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1 | use cmp; |
2 | use fmt; | |
3 | use ops::Try; | |
4 | use usize; | |
5 | use intrinsics; | |
6 | use super::{Iterator, DoubleEndedIterator, ExactSizeIterator, FusedIterator, TrustedLen}; | |
7 | use super::LoopState; | |
8 | ||
9 | mod chain; | |
10 | mod flatten; | |
11 | mod zip; | |
12 | ||
13 | pub use self::chain::Chain; | |
14 | #[stable(feature = "rust1", since = "1.0.0")] | |
15 | pub use self::flatten::{FlatMap, Flatten}; | |
16 | pub use self::zip::Zip; | |
17 | pub(crate) use self::zip::TrustedRandomAccess; | |
18 | ||
19 | /// A double-ended iterator with the direction inverted. | |
20 | /// | |
21 | /// This `struct` is created by the [`rev`] method on [`Iterator`]. See its | |
22 | /// documentation for more. | |
23 | /// | |
24 | /// [`rev`]: trait.Iterator.html#method.rev | |
25 | /// [`Iterator`]: trait.Iterator.html | |
26 | #[derive(Clone, Debug)] | |
27 | #[must_use = "iterators are lazy and do nothing unless consumed"] | |
28 | #[stable(feature = "rust1", since = "1.0.0")] | |
29 | pub struct Rev<T> { | |
30 | iter: T | |
31 | } | |
32 | impl<T> Rev<T> { | |
33 | pub(super) fn new(iter: T) -> Rev<T> { | |
34 | Rev { iter } | |
35 | } | |
36 | } | |
37 | ||
38 | #[stable(feature = "rust1", since = "1.0.0")] | |
39 | impl<I> Iterator for Rev<I> where I: DoubleEndedIterator { | |
40 | type Item = <I as Iterator>::Item; | |
41 | ||
42 | #[inline] | |
43 | fn next(&mut self) -> Option<<I as Iterator>::Item> { self.iter.next_back() } | |
44 | #[inline] | |
45 | fn size_hint(&self) -> (usize, Option<usize>) { self.iter.size_hint() } | |
46 | ||
47 | #[inline] | |
48 | fn nth(&mut self, n: usize) -> Option<<I as Iterator>::Item> { self.iter.nth_back(n) } | |
49 | ||
50 | fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R where | |
51 | Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B> | |
52 | { | |
53 | self.iter.try_rfold(init, f) | |
54 | } | |
55 | ||
56 | fn fold<Acc, F>(self, init: Acc, f: F) -> Acc | |
57 | where F: FnMut(Acc, Self::Item) -> Acc, | |
58 | { | |
59 | self.iter.rfold(init, f) | |
60 | } | |
61 | ||
62 | #[inline] | |
63 | fn find<P>(&mut self, predicate: P) -> Option<Self::Item> | |
64 | where P: FnMut(&Self::Item) -> bool | |
65 | { | |
66 | self.iter.rfind(predicate) | |
67 | } | |
68 | ||
69 | #[inline] | |
70 | fn rposition<P>(&mut self, predicate: P) -> Option<usize> where | |
71 | P: FnMut(Self::Item) -> bool | |
72 | { | |
73 | self.iter.position(predicate) | |
74 | } | |
75 | } | |
76 | ||
77 | #[stable(feature = "rust1", since = "1.0.0")] | |
78 | impl<I> DoubleEndedIterator for Rev<I> where I: DoubleEndedIterator { | |
79 | #[inline] | |
80 | fn next_back(&mut self) -> Option<<I as Iterator>::Item> { self.iter.next() } | |
81 | ||
82 | #[inline] | |
83 | fn nth_back(&mut self, n: usize) -> Option<<I as Iterator>::Item> { self.iter.nth(n) } | |
84 | ||
85 | fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R where | |
86 | Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B> | |
87 | { | |
88 | self.iter.try_fold(init, f) | |
89 | } | |
90 | ||
91 | fn rfold<Acc, F>(self, init: Acc, f: F) -> Acc | |
92 | where F: FnMut(Acc, Self::Item) -> Acc, | |
93 | { | |
94 | self.iter.fold(init, f) | |
95 | } | |
96 | ||
97 | fn rfind<P>(&mut self, predicate: P) -> Option<Self::Item> | |
98 | where P: FnMut(&Self::Item) -> bool | |
99 | { | |
100 | self.iter.find(predicate) | |
101 | } | |
102 | } | |
103 | ||
104 | #[stable(feature = "rust1", since = "1.0.0")] | |
105 | impl<I> ExactSizeIterator for Rev<I> | |
106 | where I: ExactSizeIterator + DoubleEndedIterator | |
107 | { | |
108 | fn len(&self) -> usize { | |
109 | self.iter.len() | |
110 | } | |
111 | ||
112 | fn is_empty(&self) -> bool { | |
113 | self.iter.is_empty() | |
114 | } | |
115 | } | |
116 | ||
117 | #[stable(feature = "fused", since = "1.26.0")] | |
118 | impl<I> FusedIterator for Rev<I> | |
119 | where I: FusedIterator + DoubleEndedIterator {} | |
120 | ||
121 | #[unstable(feature = "trusted_len", issue = "37572")] | |
122 | unsafe impl<I> TrustedLen for Rev<I> | |
123 | where I: TrustedLen + DoubleEndedIterator {} | |
124 | ||
125 | /// An iterator that copies the elements of an underlying iterator. | |
126 | /// | |
127 | /// This `struct` is created by the [`copied`] method on [`Iterator`]. See its | |
128 | /// documentation for more. | |
129 | /// | |
130 | /// [`copied`]: trait.Iterator.html#method.copied | |
131 | /// [`Iterator`]: trait.Iterator.html | |
132 | #[unstable(feature = "iter_copied", issue = "57127")] | |
133 | #[must_use = "iterators are lazy and do nothing unless consumed"] | |
134 | #[derive(Clone, Debug)] | |
135 | pub struct Copied<I> { | |
136 | it: I, | |
137 | } | |
138 | impl<I> Copied<I> { | |
139 | pub(super) fn new(it: I) -> Copied<I> { | |
140 | Copied { it } | |
141 | } | |
142 | } | |
143 | ||
144 | #[unstable(feature = "iter_copied", issue = "57127")] | |
145 | impl<'a, I, T: 'a> Iterator for Copied<I> | |
146 | where I: Iterator<Item=&'a T>, T: Copy | |
147 | { | |
148 | type Item = T; | |
149 | ||
150 | fn next(&mut self) -> Option<T> { | |
151 | self.it.next().copied() | |
152 | } | |
153 | ||
154 | fn size_hint(&self) -> (usize, Option<usize>) { | |
155 | self.it.size_hint() | |
156 | } | |
157 | ||
158 | fn try_fold<B, F, R>(&mut self, init: B, mut f: F) -> R where | |
159 | Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B> | |
160 | { | |
161 | self.it.try_fold(init, move |acc, &elt| f(acc, elt)) | |
162 | } | |
163 | ||
164 | fn fold<Acc, F>(self, init: Acc, mut f: F) -> Acc | |
165 | where F: FnMut(Acc, Self::Item) -> Acc, | |
166 | { | |
167 | self.it.fold(init, move |acc, &elt| f(acc, elt)) | |
168 | } | |
169 | } | |
170 | ||
171 | #[unstable(feature = "iter_copied", issue = "57127")] | |
172 | impl<'a, I, T: 'a> DoubleEndedIterator for Copied<I> | |
173 | where I: DoubleEndedIterator<Item=&'a T>, T: Copy | |
174 | { | |
175 | fn next_back(&mut self) -> Option<T> { | |
176 | self.it.next_back().copied() | |
177 | } | |
178 | ||
179 | fn try_rfold<B, F, R>(&mut self, init: B, mut f: F) -> R where | |
180 | Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B> | |
181 | { | |
182 | self.it.try_rfold(init, move |acc, &elt| f(acc, elt)) | |
183 | } | |
184 | ||
185 | fn rfold<Acc, F>(self, init: Acc, mut f: F) -> Acc | |
186 | where F: FnMut(Acc, Self::Item) -> Acc, | |
187 | { | |
188 | self.it.rfold(init, move |acc, &elt| f(acc, elt)) | |
189 | } | |
190 | } | |
191 | ||
192 | #[unstable(feature = "iter_copied", issue = "57127")] | |
193 | impl<'a, I, T: 'a> ExactSizeIterator for Copied<I> | |
194 | where I: ExactSizeIterator<Item=&'a T>, T: Copy | |
195 | { | |
196 | fn len(&self) -> usize { | |
197 | self.it.len() | |
198 | } | |
199 | ||
200 | fn is_empty(&self) -> bool { | |
201 | self.it.is_empty() | |
202 | } | |
203 | } | |
204 | ||
205 | #[unstable(feature = "iter_copied", issue = "57127")] | |
206 | impl<'a, I, T: 'a> FusedIterator for Copied<I> | |
207 | where I: FusedIterator<Item=&'a T>, T: Copy | |
208 | {} | |
209 | ||
210 | #[doc(hidden)] | |
211 | unsafe impl<'a, I, T: 'a> TrustedRandomAccess for Copied<I> | |
212 | where I: TrustedRandomAccess<Item=&'a T>, T: Copy | |
213 | { | |
214 | unsafe fn get_unchecked(&mut self, i: usize) -> Self::Item { | |
215 | *self.it.get_unchecked(i) | |
216 | } | |
217 | ||
218 | #[inline] | |
219 | fn may_have_side_effect() -> bool { | |
220 | I::may_have_side_effect() | |
221 | } | |
222 | } | |
223 | ||
224 | #[unstable(feature = "iter_copied", issue = "57127")] | |
225 | unsafe impl<'a, I, T: 'a> TrustedLen for Copied<I> | |
226 | where I: TrustedLen<Item=&'a T>, | |
227 | T: Copy | |
228 | {} | |
229 | ||
230 | /// An iterator that clones the elements of an underlying iterator. | |
231 | /// | |
232 | /// This `struct` is created by the [`cloned`] method on [`Iterator`]. See its | |
233 | /// documentation for more. | |
234 | /// | |
235 | /// [`cloned`]: trait.Iterator.html#method.cloned | |
236 | /// [`Iterator`]: trait.Iterator.html | |
237 | #[stable(feature = "iter_cloned", since = "1.1.0")] | |
238 | #[must_use = "iterators are lazy and do nothing unless consumed"] | |
239 | #[derive(Clone, Debug)] | |
240 | pub struct Cloned<I> { | |
241 | it: I, | |
242 | } | |
243 | impl<I> Cloned<I> { | |
244 | pub(super) fn new(it: I) -> Cloned<I> { | |
245 | Cloned { it } | |
246 | } | |
247 | } | |
248 | ||
249 | #[stable(feature = "iter_cloned", since = "1.1.0")] | |
250 | impl<'a, I, T: 'a> Iterator for Cloned<I> | |
251 | where I: Iterator<Item=&'a T>, T: Clone | |
252 | { | |
253 | type Item = T; | |
254 | ||
