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: Clone> Bound<&T> {
740 /// Map a `Bound<&T>` to a `Bound<T>` by cloning the contents of the bound.
741 ///
742 /// # Examples
743 ///
744 /// ```
745 /// use std::ops::Bound::*;
746 /// use std::ops::RangeBounds;
747 ///
748 /// assert_eq!((1..12).start_bound(), Included(&1));
749 /// assert_eq!((1..12).start_bound().cloned(), Included(1));
750 /// ```
751 #[must_use = "`self` will be dropped if the result is not used"]
752 #[stable(feature = "bound_cloned", since = "1.55.0")]
753 pub fn cloned(self) -> Bound<T> {
754 match self {
755 Bound::Unbounded => Bound::Unbounded,
756 Bound::Included(x) => Bound::Included(x.clone()),
757 Bound::Excluded(x) => Bound::Excluded(x.clone()),
758 }
759 }
760}
761
762/// `RangeBounds` is implemented by Rust's built-in range types, produced
763/// by range syntax like `..`, `a..`, `..b`, `..=c`, `d..e`, or `f..=g`.
764#[stable(feature = "collections_range", since = "1.28.0")]
765#[rustc_diagnostic_item = "RangeBounds"]
766pub trait RangeBounds<T: ?Sized> {
767 /// Start index bound.
768 ///
769 /// Returns the start value as a `Bound`.
770 ///
771 /// # Examples
772 ///
773 /// ```
774 /// use std::ops::Bound::*;
775 /// use std::ops::RangeBounds;
776 ///
777 /// assert_eq!((..10).start_bound(), Unbounded);
778 /// assert_eq!((3..10).start_bound(), Included(&3));
779 /// ```
780 #[stable(feature = "collections_range", since = "1.28.0")]
781 fn start_bound(&self) -> Bound<&T>;
782
783 /// End index bound.
784 ///
785 /// Returns the end value as a `Bound`.
786 ///
787 /// # Examples
788 ///
789 /// ```
790 /// use std::ops::Bound::*;
791 /// use std::ops::RangeBounds;
792 ///
793 /// assert_eq!((3..).end_bound(), Unbounded);
794 /// assert_eq!((3..10).end_bound(), Excluded(&10));
795 /// ```
796 #[stable(feature = "collections_range", since = "1.28.0")]
797 fn end_bound(&self) -> Bound<&T>;
798
799 /// Returns `true` if `item` is contained in the range.
800 ///
801 /// # Examples
802 ///
803 /// ```
804 /// assert!( (3..5).contains(&4));
805 /// assert!(!(3..5).contains(&2));
806 ///
807 /// assert!( (0.0..1.0).contains(&0.5));
808 /// assert!(!(0.0..1.0).contains(&f32::NAN));
809 /// assert!(!(0.0..f32::NAN).contains(&0.5));
810 /// assert!(!(f32::NAN..1.0).contains(&0.5));
811 #[inline]
812 #[stable(feature = "range_contains", since = "1.35.0")]
813 fn contains<U>(&self, item: &U) -> bool
814 where
815 T: PartialOrd<U>,
816 U: ?Sized + PartialOrd<T>,
817 {
818 (match self.start_bound() {
819 Included(start) => start <= item,
820 Excluded(start) => start < item,
821 Unbounded => true,
822 }) && (match self.end_bound() {
823 Included(end) => item <= end,
824 Excluded(end) => item < end,
825 Unbounded => true,
826 })
827 }
828
829 /// Returns `true` if the range contains no items.
830 /// One-sided ranges (`RangeFrom`, etc) always return `false`.
