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