core/ops/range.rs
1use crate::fmt;
2use crate::hash::Hash;
3use crate::marker::Destruct;
4/// An unbounded range (`..`).
5///
6/// `RangeFull` is primarily used as a [slicing index], its shorthand is `..`.
7/// It cannot serve as an [`Iterator`] because it doesn't have a starting point.
8///
9/// # Examples
10///
11/// The `..` syntax is a `RangeFull`:
12///
13/// ```
14/// assert_eq!(.., std::ops::RangeFull);
15/// ```
16///
17/// It does not have an [`IntoIterator`] implementation, so you can't use it in
18/// a `for` loop directly. This won't compile:
19///
20/// ```compile_fail,E0277
21/// for i in .. {
22/// // ...
23/// }
24/// ```
25///
26/// Used as a [slicing index], `RangeFull` produces the full array as a slice.
27///
28/// ```
29/// let arr = [0, 1, 2, 3, 4];
30/// assert_eq!(arr[ .. ], [0, 1, 2, 3, 4]); // This is the `RangeFull`
31/// assert_eq!(arr[ .. 3], [0, 1, 2 ]);
32/// assert_eq!(arr[ ..=3], [0, 1, 2, 3 ]);
33/// assert_eq!(arr[1.. ], [ 1, 2, 3, 4]);
34/// assert_eq!(arr[1.. 3], [ 1, 2 ]);
35/// assert_eq!(arr[1..=3], [ 1, 2, 3 ]);
36/// ```
37///
38/// [slicing index]: crate::slice::SliceIndex
39#[lang = "RangeFull"]
40#[doc(alias = "..")]
41#[derive(Copy, Hash)]
42#[derive_const(Clone, Default, PartialEq, Eq)]
43#[stable(feature = "rust1", since = "1.0.0")]
44#[ferrocene::prevalidated]
45pub struct RangeFull;
46
47#[stable(feature = "rust1", since = "1.0.0")]
48impl fmt::Debug for RangeFull {
49 #[ferrocene::prevalidated]
50 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
51 write!(fmt, "..")
52 }
53}
54
55/// A (half-open) range bounded inclusively below and exclusively above
56/// (`start..end`).
57///
58/// The range `start..end` contains all values with `start <= x < end`.
59/// It is empty if `start >= end`.
60///
61/// # Examples
62///
63/// The `start..end` syntax is a `Range`:
64///
65/// ```
66/// assert_eq!((3..5), std::ops::Range { start: 3, end: 5 });
67/// assert_eq!(3 + 4 + 5, (3..6).sum());
68/// ```
69///
70/// ```
71/// let arr = [0, 1, 2, 3, 4];
72/// assert_eq!(arr[ .. ], [0, 1, 2, 3, 4]);
73/// assert_eq!(arr[ .. 3], [0, 1, 2 ]);
74/// assert_eq!(arr[ ..=3], [0, 1, 2, 3 ]);
75/// assert_eq!(arr[1.. ], [ 1, 2, 3, 4]);
76/// assert_eq!(arr[1.. 3], [ 1, 2 ]); // This is a `Range`
77/// assert_eq!(arr[1..=3], [ 1, 2, 3 ]);
78/// ```
79#[lang = "Range"]
80#[doc(alias = "..")]
81#[derive(Eq, Hash)]
82#[derive_const(Clone, Default, PartialEq)] // not Copy -- see #27186
83#[stable(feature = "rust1", since = "1.0.0")]
84#[ferrocene::prevalidated]
85pub struct Range<Idx> {
86 /// The lower bound of the range (inclusive).
87 #[stable(feature = "rust1", since = "1.0.0")]
88 pub start: Idx,
89 /// The upper bound of the range (exclusive).
90 #[stable(feature = "rust1", since = "1.0.0")]
91 pub end: Idx,
92}
93
94#[stable(feature = "rust1", since = "1.0.0")]
95impl<Idx: fmt::Debug> fmt::Debug for Range<Idx> {
96 #[ferrocene::prevalidated]
97 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
98 self.start.fmt(fmt)?;
99 write!(fmt, "..")?;
100 self.end.fmt(fmt)?;
101 Ok(())
102 }
103}
104
105impl<Idx: PartialOrd<Idx>> Range<Idx> {
106 /// Returns `true` if `item` is contained in the range.
107 ///
108 /// # Examples
109 ///
110 /// ```
111 /// assert!(!(3..5).contains(&2));
112 /// assert!( (3..5).contains(&3));
113 /// assert!( (3..5).contains(&4));
114 /// assert!(!(3..5).contains(&5));
115 ///
116 /// assert!(!(3..3).contains(&3));
117 /// assert!(!(3..2).contains(&3));
118 ///
119 /// assert!( (0.0..1.0).contains(&0.5));
120 /// assert!(!(0.0..1.0).contains(&f32::NAN));
121 /// assert!(!(0.0..f32::NAN).contains(&0.5));
122 /// assert!(!(f32::NAN..1.0).contains(&0.5));
123 /// ```
124 #[inline]
125 #[stable(feature = "range_contains", since = "1.35.0")]
126 #[rustc_const_unstable(feature = "const_range", issue = "none")]
127 #[ferrocene::prevalidated]
128 pub const fn contains<U>(&self, item: &U) -> bool
129 where
130 Idx: [const] PartialOrd<U>,
131 U: ?Sized + [const] PartialOrd<Idx>,
132 {
133 <Self as RangeBounds<Idx>>::contains(self, item)
134 }
135
136 /// Returns `true` if the range contains no items.
137 ///
138 /// # Examples
139 ///
140 /// ```
141 /// assert!(!(3..5).is_empty());
142 /// assert!( (3..3).is_empty());
143 /// assert!( (3..2).is_empty());
144 /// ```
145 ///
146 /// The range is empty if either side is incomparable:
147 ///
148 /// ```
149 /// assert!(!(3.0..5.0).is_empty());
150 /// assert!( (3.0..f32::NAN).is_empty());
151 /// assert!( (f32::NAN..5.0).is_empty());
152 /// ```
153 #[inline]
154 #[stable(feature = "range_is_empty", since = "1.47.0")]
155 #[rustc_const_unstable(feature = "const_range", issue = "none")]
156 pub const fn is_empty(&self) -> bool
157 where
158 Idx: [const] PartialOrd<Idx>,
159 {
160 !(self.start < self.end)
161 }
162}
163
164/// A range only bounded inclusively below (`start..`).
165///
166/// The `RangeFrom` `start..` contains all values with `x >= start`.
167///
168/// *Note*: Overflow in the [`Iterator`] implementation (when the contained
169/// data type reaches its numerical limit) is allowed to panic, wrap, or
170/// saturate. This behavior is defined by the implementation of the [`Step`]
171/// trait. For primitive integers, this follows the normal rules, and respects
172/// the overflow checks profile (panic in debug, wrap in release). Note also
173/// that overflow happens earlier than you might assume: the overflow happens
174/// in the call to `next` that yields the maximum value, as the range must be
175/// set to a state to yield the next value.