255 | fn next(&mut self) -> Option<T> { | |
256 | self.it.next().cloned() | |
257 | } | |
258 | ||
259 | fn size_hint(&self) -> (usize, Option<usize>) { | |
260 | self.it.size_hint() | |
261 | } | |
262 | ||
263 | fn try_fold<B, F, R>(&mut self, init: B, mut f: F) -> R where | |
264 | Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B> | |
265 | { | |
266 | self.it.try_fold(init, move |acc, elt| f(acc, elt.clone())) | |
267 | } | |
268 | ||
269 | fn fold<Acc, F>(self, init: Acc, mut f: F) -> Acc | |
270 | where F: FnMut(Acc, Self::Item) -> Acc, | |
271 | { | |
272 | self.it.fold(init, move |acc, elt| f(acc, elt.clone())) | |
273 | } | |
274 | } | |
275 | ||
276 | #[stable(feature = "iter_cloned", since = "1.1.0")] | |
277 | impl<'a, I, T: 'a> DoubleEndedIterator for Cloned<I> | |
278 | where I: DoubleEndedIterator<Item=&'a T>, T: Clone | |
279 | { | |
280 | fn next_back(&mut self) -> Option<T> { | |
281 | self.it.next_back().cloned() | |
282 | } | |
283 | ||
284 | fn try_rfold<B, F, R>(&mut self, init: B, mut f: F) -> R where | |
285 | Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B> | |
286 | { | |
287 | self.it.try_rfold(init, move |acc, elt| f(acc, elt.clone())) | |
288 | } | |
289 | ||
290 | fn rfold<Acc, F>(self, init: Acc, mut f: F) -> Acc | |
291 | where F: FnMut(Acc, Self::Item) -> Acc, | |
292 | { | |
293 | self.it.rfold(init, move |acc, elt| f(acc, elt.clone())) | |
294 | } | |
295 | } | |
296 | ||
297 | #[stable(feature = "iter_cloned", since = "1.1.0")] | |
298 | impl<'a, I, T: 'a> ExactSizeIterator for Cloned<I> | |
299 | where I: ExactSizeIterator<Item=&'a T>, T: Clone | |
300 | { | |
301 | fn len(&self) -> usize { | |
302 | self.it.len() | |
303 | } | |
304 | ||
305 | fn is_empty(&self) -> bool { | |
306 | self.it.is_empty() | |
307 | } | |
308 | } | |
309 | ||
310 | #[stable(feature = "fused", since = "1.26.0")] | |
311 | impl<'a, I, T: 'a> FusedIterator for Cloned<I> | |
312 | where I: FusedIterator<Item=&'a T>, T: Clone | |
313 | {} | |
314 | ||
315 | #[doc(hidden)] | |
316 | unsafe impl<'a, I, T: 'a> TrustedRandomAccess for Cloned<I> | |
317 | where I: TrustedRandomAccess<Item=&'a T>, T: Clone | |
318 | { | |
319 | default unsafe fn get_unchecked(&mut self, i: usize) -> Self::Item { | |
320 | self.it.get_unchecked(i).clone() | |
321 | } | |
322 | ||
323 | #[inline] | |
324 | default fn may_have_side_effect() -> bool { true } | |
325 | } | |
326 | ||
327 | #[doc(hidden)] | |
328 | unsafe impl<'a, I, T: 'a> TrustedRandomAccess for Cloned<I> | |
329 | where I: TrustedRandomAccess<Item=&'a T>, T: Copy | |
330 | { | |
331 | unsafe fn get_unchecked(&mut self, i: usize) -> Self::Item { | |
332 | *self.it.get_unchecked(i) | |
333 | } | |
334 | ||
335 | #[inline] | |
336 | fn may_have_side_effect() -> bool { | |
337 | I::may_have_side_effect() | |
338 | } | |
339 | } | |
340 | ||
341 | #[unstable(feature = "trusted_len", issue = "37572")] | |
342 | unsafe impl<'a, I, T: 'a> TrustedLen for Cloned<I> | |
343 | where I: TrustedLen<Item=&'a T>, | |
344 | T: Clone | |
345 | {} | |
346 | ||
347 | /// An iterator that repeats endlessly. | |
348 | /// | |
349 | /// This `struct` is created by the [`cycle`] method on [`Iterator`]. See its | |
350 | /// documentation for more. | |
351 | /// | |
352 | /// [`cycle`]: trait.Iterator.html#method.cycle | |
353 | /// [`Iterator`]: trait.Iterator.html | |
354 | #[derive(Clone, Debug)] | |
355 | #[must_use = "iterators are lazy and do nothing unless consumed"] | |
356 | #[stable(feature = "rust1", since = "1.0.0")] | |
357 | pub struct Cycle<I> { | |
358 | orig: I, | |
359 | iter: I, | |
360 | } | |
361 | impl<I: Clone> Cycle<I> { | |
362 | pub(super) fn new(iter: I) -> Cycle<I> { | |
363 | Cycle { orig: iter.clone(), iter } | |
364 | } | |
365 | } | |
366 | ||
367 | #[stable(feature = "rust1", since = "1.0.0")] | |
368 | impl<I> Iterator for Cycle<I> where I: Clone + Iterator { | |
369 | type Item = <I as Iterator>::Item; | |
370 | ||
371 | #[inline] | |
372 | fn next(&mut self) -> Option<<I as Iterator>::Item> { | |
373 | match self.iter.next() { | |
374 | None => { self.iter = self.orig.clone(); self.iter.next() } | |
375 | y => y | |
376 | } | |
377 | } | |
378 | ||
379 | #[inline] | |
380 | fn size_hint(&self) -> (usize, Option<usize>) { | |
381 | // the cycle iterator is either empty or infinite | |
382 | match self.orig.size_hint() { | |
383 | sz @ (0, Some(0)) => sz, | |
384 | (0, _) => (0, None), | |
385 | _ => (usize::MAX, None) | |
386 | } | |
387 | } | |
388 | } | |
389 | ||
390 | #[stable(feature = "fused", since = "1.26.0")] | |
391 | impl<I> FusedIterator for Cycle<I> where I: Clone + Iterator {} | |
392 | ||
393 | /// An iterator for stepping iterators by a custom amount. | |
394 | /// | |
395 | /// This `struct` is created by the [`step_by`] method on [`Iterator`]. See | |
396 | /// its documentation for more. | |
397 | /// | |
398 | /// [`step_by`]: trait.Iterator.html#method.step_by | |
399 | /// [`Iterator`]: trait.Iterator.html | |
400 | #[must_use = "iterators are lazy and do nothing unless consumed"] | |
401 | #[stable(feature = "iterator_step_by", since = "1.28.0")] | |
402 | #[derive(Clone, Debug)] | |
403 | pub struct StepBy<I> { | |
404 | iter: I, | |
405 | step: usize, | |
406 | first_take: bool, | |
407 | } | |
408 | impl<I> StepBy<I> { | |
409 | pub(super) fn new(iter: I, step: usize) -> StepBy<I> { | |
410 | assert!(step != 0); | |
411 | StepBy { iter, step: step - 1, first_take: true } | |
412 | } | |
413 | } | |
414 | ||
415 | #[stable(feature = "iterator_step_by", since = "1.28.0")] | |
416 | impl<I> Iterator for StepBy<I> where I: Iterator { | |
417 | type Item = I::Item; | |
418 | ||
419 | #[inline] | |
420 | fn next(&mut self) -> Option<Self::Item> { | |
421 | if self.first_take { | |
422 | self.first_take = false; | |
423 | self.iter.next() | |
424 | } else { | |
425 | self.iter.nth(self.step) | |
426 | } | |
427 | } | |
428 | ||
429 | #[inline] | |
430 | fn size_hint(&self) -> (usize, Option<usize>) { | |
431 | let inner_hint = self.iter.size_hint(); | |
432 | ||
433 | if self.first_take { | |
434 | let f = |n| if n == 0 { 0 } else { 1 + (n-1)/(self.step+1) }; | |
435 | (f(inner_hint.0), inner_hint.1.map(f)) | |
436 | } else { | |
437 | let f = |n| n / (self.step+1); | |
438 | (f(inner_hint.0), inner_hint.1.map(f)) | |
439 | } | |
440 | } | |
441 | ||
442 | #[inline] | |
443 | fn nth(&mut self, mut n: usize) -> Option<Self::Item> { | |
444 | if self.first_take { | |
445 | self.first_take = false; | |
446 | let first = self.iter.next(); | |
447 | if n == 0 { | |
448 | return first; | |
449 | } | |
450 | n -= 1; | |
451 | } | |
452 | // n and self.step are indices, we need to add 1 to get the amount of elements | |
453 | // When calling `.nth`, we need to subtract 1 again to convert back to an index | |
454 | // step + 1 can't overflow because `.step_by` sets `self.step` to `step - 1` | |
455 | let mut step = self.step + 1; | |
456 | // n + 1 could overflow | |
457 | // thus, if n is usize::MAX, instead of adding one, we call .nth(step) | |
458 | if n == usize::MAX { | |
459 | self.iter.nth(step - 1); | |
460 | } else { | |
461 | n += 1; | |
462 | } | |
463 | ||
464 | // overflow handling | |
465 | loop { | |
466 | let mul = n.checked_mul(step); | |
467 | if unsafe { intrinsics::likely(mul.is_some()) } { | |
468 | return self.iter.nth(mul.unwrap() - 1); | |
469 | } | |
470 | let div_n = usize::MAX / n; | |
471 | let div_step = usize::MAX / step; | |
472 | let nth_n = div_n * n; | |
473 | let nth_step = div_step * step; | |
474 | let nth = if nth_n > nth_step { | |
475 | step -= div_n; | |
476 | nth_n | |
477 | } else { | |
478 | n -= div_step; | |
479 | nth_step | |
480 | }; | |
481 | self.iter.nth(nth - 1); | |
482 | } | |
483 | } | |
484 | } | |
485 | ||
486 | // StepBy can only make the iterator shorter, so the len will still fit. | |
487 | #[stable(feature = "iterator_step_by", since = "1.28.0")] | |
488 | impl<I> ExactSizeIterator for StepBy<I> where I: ExactSizeIterator {} | |
489 | ||
490 | /// An iterator that maps the values of `iter` with `f`. | |
491 | /// | |
492 | /// This `struct` is created by the [`map`] method on [`Iterator`]. See its | |
493 | /// documentation for more. | |
494 | /// | |
495 | /// [`map`]: trait.Iterator.html#method.map | |
496 | /// [`Iterator`]: trait.Iterator.html | |
497 | /// | |
498 | /// # Notes about side effects | |
499 | /// | |
500 | /// The [`map`] iterator implements [`DoubleEndedIterator`], meaning that | |
501 | /// you can also [`map`] backwards: | |
502 | /// | |
503 | /// ```rust | |
504 | /// let v: Vec<i32> = vec![1, 2, 3].into_iter().map(|x| x + 1).rev().collect(); | |