831 ///
832 /// # Examples
833 ///
834 /// ```
835 /// #![feature(range_bounds_is_empty)]
836 /// use std::ops::RangeBounds;
837 ///
838 /// assert!(!(3..).is_empty());
839 /// assert!(!(..2).is_empty());
840 /// assert!(!RangeBounds::is_empty(&(3..5)));
841 /// assert!( RangeBounds::is_empty(&(3..3)));
842 /// assert!( RangeBounds::is_empty(&(3..2)));
843 /// ```
844 ///
845 /// The range is empty if either side is incomparable:
846 ///
847 /// ```
848 /// #![feature(range_bounds_is_empty)]
849 /// use std::ops::RangeBounds;
850 ///
851 /// assert!(!RangeBounds::is_empty(&(3.0..5.0)));
852 /// assert!( RangeBounds::is_empty(&(3.0..f32::NAN)));
853 /// assert!( RangeBounds::is_empty(&(f32::NAN..5.0)));
854 /// ```
855 ///
856 /// But never empty is either side is unbounded:
857 ///
858 /// ```
859 /// #![feature(range_bounds_is_empty)]
860 /// use std::ops::RangeBounds;
861 ///
862 /// assert!(!(..0).is_empty());
863 /// assert!(!(i32::MAX..).is_empty());
864 /// assert!(!RangeBounds::<u8>::is_empty(&(..)));
865 /// ```
866 ///
867 /// `(Excluded(a), Excluded(b))` is only empty if `a >= b`:
868 ///
869 /// ```
870 /// #![feature(range_bounds_is_empty)]
871 /// use std::ops::Bound::*;
872 /// use std::ops::RangeBounds;
873 ///
874 /// assert!(!(Excluded(1), Excluded(3)).is_empty());
875 /// assert!(!(Excluded(1), Excluded(2)).is_empty());
876 /// assert!( (Excluded(1), Excluded(1)).is_empty());
877 /// assert!( (Excluded(2), Excluded(1)).is_empty());
878 /// assert!( (Excluded(3), Excluded(1)).is_empty());
879 /// ```
880 #[unstable(feature = "range_bounds_is_empty", issue = "137300")]
881 fn is_empty(&self) -> bool
882 where
883 T: PartialOrd,
884 {
885 !match (self.start_bound(), self.end_bound()) {
886 (Unbounded, _) | (_, Unbounded) => true,
887 (Included(start), Excluded(end))
888 | (Excluded(start), Included(end))
889 | (Excluded(start), Excluded(end)) => start < end,
890 (Included(start), Included(end)) => start <= end,
891 }
892 }
893}
894
895/// Used to convert a range into start and end bounds, consuming the
896/// range by value.
897///
898/// `IntoBounds` is implemented by Rust’s built-in range types, produced
899/// by range syntax like `..`, `a..`, `..b`, `..=c`, `d..e`, or `f..=g`.
900#[unstable(feature = "range_into_bounds", issue = "136903")]
901pub trait IntoBounds<T>: RangeBounds<T> {
902 /// Convert this range into the start and end bounds.
903 /// Returns `(start_bound, end_bound)`.
904 ///
905 /// # Examples
906 ///
907 /// ```
908 /// #![feature(range_into_bounds)]
909 /// use std::ops::Bound::*;
910 /// use std::ops::IntoBounds;
911 ///
912 /// assert_eq!((0..5).into_bounds(), (Included(0), Excluded(5)));
913 /// assert_eq!((..=7).into_bounds(), (Unbounded, Included(7)));
914 /// ```
915 fn into_bounds(self) -> (Bound<T>, Bound<T>);
916
917 /// Compute the intersection of `self` and `other`.
918 ///
919 /// # Examples
920 ///
921 /// ```
922 /// #![feature(range_into_bounds)]
923 /// use std::ops::Bound::*;
924 /// use std::ops::IntoBounds;
925 ///
926 /// assert_eq!((3..).intersect(..5), (Included(3), Excluded(5)));
927 /// assert_eq!((-12..387).intersect(0..256), (Included(0), Excluded(256)));
928 /// assert_eq!((1..5).intersect(..), (Included(1), Excluded(5)));
929 /// assert_eq!((1..=9).intersect(0..10), (Included(1), Included(9)));
930 /// assert_eq!((7..=13).intersect(8..13), (Included(8), Excluded(13)));
931 /// ```
932 ///
933 /// Combine with `is_empty` to determine if two ranges overlap.