176///
177/// [`Step`]: crate::iter::Step
178///
179/// # Examples
180///
181/// The `start..` syntax is a `RangeFrom`:
182///
183/// ```
184/// assert_eq!((2..), std::ops::RangeFrom { start: 2 });
185/// assert_eq!(2 + 3 + 4, (2..).take(3).sum());
186/// ```
187///
188/// ```
189/// let arr = [0, 1, 2, 3, 4];
190/// assert_eq!(arr[ .. ], [0, 1, 2, 3, 4]);
191/// assert_eq!(arr[ .. 3], [0, 1, 2 ]);
192/// assert_eq!(arr[ ..=3], [0, 1, 2, 3 ]);
193/// assert_eq!(arr[1.. ], [ 1, 2, 3, 4]); // This is a `RangeFrom`
194/// assert_eq!(arr[1.. 3], [ 1, 2 ]);
195/// assert_eq!(arr[1..=3], [ 1, 2, 3 ]);
196/// ```
197#[lang = "RangeFrom"]
198#[doc(alias = "..")]
199#[derive(Eq, Hash)]
200#[derive_const(Clone, PartialEq)] // not Copy -- see #27186
201#[stable(feature = "rust1", since = "1.0.0")]
202#[ferrocene::prevalidated]
203pub struct RangeFrom<Idx> {
204 /// The lower bound of the range (inclusive).
205 #[stable(feature = "rust1", since = "1.0.0")]
206 pub start: Idx,
207}
208
209#[stable(feature = "rust1", since = "1.0.0")]
210impl<Idx: fmt::Debug> fmt::Debug for RangeFrom<Idx> {
211 #[ferrocene::prevalidated]
212 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
213 self.start.fmt(fmt)?;
214 write!(fmt, "..")?;
215 Ok(())
216 }
217}
218
219impl<Idx: PartialOrd<Idx>> RangeFrom<Idx> {
220 /// Returns `true` if `item` is contained in the range.
221 ///
222 /// # Examples
223 ///
224 /// ```
225 /// assert!(!(3..).contains(&2));
226 /// assert!( (3..).contains(&3));
227 /// assert!( (3..).contains(&1_000_000_000));
228 ///
229 /// assert!( (0.0..).contains(&0.5));
230 /// assert!(!(0.0..).contains(&f32::NAN));
231 /// assert!(!(f32::NAN..).contains(&0.5));
232 /// ```
233 #[inline]
234 #[stable(feature = "range_contains", since = "1.35.0")]
235 #[rustc_const_unstable(feature = "const_range", issue = "none")]
236 pub const fn contains<U>(&self, item: &U) -> bool
237 where
238 Idx: [const] PartialOrd<U>,
239 U: ?Sized + [const] PartialOrd<Idx>,
240 {
241 <Self as RangeBounds<Idx>>::contains(self, item)
242 }
243}
244
245/// A range only bounded exclusively above (`..end`).
246///
247/// The `RangeTo` `..end` contains all values with `x < end`.
248/// It cannot serve as an [`Iterator`] because it doesn't have a starting point.
249///
250/// # Examples
251///
252/// The `..end` syntax is a `RangeTo`:
253///
254/// ```
255/// assert_eq!((..5), std::ops::RangeTo { end: 5 });
256/// ```
257///
258/// It does not have an [`IntoIterator`] implementation, so you can't use it in
259/// a `for` loop directly. This won't compile:
260///
261/// ```compile_fail,E0277
262/// // error[E0277]: the trait bound `std::ops::RangeTo<{integer}>:
263/// // std::iter::Iterator` is not satisfied
264/// for i in ..5 {
265/// // ...
266/// }
267/// ```
268///
269/// When used as a [slicing index], `RangeTo` produces a slice of all array
270/// elements before the index indicated by `end`.
271///
272/// ```
273/// let arr = [0, 1, 2, 3, 4];
274/// assert_eq!(arr[ .. ], [0, 1, 2, 3, 4]);
275/// assert_eq!(arr[ .. 3], [0, 1, 2 ]); // This is a `RangeTo`
276/// assert_eq!(arr[ ..=3], [0, 1, 2, 3 ]);
277/// assert_eq!(arr[1.. ], [ 1, 2, 3, 4]);
278/// assert_eq!(arr[1.. 3], [ 1, 2 ]);
279/// assert_eq!(arr[1..=3], [ 1, 2, 3 ]);
280/// ```
281///
282/// [slicing index]: crate::slice::SliceIndex
283#[lang = "RangeTo"]
284#[doc(alias = "..")]
285#[derive(Copy, Eq, Hash)]
286#[derive_const(Clone, PartialEq)]
287#[stable(feature = "rust1", since = "1.0.0")]
288#[ferrocene::prevalidated]
289pub struct RangeTo<Idx> {
290 /// The upper bound of the range (exclusive).
291 #[stable(feature = "rust1", since = "1.0.0")]
292 pub end: Idx,
293}
294
295#[stable(feature = "rust1", since = "1.0.0")]
296impl<Idx: fmt::Debug> fmt::Debug for RangeTo<Idx> {
297 #[ferrocene::prevalidated]
298 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
299 write!(fmt, "..")?;
300 self.end.fmt(fmt)?;
301 Ok(())
302 }
303}
304
305impl<Idx: PartialOrd<Idx>> RangeTo<Idx> {
306 /// Returns `true` if `item` is contained in the range.
307 ///
308 /// # Examples
309 ///
310 /// ```
311 /// assert!( (..5).contains(&-1_000_000_000));
312 /// assert!( (..5).contains(&4));
313 /// assert!(!(..5).contains(&5));
314 ///
315 /// assert!( (..1.0).contains(&0.5));
316 /// assert!(!(..1.0).contains(&f32::NAN));
317 /// assert!(!(..f32::NAN).contains(&0.5));
318 /// ```
319 #[inline]
320 #[stable(feature = "range_contains", since = "1.35.0")]
321 #[rustc_const_unstable(feature = "const_range", issue = "none")]
322 pub const fn contains<U>(&self, item: &U) -> bool
323 where
324 Idx: [const] PartialOrd<U>,
325 U: ?Sized + [const] PartialOrd<Idx>,
326 {
327 <Self as RangeBounds<Idx>>::contains(self, item)
328 }
329}
330
331/// A range bounded inclusively below and above (`start..=end`).
332///
333/// The `RangeInclusive` `start..=end` contains all values with `x >= start`
334/// and `x <= end`. It is empty unless `start <= end`.
335///
336/// This iterator is [fused], but the specific values of `start` and `end` after
337/// iteration has finished are **unspecified** other than that [`.is_empty()`]
338/// will return `true` once no more values will be produced.
339///
340/// [fused]: crate::iter::FusedIterator
341/// [`.is_empty()`]: RangeInclusive::is_empty
342///
343/// # Examples
344///
345/// The `start..=end` syntax is a `RangeInclusive`:
346///
347/// ```
348/// assert_eq!((3..=5), std::ops::RangeInclusive::new(3, 5));
349/// assert_eq!(3 + 4 + 5, (3..=5).sum());
350/// ```
351///
352/// ```
353/// let arr = [0, 1, 2, 3, 4];
354/// assert_eq!(arr[ .. ], [0, 1, 2, 3, 4]);
355/// assert_eq!(arr[ .. 3], [0, 1, 2 ]);
356/// assert_eq!(arr[ ..=3], [0, 1, 2, 3 ]);
357/// assert_eq!(arr[1.. ], [ 1, 2, 3, 4]);
358/// assert_eq!(arr[1.. 3], [ 1, 2 ]);
359/// assert_eq!(arr[1..=3], [ 1, 2, 3 ]); // This is a `RangeInclusive`
360/// ```
361#[lang = "RangeInclusive"]
362#[doc(alias = "..=")]
363#[derive(Clone, Hash)]
364#[derive_const(Eq, PartialEq)] // not Copy -- see #27186
365#[stable(feature = "inclusive_range", since = "1.26.0")]
366#[ferrocene::prevalidated]
367pub struct RangeInclusive<Idx> {
368 // Note that the fields here are not public to allow changing the
369 // representation in the future; in particular, while we could plausibly
370 // expose start/end, modifying them without changing (future/current)
371 // private fields may lead to incorrect behavior, so we don't want to
372 // support that mode.