505 | /// | |
506 | /// assert_eq!(v, [4, 3, 2]); | |
507 | /// ``` | |
508 | /// | |
509 | /// [`DoubleEndedIterator`]: trait.DoubleEndedIterator.html | |
510 | /// | |
511 | /// But if your closure has state, iterating backwards may act in a way you do | |
512 | /// not expect. Let's go through an example. First, in the forward direction: | |
513 | /// | |
514 | /// ```rust | |
515 | /// let mut c = 0; | |
516 | /// | |
517 | /// for pair in vec!['a', 'b', 'c'].into_iter() | |
518 | /// .map(|letter| { c += 1; (letter, c) }) { | |
519 | /// println!("{:?}", pair); | |
520 | /// } | |
521 | /// ``` | |
522 | /// | |
523 | /// This will print "('a', 1), ('b', 2), ('c', 3)". | |
524 | /// | |
525 | /// Now consider this twist where we add a call to `rev`. This version will | |
526 | /// print `('c', 1), ('b', 2), ('a', 3)`. Note that the letters are reversed, | |
527 | /// but the values of the counter still go in order. This is because `map()` is | |
528 | /// still being called lazily on each item, but we are popping items off the | |
529 | /// back of the vector now, instead of shifting them from the front. | |
530 | /// | |
531 | /// ```rust | |
532 | /// let mut c = 0; | |
533 | /// | |
534 | /// for pair in vec!['a', 'b', 'c'].into_iter() | |
535 | /// .map(|letter| { c += 1; (letter, c) }) | |
536 | /// .rev() { | |
537 | /// println!("{:?}", pair); | |
538 | /// } | |
539 | /// ``` | |
540 | #[must_use = "iterators are lazy and do nothing unless consumed"] | |
541 | #[stable(feature = "rust1", since = "1.0.0")] | |
542 | #[derive(Clone)] | |
543 | pub struct Map<I, F> { | |
544 | iter: I, | |
545 | f: F, | |
546 | } | |
547 | impl<I, F> Map<I, F> { | |
548 | pub(super) fn new(iter: I, f: F) -> Map<I, F> { | |
549 | Map { iter, f } | |
550 | } | |
551 | } | |
552 | ||
553 | #[stable(feature = "core_impl_debug", since = "1.9.0")] | |
554 | impl<I: fmt::Debug, F> fmt::Debug for Map<I, F> { | |
555 | fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { | |
556 | f.debug_struct("Map") | |
557 | .field("iter", &self.iter) | |
558 | .finish() | |
559 | } | |
560 | } | |
561 | ||
562 | #[stable(feature = "rust1", since = "1.0.0")] | |
563 | impl<B, I: Iterator, F> Iterator for Map<I, F> where F: FnMut(I::Item) -> B { | |
564 | type Item = B; | |
565 | ||
566 | #[inline] | |
567 | fn next(&mut self) -> Option<B> { | |
568 | self.iter.next().map(&mut self.f) | |
569 | } | |
570 | ||
571 | #[inline] | |
572 | fn size_hint(&self) -> (usize, Option<usize>) { | |
573 | self.iter.size_hint() | |
574 | } | |
575 | ||
576 | fn try_fold<Acc, G, R>(&mut self, init: Acc, mut g: G) -> R where | |
577 | Self: Sized, G: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
578 | { | |
579 | let f = &mut self.f; | |
580 | self.iter.try_fold(init, move |acc, elt| g(acc, f(elt))) | |
581 | } | |
582 | ||
583 | fn fold<Acc, G>(self, init: Acc, mut g: G) -> Acc | |
584 | where G: FnMut(Acc, Self::Item) -> Acc, | |
585 | { | |
586 | let mut f = self.f; | |
587 | self.iter.fold(init, move |acc, elt| g(acc, f(elt))) | |
588 | } | |
589 | } | |
590 | ||
591 | #[stable(feature = "rust1", since = "1.0.0")] | |
592 | impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for Map<I, F> where | |
593 | F: FnMut(I::Item) -> B, | |
594 | { | |
595 | #[inline] | |
596 | fn next_back(&mut self) -> Option<B> { | |
597 | self.iter.next_back().map(&mut self.f) | |
598 | } | |
599 | ||
600 | fn try_rfold<Acc, G, R>(&mut self, init: Acc, mut g: G) -> R where | |
601 | Self: Sized, G: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
602 | { | |
603 | let f = &mut self.f; | |
604 | self.iter.try_rfold(init, move |acc, elt| g(acc, f(elt))) | |
605 | } | |
606 | ||
607 | fn rfold<Acc, G>(self, init: Acc, mut g: G) -> Acc | |
608 | where G: FnMut(Acc, Self::Item) -> Acc, | |
609 | { | |
610 | let mut f = self.f; | |
611 | self.iter.rfold(init, move |acc, elt| g(acc, f(elt))) | |
612 | } | |
613 | } | |
614 | ||
615 | #[stable(feature = "rust1", since = "1.0.0")] | |
616 | impl<B, I: ExactSizeIterator, F> ExactSizeIterator for Map<I, F> | |
617 | where F: FnMut(I::Item) -> B | |
618 | { | |
619 | fn len(&self) -> usize { | |
620 | self.iter.len() | |
621 | } | |
622 | ||
623 | fn is_empty(&self) -> bool { | |
624 | self.iter.is_empty() | |
625 | } | |
626 | } | |
627 | ||
628 | #[stable(feature = "fused", since = "1.26.0")] | |
629 | impl<B, I: FusedIterator, F> FusedIterator for Map<I, F> | |
630 | where F: FnMut(I::Item) -> B {} | |
631 | ||
632 | #[unstable(feature = "trusted_len", issue = "37572")] | |
633 | unsafe impl<B, I, F> TrustedLen for Map<I, F> | |
634 | where I: TrustedLen, | |
635 | F: FnMut(I::Item) -> B {} | |
636 | ||
637 | #[doc(hidden)] | |
638 | unsafe impl<B, I, F> TrustedRandomAccess for Map<I, F> | |
639 | where I: TrustedRandomAccess, | |
640 | F: FnMut(I::Item) -> B, | |
641 | { | |
642 | unsafe fn get_unchecked(&mut self, i: usize) -> Self::Item { | |
643 | (self.f)(self.iter.get_unchecked(i)) | |
644 | } | |
645 | #[inline] | |
646 | fn may_have_side_effect() -> bool { true } | |
647 | } | |
648 | ||
649 | /// An iterator that filters the elements of `iter` with `predicate`. | |
650 | /// | |
651 | /// This `struct` is created by the [`filter`] method on [`Iterator`]. See its | |
652 | /// documentation for more. | |
653 | /// | |
654 | /// [`filter`]: trait.Iterator.html#method.filter | |
655 | /// [`Iterator`]: trait.Iterator.html | |
656 | #[must_use = "iterators are lazy and do nothing unless consumed"] | |
657 | #[stable(feature = "rust1", since = "1.0.0")] | |
658 | #[derive(Clone)] | |
659 | pub struct Filter<I, P> { | |
660 | iter: I, | |
661 | predicate: P, | |
662 | } | |
663 | impl<I, P> Filter<I, P> { | |
664 | pub(super) fn new(iter: I, predicate: P) -> Filter<I, P> { | |
665 | Filter { iter, predicate } | |
666 | } | |
667 | } | |
668 | ||
669 | #[stable(feature = "core_impl_debug", since = "1.9.0")] | |
670 | impl<I: fmt::Debug, P> fmt::Debug for Filter<I, P> { | |
671 | fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { | |
672 | f.debug_struct("Filter") | |
673 | .field("iter", &self.iter) | |
674 | .finish() | |
675 | } | |
676 | } | |
677 | ||
678 | #[stable(feature = "rust1", since = "1.0.0")] | |
679 | impl<I: Iterator, P> Iterator for Filter<I, P> where P: FnMut(&I::Item) -> bool { | |
680 | type Item = I::Item; | |
681 | ||
682 | #[inline] | |
683 | fn next(&mut self) -> Option<I::Item> { | |
532ac7d7 | 684 | self.try_for_each(Err).err() |
9fa01778 XL |
685 | } |
686 | ||
687 | #[inline] | |
688 | fn size_hint(&self) -> (usize, Option<usize>) { | |
689 | let (_, upper) = self.iter.size_hint(); | |
690 | (0, upper) // can't know a lower bound, due to the predicate | |
691 | } | |
692 | ||
693 | // this special case allows the compiler to make `.filter(_).count()` | |
694 | // branchless. Barring perfect branch prediction (which is unattainable in | |
695 | // the general case), this will be much faster in >90% of cases (containing | |
696 | // virtually all real workloads) and only a tiny bit slower in the rest. | |
697 | // | |
698 | // Having this specialization thus allows us to write `.filter(p).count()` | |
699 | // where we would otherwise write `.map(|x| p(x) as usize).sum()`, which is | |
700 | // less readable and also less backwards-compatible to Rust before 1.10. | |
701 | // | |
702 | // Using the branchless version will also simplify the LLVM byte code, thus | |
703 | // leaving more budget for LLVM optimizations. | |
704 | #[inline] | |
532ac7d7 XL |
705 | fn count(self) -> usize { |
706 | let mut predicate = self.predicate; | |
707 | self.iter.map(|x| predicate(&x) as usize).sum() | |
9fa01778 XL |
708 | } |
709 | ||
710 | #[inline] | |
711 | fn try_fold<Acc, Fold, R>(&mut self, init: Acc, mut fold: Fold) -> R where | |
712 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
713 | { | |
714 | let predicate = &mut self.predicate; | |
715 | self.iter.try_fold(init, move |acc, item| if predicate(&item) { | |
716 | fold(acc, item) | |
717 | } else { | |
718 | Try::from_ok(acc) | |
719 | }) | |
720 | } | |
721 | ||
722 | #[inline] | |
723 | fn fold<Acc, Fold>(self, init: Acc, mut fold: Fold) -> Acc | |
724 | where Fold: FnMut(Acc, Self::Item) -> Acc, | |
725 | { | |
726 | let mut predicate = self.predicate; | |
727 | self.iter.fold(init, move |acc, item| if predicate(&item) { | |
728 | fold(acc, item) | |
729 | } else { | |
730 | acc | |
731 | }) | |
732 | } | |
733 | } | |
734 | ||
735 | #[stable(feature = "rust1", since = "1.0.0")] | |
736 | impl<I: DoubleEndedIterator, P> DoubleEndedIterator for Filter<I, P> | |
