117 assert_eq!(it.last(), None);
121 fn test_iterator_peekable_fold() {
122 let xs = [0, 1, 2, 3, 4, 5];
123 let mut it = xs.iter().peekable();
124 assert_eq!(it.peek(), Some(&&0));
125 let i = it.fold(0, |i, &x| {
126 assert_eq!(x, xs[i]);
129 assert_eq!(i, xs.len());
133 fn test_iterator_peekable_rfold() {
134 let xs = [0, 1, 2, 3, 4, 5];
135 let mut it = xs.iter().peekable();
136 assert_eq!(it.peek(), Some(&&0));
137 let i = it.rfold(0, |i, &x| {
138 assert_eq!(x, xs[xs.len() - 1 - i]);
141 assert_eq!(i, xs.len());
145 fn test_iterator_peekable_next_if_eq() {
146 // first, try on references
147 let xs = ["Heart", "of", "Gold"];
148 let mut it = xs.into_iter().peekable();
149 // try before `peek()`
150 assert_eq!(it.next_if_eq(&"trillian"), None);
151 assert_eq!(it.next_if_eq(&"Heart"), Some("Heart"));
153 assert_eq!(it.peek(), Some(&"of"));
154 assert_eq!(it.next_if_eq(&"of"), Some("of"));
155 assert_eq!(it.next_if_eq(&"zaphod"), None);
156 // make sure `next()` still behaves
157 assert_eq!(it.next(), Some("Gold"));
159 // make sure comparison works for owned values
160 let xs = [String::from("Ludicrous"), "speed".into()];
161 let mut it = xs.into_iter().peekable();
162 // make sure basic functionality works
163 assert_eq!(it.next_if_eq("Ludicrous"), Some("Ludicrous".into()));
164 assert_eq!(it.next_if_eq("speed"), Some("speed".into()));
165 assert_eq!(it.next_if_eq(""), None);
169 fn test_iterator_peekable_mut() {
170 let mut it = [1, 2, 3].into_iter().peekable();
171 if let Some(p) = it.peek_mut() {
176 assert_eq!(it.collect::<Vec<_>>(), vec![5, 2, 3]);
180 fn test_iterator_peekable_remember_peek_none_1() {
181 // Check that the loop using .peek() terminates
182 let data = [1, 2, 3];
183 let mut iter = CycleIter::new(&data).peekable();
186 while let Some(_) = iter.next() {
187 let is_the_last = iter.peek().is_none();
188 assert_eq!(is_the_last, n == data.len() - 1);
194 assert_eq!(n, data.len());
198 fn test_iterator_peekable_remember_peek_none_2() {
200 let mut iter = CycleIter::new(&data).peekable();
202 assert_eq!(iter.peek(), None);
203 assert_eq!(iter.last(), None);
207 fn test_iterator_peekable_remember_peek_none_3() {
209 let mut iter = CycleIter::new(&data).peekable();
211 assert_eq!(iter.nth(0), Some(&0));
213 let mut iter = CycleIter::new(&data).peekable();
215 assert_eq!(iter.peek(), None);
216 assert_eq!(iter.nth(0), None);
220 fn test_peek_try_folds() {
221 let f = &|acc, x| i32::checked_add(2 * acc, x);
223 assert_eq!((1..20).peekable().try_fold(7, f), (1..20).try_fold(7, f));
224 assert_eq!((1..20).peekable().try_rfold(7, f), (1..20).try_rfold(7, f));
226 let mut iter = (1..20).peekable();
227 assert_eq!(iter.peek(), Some(&1));
228 assert_eq!(iter.try_fold(7, f), (1..20).try_fold(7, f));
230 let mut iter = (1..20).peekable();
231 assert_eq!(iter.peek(), Some(&1));
232 assert_eq!(iter.try_rfold(7, f), (1..20).try_rfold(7, f));
234 let mut iter = [100, 20, 30, 40, 50, 60, 70].iter().cloned().peekable();
235 assert_eq!(iter.peek(), Some(&100));
236 assert_eq!(iter.try_fold(0, i8::checked_add), None);
237 assert_eq!(iter.peek(), Some(&40));
239 let mut iter = [100, 20, 30, 40, 50, 60, 70].iter().cloned().peekable();
240 assert_eq!(iter.peek(), Some(&100));
241 assert_eq!(iter.try_rfold(0, i8::checked_add), None);
242 assert_eq!(iter.peek(), Some(&100));
243 assert_eq!(iter.next_back(), Some(50));
245 let mut iter = (2..5).peekable();
246 assert_eq!(iter.peek(), Some(&2));
247 assert_eq!(iter.try_for_each(Err), Err(2));
248 assert_eq!(iter.peek(), Some(&3));
249 assert_eq!(iter.try_for_each(Err), Err(3));
250 assert_eq!(iter.peek(), Some(&4));
251 assert_eq!(iter.try_for_each(Err), Err(4));
252 assert_eq!(iter.peek(), None);
253 assert_eq!(iter.try_for_each(Err), Ok(()));
255 let mut iter = (2..5).peekable();
256 assert_eq!(iter.peek(), Some(&2));
257 assert_eq!(iter.try_rfold((), |(), x| Err(x)), Err(4));
258 assert_eq!(iter.peek(), Some(&2));
259 assert_eq!(iter.try_rfold((), |(), x| Err(x)), Err(3));
260 assert_eq!(iter.peek(), Some(&2));
261 assert_eq!(iter.try_rfold((), |(), x| Err(x)), Err(2));
262 assert_eq!(iter.peek(), None);
263 assert_eq!(iter.try_rfold((), |(), x| Err(x)), Ok(()));
267 fn test_peekable_non_fused() {
268 let mut iter = NonFused::new(empty::<i32>()).peekable();
270 assert_eq!(iter.peek(), None);
271 assert_eq!(iter.next_back(), None);