373 pub(crate) start: Idx,
374 pub(crate) end: Idx,
375
376 // This field represents an overflow flag for either bound (start or end):
377 // - `false` upon construction
378 // - `false` when iteration has yielded an element and
379 // neither bound has overflowed the valid range of `Idx`
380 // - `true` when iteration has caused either bound to
381 // overflow the valid range of `Idx`
382 //
383 // When this is true, `start` or `end` may be left in an unspecified state,
384 // often wrapping (modular arithmetic) around at the boundary of `Idx`.
385 //
386 // This is required to support PartialEq and Hash without a PartialOrd bound or specialization.
387 pub(crate) exhausted: bool,
388}
389
390impl<Idx> RangeInclusive<Idx> {
391 /// Creates a new inclusive range. Equivalent to writing `start..=end`.
392 ///
393 /// # Examples
394 ///
395 /// ```
396 /// use std::ops::RangeInclusive;
397 ///
398 /// assert_eq!(3..=5, RangeInclusive::new(3, 5));
399 /// ```
400 #[lang = "range_inclusive_new"]
401 #[stable(feature = "inclusive_range_methods", since = "1.27.0")]
402 #[inline]
403 #[rustc_promotable]
404 #[rustc_const_stable(feature = "const_range_new", since = "1.32.0")]
405 #[ferrocene::prevalidated]
406 pub const fn new(start: Idx, end: Idx) -> Self {
407 Self { start, end, exhausted: false }
408 }
409
410 /// Returns the lower bound of the range (inclusive).
411 ///
412 /// When using an inclusive range for iteration, the values of `start()` and
413 /// [`end()`] are unspecified after the iteration ended. To determine
414 /// whether the inclusive range is empty, use the [`is_empty()`] method
415 /// instead of comparing `start() > end()`.
416 ///
417 /// Note: the value returned by this method is unspecified after the range
418 /// has been iterated to exhaustion.
419 ///
420 /// [`end()`]: RangeInclusive::end
421 /// [`is_empty()`]: RangeInclusive::is_empty
422 ///
423 /// # Examples
424 ///
425 /// ```
426 /// assert_eq!((3..=5).start(), &3);
427 /// ```
428 #[stable(feature = "inclusive_range_methods", since = "1.27.0")]
429 #[rustc_const_stable(feature = "const_inclusive_range_methods", since = "1.32.0")]
430 #[inline]
431 #[ferrocene::prevalidated]
432 pub const fn start(&self) -> &Idx {
433 &self.start
434 }
435
436 /// Returns the upper bound of the range (inclusive).
437 ///
438 /// When using an inclusive range for iteration, the values of [`start()`]
439 /// and `end()` are unspecified after the iteration ended. To determine
440 /// whether the inclusive range is empty, use the [`is_empty()`] method
441 /// instead of comparing `start() > end()`.
442 ///
443 /// Note: the value returned by this method is unspecified after the range
444 /// has been iterated to exhaustion.
445 ///
446 /// [`start()`]: RangeInclusive::start
447 /// [`is_empty()`]: RangeInclusive::is_empty
448 ///
449 /// # Examples
450 ///
451 /// ```
452 /// assert_eq!((3..=5).end(), &5);
453 /// ```
454 #[stable(feature = "inclusive_range_methods", since = "1.27.0")]
455 #[rustc_const_stable(feature = "const_inclusive_range_methods", since = "1.32.0")]
456 #[inline]
457 #[ferrocene::prevalidated]
458 pub const fn end(&self) -> &Idx {
459 &self.end
460 }
461
462 /// Destructures the `RangeInclusive` into (lower bound, upper (inclusive) bound).
463 ///
464 /// Note: the value returned by this method is unspecified after the range
465 /// has been iterated to exhaustion.
466 ///
467 /// # Examples
468 ///
469 /// ```
470 /// assert_eq!((3..=5).into_inner(), (3, 5));
471 /// ```
472 #[stable(feature = "inclusive_range_methods", since = "1.27.0")]
473 #[inline]
474 #[rustc_const_unstable(feature = "const_range_bounds", issue = "108082")]
475 #[ferrocene::prevalidated]
476 pub const fn into_inner(self) -> (Idx, Idx) {
477 (self.start, self.end)
478 }
479}
480
481impl RangeInclusive<usize> {
482 /// Converts to an exclusive `Range` for `SliceIndex` implementations.
483 /// The caller is responsible for dealing with `end == usize::MAX`.
484 #[inline]
485 #[ferrocene::prevalidated]
486 pub(crate) const fn into_slice_range(self) -> Range<usize> {
487 // Typically users should not be indexing with exhausted instances,
488 // but this heuristic should apply to most cases. This doesn't
489 // handle reverse iteration well (`next_back` and `nth_back` can
490 // cause `end` to wrap around to values at or near `usize::MAX`),
491 // but using an exhausted `RangeInclusive` after reverse iteration
492 // is an exceedingly rare case.
493
494 // If we're not exhausted, we want to simply slice `start..end + 1`.
495 // If we are exhausted, then slicing with `end + 1..end + 1` gives us an
496 // empty range that is still subject to bounds-checks for that endpoint.
497 let exclusive_end = self.end + 1;
498 let start = if self.exhausted { exclusive_end } else { self.start };
499 start..exclusive_end
500 }
501}
502
503#[stable(feature = "inclusive_range", since = "1.26.0")]
504impl<Idx: fmt::Debug> fmt::Debug for RangeInclusive<Idx> {
505 #[ferrocene::prevalidated]
506 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
507 self.start.fmt(fmt)?;
508 write!(fmt, "..=")?;
509 self.end.fmt(fmt)?;
510 if self.exhausted {
511 write!(fmt, " (exhausted)")?;
512 }
513 Ok(())
514 }
515}
516
517impl<Idx: PartialOrd<Idx>> RangeInclusive<Idx> {
518 /// Returns `true` if `item` is contained in the range.
519 ///
520 /// # Examples
521 ///
522 /// ```
523 /// assert!(!(3..=5).contains(&2));
524 /// assert!( (3..=5).contains(&3));
525 /// assert!( (3..=5).contains(&4));
526 /// assert!( (3..=5).contains(&5));
527 /// assert!(!(3..=5).contains(&6));
528 ///
529 /// assert!( (3..=3).contains(&3));
530 /// assert!(!(3..=2).contains(&3));
531 ///
532 /// assert!( (0.0..=1.0).contains(&1.0));
533 /// assert!(!(0.0..=1.0).contains(&f32::NAN));
534 /// assert!(!(0.0..=f32::NAN).contains(&0.0));
535 /// assert!(!(f32::NAN..=1.0).contains(&1.0));
536 /// ```
537 ///
538 /// This method always returns `false` after iteration has finished:
539 ///
540 /// ```
541 /// let mut r = 3..=5;
542 /// assert!(r.contains(&3) && r.contains(&5));
543 /// for _ in r.by_ref() {}
544 /// // Precise field values are unspecified here
545 /// assert!(!r.contains(&3) && !r.contains(&5));
546 /// ```
547 #[inline]
548 #[stable(feature = "range_contains", since = "1.35.0")]
549 #[rustc_const_unstable(feature = "const_range", issue = "none")]
550 #[ferrocene::prevalidated]
551 pub const fn contains<U>(&self, item: &U) -> bool
552 where
553 Idx: [const] PartialOrd<U>,
554 U: ?Sized + [const] PartialOrd<Idx>,
555 {
556 <Self as RangeBounds<Idx>>::contains(self, item)
557 }
558
559 /// Returns `true` if the range contains no items.