737 | where P: FnMut(&I::Item) -> bool, | |
738 | { | |
739 | #[inline] | |
740 | fn next_back(&mut self) -> Option<I::Item> { | |
532ac7d7 | 741 | self.try_rfold((), |_, x| Err(x)).err() |
9fa01778 XL |
742 | } |
743 | ||
744 | #[inline] | |
745 | fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, mut fold: Fold) -> R where | |
746 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
747 | { | |
748 | let predicate = &mut self.predicate; | |
749 | self.iter.try_rfold(init, move |acc, item| if predicate(&item) { | |
750 | fold(acc, item) | |
751 | } else { | |
752 | Try::from_ok(acc) | |
753 | }) | |
754 | } | |
755 | ||
756 | #[inline] | |
757 | fn rfold<Acc, Fold>(self, init: Acc, mut fold: Fold) -> Acc | |
758 | where Fold: FnMut(Acc, Self::Item) -> Acc, | |
759 | { | |
760 | let mut predicate = self.predicate; | |
761 | self.iter.rfold(init, move |acc, item| if predicate(&item) { | |
762 | fold(acc, item) | |
763 | } else { | |
764 | acc | |
765 | }) | |
766 | } | |
767 | } | |
768 | ||
769 | #[stable(feature = "fused", since = "1.26.0")] | |
770 | impl<I: FusedIterator, P> FusedIterator for Filter<I, P> | |
771 | where P: FnMut(&I::Item) -> bool {} | |
772 | ||
773 | /// An iterator that uses `f` to both filter and map elements from `iter`. | |
774 | /// | |
775 | /// This `struct` is created by the [`filter_map`] method on [`Iterator`]. See its | |
776 | /// documentation for more. | |
777 | /// | |
778 | /// [`filter_map`]: trait.Iterator.html#method.filter_map | |
779 | /// [`Iterator`]: trait.Iterator.html | |
780 | #[must_use = "iterators are lazy and do nothing unless consumed"] | |
781 | #[stable(feature = "rust1", since = "1.0.0")] | |
782 | #[derive(Clone)] | |
783 | pub struct FilterMap<I, F> { | |
784 | iter: I, | |
785 | f: F, | |
786 | } | |
787 | impl<I, F> FilterMap<I, F> { | |
788 | pub(super) fn new(iter: I, f: F) -> FilterMap<I, F> { | |
789 | FilterMap { iter, f } | |
790 | } | |
791 | } | |
792 | ||
793 | #[stable(feature = "core_impl_debug", since = "1.9.0")] | |
794 | impl<I: fmt::Debug, F> fmt::Debug for FilterMap<I, F> { | |
795 | fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { | |
796 | f.debug_struct("FilterMap") | |
797 | .field("iter", &self.iter) | |
798 | .finish() | |
799 | } | |
800 | } | |
801 | ||
802 | #[stable(feature = "rust1", since = "1.0.0")] | |
803 | impl<B, I: Iterator, F> Iterator for FilterMap<I, F> | |
804 | where F: FnMut(I::Item) -> Option<B>, | |
805 | { | |
806 | type Item = B; | |
807 | ||
808 | #[inline] | |
809 | fn next(&mut self) -> Option<B> { | |
532ac7d7 | 810 | self.try_for_each(Err).err() |
9fa01778 XL |
811 | } |
812 | ||
813 | #[inline] | |
814 | fn size_hint(&self) -> (usize, Option<usize>) { | |
815 | let (_, upper) = self.iter.size_hint(); | |
816 | (0, upper) // can't know a lower bound, due to the predicate | |
817 | } | |
818 | ||
819 | #[inline] | |
820 | fn try_fold<Acc, Fold, R>(&mut self, init: Acc, mut fold: Fold) -> R where | |
821 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
822 | { | |
823 | let f = &mut self.f; | |
824 | self.iter.try_fold(init, move |acc, item| match f(item) { | |
825 | Some(x) => fold(acc, x), | |
826 | None => Try::from_ok(acc), | |
827 | }) | |
828 | } | |
829 | ||
830 | #[inline] | |
831 | fn fold<Acc, Fold>(self, init: Acc, mut fold: Fold) -> Acc | |
832 | where Fold: FnMut(Acc, Self::Item) -> Acc, | |
833 | { | |
834 | let mut f = self.f; | |
835 | self.iter.fold(init, move |acc, item| match f(item) { | |
836 | Some(x) => fold(acc, x), | |
837 | None => acc, | |
838 | }) | |
839 | } | |
840 | } | |
841 | ||
842 | #[stable(feature = "rust1", since = "1.0.0")] | |
843 | impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for FilterMap<I, F> | |
844 | where F: FnMut(I::Item) -> Option<B>, | |
845 | { | |
846 | #[inline] | |
847 | fn next_back(&mut self) -> Option<B> { | |
532ac7d7 | 848 | self.try_rfold((), |_, x| Err(x)).err() |
9fa01778 XL |
849 | } |
850 | ||
851 | #[inline] | |
852 | fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, mut fold: Fold) -> R where | |
853 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
854 | { | |
855 | let f = &mut self.f; | |
856 | self.iter.try_rfold(init, move |acc, item| match f(item) { | |
857 | Some(x) => fold(acc, x), | |
858 | None => Try::from_ok(acc), | |
859 | }) | |
860 | } | |
861 | ||
862 | #[inline] | |
863 | fn rfold<Acc, Fold>(self, init: Acc, mut fold: Fold) -> Acc | |
864 | where Fold: FnMut(Acc, Self::Item) -> Acc, | |
865 | { | |
866 | let mut f = self.f; | |
867 | self.iter.rfold(init, move |acc, item| match f(item) { | |
868 | Some(x) => fold(acc, x), | |
869 | None => acc, | |
870 | }) | |
871 | } | |
872 | } | |
873 | ||
874 | #[stable(feature = "fused", since = "1.26.0")] | |
875 | impl<B, I: FusedIterator, F> FusedIterator for FilterMap<I, F> | |
876 | where F: FnMut(I::Item) -> Option<B> {} | |
877 | ||
878 | /// An iterator that yields the current count and the element during iteration. | |
879 | /// | |
880 | /// This `struct` is created by the [`enumerate`] method on [`Iterator`]. See its | |
881 | /// documentation for more. | |
882 | /// | |
883 | /// [`enumerate`]: trait.Iterator.html#method.enumerate | |
884 | /// [`Iterator`]: trait.Iterator.html | |
885 | #[derive(Clone, Debug)] | |
886 | #[must_use = "iterators are lazy and do nothing unless consumed"] | |
887 | #[stable(feature = "rust1", since = "1.0.0")] | |
888 | pub struct Enumerate<I> { | |
889 | iter: I, | |
890 | count: usize, | |
891 | } | |
892 | impl<I> Enumerate<I> { | |
893 | pub(super) fn new(iter: I) -> Enumerate<I> { | |
894 | Enumerate { iter, count: 0 } | |
895 | } | |
896 | } | |
897 | ||
898 | #[stable(feature = "rust1", since = "1.0.0")] | |
899 | impl<I> Iterator for Enumerate<I> where I: Iterator { | |
900 | type Item = (usize, <I as Iterator>::Item); | |
901 | ||
902 | /// # Overflow Behavior | |
903 | /// | |
904 | /// The method does no guarding against overflows, so enumerating more than | |
905 | /// `usize::MAX` elements either produces the wrong result or panics. If | |
906 | /// debug assertions are enabled, a panic is guaranteed. | |
907 | /// | |
908 | /// # Panics | |
909 | /// | |
910 | /// Might panic if the index of the element overflows a `usize`. | |
911 | #[inline] | |
912 | #[rustc_inherit_overflow_checks] | |
913 | fn next(&mut self) -> Option<(usize, <I as Iterator>::Item)> { | |
914 | self.iter.next().map(|a| { | |
915 | let ret = (self.count, a); | |
916 | // Possible undefined overflow. | |
917 | self.count += 1; | |
918 | ret | |
919 | }) | |
920 | } | |
921 | ||
922 | #[inline] | |
923 | fn size_hint(&self) -> (usize, Option<usize>) { | |
924 | self.iter.size_hint() | |
925 | } | |
926 | ||
927 | #[inline] | |
928 | #[rustc_inherit_overflow_checks] | |
929 | fn nth(&mut self, n: usize) -> Option<(usize, I::Item)> { | |
930 | self.iter.nth(n).map(|a| { | |
931 | let i = self.count + n; | |
932 | self.count = i + 1; | |
933 | (i, a) | |
934 | }) | |
935 | } | |
936 | ||
937 | #[inline] | |
938 | fn count(self) -> usize { | |
939 | self.iter.count() | |
940 | } | |
941 | ||
942 | #[inline] | |
943 | #[rustc_inherit_overflow_checks] | |
944 | fn try_fold<Acc, Fold, R>(&mut self, init: Acc, mut fold: Fold) -> R where | |
945 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
946 | { | |
947 | let count = &mut self.count; | |
948 | self.iter.try_fold(init, move |acc, item| { | |
949 | let acc = fold(acc, (*count, item)); | |
950 | *count += 1; | |
951 | acc | |
952 | }) | |
953 | } | |
954 | ||
955 | #[inline] | |
956 | #[rustc_inherit_overflow_checks] | |
957 | fn fold<Acc, Fold>(self, init: Acc, mut fold: Fold) -> Acc | |
958 | where Fold: FnMut(Acc, Self::Item) -> Acc, | |
959 | { | |
960 | let mut count = self.count; | |
961 | self.iter.fold(init, move |acc, item| { | |
962 | let acc = fold(acc, (count, item)); | |
963 | count += 1; | |
964 | acc | |
965 | }) | |
966 | } | |
967 | } | |
968 | ||
969 | #[stable(feature = "rust1", since = "1.0.0")] | |
970 | impl<I> DoubleEndedIterator for Enumerate<I> where | |
971 | I: ExactSizeIterator + DoubleEndedIterator | |
972 | { | |
973 | #[inline] | |
974 | fn next_back(&mut self) -> Option<(usize, <I as Iterator>::Item)> { | |
975 | self.iter.next_back().map(|a| { | |
976 | let len = self.iter.len(); | |
977 | // Can safely add, `ExactSizeIterator` promises that the number of | |
978 | // elements fits into a `usize`. | |
979 | (self.count + len, a) | |
980 | }) | |
981 | } | |
982 | ||
983 | #[inline] | |
984 | fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, mut fold: Fold) -> R where | |
985 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