934 ///
935 /// ```
936 /// #![feature(range_into_bounds)]
937 /// #![feature(range_bounds_is_empty)]
938 /// use std::ops::{RangeBounds, IntoBounds};
939 ///
940 /// assert!(!(3..).intersect(..5).is_empty());
941 /// assert!(!(-12..387).intersect(0..256).is_empty());
942 /// assert!((1..5).intersect(6..).is_empty());
943 /// ```
944 fn intersect<R>(self, other: R) -> (Bound<T>, Bound<T>)
945 where
946 Self: Sized,
947 T: Ord,
948 R: Sized + IntoBounds<T>,
949 {
950 let (self_start, self_end) = IntoBounds::into_bounds(self);
951 let (other_start, other_end) = IntoBounds::into_bounds(other);
952
953 let start = match (self_start, other_start) {
954 (Included(a), Included(b)) => Included(Ord::max(a, b)),
955 (Excluded(a), Excluded(b)) => Excluded(Ord::max(a, b)),
956 (Unbounded, Unbounded) => Unbounded,
957
958 (x, Unbounded) | (Unbounded, x) => x,
959
960 (Included(i), Excluded(e)) | (Excluded(e), Included(i)) => {
961 if i > e {
962 Included(i)
963 } else {
964 Excluded(e)
965 }
966 }
967 };
968 let end = match (self_end, other_end) {
969 (Included(a), Included(b)) => Included(Ord::min(a, b)),
970 (Excluded(a), Excluded(b)) => Excluded(Ord::min(a, b)),
971 (Unbounded, Unbounded) => Unbounded,
972
973 (x, Unbounded) | (Unbounded, x) => x,
974
975 (Included(i), Excluded(e)) | (Excluded(e), Included(i)) => {
976 if i < e {
977 Included(i)
978 } else {
979 Excluded(e)
980 }
981 }
982 };
983
984 (start, end)
985 }
986}
987
988use self::Bound::{Excluded, Included, Unbounded};
989
990#[stable(feature = "collections_range", since = "1.28.0")]
991impl<T: ?Sized> RangeBounds<T> for RangeFull {
992 fn start_bound(&self) -> Bound<&T> {
993 Unbounded
994 }
995 fn end_bound(&self) -> Bound<&T> {
996 Unbounded
997 }
998}
999
1000#[unstable(feature = "range_into_bounds", issue = "136903")]
1001impl<T> IntoBounds<T> for RangeFull {
1002 fn into_bounds(self) -> (Bound<T>, Bound<T>) {
1003 (Unbounded, Unbounded)
1004 }
1005}
1006
1007#[stable(feature = "collections_range", since = "1.28.0")]
1008impl<T> RangeBounds<T> for RangeFrom<T> {
1009 fn start_bound(&self) -> Bound<&T> {
1010 Included(&self.start)
1011 }
1012 fn end_bound(&self) -> Bound<&T> {
1013 Unbounded
1014 }
1015}
1016
1017#[unstable(feature = "range_into_bounds", issue = "136903")]
1018impl<T> IntoBounds<T> for RangeFrom<T> {
1019 fn into_bounds(self) -> (Bound<T>, Bound<T>) {
1020 (Included(self.start), Unbounded)
1021 }
1022}
1023
1024#[stable(feature = "collections_range", since = "1.28.0")]
1025impl<T> RangeBounds<T> for RangeTo<T> {
1026 fn start_bound(&self) -> Bound<&T> {
1027 Unbounded
1028 }
1029 fn end_bound(&self) -> Bound<&T> {
1030 Excluded(&self.end)
1031 }
1032}
1033
1034#[unstable(feature = "range_into_bounds", issue = "136903")]
1035impl<T> IntoBounds<T> for RangeTo<T> {
1036 fn into_bounds(self) -> (Bound<T>, Bound<T>) {
1037 (Unbounded, Excluded(self.end))
1038 }
1039}
1040
1041#[stable(feature = "collections_range", since = "1.28.0")]
1042impl<T> RangeBounds<T> for Range<T> {
1043 fn start_bound(&self) -> Bound<&T> {
1044 Included(&self.start)
1045 }
1046 fn end_bound(&self) -> Bound<&T> {
1047 Excluded(&self.end)
1048 }
1049}
1050
1051#[unstable(feature = "range_into_bounds", issue = "136903")]
1052impl<T> IntoBounds<T> for Range<T> {
1053 fn into_bounds(self) -> (Bound<T>, Bound<T>) {
1054 (Included(self.start), Excluded(self.end))
1055 }
1056}
1057
1058#[stable(feature = "collections_range", since = "1.28.0")]
1059impl<T> RangeBounds<T> for RangeInclusive<T> {
1060 fn start_bound(&self) -> Bound<&T> {
1061 Included(&self.start)
1062 }
1063 fn end_bound(&self) -> Bound<&T> {
1064 if self.exhausted {
1065 // When the iterator is exhausted, we usually have start == end,
1066 // but we want the range to appear empty, containing nothing.