560 ///
561 /// # Examples
562 ///
563 /// ```
564 /// assert!(!(3..=5).is_empty());
565 /// assert!(!(3..=3).is_empty());
566 /// assert!( (3..=2).is_empty());
567 /// ```
568 ///
569 /// The range is empty if either side is incomparable:
570 ///
571 /// ```
572 /// assert!(!(3.0..=5.0).is_empty());
573 /// assert!( (3.0..=f32::NAN).is_empty());
574 /// assert!( (f32::NAN..=5.0).is_empty());
575 /// ```
576 ///
577 /// This method returns `true` after iteration has finished:
578 ///
579 /// ```
580 /// let mut r = 3..=5;
581 /// for _ in r.by_ref() {}
582 /// // Precise field values are unspecified here
583 /// assert!(r.is_empty());
584 /// ```
585 #[stable(feature = "range_is_empty", since = "1.47.0")]
586 #[inline]
587 #[rustc_const_unstable(feature = "const_range", issue = "none")]
588 #[ferrocene::prevalidated]
589 pub const fn is_empty(&self) -> bool
590 where
591 Idx: [const] PartialOrd,
592 {
593 self.exhausted || !(self.start <= self.end)
594 }
595}
596
597/// A range only bounded inclusively above (`..=end`).
598///
599/// The `RangeToInclusive` `..=end` contains all values with `x <= end`.
600/// It cannot serve as an [`Iterator`] because it doesn't have a starting point.
601///
602/// # Examples
603///
604/// The `..=end` syntax is a `RangeToInclusive`:
605///
606/// ```
607/// assert_eq!((..=5), std::ops::RangeToInclusive{ end: 5 });
608/// ```
609///
610/// It does not have an [`IntoIterator`] implementation, so you can't use it in a
611/// `for` loop directly. This won't compile:
612///
613/// ```compile_fail,E0277
614/// // error[E0277]: the trait bound `std::ops::RangeToInclusive<{integer}>:
615/// // std::iter::Iterator` is not satisfied
616/// for i in ..=5 {
617/// // ...
618/// }
619/// ```
620///
621/// When used as a [slicing index], `RangeToInclusive` produces a slice of all
622/// array elements up to and including the index indicated by `end`.
623///
624/// ```
625/// let arr = [0, 1, 2, 3, 4];
626/// assert_eq!(arr[ .. ], [0, 1, 2, 3, 4]);
627/// assert_eq!(arr[ .. 3], [0, 1, 2 ]);
628/// assert_eq!(arr[ ..=3], [0, 1, 2, 3 ]); // This is a `RangeToInclusive`
629/// assert_eq!(arr[1.. ], [ 1, 2, 3, 4]);
630/// assert_eq!(arr[1.. 3], [ 1, 2 ]);
631/// assert_eq!(arr[1..=3], [ 1, 2, 3 ]);
632/// ```
633///
634/// [slicing index]: crate::slice::SliceIndex
635#[lang = "RangeToInclusive"]
636#[doc(alias = "..=")]
637#[derive(Copy, Hash)]
638#[derive(Clone, PartialEq, Eq)]
639#[stable(feature = "inclusive_range", since = "1.26.0")]
640#[ferrocene::prevalidated]
641pub struct RangeToInclusive<Idx> {
642 /// The upper bound of the range (inclusive)
643 #[stable(feature = "inclusive_range", since = "1.26.0")]
644 pub end: Idx,
645}
646
647#[stable(feature = "inclusive_range", since = "1.26.0")]
648impl<Idx: fmt::Debug> fmt::Debug for RangeToInclusive<Idx> {
649 #[ferrocene::prevalidated]
650 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
651 write!(fmt, "..=")?;
652 self.end.fmt(fmt)?;
653 Ok(())
654 }
655}
656
657impl<Idx: PartialOrd<Idx>> RangeToInclusive<Idx> {
658 /// Returns `true` if `item` is contained in the range.
659 ///
660 /// # Examples
661 ///
662 /// ```
663 /// assert!( (..=5).contains(&-1_000_000_000));
664 /// assert!( (..=5).contains(&5));
665 /// assert!(!(..=5).contains(&6));
666 ///
667 /// assert!( (..=1.0).contains(&1.0));
668 /// assert!(!(..=1.0).contains(&f32::NAN));
669 /// assert!(!(..=f32::NAN).contains(&0.5));
670 /// ```
671 #[inline]
672 #[stable(feature = "range_contains", since = "1.35.0")]
673 #[rustc_const_unstable(feature = "const_range", issue = "none")]
674 pub const fn contains<U>(&self, item: &U) -> bool
675 where
676 Idx: [const] PartialOrd<U>,
677 U: ?Sized + [const] PartialOrd<Idx>,
678 {
679 <Self as RangeBounds<Idx>>::contains(self, item)
680 }
681}
682
683// RangeToInclusive<Idx> cannot impl From<RangeTo<Idx>>
684// because underflow would be possible with (..0).into()
685
686/// An endpoint of a range of keys.
687///
688/// # Examples
689///
690/// `Bound`s are range endpoints:
691///
692/// ```
693/// use std::ops::Bound::*;
694/// use std::ops::RangeBounds;
695///
696/// assert_eq!((..100).start_bound(), Unbounded);
697/// assert_eq!((1..12).start_bound(), Included(&1));
698/// assert_eq!((1..12).end_bound(), Excluded(&12));
699/// ```
700///
701/// Using a tuple of `Bound`s as an argument to [`BTreeMap::range`].
702/// Note that in most cases, it's better to use range syntax (`1..5`) instead.
703///
704/// ```
705/// use std::collections::BTreeMap;
706/// use std::ops::Bound::{Excluded, Included, Unbounded};
707///
708/// let mut map = BTreeMap::new();
709/// map.insert(3, "a");
710/// map.insert(5, "b");
711/// map.insert(8, "c");
712///
713/// for (key, value) in map.range((Excluded(3), Included(8))) {
714/// println!("{key}: {value}");
715/// }
716///
717/// assert_eq!(Some((&3, &"a")), map.range((Unbounded, Included(5))).next());
718/// ```
719///
720/// [`BTreeMap::range`]: ../../std/collections/btree_map/struct.BTreeMap.html#method.range
721#[stable(feature = "collections_bound", since = "1.17.0")]
722#[derive(Copy, Debug, Hash)]
723#[derive_const(Clone, Eq, PartialEq)]
724#[ferrocene::prevalidated]
725pub enum Bound<T> {
726 /// An inclusive bound.
727 #[stable(feature = "collections_bound", since = "1.17.0")]
728 Included(#[stable(feature = "collections_bound", since = "1.17.0")] T),
729 /// An exclusive bound.