986 | { | |
987 | // Can safely add and subtract the count, as `ExactSizeIterator` promises | |
988 | // that the number of elements fits into a `usize`. | |
989 | let mut count = self.count + self.iter.len(); | |
990 | self.iter.try_rfold(init, move |acc, item| { | |
991 | count -= 1; | |
992 | fold(acc, (count, item)) | |
993 | }) | |
994 | } | |
995 | ||
996 | #[inline] | |
997 | fn rfold<Acc, Fold>(self, init: Acc, mut fold: Fold) -> Acc | |
998 | where Fold: FnMut(Acc, Self::Item) -> Acc, | |
999 | { | |
1000 | // Can safely add and subtract the count, as `ExactSizeIterator` promises | |
1001 | // that the number of elements fits into a `usize`. | |
1002 | let mut count = self.count + self.iter.len(); | |
1003 | self.iter.rfold(init, move |acc, item| { | |
1004 | count -= 1; | |
1005 | fold(acc, (count, item)) | |
1006 | }) | |
1007 | } | |
1008 | } | |
1009 | ||
1010 | #[stable(feature = "rust1", since = "1.0.0")] | |
1011 | impl<I> ExactSizeIterator for Enumerate<I> where I: ExactSizeIterator { | |
1012 | fn len(&self) -> usize { | |
1013 | self.iter.len() | |
1014 | } | |
1015 | ||
1016 | fn is_empty(&self) -> bool { | |
1017 | self.iter.is_empty() | |
1018 | } | |
1019 | } | |
1020 | ||
1021 | #[doc(hidden)] | |
1022 | unsafe impl<I> TrustedRandomAccess for Enumerate<I> | |
1023 | where I: TrustedRandomAccess | |
1024 | { | |
1025 | unsafe fn get_unchecked(&mut self, i: usize) -> (usize, I::Item) { | |
1026 | (self.count + i, self.iter.get_unchecked(i)) | |
1027 | } | |
1028 | ||
1029 | fn may_have_side_effect() -> bool { | |
1030 | I::may_have_side_effect() | |
1031 | } | |
1032 | } | |
1033 | ||
1034 | #[stable(feature = "fused", since = "1.26.0")] | |
1035 | impl<I> FusedIterator for Enumerate<I> where I: FusedIterator {} | |
1036 | ||
1037 | #[unstable(feature = "trusted_len", issue = "37572")] | |
1038 | unsafe impl<I> TrustedLen for Enumerate<I> | |
1039 | where I: TrustedLen, | |
1040 | {} | |
1041 | ||
1042 | ||
1043 | /// An iterator with a `peek()` that returns an optional reference to the next | |
1044 | /// element. | |
1045 | /// | |
1046 | /// This `struct` is created by the [`peekable`] method on [`Iterator`]. See its | |
1047 | /// documentation for more. | |
1048 | /// | |
1049 | /// [`peekable`]: trait.Iterator.html#method.peekable | |
1050 | /// [`Iterator`]: trait.Iterator.html | |
1051 | #[derive(Clone, Debug)] | |
1052 | #[must_use = "iterators are lazy and do nothing unless consumed"] | |
1053 | #[stable(feature = "rust1", since = "1.0.0")] | |
1054 | pub struct Peekable<I: Iterator> { | |
1055 | iter: I, | |
1056 | /// Remember a peeked value, even if it was None. | |
1057 | peeked: Option<Option<I::Item>>, | |
1058 | } | |
1059 | impl<I: Iterator> Peekable<I> { | |
1060 | pub(super) fn new(iter: I) -> Peekable<I> { | |
1061 | Peekable { iter, peeked: None } | |
1062 | } | |
1063 | } | |
1064 | ||
1065 | // Peekable must remember if a None has been seen in the `.peek()` method. | |
1066 | // It ensures that `.peek(); .peek();` or `.peek(); .next();` only advances the | |
1067 | // underlying iterator at most once. This does not by itself make the iterator | |
1068 | // fused. | |
1069 | #[stable(feature = "rust1", since = "1.0.0")] | |
1070 | impl<I: Iterator> Iterator for Peekable<I> { | |
1071 | type Item = I::Item; | |
1072 | ||
1073 | #[inline] | |
1074 | fn next(&mut self) -> Option<I::Item> { | |
1075 | match self.peeked.take() { | |
1076 | Some(v) => v, | |
1077 | None => self.iter.next(), | |
1078 | } | |
1079 | } | |
1080 | ||
1081 | #[inline] | |
1082 | #[rustc_inherit_overflow_checks] | |
1083 | fn count(mut self) -> usize { | |
1084 | match self.peeked.take() { | |
1085 | Some(None) => 0, | |
1086 | Some(Some(_)) => 1 + self.iter.count(), | |
1087 | None => self.iter.count(), | |
1088 | } | |
1089 | } | |
1090 | ||
1091 | #[inline] | |
1092 | fn nth(&mut self, n: usize) -> Option<I::Item> { | |
1093 | match self.peeked.take() { | |
1094 | Some(None) => None, | |
1095 | Some(v @ Some(_)) if n == 0 => v, | |
1096 | Some(Some(_)) => self.iter.nth(n - 1), | |
1097 | None => self.iter.nth(n), | |
1098 | } | |
1099 | } | |
1100 | ||
1101 | #[inline] | |
1102 | fn last(mut self) -> Option<I::Item> { | |
1103 | let peek_opt = match self.peeked.take() { | |
1104 | Some(None) => return None, | |
1105 | Some(v) => v, | |
1106 | None => None, | |
1107 | }; | |
1108 | self.iter.last().or(peek_opt) | |
1109 | } | |
1110 | ||
1111 | #[inline] | |
1112 | fn size_hint(&self) -> (usize, Option<usize>) { | |
1113 | let peek_len = match self.peeked { | |
1114 | Some(None) => return (0, Some(0)), | |
1115 | Some(Some(_)) => 1, | |
1116 | None => 0, | |
1117 | }; | |
1118 | let (lo, hi) = self.iter.size_hint(); | |
1119 | let lo = lo.saturating_add(peek_len); | |
1120 | let hi = hi.and_then(|x| x.checked_add(peek_len)); | |
1121 | (lo, hi) | |
1122 | } | |
1123 | ||
1124 | #[inline] | |
1125 | fn try_fold<B, F, R>(&mut self, init: B, mut f: F) -> R where | |
1126 | Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B> | |
1127 | { | |
1128 | let acc = match self.peeked.take() { | |
1129 | Some(None) => return Try::from_ok(init), | |
1130 | Some(Some(v)) => f(init, v)?, | |
1131 | None => init, | |
1132 | }; | |
1133 | self.iter.try_fold(acc, f) | |
1134 | } | |
1135 | ||
1136 | #[inline] | |
1137 | fn fold<Acc, Fold>(self, init: Acc, mut fold: Fold) -> Acc | |
1138 | where Fold: FnMut(Acc, Self::Item) -> Acc, | |
1139 | { | |
1140 | let acc = match self.peeked { | |
1141 | Some(None) => return init, | |
1142 | Some(Some(v)) => fold(init, v), | |
1143 | None => init, | |
1144 | }; | |
1145 | self.iter.fold(acc, fold) | |
1146 | } | |
1147 | } | |
1148 | ||
1149 | #[stable(feature = "rust1", since = "1.0.0")] | |
1150 | impl<I: ExactSizeIterator> ExactSizeIterator for Peekable<I> {} | |
1151 | ||
1152 | #[stable(feature = "fused", since = "1.26.0")] | |
1153 | impl<I: FusedIterator> FusedIterator for Peekable<I> {} | |
1154 | ||
1155 | impl<I: Iterator> Peekable<I> { | |
1156 | /// Returns a reference to the next() value without advancing the iterator. | |
1157 | /// | |
1158 | /// Like [`next`], if there is a value, it is wrapped in a `Some(T)`. | |
1159 | /// But if the iteration is over, `None` is returned. | |
1160 | /// | |
1161 | /// [`next`]: trait.Iterator.html#tymethod.next | |
1162 | /// | |
1163 | /// Because `peek()` returns a reference, and many iterators iterate over | |
1164 | /// references, there can be a possibly confusing situation where the | |
1165 | /// return value is a double reference. You can see this effect in the | |
1166 | /// examples below. | |
1167 | /// | |
1168 | /// # Examples | |
1169 | /// | |
1170 | /// Basic usage: | |
1171 | /// | |
1172 | /// ``` | |
1173 | /// let xs = [1, 2, 3]; | |
1174 | /// | |
1175 | /// let mut iter = xs.iter().peekable(); | |
1176 | /// | |
1177 | /// // peek() lets us see into the future | |
1178 | /// assert_eq!(iter.peek(), Some(&&1)); | |
1179 | /// assert_eq!(iter.next(), Some(&1)); | |
1180 | /// | |
1181 | /// assert_eq!(iter.next(), Some(&2)); | |
1182 | /// | |
1183 | /// // The iterator does not advance even if we `peek` multiple times | |
1184 | /// assert_eq!(iter.peek(), Some(&&3)); | |
1185 | /// assert_eq!(iter.peek(), Some(&&3)); | |
1186 | /// | |
1187 | /// assert_eq!(iter.next(), Some(&3)); | |
1188 | /// | |
1189 | /// // After the iterator is finished, so is `peek()` | |
1190 | /// assert_eq!(iter.peek(), None); | |
1191 | /// assert_eq!(iter.next(), None); | |
1192 | /// ``` | |
1193 | #[inline] | |
1194 | #[stable(feature = "rust1", since = "1.0.0")] | |
1195 | pub fn peek(&mut self) -> Option<&I::Item> { | |
1196 | let iter = &mut self.iter; | |
1197 | self.peeked.get_or_insert_with(|| iter.next()).as_ref() | |
1198 | } | |
1199 | } | |
1200 | ||
532ac7d7 | 1201 | /// An iterator that rejects elements while `predicate` returns `true`. |
9fa01778 XL |
1202 | /// |
1203 | /// This `struct` is created by the [`skip_while`] method on [`Iterator`]. See its | |
1204 | /// documentation for more. | |
1205 | /// | |
1206 | /// [`skip_while`]: trait.Iterator.html#method.skip_while | |
1207 | /// [`Iterator`]: trait.Iterator.html | |
1208 | #[must_use = "iterators are lazy and do nothing unless consumed"] | |
1209 | #[stable(feature = "rust1", since = "1.0.0")] | |
1210 | #[derive(Clone)] | |
1211 | pub struct SkipWhile<I, P> { | |
1212 | iter: I, | |
1213 | flag: bool, | |
1214 | predicate: P, | |
1215 | } | |
1216 | impl<I, P> SkipWhile<I, P> { | |
1217 | pub(super) fn new(iter: I, predicate: P) -> SkipWhile<I, P> { | |
1218 | SkipWhile { iter, flag: false, predicate } | |
