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