730 #[stable(feature = "collections_bound", since = "1.17.0")]
731 Excluded(#[stable(feature = "collections_bound", since = "1.17.0")] T),
732 /// An infinite endpoint. Indicates that there is no bound in this direction.
733 #[stable(feature = "collections_bound", since = "1.17.0")]
734 Unbounded,
735}
736
737impl<T> Bound<T> {
738 /// Converts from `&Bound<T>` to `Bound<&T>`.
739 #[inline]
740 #[stable(feature = "bound_as_ref_shared", since = "1.65.0")]
741 #[rustc_const_unstable(feature = "const_range", issue = "none")]
742 #[ferrocene::prevalidated]
743 pub const fn as_ref(&self) -> Bound<&T> {
744 match *self {
745 Included(ref x) => Included(x),
746 Excluded(ref x) => Excluded(x),
747 Unbounded => Unbounded,
748 }
749 }
750
751 /// Converts from `&mut Bound<T>` to `Bound<&mut T>`.
752 #[inline]
753 #[unstable(feature = "bound_as_ref", issue = "80996")]
754 #[ferrocene::prevalidated]
755 pub const fn as_mut(&mut self) -> Bound<&mut T> {
756 match *self {
757 Included(ref mut x) => Included(x),
758 Excluded(ref mut x) => Excluded(x),
759 Unbounded => Unbounded,
760 }
761 }
762
763 /// Maps a `Bound<T>` to a `Bound<U>` by applying a function to the contained value (including
764 /// both `Included` and `Excluded`), returning a `Bound` of the same kind.
765 ///
766 /// # Examples
767 ///
768 /// ```
769 /// use std::ops::Bound::*;
770 ///
771 /// let bound_string = Included("Hello, World!");
772 ///
773 /// assert_eq!(bound_string.map(|s| s.len()), Included(13));
774 /// ```
775 ///
776 /// ```
777 /// use std::ops::Bound;
778 /// use Bound::*;
779 ///
780 /// let unbounded_string: Bound<String> = Unbounded;
781 ///
782 /// assert_eq!(unbounded_string.map(|s| s.len()), Unbounded);
783 /// ```
784 #[inline]
785 #[stable(feature = "bound_map", since = "1.77.0")]
786 #[ferrocene::prevalidated]
787 pub fn map<U, F: FnOnce(T) -> U>(self, f: F) -> Bound<U> {
788 match self {
789 Unbounded => Unbounded,
790 Included(x) => Included(f(x)),
791 Excluded(x) => Excluded(f(x)),
792 }
793 }
794}
795
796impl<T: Copy> Bound<&T> {
797 /// Map a `Bound<&T>` to a `Bound<T>` by copying the contents of the bound.
798 ///
799 /// # Examples
800 ///
801 /// ```
802 /// #![feature(bound_copied)]
803 ///
804 /// use std::ops::Bound::*;
805 /// use std::ops::RangeBounds;
806 ///
807 /// assert_eq!((1..12).start_bound(), Included(&1));
808 /// assert_eq!((1..12).start_bound().copied(), Included(1));
809 /// ```
810 #[unstable(feature = "bound_copied", issue = "145966")]
811 #[must_use]
812 #[ferrocene::prevalidated]
813 pub const fn copied(self) -> Bound<T> {
814 match self {
815 Bound::Unbounded => Bound::Unbounded,
816 Bound::Included(x) => Bound::Included(*x),
817 Bound::Excluded(x) => Bound::Excluded(*x),
818 }
819 }
820}
821
822impl<T: Clone> Bound<&T> {
823 /// Map a `Bound<&T>` to a `Bound<T>` by cloning the contents of the bound.
824 ///
825 /// # Examples
826 ///
827 /// ```
828 /// use std::ops::Bound::*;
829 /// use std::ops::RangeBounds;
830 ///
831 /// let a1 = String::from("a");
832 /// let (a2, a3, a4) = (a1.clone(), a1.clone(), a1.clone());
833 ///
834 /// assert_eq!(Included(&a1), (a2..).start_bound());
835 /// assert_eq!(Included(a3), (a4..).start_bound().cloned());
836 /// ```
837 #[must_use = "`self` will be dropped if the result is not used"]
838 #[stable(feature = "bound_cloned", since = "1.55.0")]
839 #[rustc_const_unstable(feature = "const_range", issue = "none")]
840 #[ferrocene::prevalidated]
841 pub const fn cloned(self) -> Bound<T>
842 where
843 T: [const] Clone,
844 {
845 match self {
846 Bound::Unbounded => Bound::Unbounded,
847 Bound::Included(x) => Bound::Included(x.clone()),
848 Bound::Excluded(x) => Bound::Excluded(x.clone()),
849 }
850 }
851}
852
853/// `RangeBounds` is implemented by Rust's built-in range types, produced
854/// by range syntax like `..`, `a..`, `..b`, `..=c`, `d..e`, or `f..=g`.
855#[stable(feature = "collections_range", since = "1.28.0")]
856#[rustc_diagnostic_item = "RangeBounds"]
857#[rustc_const_unstable(feature = "const_range", issue = "none")]
858pub const trait RangeBounds<T: ?Sized> {
859 /// Start index bound.
860 ///
861 /// Returns the start value as a `Bound`.
862 ///
863 /// # Examples
864 ///
865 /// ```
866 /// use std::ops::Bound::*;
867 /// use std::ops::RangeBounds;
868 ///
869 /// assert_eq!((..10).start_bound(), Unbounded);
870 /// assert_eq!((3..10).start_bound(), Included(&3));
871 /// ```
872 #[stable(feature = "collections_range", since = "1.28.0")]
873 fn start_bound(&self) -> Bound<&T>;
874
875 /// End index bound.
876 ///
877 /// Returns the end value as a `Bound`.
878 ///
879 /// # Examples
880 ///
881 /// ```
882 /// use std::ops::Bound::*;
883 /// use std::ops::RangeBounds;
884 ///
885 /// assert_eq!((3..).end_bound(), Unbounded);
886 /// assert_eq!((3..10).end_bound(), Excluded(&10));
887 /// ```
888 #[stable(feature = "collections_range", since = "1.28.0")]
889 fn end_bound(&self) -> Bound<&T>;
890
891 /// Returns `true` if `item` is contained in the range.
892 ///
893 /// # Examples
894 ///
895 /// ```
896 /// assert!( (3..5).contains(&4));
897 /// assert!(!(3..5).contains(&2));
898 ///
899 /// assert!( (0.0..1.0).contains(&0.5));
900 /// assert!(!(0.0..1.0).contains(&f32::NAN));
901 /// assert!(!(0.0..f32::NAN).contains(&0.5));
902 /// assert!(!(f32::NAN..1.0).contains(&0.5));
903 /// ```
904 #[inline]
905 #[stable(feature = "range_contains", since = "1.35.0")]
906 #[ferrocene::prevalidated]
907 fn contains<U>(&self, item: &U) -> bool
908 where
909 T: [const] PartialOrd<U>,
910 U: ?Sized + [const] PartialOrd<T>,
911 {
912 (match self.start_bound() {
913 Included(start) => start <= item,
914 Excluded(start) => start < item,
915 Unbounded => true,
916 }) && (match self.end_bound() {
917 Included(end) => item <= end,
918 Excluded(end) => item < end,
919 Unbounded => true,
920 })
921 }
922
923 /// Returns `true` if the range contains no items.