1219 | } | |
1220 | } | |
1221 | ||
1222 | #[stable(feature = "core_impl_debug", since = "1.9.0")] | |
1223 | impl<I: fmt::Debug, P> fmt::Debug for SkipWhile<I, P> { | |
1224 | fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { | |
1225 | f.debug_struct("SkipWhile") | |
1226 | .field("iter", &self.iter) | |
1227 | .field("flag", &self.flag) | |
1228 | .finish() | |
1229 | } | |
1230 | } | |
1231 | ||
1232 | #[stable(feature = "rust1", since = "1.0.0")] | |
1233 | impl<I: Iterator, P> Iterator for SkipWhile<I, P> | |
1234 | where P: FnMut(&I::Item) -> bool | |
1235 | { | |
1236 | type Item = I::Item; | |
1237 | ||
1238 | #[inline] | |
1239 | fn next(&mut self) -> Option<I::Item> { | |
1240 | let flag = &mut self.flag; | |
1241 | let pred = &mut self.predicate; | |
1242 | self.iter.find(move |x| { | |
1243 | if *flag || !pred(x) { | |
1244 | *flag = true; | |
1245 | true | |
1246 | } else { | |
1247 | false | |
1248 | } | |
1249 | }) | |
1250 | } | |
1251 | ||
1252 | #[inline] | |
1253 | fn size_hint(&self) -> (usize, Option<usize>) { | |
1254 | let (_, upper) = self.iter.size_hint(); | |
1255 | (0, upper) // can't know a lower bound, due to the predicate | |
1256 | } | |
1257 | ||
1258 | #[inline] | |
1259 | fn try_fold<Acc, Fold, R>(&mut self, mut init: Acc, mut fold: Fold) -> R where | |
1260 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
1261 | { | |
1262 | if !self.flag { | |
1263 | match self.next() { | |
1264 | Some(v) => init = fold(init, v)?, | |
1265 | None => return Try::from_ok(init), | |
1266 | } | |
1267 | } | |
1268 | self.iter.try_fold(init, fold) | |
1269 | } | |
1270 | ||
1271 | #[inline] | |
1272 | fn fold<Acc, Fold>(mut self, mut init: Acc, mut fold: Fold) -> Acc | |
1273 | where Fold: FnMut(Acc, Self::Item) -> Acc, | |
1274 | { | |
1275 | if !self.flag { | |
1276 | match self.next() { | |
1277 | Some(v) => init = fold(init, v), | |
1278 | None => return init, | |
1279 | } | |
1280 | } | |
1281 | self.iter.fold(init, fold) | |
1282 | } | |
1283 | } | |
1284 | ||
1285 | #[stable(feature = "fused", since = "1.26.0")] | |
1286 | impl<I, P> FusedIterator for SkipWhile<I, P> | |
1287 | where I: FusedIterator, P: FnMut(&I::Item) -> bool {} | |
1288 | ||
532ac7d7 | 1289 | /// An iterator that only accepts elements while `predicate` returns `true`. |
9fa01778 XL |
1290 | /// |
1291 | /// This `struct` is created by the [`take_while`] method on [`Iterator`]. See its | |
1292 | /// documentation for more. | |
1293 | /// | |
1294 | /// [`take_while`]: trait.Iterator.html#method.take_while | |
1295 | /// [`Iterator`]: trait.Iterator.html | |
1296 | #[must_use = "iterators are lazy and do nothing unless consumed"] | |
1297 | #[stable(feature = "rust1", since = "1.0.0")] | |
1298 | #[derive(Clone)] | |
1299 | pub struct TakeWhile<I, P> { | |
1300 | iter: I, | |
1301 | flag: bool, | |
1302 | predicate: P, | |
1303 | } | |
1304 | impl<I, P> TakeWhile<I, P> { | |
1305 | pub(super) fn new(iter: I, predicate: P) -> TakeWhile<I, P> { | |
1306 | TakeWhile { iter, flag: false, predicate } | |
1307 | } | |
1308 | } | |
1309 | ||
1310 | #[stable(feature = "core_impl_debug", since = "1.9.0")] | |
1311 | impl<I: fmt::Debug, P> fmt::Debug for TakeWhile<I, P> { | |
1312 | fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { | |
1313 | f.debug_struct("TakeWhile") | |
1314 | .field("iter", &self.iter) | |
1315 | .field("flag", &self.flag) | |
1316 | .finish() | |
1317 | } | |
1318 | } | |
1319 | ||
1320 | #[stable(feature = "rust1", since = "1.0.0")] | |
1321 | impl<I: Iterator, P> Iterator for TakeWhile<I, P> | |
1322 | where P: FnMut(&I::Item) -> bool | |
1323 | { | |
1324 | type Item = I::Item; | |
1325 | ||
1326 | #[inline] | |
1327 | fn next(&mut self) -> Option<I::Item> { | |
1328 | if self.flag { | |
1329 | None | |
1330 | } else { | |
1331 | self.iter.next().and_then(|x| { | |
1332 | if (self.predicate)(&x) { | |
1333 | Some(x) | |
1334 | } else { | |
1335 | self.flag = true; | |
1336 | None | |
1337 | } | |
1338 | }) | |
1339 | } | |
1340 | } | |
1341 | ||
1342 | #[inline] | |
1343 | fn size_hint(&self) -> (usize, Option<usize>) { | |
1344 | if self.flag { | |
1345 | (0, Some(0)) | |
1346 | } else { | |
1347 | let (_, upper) = self.iter.size_hint(); | |
1348 | (0, upper) // can't know a lower bound, due to the predicate | |
1349 | } | |
1350 | } | |
1351 | ||
1352 | #[inline] | |
1353 | fn try_fold<Acc, Fold, R>(&mut self, init: Acc, mut fold: Fold) -> R where | |
1354 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
1355 | { | |
1356 | if self.flag { | |
1357 | Try::from_ok(init) | |
1358 | } else { | |
1359 | let flag = &mut self.flag; | |
1360 | let p = &mut self.predicate; | |
1361 | self.iter.try_fold(init, move |acc, x|{ | |
1362 | if p(&x) { | |
1363 | LoopState::from_try(fold(acc, x)) | |
1364 | } else { | |
1365 | *flag = true; | |
1366 | LoopState::Break(Try::from_ok(acc)) | |
1367 | } | |
1368 | }).into_try() | |
1369 | } | |
1370 | } | |
1371 | } | |
1372 | ||
1373 | #[stable(feature = "fused", since = "1.26.0")] | |
1374 | impl<I, P> FusedIterator for TakeWhile<I, P> | |
1375 | where I: FusedIterator, P: FnMut(&I::Item) -> bool {} | |
1376 | ||
1377 | /// An iterator that skips over `n` elements of `iter`. | |
1378 | /// | |
1379 | /// This `struct` is created by the [`skip`] method on [`Iterator`]. See its | |
1380 | /// documentation for more. | |
1381 | /// | |
1382 | /// [`skip`]: trait.Iterator.html#method.skip | |
1383 | /// [`Iterator`]: trait.Iterator.html | |
1384 | #[derive(Clone, Debug)] | |
1385 | #[must_use = "iterators are lazy and do nothing unless consumed"] | |
1386 | #[stable(feature = "rust1", since = "1.0.0")] | |
1387 | pub struct Skip<I> { | |
1388 | iter: I, | |
1389 | n: usize | |
1390 | } | |
1391 | impl<I> Skip<I> { | |
1392 | pub(super) fn new(iter: I, n: usize) -> Skip<I> { | |
1393 | Skip { iter, n } | |
1394 | } | |
1395 | } | |
1396 | ||
1397 | #[stable(feature = "rust1", since = "1.0.0")] | |
1398 | impl<I> Iterator for Skip<I> where I: Iterator { | |
1399 | type Item = <I as Iterator>::Item; | |
1400 | ||
1401 | #[inline] | |
1402 | fn next(&mut self) -> Option<I::Item> { | |
1403 | if self.n == 0 { | |
1404 | self.iter.next() | |
1405 | } else { | |
1406 | let old_n = self.n; | |
1407 | self.n = 0; | |
1408 | self.iter.nth(old_n) | |
1409 | } | |
1410 | } | |
1411 | ||
1412 | #[inline] | |
1413 | fn nth(&mut self, n: usize) -> Option<I::Item> { | |
1414 | // Can't just add n + self.n due to overflow. | |
1415 | if self.n == 0 { | |
1416 | self.iter.nth(n) | |
1417 | } else { | |
1418 | let to_skip = self.n; | |
1419 | self.n = 0; | |
1420 | // nth(n) skips n+1 | |
1421 | if self.iter.nth(to_skip-1).is_none() { | |
1422 | return None; | |
1423 | } | |
1424 | self.iter.nth(n) | |
1425 | } | |
1426 | } | |
1427 | ||
1428 | #[inline] | |
1429 | fn count(self) -> usize { | |
1430 | self.iter.count().saturating_sub(self.n) | |
1431 | } | |
1432 | ||
1433 | #[inline] | |
1434 | fn last(mut self) -> Option<I::Item> { | |
1435 | if self.n == 0 { | |
1436 | self.iter.last() | |
1437 | } else { | |
1438 | let next = self.next(); | |
1439 | if next.is_some() { | |
1440 | // recurse. n should be 0. | |
1441 | self.last().or(next) | |
1442 | } else { | |
1443 | None | |
1444 | } | |
1445 | } | |
1446 | } | |
1447 | ||
1448 | #[inline] | |
1449 | fn size_hint(&self) -> (usize, Option<usize>) { | |
1450 | let (lower, upper) = self.iter.size_hint(); | |
1451 | ||
1452 | let lower = lower.saturating_sub(self.n); | |
1453 | let upper = upper.map(|x| x.saturating_sub(self.n)); | |
1454 | ||
1455 | (lower, upper) | |
1456 | } | |
1457 | ||
1458 | #[inline] | |
1459 | fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where | |
1460 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
1461 | { | |
1462 | let n = self.n; | |
1463 | self.n = 0; | |
1464 | if n > 0 { | |
1465 | // nth(n) skips n+1 | |
1466 | if self.iter.nth(n - 1).is_none() { | |
1467 | return Try::from_ok(init); | |
1468 | } | |
1469 | } | |
1470 | self.iter.try_fold(init, fold) | |
1471 | } | |
1472 | ||
1473 | #[inline] | |
1474 | fn fold<Acc, Fold>(mut self, init: Acc, fold: Fold) -> Acc | |
1475 | where Fold: FnMut(Acc, Self::Item) -> Acc, | |
1476 | { | |
1477 | if self.n > 0 { | |
1478 | // nth(n) skips n+1 | |
1479 | if self.iter.nth(self.n - 1).is_none() { | |
1480 | return init; | |
1481 | } | |
1482 | } | |
1483 | self.iter.fold(init, fold) | |
1484 | } | |
1485 | } | |
1486 | ||
1487 | #[stable(feature = "rust1", since = "1.0.0")] | |
1488 | impl<I> ExactSizeIterator for Skip<I> where I: ExactSizeIterator {} | |
1489 | ||