1067 Excluded(&self.end)
1068 } else {
1069 Included(&self.end)
1070 }
1071 }
1072}
1073
1074#[unstable(feature = "range_into_bounds", issue = "136903")]
1075impl<T> IntoBounds<T> for RangeInclusive<T> {
1076 fn into_bounds(self) -> (Bound<T>, Bound<T>) {
1077 (
1078 Included(self.start),
1079 if self.exhausted {
1080 // When the iterator is exhausted, we usually have start == end,
1081 // but we want the range to appear empty, containing nothing.
1082 Excluded(self.end)
1083 } else {
1084 Included(self.end)
1085 },
1086 )
1087 }
1088}
1089
1090#[stable(feature = "collections_range", since = "1.28.0")]
1091impl<T> RangeBounds<T> for RangeToInclusive<T> {
1092 fn start_bound(&self) -> Bound<&T> {
1093 Unbounded
1094 }
1095 fn end_bound(&self) -> Bound<&T> {
1096 Included(&self.end)
1097 }
1098}
1099
1100#[unstable(feature = "range_into_bounds", issue = "136903")]
1101impl<T> IntoBounds<T> for RangeToInclusive<T> {
1102 fn into_bounds(self) -> (Bound<T>, Bound<T>) {
1103 (Unbounded, Included(self.end))
1104 }
1105}
1106
1107#[stable(feature = "collections_range", since = "1.28.0")]
1108impl<T> RangeBounds<T> for (Bound<T>, Bound<T>) {
1109 fn start_bound(&self) -> Bound<&T> {
1110 match *self {
1111 (Included(ref start), _) => Included(start),
1112 (Excluded(ref start), _) => Excluded(start),
1113 (Unbounded, _) => Unbounded,
1114 }
1115 }
1116
1117 fn end_bound(&self) -> Bound<&T> {
1118 match *self {
1119 (_, Included(ref end)) => Included(end),
1120 (_, Excluded(ref end)) => Excluded(end),
1121 (_, Unbounded) => Unbounded,
1122 }
1123 }
1124}
1125
1126#[unstable(feature = "range_into_bounds", issue = "136903")]
1127impl<T> IntoBounds<T> for (Bound<T>, Bound<T>) {
1128 fn into_bounds(self) -> (Bound<T>, Bound<T>) {
1129 self
1130 }
1131}
1132
1133#[stable(feature = "collections_range", since = "1.28.0")]
1134impl<'a, T: ?Sized + 'a> RangeBounds<T> for (Bound<&'a T>, Bound<&'a T>) {
1135 fn start_bound(&self) -> Bound<&T> {
1136 self.0
1137 }
1138
1139 fn end_bound(&self) -> Bound<&T> {
1140 self.1
1141 }
1142}
1143
1144#[stable(feature = "collections_range", since = "1.28.0")]
1145impl<T> RangeBounds<T> for RangeFrom<&T> {
1146 fn start_bound(&self) -> Bound<&T> {
1147 Included(self.start)
1148 }
1149 fn end_bound(&self) -> Bound<&T> {
1150 Unbounded
1151 }
1152}
1153
1154#[stable(feature = "collections_range", since = "1.28.0")]
1155impl<T> RangeBounds<T> for RangeTo<&T> {
1156 fn start_bound(&self) -> Bound<&T> {
1157 Unbounded
1158 }
1159 fn end_bound(&self) -> Bound<&T> {
1160 Excluded(self.end)
1161 }
1162}
1163
1164#[stable(feature = "collections_range", since = "1.28.0")]
1165impl<T> RangeBounds<T> for Range<&T> {
1166 fn start_bound(&self) -> Bound<&T> {