924 /// One-sided ranges (`RangeFrom`, etc) always return `false`.
925 ///
926 /// # Examples
927 ///
928 /// ```
929 /// #![feature(range_bounds_is_empty)]
930 /// use std::ops::RangeBounds;
931 ///
932 /// assert!(!(3..).is_empty());
933 /// assert!(!(..2).is_empty());
934 /// assert!(!RangeBounds::is_empty(&(3..5)));
935 /// assert!( RangeBounds::is_empty(&(3..3)));
936 /// assert!( RangeBounds::is_empty(&(3..2)));
937 /// ```
938 ///
939 /// The range is empty if either side is incomparable:
940 ///
941 /// ```
942 /// #![feature(range_bounds_is_empty)]
943 /// use std::ops::RangeBounds;
944 ///
945 /// assert!(!RangeBounds::is_empty(&(3.0..5.0)));
946 /// assert!( RangeBounds::is_empty(&(3.0..f32::NAN)));
947 /// assert!( RangeBounds::is_empty(&(f32::NAN..5.0)));
948 /// ```
949 ///
950 /// But never empty if either side is unbounded:
951 ///
952 /// ```
953 /// #![feature(range_bounds_is_empty)]
954 /// use std::ops::RangeBounds;
955 ///
956 /// assert!(!(..0).is_empty());
957 /// assert!(!(i32::MAX..).is_empty());
958 /// assert!(!RangeBounds::<u8>::is_empty(&(..)));
959 /// ```
960 ///
961 /// `(Excluded(a), Excluded(b))` is only empty if `a >= b`:
962 ///
963 /// ```
964 /// #![feature(range_bounds_is_empty)]
965 /// use std::ops::Bound::*;
966 /// use std::ops::RangeBounds;
967 ///
968 /// assert!(!(Excluded(1), Excluded(3)).is_empty());
969 /// assert!(!(Excluded(1), Excluded(2)).is_empty());
970 /// assert!( (Excluded(1), Excluded(1)).is_empty());
971 /// assert!( (Excluded(2), Excluded(1)).is_empty());
972 /// assert!( (Excluded(3), Excluded(1)).is_empty());
973 /// ```
974 #[unstable(feature = "range_bounds_is_empty", issue = "137300")]
975 fn is_empty(&self) -> bool
976 where
977 T: [const] PartialOrd,
978 {
979 !match (self.start_bound(), self.end_bound()) {
980 (Unbounded, _) | (_, Unbounded) => true,
981 (Included(start), Excluded(end))
982 | (Excluded(start), Included(end))
983 | (Excluded(start), Excluded(end)) => start < end,
984 (Included(start), Included(end)) => start <= end,
985 }
986 }
987}
988
989/// Used to convert a range into start and end bounds, consuming the
990/// range by value.
991///
992/// `IntoBounds` is implemented by Rust’s built-in range types, produced
993/// by range syntax like `..`, `a..`, `..b`, `..=c`, `d..e`, or `f..=g`.
994#[unstable(feature = "range_into_bounds", issue = "136903")]
995#[rustc_const_unstable(feature = "const_range", issue = "none")]
996pub const trait IntoBounds<T>: [const] RangeBounds<T> {
997 /// Convert this range into the start and end bounds.
998 /// Returns `(start_bound, end_bound)`.
999 ///
1000 /// # Examples
1001 ///
1002 /// ```
1003 /// #![feature(range_into_bounds)]
1004 /// use std::ops::Bound::*;
1005 /// use std::ops::IntoBounds;
1006 ///
1007 /// assert_eq!((0..5).into_bounds(), (Included(0), Excluded(5)));
1008 /// assert_eq!((..=7).into_bounds(), (Unbounded, Included(7)));
1009 /// ```
1010 fn into_bounds(self) -> (Bound<T>, Bound<T>);
1011
1012 /// Compute the intersection of `self` and `other`.
1013 ///
1014 /// # Examples
1015 ///
1016 /// ```
1017 /// #![feature(range_into_bounds)]
1018 /// use std::ops::Bound::*;
1019 /// use std::ops::IntoBounds;
1020 ///
1021 /// assert_eq!((3..).intersect(..5), (Included(3), Excluded(5)));
1022 /// assert_eq!((-12..387).intersect(0..256), (Included(0), Excluded(256)));
1023 /// assert_eq!((1..5).intersect(..), (Included(1), Excluded(5)));
1024 /// assert_eq!((1..=9).intersect(0..10), (Included(1), Included(9)));
1025 /// assert_eq!((7..=13).intersect(8..13), (Included(8), Excluded(13)));
1026 /// ```
1027 ///
1028 /// Combine with `is_empty` to determine if two ranges overlap.
1029 ///
1030 /// ```
1031 /// #![feature(range_into_bounds)]
1032 /// #![feature(range_bounds_is_empty)]
1033 /// use std::ops::{RangeBounds, IntoBounds};
1034 ///
1035 /// assert!(!(3..).intersect(..5).is_empty());
1036 /// assert!(!(-12..387).intersect(0..256).is_empty());
1037 /// assert!((1..5).intersect(6..).is_empty());
1038 /// ```
1039 fn intersect<R>(self, other: R) -> (Bound<T>, Bound<T>)
1040 where
1041 Self: Sized,
1042 T: [const] Ord + [const] Destruct,
1043 R: Sized + [const] IntoBounds<T>,
1044 {
1045 let (self_start, self_end) = IntoBounds::into_bounds(self);
1046 let (other_start, other_end) = IntoBounds::into_bounds(other);
1047
1048 let start = match (self_start, other_start) {
1049 (Included(a), Included(b)) => Included(Ord::max(a, b)),
1050 (Excluded(a), Excluded(b)) => Excluded(Ord::max(a, b)),
1051 (Unbounded, Unbounded) => Unbounded,
1052
1053 (x, Unbounded) | (Unbounded, x) => x,
1054
1055 (Included(i), Excluded(e)) | (Excluded(e), Included(i)) => {
1056 if i > e {
1057 Included(i)
1058 } else {
1059 Excluded(e)
1060 }
1061 }
1062 };
1063 let end = match (self_end, other_end) {
1064 (Included(a), Included(b)) => Included(Ord::min(a, b)),
1065 (Excluded(a), Excluded(b)) => Excluded(Ord::min(a, b)),
1066 (Unbounded, Unbounded) => Unbounded,
1067
1068 (x, Unbounded) | (Unbounded, x) => x,
1069
1070 (Included(i), Excluded(e)) | (Excluded(e), Included(i)) => {
1071 if i < e {
1072 Included(i)
1073 } else {
1074 Excluded(e)
1075 }
1076 }
1077 };
1078
1079 (start, end)
1080 }
1081}
1082
1083use self::Bound::{Excluded, Included, Unbounded};
1084
1085#[stable(feature = "collections_range", since = "1.28.0")]
1086#[rustc_const_unstable(feature = "const_range", issue = "none")]
1087const impl<T: ?Sized> RangeBounds<T> for RangeFull {
1088 #[ferrocene::prevalidated]
1089 fn start_bound(&self) -> Bound<&T> {
1090 Unbounded
1091 }
1092 #[ferrocene::prevalidated]
1093 fn end_bound(&self) -> Bound<&T> {
1094 Unbounded
1095 }
1096}
1097
1098#[unstable(feature = "range_into_bounds", issue = "136903")]
1099#[rustc_const_unstable(feature = "const_range", issue = "none")]