1490 | #[stable(feature = "double_ended_skip_iterator", since = "1.9.0")] | |
1491 | impl<I> DoubleEndedIterator for Skip<I> where I: DoubleEndedIterator + ExactSizeIterator { | |
1492 | fn next_back(&mut self) -> Option<Self::Item> { | |
1493 | if self.len() > 0 { | |
1494 | self.iter.next_back() | |
1495 | } else { | |
1496 | None | |
1497 | } | |
1498 | } | |
1499 | ||
1500 | fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, mut fold: Fold) -> R where | |
1501 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
1502 | { | |
1503 | let mut n = self.len(); | |
1504 | if n == 0 { | |
1505 | Try::from_ok(init) | |
1506 | } else { | |
1507 | self.iter.try_rfold(init, move |acc, x| { | |
1508 | n -= 1; | |
1509 | let r = fold(acc, x); | |
1510 | if n == 0 { LoopState::Break(r) } | |
1511 | else { LoopState::from_try(r) } | |
1512 | }).into_try() | |
1513 | } | |
1514 | } | |
1515 | } | |
1516 | ||
1517 | #[stable(feature = "fused", since = "1.26.0")] | |
1518 | impl<I> FusedIterator for Skip<I> where I: FusedIterator {} | |
1519 | ||
1520 | /// An iterator that only iterates over the first `n` iterations of `iter`. | |
1521 | /// | |
1522 | /// This `struct` is created by the [`take`] method on [`Iterator`]. See its | |
1523 | /// documentation for more. | |
1524 | /// | |
1525 | /// [`take`]: trait.Iterator.html#method.take | |
1526 | /// [`Iterator`]: trait.Iterator.html | |
1527 | #[derive(Clone, Debug)] | |
1528 | #[must_use = "iterators are lazy and do nothing unless consumed"] | |
1529 | #[stable(feature = "rust1", since = "1.0.0")] | |
1530 | pub struct Take<I> { | |
1531 | pub(super) iter: I, | |
1532 | pub(super) n: usize | |
1533 | } | |
1534 | impl<I> Take<I> { | |
1535 | pub(super) fn new(iter: I, n: usize) -> Take<I> { | |
1536 | Take { iter, n } | |
1537 | } | |
1538 | } | |
1539 | ||
1540 | #[stable(feature = "rust1", since = "1.0.0")] | |
1541 | impl<I> Iterator for Take<I> where I: Iterator{ | |
1542 | type Item = <I as Iterator>::Item; | |
1543 | ||
1544 | #[inline] | |
1545 | fn next(&mut self) -> Option<<I as Iterator>::Item> { | |
1546 | if self.n != 0 { | |
1547 | self.n -= 1; | |
1548 | self.iter.next() | |
1549 | } else { | |
1550 | None | |
1551 | } | |
1552 | } | |
1553 | ||
1554 | #[inline] | |
1555 | fn nth(&mut self, n: usize) -> Option<I::Item> { | |
1556 | if self.n > n { | |
1557 | self.n -= n + 1; | |
1558 | self.iter.nth(n) | |
1559 | } else { | |
1560 | if self.n > 0 { | |
1561 | self.iter.nth(self.n - 1); | |
1562 | self.n = 0; | |
1563 | } | |
1564 | None | |
1565 | } | |
1566 | } | |
1567 | ||
1568 | #[inline] | |
1569 | fn size_hint(&self) -> (usize, Option<usize>) { | |
1570 | if self.n == 0 { | |
1571 | return (0, Some(0)); | |
1572 | } | |
1573 | ||
1574 | let (lower, upper) = self.iter.size_hint(); | |
1575 | ||
1576 | let lower = cmp::min(lower, self.n); | |
1577 | ||
1578 | let upper = match upper { | |
1579 | Some(x) if x < self.n => Some(x), | |
1580 | _ => Some(self.n) | |
1581 | }; | |
1582 | ||
1583 | (lower, upper) | |
1584 | } | |
1585 | ||
1586 | #[inline] | |
1587 | fn try_fold<Acc, Fold, R>(&mut self, init: Acc, mut fold: Fold) -> R where | |
1588 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
1589 | { | |
1590 | if self.n == 0 { | |
1591 | Try::from_ok(init) | |
1592 | } else { | |
1593 | let n = &mut self.n; | |
1594 | self.iter.try_fold(init, move |acc, x| { | |
1595 | *n -= 1; | |
1596 | let r = fold(acc, x); | |
1597 | if *n == 0 { LoopState::Break(r) } | |
1598 | else { LoopState::from_try(r) } | |
1599 | }).into_try() | |
1600 | } | |
1601 | } | |
1602 | } | |
1603 | ||
1604 | #[stable(feature = "rust1", since = "1.0.0")] | |
1605 | impl<I> ExactSizeIterator for Take<I> where I: ExactSizeIterator {} | |
1606 | ||
1607 | #[stable(feature = "fused", since = "1.26.0")] | |
1608 | impl<I> FusedIterator for Take<I> where I: FusedIterator {} | |
1609 | ||
1610 | #[unstable(feature = "trusted_len", issue = "37572")] | |
1611 | unsafe impl<I: TrustedLen> TrustedLen for Take<I> {} | |
1612 | ||
1613 | /// An iterator to maintain state while iterating another iterator. | |
1614 | /// | |
1615 | /// This `struct` is created by the [`scan`] method on [`Iterator`]. See its | |
1616 | /// documentation for more. | |
1617 | /// | |
1618 | /// [`scan`]: trait.Iterator.html#method.scan | |
1619 | /// [`Iterator`]: trait.Iterator.html | |
1620 | #[must_use = "iterators are lazy and do nothing unless consumed"] | |
1621 | #[stable(feature = "rust1", since = "1.0.0")] | |
1622 | #[derive(Clone)] | |
1623 | pub struct Scan<I, St, F> { | |
1624 | iter: I, | |
1625 | f: F, | |
1626 | state: St, | |
1627 | } | |
1628 | impl<I, St, F> Scan<I, St, F> { | |
1629 | pub(super) fn new(iter: I, state: St, f: F) -> Scan<I, St, F> { | |
1630 | Scan { iter, state, f } | |
1631 | } | |
1632 | } | |
1633 | ||
1634 | #[stable(feature = "core_impl_debug", since = "1.9.0")] | |
1635 | impl<I: fmt::Debug, St: fmt::Debug, F> fmt::Debug for Scan<I, St, F> { | |
1636 | fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { | |
1637 | f.debug_struct("Scan") | |
1638 | .field("iter", &self.iter) | |
1639 | .field("state", &self.state) | |
1640 | .finish() | |
1641 | } | |
1642 | } | |
1643 | ||
1644 | #[stable(feature = "rust1", since = "1.0.0")] | |
1645 | impl<B, I, St, F> Iterator for Scan<I, St, F> where | |
1646 | I: Iterator, | |
1647 | F: FnMut(&mut St, I::Item) -> Option<B>, | |
1648 | { | |
1649 | type Item = B; | |
1650 | ||
1651 | #[inline] | |
1652 | fn next(&mut self) -> Option<B> { | |
1653 | self.iter.next().and_then(|a| (self.f)(&mut self.state, a)) | |
1654 | } | |
1655 | ||
1656 | #[inline] | |
1657 | fn size_hint(&self) -> (usize, Option<usize>) { | |
1658 | let (_, upper) = self.iter.size_hint(); | |
1659 | (0, upper) // can't know a lower bound, due to the scan function | |
1660 | } | |
1661 | ||
1662 | #[inline] | |
1663 | fn try_fold<Acc, Fold, R>(&mut self, init: Acc, mut fold: Fold) -> R where | |
1664 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
1665 | { | |
1666 | let state = &mut self.state; | |
1667 | let f = &mut self.f; | |
1668 | self.iter.try_fold(init, move |acc, x| { | |
1669 | match f(state, x) { | |
1670 | None => LoopState::Break(Try::from_ok(acc)), | |
1671 | Some(x) => LoopState::from_try(fold(acc, x)), | |
1672 | } | |
1673 | }).into_try() | |
1674 | } | |
1675 | } | |
1676 | ||
1677 | /// An iterator that yields `None` forever after the underlying iterator | |
1678 | /// yields `None` once. | |
1679 | /// | |
1680 | /// This `struct` is created by the [`fuse`] method on [`Iterator`]. See its | |
1681 | /// documentation for more. | |
1682 | /// | |
1683 | /// [`fuse`]: trait.Iterator.html#method.fuse | |
1684 | /// [`Iterator`]: trait.Iterator.html | |
1685 | #[derive(Clone, Debug)] | |
1686 | #[must_use = "iterators are lazy and do nothing unless consumed"] | |
1687 | #[stable(feature = "rust1", since = "1.0.0")] | |
1688 | pub struct Fuse<I> { | |
1689 | iter: I, | |
1690 | done: bool | |
1691 | } | |
1692 | impl<I> Fuse<I> { | |
1693 | pub(super) fn new(iter: I) -> Fuse<I> { | |
1694 | Fuse { iter, done: false } | |
1695 | } | |
1696 | } | |
1697 | ||
1698 | #[stable(feature = "fused", since = "1.26.0")] | |
1699 | impl<I> FusedIterator for Fuse<I> where I: Iterator {} | |
1700 | ||
1701 | #[stable(feature = "rust1", since = "1.0.0")] | |
1702 | impl<I> Iterator for Fuse<I> where I: Iterator { | |
1703 | type Item = <I as Iterator>::Item; | |
1704 | ||
1705 | #[inline] | |
1706 | default fn next(&mut self) -> Option<<I as Iterator>::Item> { | |
1707 | if self.done { | |
1708 | None | |
1709 | } else { | |
1710 | let next = self.iter.next(); | |
1711 | self.done = next.is_none(); | |
1712 | next | |
1713 | } | |
1714 | } | |
1715 | ||
1716 | #[inline] | |
1717 | default fn nth(&mut self, n: usize) -> Option<I::Item> { | |
1718 | if self.done { | |
1719 | None | |
1720 | } else { | |
1721 | let nth = self.iter.nth(n); | |
1722 | self.done = nth.is_none(); | |
1723 | nth | |
1724 | } | |
1725 | } | |
1726 | ||
1727 | #[inline] | |
1728 | default fn last(self) -> Option<I::Item> { | |
1729 | if self.done { | |
1730 | None | |
1731 | } else { | |
1732 | self.iter.last() | |
1733 | } | |
1734 | } | |
1735 | ||
1736 | #[inline] | |
1737 | default fn count(self) -> usize { | |
1738 | if self.done { | |
1739 | 0 | |
1740 | } else { | |
1741 | self.iter.count() | |
1742 | } | |
1743 | } | |
1744 | ||
1745 | #[inline] | |
1746 | default fn size_hint(&self) -> (usize, Option<usize>) { | |
1747 | if self.done { | |
1748 | (0, Some(0)) | |
1749 | } else { | |
1750 | self.iter.size_hint() | |
1751 | } | |
1752 | } | |
1753 | ||
1754 | #[inline] | |