1167 Included(self.start)
1168 }
1169 fn end_bound(&self) -> Bound<&T> {
1170 Excluded(self.end)
1171 }
1172}
1173
1174#[stable(feature = "collections_range", since = "1.28.0")]
1175impl<T> RangeBounds<T> for RangeInclusive<&T> {
1176 fn start_bound(&self) -> Bound<&T> {
1177 Included(self.start)
1178 }
1179 fn end_bound(&self) -> Bound<&T> {
1180 Included(self.end)
1181 }
1182}
1183
1184#[stable(feature = "collections_range", since = "1.28.0")]
1185impl<T> RangeBounds<T> for RangeToInclusive<&T> {
1186 fn start_bound(&self) -> Bound<&T> {
1187 Unbounded
1188 }
1189 fn end_bound(&self) -> Bound<&T> {
1190 Included(self.end)
1191 }
1192}
1193
1194/// An internal helper for `split_off` functions indicating
1195/// which end a `OneSidedRange` is bounded on.
1196#[unstable(feature = "one_sided_range", issue = "69780")]
1197#[allow(missing_debug_implementations)]
1198pub enum OneSidedRangeBound {
1199 /// The range is bounded inclusively from below and is unbounded above.
1200 StartInclusive,
1201 /// The range is bounded exclusively from above and is unbounded below.
1202 End,
1203 /// The range is bounded inclusively from above and is unbounded below.
1204 EndInclusive,
1205}
1206
1207/// `OneSidedRange` is implemented for built-in range types that are unbounded
1208/// on one side. For example, `a..`, `..b` and `..=c` implement `OneSidedRange`,
1209/// but `..`, `d..e`, and `f..=g` do not.
1210///
1211/// Types that implement `OneSidedRange<T>` must return `Bound::Unbounded`
1212/// from one of `RangeBounds::start_bound` or `RangeBounds::end_bound`.
1213#[unstable(feature = "one_sided_range", issue = "69780")]
1214pub trait OneSidedRange<T>: RangeBounds<T> {
1215 /// An internal-only helper function for `split_off` and
1216 /// `split_off_mut` that returns the bound of the one-sided range.
1217 fn bound(self) -> (OneSidedRangeBound, T);
1218}
1219
1220#[unstable(feature = "one_sided_range", issue = "69780")]
1221impl<T> OneSidedRange<T> for RangeTo<T>
1222where
1223 Self: RangeBounds<T>,
1224{
1225 fn bound(self) -> (OneSidedRangeBound, T) {
1226 (OneSidedRangeBound::End, self.end)
1227 }
1228}
1229
1230#[unstable(feature = "one_sided_range", issue = "69780")]
1231impl<T> OneSidedRange<T> for RangeFrom<T>
1232where
1233 Self: RangeBounds<T>,
1234{
1235 fn bound(self) -> (OneSidedRangeBound, T) {
1236 (OneSidedRangeBound::StartInclusive, self.start)
1237 }
1238}
1239
1240#[unstable(feature = "one_sided_range", issue = "69780")]
1241impl<T> OneSidedRange<T> for RangeToInclusive<T>
1242where
1243 Self: RangeBounds<T>,
1244{
1245 fn bound(self) -> (OneSidedRangeBound, T) {
1246 (OneSidedRangeBound::EndInclusive, self.end)
1247 }
1248}