1100const impl<T> IntoBounds<T> for RangeFull {
1101 #[ferrocene::prevalidated]
1102 fn into_bounds(self) -> (Bound<T>, Bound<T>) {
1103 (Unbounded, Unbounded)
1104 }
1105}
1106
1107#[stable(feature = "collections_range", since = "1.28.0")]
1108#[rustc_const_unstable(feature = "const_range", issue = "none")]
1109const impl<T> RangeBounds<T> for RangeFrom<T> {
1110 #[ferrocene::prevalidated]
1111 fn start_bound(&self) -> Bound<&T> {
1112 Included(&self.start)
1113 }
1114 #[ferrocene::prevalidated]
1115 fn end_bound(&self) -> Bound<&T> {
1116 Unbounded
1117 }
1118}
1119
1120#[unstable(feature = "range_into_bounds", issue = "136903")]
1121#[rustc_const_unstable(feature = "const_range", issue = "none")]
1122const impl<T> IntoBounds<T> for RangeFrom<T> {
1123 #[ferrocene::prevalidated]
1124 fn into_bounds(self) -> (Bound<T>, Bound<T>) {
1125 (Included(self.start), Unbounded)
1126 }
1127}
1128
1129#[stable(feature = "collections_range", since = "1.28.0")]
1130#[rustc_const_unstable(feature = "const_range", issue = "none")]
1131const impl<T> RangeBounds<T> for RangeTo<T> {
1132 #[ferrocene::prevalidated]
1133 fn start_bound(&self) -> Bound<&T> {
1134 Unbounded
1135 }
1136 #[ferrocene::prevalidated]
1137 fn end_bound(&self) -> Bound<&T> {
1138 Excluded(&self.end)
1139 }
1140}
1141
1142#[unstable(feature = "range_into_bounds", issue = "136903")]
1143#[rustc_const_unstable(feature = "const_range", issue = "none")]
1144const impl<T> IntoBounds<T> for RangeTo<T> {
1145 #[ferrocene::prevalidated]
1146 fn into_bounds(self) -> (Bound<T>, Bound<T>) {
1147 (Unbounded, Excluded(self.end))
1148 }
1149}
1150
1151#[stable(feature = "collections_range", since = "1.28.0")]
1152#[rustc_const_unstable(feature = "const_range", issue = "none")]
1153const impl<T> RangeBounds<T> for Range<T> {
1154 #[ferrocene::prevalidated]
1155 fn start_bound(&self) -> Bound<&T> {
1156 Included(&self.start)
1157 }
1158 #[ferrocene::prevalidated]
1159 fn end_bound(&self) -> Bound<&T> {
1160 Excluded(&self.end)
1161 }
1162}
1163
1164#[unstable(feature = "range_into_bounds", issue = "136903")]
1165#[rustc_const_unstable(feature = "const_range", issue = "none")]
1166const impl<T> IntoBounds<T> for Range<T> {
1167 #[ferrocene::prevalidated]
1168 fn into_bounds(self) -> (Bound<T>, Bound<T>) {
1169 (Included(self.start), Excluded(self.end))
1170 }
1171}
1172
1173#[stable(feature = "collections_range", since = "1.28.0")]
1174#[rustc_const_unstable(feature = "const_range", issue = "none")]
1175const impl<T> RangeBounds<T> for RangeInclusive<T> {
1176 #[ferrocene::prevalidated]
1177 fn start_bound(&self) -> Bound<&T> {
1178 Included(&self.start)
1179 }
1180 #[ferrocene::prevalidated]
1181 fn end_bound(&self) -> Bound<&T> {
1182 if self.exhausted {
1183 // When the iterator is exhausted, it might have overflowed,
1184 // but we want the range to appear empty, containing nothing.
1185 // So in that case, we return bounds which are always empty:
1186 // Included(start)..Excluded(start)
1187 Excluded(&self.start)
1188 } else {
1189 Included(&self.end)
1190 }
1191 }
1192}
1193
1194#[unstable(feature = "range_into_bounds", issue = "136903")]
1195#[rustc_const_unstable(feature = "const_range", issue = "none")]
1196const impl<T> IntoBounds<T> for RangeInclusive<T> {
1197 #[ferrocene::prevalidated]
1198 fn into_bounds(self) -> (Bound<T>, Bound<T>) {
1199 assert!(
1200 !self.exhausted,
1201 "attempted to convert from an exhausted `RangeInclusive` (unspecified behavior)"
1202 );
1203
1204 (Included(self.start), Included(self.end))
1205 }
1206}
1207
1208#[stable(feature = "collections_range", since = "1.28.0")]
1209#[rustc_const_unstable(feature = "const_range", issue = "none")]
1210const impl<T> RangeBounds<T> for RangeToInclusive<T> {
1211 #[ferrocene::prevalidated]
1212 fn start_bound(&self) -> Bound<&T> {
1213 Unbounded
1214 }
1215 #[ferrocene::prevalidated]
1216 fn end_bound(&self) -> Bound<&T> {
1217 Included(&self.end)
1218 }
1219}
1220
1221#[unstable(feature = "range_into_bounds", issue = "136903")]
1222#[rustc_const_unstable(feature = "const_range", issue = "none")]
1223const impl<T> IntoBounds<T> for RangeToInclusive<T> {
1224 #[ferrocene::prevalidated]
1225 fn into_bounds(self) -> (Bound<T>, Bound<T>) {
1226 (Unbounded, Included(self.end))
1227 }
1228}
1229
1230#[stable(feature = "collections_range", since = "1.28.0")]
1231#[rustc_const_unstable(feature = "const_range", issue = "none")]
1232const impl<T> RangeBounds<T> for (Bound<T>, Bound<T>) {
1233 #[ferrocene::prevalidated]
1234 fn start_bound(&self) -> Bound<&T> {
1235 match *self {
1236 (Included(ref start), _) => Included(start),
1237 (Excluded(ref start), _) => Excluded(start),
1238 (Unbounded, _) => Unbounded,
1239 }
1240 }
1241
1242 #[ferrocene::prevalidated]
1243 fn end_bound(&self) -> Bound<&T> {
1244 match *self {
1245 (_, Included(ref end)) => Included(end),
1246 (_, Excluded(ref end)) => Excluded(end),
1247 (_, Unbounded) => Unbounded,
1248 }
1249 }
1250}
1251
1252#[unstable(feature = "range_into_bounds", issue = "136903")]
1253#[rustc_const_unstable(feature = "const_range", issue = "none")]
1254const impl<T> IntoBounds<T> for (Bound<T>, Bound<T>) {
1255 #[ferrocene::prevalidated]
1256 fn into_bounds(self) -> (Bound<T>, Bound<T>) {
1257 self
1258 }
1259}
1260
1261#[stable(feature = "collections_range", since = "1.28.0")]
1262#[rustc_const_unstable(feature = "const_range", issue = "none")]
1263const impl<'a, T: ?Sized + 'a> RangeBounds<T> for (Bound<&'a T>, Bound<&'a T>) {
1264 fn start_bound(&self) -> Bound<&T> {
1265 self.0
1266 }
1267
1268 fn end_bound(&self) -> Bound<&T> {
1269 self.1
1270 }
1271}
1272
1273// This impl intentionally does not have `T: ?Sized`;
1274// see https://github.com/rust-lang/rust/pull/61584 for discussion of why.