1755 | default fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where | |
1756 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
1757 | { | |
1758 | if self.done { | |
1759 | Try::from_ok(init) | |
1760 | } else { | |
1761 | let acc = self.iter.try_fold(init, fold)?; | |
1762 | self.done = true; | |
1763 | Try::from_ok(acc) | |
1764 | } | |
1765 | } | |
1766 | ||
1767 | #[inline] | |
1768 | default fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc | |
1769 | where Fold: FnMut(Acc, Self::Item) -> Acc, | |
1770 | { | |
1771 | if self.done { | |
1772 | init | |
1773 | } else { | |
1774 | self.iter.fold(init, fold) | |
1775 | } | |
1776 | } | |
1777 | } | |
1778 | ||
1779 | #[stable(feature = "rust1", since = "1.0.0")] | |
1780 | impl<I> DoubleEndedIterator for Fuse<I> where I: DoubleEndedIterator { | |
1781 | #[inline] | |
1782 | default fn next_back(&mut self) -> Option<<I as Iterator>::Item> { | |
1783 | if self.done { | |
1784 | None | |
1785 | } else { | |
1786 | let next = self.iter.next_back(); | |
1787 | self.done = next.is_none(); | |
1788 | next | |
1789 | } | |
1790 | } | |
1791 | ||
1792 | #[inline] | |
1793 | default fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where | |
1794 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
1795 | { | |
1796 | if self.done { | |
1797 | Try::from_ok(init) | |
1798 | } else { | |
1799 | let acc = self.iter.try_rfold(init, fold)?; | |
1800 | self.done = true; | |
1801 | Try::from_ok(acc) | |
1802 | } | |
1803 | } | |
1804 | ||
1805 | #[inline] | |
1806 | default fn rfold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc | |
1807 | where Fold: FnMut(Acc, Self::Item) -> Acc, | |
1808 | { | |
1809 | if self.done { | |
1810 | init | |
1811 | } else { | |
1812 | self.iter.rfold(init, fold) | |
1813 | } | |
1814 | } | |
1815 | } | |
1816 | ||
1817 | unsafe impl<I> TrustedRandomAccess for Fuse<I> | |
1818 | where I: TrustedRandomAccess, | |
1819 | { | |
1820 | unsafe fn get_unchecked(&mut self, i: usize) -> I::Item { | |
1821 | self.iter.get_unchecked(i) | |
1822 | } | |
1823 | ||
1824 | fn may_have_side_effect() -> bool { | |
1825 | I::may_have_side_effect() | |
1826 | } | |
1827 | } | |
1828 | ||
1829 | #[stable(feature = "fused", since = "1.26.0")] | |
1830 | impl<I> Iterator for Fuse<I> where I: FusedIterator { | |
1831 | #[inline] | |
1832 | fn next(&mut self) -> Option<<I as Iterator>::Item> { | |
1833 | self.iter.next() | |
1834 | } | |
1835 | ||
1836 | #[inline] | |
1837 | fn nth(&mut self, n: usize) -> Option<I::Item> { | |
1838 | self.iter.nth(n) | |
1839 | } | |
1840 | ||
1841 | #[inline] | |
1842 | fn last(self) -> Option<I::Item> { | |
1843 | self.iter.last() | |
1844 | } | |
1845 | ||
1846 | #[inline] | |
1847 | fn count(self) -> usize { | |
1848 | self.iter.count() | |
1849 | } | |
1850 | ||
1851 | #[inline] | |
1852 | fn size_hint(&self) -> (usize, Option<usize>) { | |
1853 | self.iter.size_hint() | |
1854 | } | |
1855 | ||
1856 | #[inline] | |
1857 | fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where | |
1858 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
1859 | { | |
1860 | self.iter.try_fold(init, fold) | |
1861 | } | |
1862 | ||
1863 | #[inline] | |
1864 | fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc | |
1865 | where Fold: FnMut(Acc, Self::Item) -> Acc, | |
1866 | { | |
1867 | self.iter.fold(init, fold) | |
1868 | } | |
1869 | } | |
1870 | ||
1871 | #[stable(feature = "fused", since = "1.26.0")] | |
1872 | impl<I> DoubleEndedIterator for Fuse<I> | |
1873 | where I: DoubleEndedIterator + FusedIterator | |
1874 | { | |
1875 | #[inline] | |
1876 | fn next_back(&mut self) -> Option<<I as Iterator>::Item> { | |
1877 | self.iter.next_back() | |
1878 | } | |
1879 | ||
1880 | #[inline] | |
1881 | fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where | |
1882 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
1883 | { | |
1884 | self.iter.try_rfold(init, fold) | |
1885 | } | |
1886 | ||
1887 | #[inline] | |
1888 | fn rfold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc | |
1889 | where Fold: FnMut(Acc, Self::Item) -> Acc, | |
1890 | { | |
1891 | self.iter.rfold(init, fold) | |
1892 | } | |
1893 | } | |
1894 | ||
1895 | ||
1896 | #[stable(feature = "rust1", since = "1.0.0")] | |
1897 | impl<I> ExactSizeIterator for Fuse<I> where I: ExactSizeIterator { | |
1898 | fn len(&self) -> usize { | |
1899 | self.iter.len() | |
1900 | } | |
1901 | ||
1902 | fn is_empty(&self) -> bool { | |
1903 | self.iter.is_empty() | |
1904 | } | |
1905 | } | |
1906 | ||
1907 | /// An iterator that calls a function with a reference to each element before | |
1908 | /// yielding it. | |
1909 | /// | |
1910 | /// This `struct` is created by the [`inspect`] method on [`Iterator`]. See its | |
1911 | /// documentation for more. | |
1912 | /// | |
1913 | /// [`inspect`]: trait.Iterator.html#method.inspect | |
1914 | /// [`Iterator`]: trait.Iterator.html | |
1915 | #[must_use = "iterators are lazy and do nothing unless consumed"] | |
1916 | #[stable(feature = "rust1", since = "1.0.0")] | |
1917 | #[derive(Clone)] | |
1918 | pub struct Inspect<I, F> { | |
1919 | iter: I, | |
1920 | f: F, | |
1921 | } | |
1922 | impl<I, F> Inspect<I, F> { | |
1923 | pub(super) fn new(iter: I, f: F) -> Inspect<I, F> { | |
1924 | Inspect { iter, f } | |
1925 | } | |
1926 | } | |
1927 | ||
1928 | #[stable(feature = "core_impl_debug", since = "1.9.0")] | |
1929 | impl<I: fmt::Debug, F> fmt::Debug for Inspect<I, F> { | |
1930 | fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { | |
1931 | f.debug_struct("Inspect") | |
1932 | .field("iter", &self.iter) | |
1933 | .finish() | |
1934 | } | |
1935 | } | |
1936 | ||
1937 | impl<I: Iterator, F> Inspect<I, F> where F: FnMut(&I::Item) { | |
1938 | #[inline] | |
1939 | fn do_inspect(&mut self, elt: Option<I::Item>) -> Option<I::Item> { | |
1940 | if let Some(ref a) = elt { | |
1941 | (self.f)(a); | |
1942 | } | |
1943 | ||
1944 | elt | |
1945 | } | |
1946 | } | |
1947 | ||
1948 | #[stable(feature = "rust1", since = "1.0.0")] | |
1949 | impl<I: Iterator, F> Iterator for Inspect<I, F> where F: FnMut(&I::Item) { | |
1950 | type Item = I::Item; | |
1951 | ||
1952 | #[inline] | |
1953 | fn next(&mut self) -> Option<I::Item> { | |
1954 | let next = self.iter.next(); | |
1955 | self.do_inspect(next) | |
1956 | } | |
1957 | ||
1958 | #[inline] | |
1959 | fn size_hint(&self) -> (usize, Option<usize>) { | |
1960 | self.iter.size_hint() | |
1961 | } | |
1962 | ||
1963 | #[inline] | |
1964 | fn try_fold<Acc, Fold, R>(&mut self, init: Acc, mut fold: Fold) -> R where | |
1965 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
1966 | { | |
1967 | let f = &mut self.f; | |
1968 | self.iter.try_fold(init, move |acc, item| { f(&item); fold(acc, item) }) | |
1969 | } | |
1970 | ||
1971 | #[inline] | |
1972 | fn fold<Acc, Fold>(self, init: Acc, mut fold: Fold) -> Acc | |
1973 | where Fold: FnMut(Acc, Self::Item) -> Acc, | |
1974 | { | |
1975 | let mut f = self.f; | |
1976 | self.iter.fold(init, move |acc, item| { f(&item); fold(acc, item) }) | |
1977 | } | |
1978 | } | |
1979 | ||
1980 | #[stable(feature = "rust1", since = "1.0.0")] | |
1981 | impl<I: DoubleEndedIterator, F> DoubleEndedIterator for Inspect<I, F> | |
1982 | where F: FnMut(&I::Item), | |
1983 | { | |
1984 | #[inline] | |
1985 | fn next_back(&mut self) -> Option<I::Item> { | |
1986 | let next = self.iter.next_back(); | |
1987 | self.do_inspect(next) | |
1988 | } | |
1989 | ||
1990 | #[inline] | |
1991 | fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, mut fold: Fold) -> R where | |
1992 | Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc> | |
1993 | { | |
1994 | let f = &mut self.f; | |
1995 | self.iter.try_rfold(init, move |acc, item| { f(&item); fold(acc, item) }) | |
1996 | } | |
1997 | ||
1998 | #[inline] | |
1999 | fn rfold<Acc, Fold>(self, init: Acc, mut fold: Fold) -> Acc | |
2000 | where Fold: FnMut(Acc, Self::Item) -> Acc, | |
2001 | { | |
2002 | let mut f = self.f; | |
2003 | self.iter.rfold(init, move |acc, item| { f(&item); fold(acc, item) }) | |
2004 | } | |
2005 | } | |
2006 | ||
2007 | #[stable(feature = "rust1", since = "1.0.0")] | |
2008 | impl<I: ExactSizeIterator, F> ExactSizeIterator for Inspect<I, F> | |
2009 | where F: FnMut(&I::Item) | |
2010 | { | |
2011 | fn len(&self) -> usize { | |
2012 | self.iter.len() | |
2013 | } | |
2014 | ||
2015 | fn is_empty(&self) -> bool { | |
2016 | self.iter.is_empty() | |
2017 | } | |
2018 | } | |
2019 | ||
2020 | #[stable(feature = "fused", since = "1.26.0")] | |
2021 | impl<I: FusedIterator, F> FusedIterator for Inspect<I, F> | |
2022 | where F: FnMut(&I::Item) {} |