1275//
1276/// If you need to use this implementation where `T` is unsized,
1277/// consider using the `RangeBounds` impl for a 2-tuple of [`Bound<&T>`][Bound],
1278/// i.e. replace `start..` with `(Bound::Included(start), Bound::Unbounded)`.
1279#[stable(feature = "collections_range", since = "1.28.0")]
1280#[rustc_const_unstable(feature = "const_range", issue = "none")]
1281const impl<T> RangeBounds<T> for RangeFrom<&T> {
1282 #[ferrocene::prevalidated]
1283 fn start_bound(&self) -> Bound<&T> {
1284 Included(self.start)
1285 }
1286 #[ferrocene::prevalidated]
1287 fn end_bound(&self) -> Bound<&T> {
1288 Unbounded
1289 }
1290}
1291
1292// This impl intentionally does not have `T: ?Sized`;
1293// see https://github.com/rust-lang/rust/pull/61584 for discussion of why.
1294//
1295/// If you need to use this implementation where `T` is unsized,
1296/// consider using the `RangeBounds` impl for a 2-tuple of [`Bound<&T>`][Bound],
1297/// i.e. replace `..end` with `(Bound::Unbounded, Bound::Excluded(end))`.
1298#[stable(feature = "collections_range", since = "1.28.0")]
1299#[rustc_const_unstable(feature = "const_range", issue = "none")]
1300const impl<T> RangeBounds<T> for RangeTo<&T> {
1301 #[ferrocene::prevalidated]
1302 fn start_bound(&self) -> Bound<&T> {
1303 Unbounded
1304 }
1305 #[ferrocene::prevalidated]
1306 fn end_bound(&self) -> Bound<&T> {
1307 Excluded(self.end)
1308 }
1309}
1310
1311// This impl intentionally does not have `T: ?Sized`;
1312// see https://github.com/rust-lang/rust/pull/61584 for discussion of why.
1313//
1314/// If you need to use this implementation where `T` is unsized,
1315/// consider using the `RangeBounds` impl for a 2-tuple of [`Bound<&T>`][Bound],
1316/// i.e. replace `start..end` with `(Bound::Included(start), Bound::Excluded(end))`.
1317#[stable(feature = "collections_range", since = "1.28.0")]
1318#[rustc_const_unstable(feature = "const_range", issue = "none")]
1319const impl<T> RangeBounds<T> for Range<&T> {
1320 #[ferrocene::prevalidated]
1321 fn start_bound(&self) -> Bound<&T> {
1322 Included(self.start)
1323 }
1324 #[ferrocene::prevalidated]
1325 fn end_bound(&self) -> Bound<&T> {
1326 Excluded(self.end)
1327 }
1328}
1329
1330// This impl intentionally does not have `T: ?Sized`;
1331// see https://github.com/rust-lang/rust/pull/61584 for discussion of why.
1332//
1333/// If you need to use this implementation where `T` is unsized,
1334/// consider using the `RangeBounds` impl for a 2-tuple of [`Bound<&T>`][Bound],
1335/// i.e. replace `start..=end` with `(Bound::Included(start), Bound::Included(end))`.
1336#[stable(feature = "collections_range", since = "1.28.0")]
1337#[rustc_const_unstable(feature = "const_range", issue = "none")]
1338const impl<T> RangeBounds<T> for RangeInclusive<&T> {
1339 #[ferrocene::prevalidated]
1340 fn start_bound(&self) -> Bound<&T> {
1341 Included(self.start)
1342 }
1343 #[ferrocene::prevalidated]
1344 fn end_bound(&self) -> Bound<&T> {
1345 Included(self.end)
1346 }
1347}
1348
1349// This impl intentionally does not have `T: ?Sized`;
1350// see https://github.com/rust-lang/rust/pull/61584 for discussion of why.
1351//
1352/// If you need to use this implementation where `T` is unsized,
1353/// consider using the `RangeBounds` impl for a 2-tuple of [`Bound<&T>`][Bound],
1354/// i.e. replace `..=end` with `(Bound::Unbounded, Bound::Included(end))`.
1355#[stable(feature = "collections_range", since = "1.28.0")]
1356#[rustc_const_unstable(feature = "const_range", issue = "none")]
1357const impl<T> RangeBounds<T> for RangeToInclusive<&T> {
1358 #[ferrocene::prevalidated]
1359 fn start_bound(&self) -> Bound<&T> {
1360 Unbounded
1361 }
1362 #[ferrocene::prevalidated]
1363 fn end_bound(&self) -> Bound<&T> {
1364 Included(self.end)
1365 }
1366}
1367
1368/// An internal helper for `split_off` functions indicating
1369/// which end a `OneSidedRange` is bounded on.
1370#[unstable(feature = "one_sided_range", issue = "69780")]
1371#[allow(missing_debug_implementations)]
1372#[ferrocene::prevalidated]
1373pub enum OneSidedRangeBound {
1374 /// The range is bounded inclusively from below and is unbounded above.
1375 StartInclusive,
1376 /// The range is bounded exclusively from above and is unbounded below.
1377 End,
1378 /// The range is bounded inclusively from above and is unbounded below.
1379 EndInclusive,
1380}
1381
1382/// `OneSidedRange` is implemented for built-in range types that are unbounded
1383/// on one side. For example, `a..`, `..b` and `..=c` implement `OneSidedRange`,
1384/// but `..`, `d..e`, and `f..=g` do not.
1385///
1386/// Types that implement `OneSidedRange<T>` must return `Bound::Unbounded`
1387/// from one of `RangeBounds::start_bound` or `RangeBounds::end_bound`.
1388#[unstable(feature = "one_sided_range", issue = "69780")]
1389#[rustc_const_unstable(feature = "const_range", issue = "none")]
1390pub const trait OneSidedRange<T>: RangeBounds<T> {
1391 /// An internal-only helper function for `split_off` and
1392 /// `split_off_mut` that returns the bound of the one-sided range.
1393 fn bound(self) -> (OneSidedRangeBound, T);
1394}
1395
1396#[unstable(feature = "one_sided_range", issue = "69780")]
1397#[rustc_const_unstable(feature = "const_range", issue = "none")]
1398const impl<T> OneSidedRange<T> for RangeTo<T>
1399where
1400 Self: RangeBounds<T>,
1401{
1402 #[ferrocene::prevalidated]
1403 fn bound(self) -> (OneSidedRangeBound, T) {
1404 (OneSidedRangeBound::End, self.end)
1405 }
1406}
1407
1408#[unstable(feature = "one_sided_range", issue = "69780")]
1409#[rustc_const_unstable(feature = "const_range", issue = "none")]
1410const impl<T> OneSidedRange<T> for RangeFrom<T>
1411where
1412 Self: RangeBounds<T>,
1413{
1414 #[ferrocene::prevalidated]
1415 fn bound(self) -> (OneSidedRangeBound, T) {
1416 (OneSidedRangeBound::StartInclusive, self.start)
1417 }
1418}
1419
1420#[unstable(feature = "one_sided_range", issue = "69780")]
1421#[rustc_const_unstable(feature = "const_range", issue = "none")]
1422const impl<T> OneSidedRange<T> for RangeToInclusive<T>
1423where
1424 Self: RangeBounds<T>,
1425{
1426 #[ferrocene::prevalidated]
1427 fn bound(self) -> (OneSidedRangeBound, T) {
1428 (OneSidedRangeBound::EndInclusive, self.end)
1429 }
1430}